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| www.motorola.com/semiconductors m68hc08 microcontrollers mc68HC908AS32A/d r e v . 0, 5 / 20 0 2 mc68HC908AS32A advance information f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . .
f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola 3 mc68HC908AS32A advance information ? rev 0.0 motorola reserves the right to make changes without further notice to any products herein. motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "typical" parameters which may be provided in motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including "typicals" must be validated for each customer application by customer?s technical experts. motorola does not convey any license under its patent rights nor the rights of others. motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the motorola product could create a situation where personal injury or death may occur. should buyer purchase or use motorola products for any such unintended or unauthorized application, buyer shall indemnify and hold motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that motorola was negligent regarding the design or manufacture of the part. motorola, inc. is an equal opportunity/affirmative action employer. motorola and are registered trademarks of motorola, inc. digitaldna is a trademark of motorola, inc. ? motorola, inc., 2001 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . advance information mc68HC908AS32A ? rev 0.0 4 motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola list of paragraphs 5 technical data ? mc68HC908AS32A list of paragraphs list of paragraphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 table of contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 list of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 list of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 section 1. general description . . . . . . . . . . . . . . . . . . . . 25 section 2. memory map . . . . . . . . . . . . . . . . . . . . . . . . . . 37 section 3. ram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 section 4. flash memory . . . . . . . . . . . . . . . . . . . . . . . . 51 section 5. eeprom memory . . . . . . . . . . . . . . . . . . . . . . 63 section 6. central processor unit (cpu) . . . . . . . . . . . . 83 section 7. system integration module (sim) . . . . . . . . 101 section 8. clock generator module (cgm) . . . . . . . . . . 123 section 9. configuration register (config-1). . . . . . . 151 section 10. configuration register (config-2). . . . . . 155 section 11. break module (brk) . . . . . . . . . . . . . . . . . . 157 section 12. monitor rom (mon) . . . . . . . . . . . . . . . . . . 163 section 13. computer operating properly (cop) . . . . 175 section 14. low voltage inhibit (lvi) . . . . . . . . . . . . . . 181 section 15. external interrupt module (irq) . . . . . . . . . 187 section 16. serial communications interface (sci) . . . 195 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of paragraphs advance information mc68HC908AS32A ? rev 0.0 6 list of paragraphs motorola section 17. serial peripheral interface (spi). . . . . . . . . 235 section 18. timer interface module b (timb) . . . . . . . . 267 section 19. programmable interrupt timer (pit) . . . . . 293 section 20. input/output ports . . . . . . . . . . . . . . . . . . . 303 section 21. keyboard module (kbd) . . . . . . . . . . . . . . . 323 section 22. timer interface module a (tima) . . . . . . . . 331 section 23. analog-to-digital converter (adc) . . . . . . 361 section 24. byte data link controller (bdlc) . . . . . . . 373 section 25. electrical specification. . . . . . . . . . . . . . . . 419 glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola table of contents 7 technical data ? mc68HC908AS32A table of contents list of paragraphs table of contents list of figures list of tables section 1. general description 1.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 1.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 1.4 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.5 pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.6 ordering information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 section 2. memory map 2.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 2.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.3 i/o section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.4 additional status and control registers . . . . . . . . . . . . . . . . . . 45 2.5 vector addresses and priority . . . . . . . . . . . . . . . . . . . . . . . . . 46 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents advance information mc68HC908AS32A ? rev 0.0 8 table of contents motorola section 3. ram 3.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 3.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 section 4. flash memory 4.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 4.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.4 flash control and block protect registers . . . . . . . . . . . . . . 52 4.5 flash block protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 4.6 flash mass erase operation . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.7 flash page erase operation . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.8 flash program operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.9 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62 section 5. eeprom memory 5.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 5.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64 5.4 eeprom register summary . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.6 eeprom register descriptions . . . . . . . . . . . . . . . . . . . . . . . . 73 5.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents mc68HC908AS32A ? rev 0.0 advance information motorola table of contents 9 section 6. central processor unit (cpu) 6.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 6.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84 6.4 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.5 arithmetic/logic unit (alu) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 6.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90 6.7 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.8 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.9 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 section 7. system integration module (sim) 7.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101 7.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.3 sim bus clock control and generation . . . . . . . . . . . . . . . . . 104 7.4 reset and system initialization. . . . . . . . . . . . . . . . . . . . . . . . 106 7.5 sim counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110 7.6 program exception control. . . . . . . . . . . . . . . . . . . . . . . . . . . 111 7.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 7.8 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 section 8. clock generator module (cgm) 8.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 8.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 8.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124 8.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.5 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents advance information mc68HC908AS32A ? rev 0.0 10 table of contents motorola 8.6 cgm registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 8.7 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 8.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 8.9 cgm during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 144 8.10 acquisition/lock time specifications . . . . . . . . . . . . . . . . . . .144 section 9. configuration register (config-1) 9.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151 9.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 9.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 section 10. configuration register (config-2) 10.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 10.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 10.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 section 11. break module (brk) 11.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 11.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 11.6 break module registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161 section 12. monitor rom (mon) 12.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 12.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 12.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents mc68HC908AS32A ? rev 0.0 advance information motorola table of contents 11 12.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 section 13. computer operating properly (cop) 13.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 13.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 13.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 13.4 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13.5 cop control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.7 monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 13.9 cop module during break interrupts . . . . . . . . . . . . . . . . . . . 180 section 14. low voltage inhibit (lvi) 14.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 14.5 lvi status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 14.6 lvi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 14.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185 section 15. external interrupt module (irq) 15.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents advance information mc68HC908AS32A ? rev 0.0 12 table of contents motorola 15.5 irq pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 15.6 irq module during break interrupts . . . . . . . . . . . . . . . . . . .192 15.7 irq status and control register . . . . . . . . . . . . . . . . . . . . . . 192 section 16. serial communications interface (sci) 16.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 16.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 16.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 16.4 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 16.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 16.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 16.7 sci during break module interrupts. . . . . . . . . . . . . . . . . . . . 216 16.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 16.9 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 section 17. serial peripheral interface (spi) 17.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 17.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 17.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 17.4 pin name and register name conventions . . . . . . . . . . . . . . 237 17.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 17.6 transmission formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 17.7 error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 17.8 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 17.9 queuing transmission data . . . . . . . . . . . . . . . . . . . . . . . . . . 252 17.10 resetting the spi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 17.11 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .255 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents mc68HC908AS32A ? rev 0.0 advance information motorola table of contents 13 17.12 spi during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .255 17.13 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 17.14 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 section 18. timer interface module b (timb) 18.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 18.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 18.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 18.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 18.5 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 18.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279 18.7 timb during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 279 18.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 18.9 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 section 19. programmable interrupt timer (pit) 19.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 19.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 19.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 19.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 19.5 pit counter prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 19.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296 19.7 pit during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .297 19.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents advance information mc68HC908AS32A ? rev 0.0 14 table of contents motorola section 20. input/output ports 20.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 20.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 20.3 port a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 20.4 port b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 20.5 port c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 20.6 port d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 20.7 port e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 20.8 port f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 section 21. keyboard module (kbd) 21.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 21.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 21.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 21.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 21.5 keyboard initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 21.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .328 21.7 keyboard module during break interrupts . . . . . . . . . . . . . . .328 21.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 section 22. timer interface module a (tima) 22.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 22.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 22.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 22.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 22.5 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 22.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents mc68HC908AS32A ? rev 0.0 advance information motorola table of contents 15 22.7 tima during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 345 22.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 22.9 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 section 23. analog-to-digital converter (adc) 23.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 23.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 23.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 23.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 23.5 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 23.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365 23.7 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 23.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 section 24. byte data link controller (bdlc) 24.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 24.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 24.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 24.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 24.5 bdlc mux interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 24.6 bdlc protocol handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 24.7 bdlc cpu interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 24.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .417 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . table of contents advance information mc68HC908AS32A ? rev 0.0 16 table of contents motorola section 25. electrical specification 25.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 25.2 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 25.3 mechanical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 434 glossary f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola list of figures 17 technical data ? mc68HC908AS32A list of figures figure title page 1-1 mcu block diagram for the mc68HC908AS32A (52-pin plcc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 1-2 mc68HC908AS32A (52-pin plcc) . . . . . . . . . . . . . . . . . . . . . 29 1-3 power supply bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 2-1 memory map (continued) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2-2 i/o data, status and control registers . . . . . . . . . . . . . . . . . . 41 2-3 additional status and control registers . . . . . . . . . . . . . . . . . . 45 4-1 flash control register (flcr) . . . . . . . . . . . . . . . . . . . . . . . 53 4-2 flash block protect register (flbpr). . . . . . . . . . . . . . . . . . 54 4-3 flash block protect start address . . . . . . . . . . . . . . . . . . . . . 54 4-4 flash programming algorithm flowchart. . . . . . . . . . . . . . . .61 5-1 eeprom register summary . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5-2 eeprom control register (eecr) . . . . . . . . . . . . . . . . . . . . . 73 5-3 eeprom array configuration register (eeacr) . . . . . . . . . . 75 5-4 eeprom nonvolatile register (eenvr) . . . . . . . . . . . . . . . . . 77 5-5 eediv divider high register (eedivh) . . . . . . . . . . . . . . . . . . 78 5-6 eediv divider low register (eedivl). . . . . . . . . . . . . . . . . . . 78 5-7 eeprom divider non-volatile register high (eedivhnvr)) . 80 5-8 eeprom divider non-volatile register low (eedivlnvr) . . 80 6-1 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6-2 accumulator (a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6-3 index register (h:x). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6-4 stack pointer (sp). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6-5 program counter (pc). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6-6 condition code register (ccr) . . . . . . . . . . . . . . . . . . . . . . . . . 87 7-1 sim block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7-2 sim i/o register summary. . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7-3 cgm clock signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 7-4 external reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of figures advance information mc68HC908AS32A ? rev 0.0 18 list of figures motorola 7-5 internal reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7-6 sources of internal reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 7-7 por recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7-8 interrupt entry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 7-9 interrupt processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 7-10 interrupt recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 7-11 interrupt recognition example . . . . . . . . . . . . . . . . . . . . . . . . 115 7-12 wait mode entry timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117 7-13 wait recovery from interrupt or break . . . . . . . . . . . . . . . . . . 117 7-14 wait recovery from internal reset. . . . . . . . . . . . . . . . . . . . . 118 7-15 stop mode entry timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 7-16 stop mode recovery from interrupt or break . . . . . . . . . . . . . 119 7-17 sim break status register (sbsr) . . . . . . . . . . . . . . . . . . . . 120 7-18 sim reset status register (srsr) . . . . . . . . . . . . . . . . . . . . 121 7-19 sim break flag control register (sbfcr) . . . . . . . . . . . . . . 122 8-1 cgm block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 8-2 i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 8-3 cgm external connections . . . . . . . . . . . . . . . . . . . . . . . . . .135 8-4 pll control register (pctl) . . . . . . . . . . . . . . . . . . . . . . . . . 137 8-5 pll bandwidth control register (pbwc) . . . . . . . . . . . . . . . 139 8-6 pll programming register (ppg) . . . . . . . . . . . . . . . . . . . . . 141 9-1 configuration register (config-1) . . . . . . . . . . . . . . . . . . . . 152 10-1 configuration register (config-2) . . . . . . . . . . . . . . . . . . . . 155 11-1 break module block diagram . . . . . . . . . . . . . . . . . . . . . . . . . 158 11-2 i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 11-3 break status and control register (bscr) . . . . . . . . . . . . . . 161 11-4 break address registers (brkh and brkl) . . . . . . . . . . . . . 162 12-1 monitor mode circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 12-2 monitor data format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 12-3 sample monitor waveforms . . . . . . . . . . . . . . . . . . . . . . . . . .167 12-4 read transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12-5 break transaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12-6 monitor mode entry timing. . . . . . . . . . . . . . . . . . . . . . . . . . . 173 13-1 cop block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13-2 cop control register (copctl) . . . . . . . . . . . . . . . . . . . . . .179 14-1 lvi module block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14-2 lvi i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14-3 lvi status register (lvisr) . . . . . . . . . . . . . . . . . . . . . . . . . . 184 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of figures mc68HC908AS32A ? rev 0.0 advance information motorola list of figures 19 15-1 irq block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 15-2 irq interrupt flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 15-3 irq status and control register (iscr) . . . . . . . . . . . . . . . . 192 16-1 sci module block diagram . . . . . . . . . . . . . . . . . . . . . . . . 198 16-2 sci i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 16-3 sci data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 16-4 sci transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 16-5 sci transmitter i/o register summary . . . . . . . . . . . . . . . . . 203 16-6 sci receiver block diagram . . . . . . . . . . . . . . . . . . . . . . 206 16-7 sci i/o receiver register summary . . . . . . . . . . . . . . . . . . .207 16-8 receiver data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209 16-9 slow data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 16-10 fast data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212 16-11 sci control register 1 (scc1). . . . . . . . . . . . . . . . . . . . . . . .218 16-12 sci control register 2 (scc2). . . . . . . . . . . . . . . . . . . . . . . .221 16-13 sci control register 3 (scc3). . . . . . . . . . . . . . . . . . . . . . . .224 16-14 sci status register 1 (scs1) . . . . . . . . . . . . . . . . . . . . . . . . 226 16-15 flag clearing sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228 16-16 sci status register 2 (scs2) . . . . . . . . . . . . . . . . . . . . . . . . 230 16-17 sci data register (scdr) . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 16-18 sci baud rate register (scbr) . . . . . . . . . . . . . . . . . . . . . . 231 17-1 spi module block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . 239 17-2 full-duplex master-slave connections . . . . . . . . . . . . . . . . . 240 17-3 transmission format (cpha = 0) . . . . . . . . . . . . . . . . . . . . . 243 17-4 transmission format (cpha = 1) . . . . . . . . . . . . . . . . . . . . . 244 17-5 transmission start delay (master) . . . . . . . . . . . . . . . . . . . . . 246 17-6 missed read of overflow condition . . . . . . . . . . . . . . . . . . . . 248 17-7 clearing sprf when ovrf interrupt is not enabled . . . . . . 249 17-8 spi interrupt request generation . . . . . . . . . . . . . . . . . . . . . 252 17-9 sprf/spte cpu interrupt timing . . . . . . . . . . . . . . . . . . . . . 253 17-10 cpha/ss timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 17-11 spi control register (spcr) . . . . . . . . . . . . . . . . . . . . . . . . . 260 17-12 spi status and control register (spscr) . . . . . . . . . . . . . . .263 17-13 spi data register (spdr) . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 18-1 timb block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 18-2 timb i/o register summary. . . . . . . . . . . . . . . . . . . . . . . . . . 270 18-3 pwm period and pulse width . . . . . . . . . . . . . . . . . . . . . . . . 275 18-4 timb status and control register (tbsc) . . . . . . . . . . . . . . .281 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of figures advance information mc68HC908AS32A ? rev 0.0 20 list of figures motorola 18-5 timb counter registers (tbcnth and tbcntl) . . . . . . . . . 284 18-6 timb counter modulo registers (tbmodh and tbmodl) .285 18-7 timb channel status and control registers (tbsc0 ? tbsc1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 18-8 chxmax latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 18-9 timb channel registers (tbch0h/l ? tbch1h/l) . . . . . . . . 291 19-1 pit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294 19-2 pit i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 19-3 pit status and control register (psc) . . . . . . . . . . . . . . . . . 298 19-4 pit counter registers (pcnth ? pcntl). . . . . . . . . . . . . . . . 300 19-5 pit counter modulo registers (pmodh ? pmodl) . . . . . . . . 301 20-1 i/o port register summary. . . . . . . . . . . . . . . . . . . . . . . . . . . 304 20-2 port a data register (pta) . . . . . . . . . . . . . . . . . . . . . . . . . .305 20-3 data direction register a (ddra) . . . . . . . . . . . . . . . . . . . . . 305 20-4 port a i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 20-5 port b data register (ptb) . . . . . . . . . . . . . . . . . . . . . . . . . .307 20-6 data direction register b (ddrb) . . . . . . . . . . . . . . . . . . . . . 308 20-7 port b i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 20-8 port c data register (ptc) . . . . . . . . . . . . . . . . . . . . . . . . . .310 20-9 data direction register c (ddrc) . . . . . . . . . . . . . . . . . . . . . 311 20-10 port c i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 20-11 port d data register (ptd) . . . . . . . . . . . . . . . . . . . . . . . . . .313 20-12 data direction register d (ddrd) . . . . . . . . . . . . . . . . . . . . . 314 20-13 port d i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 20-14 port e data register (pte) . . . . . . . . . . . . . . . . . . . . . . . . . .316 20-15 data direction register e (ddre) . . . . . . . . . . . . . . . . . . . . . 318 20-16 port e i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 20-17 port f data register (ptf). . . . . . . . . . . . . . . . . . . . . . . . . . . 320 20-18 data direction register f (ddrf) . . . . . . . . . . . . . . . . . . . . . 321 20-19 port f i/o circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 21-1 keyboard module block diagram . . . . . . . . . . . . . . . . . . . . 325 21-2 i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 21-3 keyboard status and control register (kbscr) . . . . . . . . . . 329 21-4 keyboard interrupt enable register (kbier) . . . . . . . . . . . . . 330 22-1 tima block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 22-2 tima i/o register summary. . . . . . . . . . . . . . . . . . . . . . . . . . 334 22-3 pwm period and pulse width . . . . . . . . . . . . . . . . . . . . . . . . 340 22-4 tima status and control register (tasc) . . . . . . . . . . . . . . .347 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of figures mc68HC908AS32A ? rev 0.0 advance information motorola list of figures 21 22-5 tima counter registers (tacnth and tacntl) . . . . . . . . . 350 22-6 tima counter modulo registers (tamodh and tamodl) .351 22-7 tima channel status and control registers (tasc0 ? tasc5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 22-8 chxmax latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 22-9 tima channel registers (tach0h/l ? tach5h/l) . . . . . . . . 358 23-1 adc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 23-2 adc status and control register (adscr) . . . . . . . . . . . . . . 367 23-3 adc data register (adr) . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 23-4 adc input clock register (adiclk) . . . . . . . . . . . . . . . . . . .370 24-1 bdlc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 24-2 bdlc operating modes state diagram . . . . . . . . . . . . . . . . . 377 24-3 bdlc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 24-4 bdlc rx digital filter block diagram . . . . . . . . . . . . . . . . . . 381 24-5 j1850 bus message format (vpw) . . . . . . . . . . . . . . . . . . . . 383 24-6 j1850 vpw symbols with nominal symbol times. . . . . . . . . 388 24-7 j1850 vpw received passive symbol times . . . . . . . . . . . . 391 24-8 j1850 vpw received passive eof and ifs symbol times .392 24-9 j1850 vpw received active symbol times . . . . . . . . . . . . . 393 24-10 j1850 vpw received break symbol times . . . . . . . . . . . .394 24-11 j1850 vpw bitwise arbitrations . . . . . . . . . . . . . . . . . . . . . . . 395 24-12 bdlc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 24-13 bdlc protocol handler outline . . . . . . . . . . . . . . . . . . . . . . . 397 24-14 bdlc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 24-15 bdlc analog and roundtrip delay register (bard) . . . . . .403 24-16 bdlc control register 1 (bcr1) . . . . . . . . . . . . . . . . . . . . . .404 24-17 bdlc control register 2 (bcr2) . . . . . . . . . . . . . . . . . . . . . .407 24-18 types of in-frame response (ifr) . . . . . . . . . . . . . . . . . . . . 410 24-19 bdlc state vector register (bsvr) . . . . . . . . . . . . . . . . . . .414 24-20 bdlc data register (bdr) . . . . . . . . . . . . . . . . . . . . . . . . . .416 25-1 spi master timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . .426 25-2 spi slave timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 25-3 bdlc variable pulse width modulation (vpw) symbol timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of figures advance information mc68HC908AS32A ? rev 0.0 22 list of figures motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola list of tables 23 technical data ? mc68HC908AS32A list of tables table title page 1-1 external pins summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 1-3 clock source summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 1-2 clock signal naming conventions . . . . . . . . . . . . . . . . . . . . . . 35 1-4 mc order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2-1 vector addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 5-1 eeprom array address blocks. . . . . . . . . . . . . . . . . . . . . . . . 68 5-2 example selective bit programming description . . . . . . . . . . . 69 5-3 eeprom program/erase mode select . . . . . . . . . . . . . . . . . . 73 5-4 eeprom block protect and security summary. . . . . . . . . . . . 76 6-1 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6-2 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7-1 i/o register address summary . . . . . . . . . . . . . . . . . . . . . . . 104 7-2 signal name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7-3 pin bit set timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106 8-1 i/o register address summary . . . . . . . . . . . . . . . . . . . . . . . 127 8-2 variable definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 8-3 vco frequency multiplier (n) selection. . . . . . . . . . . . . . . . . 142 11-1 i/o register address summary . . . . . . . . . . . . . . . . . . . . . . . 159 12-1 mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 12-2 mode differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 12-3 read (read memory) command . . . . . . . . . . . . . . . . . . . . . 169 12-4 write (write memory) command. . . . . . . . . . . . . . . . . . . . . 170 12-5 iread (indexed read) command . . . . . . . . . . . . . . . . . . . . . 170 12-6 iwrite (indexed write) command . . . . . . . . . . . . . . . . . . . . 171 12-7 readsp (read stack pointer) command . . . . . . . . . . . . . . .171 12-8 run (run user program) command . . . . . . . . . . . . . . . . . . . 172 12-9 mc68hc908as60a monitor baud rate selection . . . . . . . . . 172 14-1 lviout bit indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 15-1 irq i/o register summary. . . . . . . . . . . . . . . . . . . . . . . . . . . 189 16-1 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . list of tables advance information mc68HC908AS32A ? rev 0.0 24 list of tables motorola 16-2 sci i/o register address summary . . . . . . . . . . . . . . . . . . . . 199 16-3 sci transmitter i/o address summary . . . . . . . . . . . . . . . . . 203 16-4 sci receiver i/o address summary . . . . . . . . . . . . . . . . . . .207 16-5 start bit verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 16-6 data bit recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 16-7 stop bit recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 16-8 character format selection . . . . . . . . . . . . . . . . . . . . . . . . . .220 16-9 sci baud rate prescaling . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 16-10 sci baud rate selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 16-11 sci baud rate selection examples . . . . . . . . . . . . . . . . . . . . 233 17-1 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 17-2 i/o register addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 17-3 spi i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 17-4 spi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 17-5 spi configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 17-6 spi master baud rate selection . . . . . . . . . . . . . . . . . . . . . . 265 18-1 prescaler selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 18-2 mode, edge, and level selection . . . . . . . . . . . . . . . . . . . . . .289 19-1 pit i/o register address summary . . . . . . . . . . . . . . . . . . . . 295 19-2 prescaler selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 20-1 port a pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 20-2 port b pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 20-3 port c pin functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 20-4 port d pin functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315 20-5 port e pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 20-6 port f pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 21-1 i/o register address summary . . . . . . . . . . . . . . . . . . . . . . . 325 22-1 prescaler selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 22-2 mode, edge, and level selection . . . . . . . . . . . . . . . . . . . . . .356 23-1 mux channel select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368 23-2 adc clock divide ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 24-1 bdlc i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . 376 24-2 bdlc j1850 bus error summary. . . . . . . . . . . . . . . . . . . . . .401 24-3 bdlc transceiver delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404 24-4 bdlc rate selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406 24-5 bdlc transmit in-frame response control bit priority encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 24-6 bdlc interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola general description 25 technical data ? mc68HC908AS32A section 1. general description 1.1 contents 1.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.226 1.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.4 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.5 pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.5.1 power supply pins (v dd and v ss ) . . . . . . . . . . . . . . . . . . 30 1.5.2 oscillator pins (osc1 and osc2) . . . . . . . . . . . . . . . . . . . 31 1.5.3 external reset pin (rst) . . . . . . . . . . . . . . . . . . . . . . . . . . 31 1.5.4 external interrupt pin (irq) . . . . . . . . . . . . . . . . . . . . . . . . 31 1.5.5 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . . 31 1.5.6 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . . 31 1.5.7 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . . 31 1.5.8 adc reference high voltage pin (vrefh) . . . . . . . . . . . 32 1.5.9 port a input/output (i/o) pins (pta7 ? pta0) . . . . . . . . . . 32 1.5.10 port b i/o pins (ptb7/atd7 ? ptb0/atd0) . . . . . . . . . . . . 32 1.5.11 port c i/o pins (ptc4 ? ptc0) . . . . . . . . . . . . . . . . . . . . . . 32 1.5.12 port d i/o pins (ptd6 ? ptd0/atd8) . . . . . . . . . . . . . . . . . 32 1.5.13 port e i/o pins (pte7/spsck ? pte0/txd) . . . . . . . . . . . . 32 1.5.14 port f i/o pins (ptf3 ? ptf0/tach2) . . . . . . . . . . . . . . . . . 33 1.5.15 bdlc transmit pin (bdtxd) . . . . . . . . . . . . . . . . . . . . . . . 33 1.5.16 bdlc receive pin (bdrxd) . . . . . . . . . . . . . . . . . . . . . . . 33 1.6 ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 1.6.1 mc order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description advance information mc68HC908AS32A ? rev 0.0 26 general description motorola 1.2 introduction the mc68hc908as60a is a member of the low-cost, high-performance m68hc08 family of 8-bit microcontroller units (mcus). the m68hc08 family is based on the customer-specified integrated circuit (csic) design strategy. all mcus in the family use the enhanced m68hc08 central processor unit (cpu08) and are available with a variety of modules, memory sizes and types, and package types. 1.3 features features of the mc68hc908as60a include: high-performance m68hc08 architecture fully upward-compatible object code with m6805, m146805, and m68hc05 families 8.4 mhz internal bus frequency 32,256 bytes of flash electrically erasable read-only memory (flash) flash data security 512 bytes of on-chip electrically erasable programmable read- only memory with security option (eeprom) 1 kbyte of on-chip ram clock generator module (cgm) serial peripheral interface module (spi) serial communications interface module (sci) 8-bit, 15-channel analog-to-digital converter (adc-15) 16-bit, 6-channel timer interface module (tima-6) programmable interrupt timer (pit) system protection features ? computer operating properly (cop) with optional reset ? low-voltage detection with optional reset f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description mcu block diagram mc68HC908AS32A ? rev 0.0 advance information motorola general description 27 ? illegal opcode detection with optional reset ? illegal address detection with optional reset low-power design (fully static with stop and wait modes) master reset pin and power-on reset sae j1850 byte data link controller digital module features of the cpu08 include: enhanced hc05 programming model extensive loop control functions 16 addressing modes (eight more than the hc05) 16-bit index register and stack pointer memory-to-memory data transfers fast 8 8 multiply instruction fast 16/8 divide instruction binary-coded decimal (bcd) instructions optimization for controller applications c language support 1.4 mcu block diagram figure 1-1 shows the structure of the mc68hc908as60a. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . advance information mc68HC908AS32A ? rev 0.0 28 general description motorola general description break module clock generator module system integration module analog-to-digital module serial communications interface module serial peripheral interface module timer a 6 channel interface module low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit (alu) cpu registers m68hc08 cpu control and status registers user flash ? 32, 256 bytes user ram ? 1024 bytes user eeprom ? 512 bytes monitor rom ? 256 bytes irq module ddrd ptd ddre pte osc1 osc2 cgmxfc rst irq v dd v dda v ssa pte7/spsck pte6/mosi pte5/miso pte4/ss pte3/tach1 pte2/tach0 pte1/rxd pte0/txd ptf3/tach5-ptf0/tach2 ptf ddrf power pta ddra ddrb ptb ddrc ptc pta7 ? pta0 ptb7/atd7 ? ptb0/atd0 ptc2/mclk ptc1 ? ptc0 v refh v ss user flash vector space ? 52 bytes v ddaref av ss /v refl figure 1-1. mcu block diagram for the mc68HC908AS32A (52-pin plcc) ptd3/atd11-ptd0/atd8 ptd6/atd14/taclk ptd5/atd13 ptd4/atd12/tbclk bdtxd bdrxd byte data link controller programmable interrupt timer module ptc4 ptc3 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description pin assignments mc68HC908AS32A ? rev 0.0 advance information motorola general description 29 1.5 pin assignments figure 1-2 shows mc68hc908as60a 52-pin plcc pin assignments. figure 1-2. mc68HC908AS32A (52-pin plcc) bdrxd cgmxfc ptb4/atd4 ptf3/tach5 ptf2/tach4 ptf1/tach3 ptf0/tach2 rst irq ptc4 bdtxd pte0/txd pte1/rxd pte2/tach0 pte3/tach1 ptd3/atd11 ptd2/atd10 ptd1/atd9 ptd0/atd8 ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 pta7 v ssa /v refl v dda /v ddaref v refh ptd6/atd14/taclk ptd5/atd13 ptd4/atd12 ptc3 ptc2/mclk ptc1 ptc0 osc1 osc2 pte5/miso pte4/ss pte6/mosi pte7/spsck v ss v dd pta0 pta1 pta2 pta3 pta4 pta5 pta6 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 46 45 44 43 42 41 40 39 38 37 36 35 34 7 6 5 4 3 2 1 52 51 50 49 48 47 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description advance information mc68HC908AS32A ? rev 0.0 30 general description motorola note: the following pin descriptions are just a quick reference. for a more detailed representation, see input/output ports on page 303 . 1.5.1 power supply pins (v dd and v ss ) v dd and v ss are the power supply and ground pins. the mcu operates from a single power supply. fast signal transitions on mcu pins place high, short-duration current demands on the power supply. to prevent noise problems, take special care to provide power supply bypassing at the mcu as shown in figure 1-3 . place the c1 bypass capacitor as close to the mcu as possible. use a high-frequency response ceramic capacitor for c1. c2 is an optional bulk current bypass capacitor for use in applications that require the port pins to source high current levels. v ss is also the ground for the port output buffers and the ground return for the serial clock in the serial peripheral interface module (spi). see serial peripheral interface (spi) on page 235. note: v ss must be grounded for proper mcu operation. figure 1-3. power supply bypassing mcu v dd c2 c1 0.1 f v ss v dd + note: component values shown represent typical applications. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description pin assignments mc68HC908AS32A ? rev 0.0 advance information motorola general description 31 1.5.2 oscillator pins (osc1 and osc2) the osc1 and osc2 pins are the connections for the on-chip oscillator circuit. see clock generator module (cgm) on page 123. 1.5.3 external reset pin (rst ) a logic 0 on the rst pin forces the mcu to a known startup state. rst is bidirectional, allowing a reset of the entire system. it is driven low when any internal reset source is asserted. see system integration module (sim) on page 101 for more information. 1.5.4 external interrupt pin (irq ) irq is an asynchronous external interrupt pin. see external interrupt module (irq) on page 187. 1.5.5 external filter capacitor pin (cgmxfc) cgmxfc is an external filter capacitor connection for the clock generator module (cgm). see clock generator module (cgm) on page 123. 1.5.6 analog power supply pin (v dda/ v ddaref ) v dda/ v ddaref is the power supply pin for the analog portion of the analog-to-digital converter (adc) and the clock generator module (cgm). see analog-to-digital converter (adc) on page 361. see clock generator module (cgm) on page 123. 1.5.7 analog ground pin (v ssa /v refl ) the vssa/v refl pin provides both the analog ground connection and the reference low voltage for the analog-to-digital converter (adc) as well as the ground connection for the clock generator module (cgm). see analog-to-digital converter (adc) on page 361. see clock generator module (cgm) on page 123. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description advance information mc68HC908AS32A ? rev 0.0 32 general description motorola 1.5.8 adc reference high voltage pin (v refh ) v refh provides the reference high voltage for the analog-to-digital converter (adc). see analog-to-digital converter (adc) on page 361. 1.5.9 port a input/output (i/o) pins (pta7 ? pta0) pta7 ? pta0 are general-purpose bidirectional i/o port pins. see input/output ports on page 303. 1.5.10 port b i/o pins (ptb7/atd7 ? ptb0/atd0) port b is an 8-bit special function port that shares all eight pins with the analog-to-digital converter (adc). see analog-to-digital converter (adc) on page 361 and input/output ports on page 303. 1.5.11 port c i/o pins (ptc4 ? ptc0) ptc4 ? ptc3 and ptc1 ? ptc0 are general-purpose bidirectional i/o port pins. ptc2/mclk is a special function port that shares its pin with the system clock which has a frequency equivalent to the system clock. see input/output ports on page 303. 1.5.12 port d i/o pins (ptd6 ? ptd0/atd8) port d is an 7-bit special-function port that shares seven of its pins with the analog-to-digital converter module (adc-15), one of its pins with the timer interface module a (tima). see timer interface module a (tima) on page 331, analog-to-digital converter (adc) on page 361 and input/output ports on page 303. 1.5.13 port e i/o pins (pte7/spsck ? pte0/txd) port e is an 8-bit special function port that shares two of its pins with the timer interface module a (tima), four of its pins with the serial peripheral interface module (spi), and two of its pins with the serial f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description pin assignments mc68HC908AS32A ? rev 0.0 advance information motorola general description 33 communication interface module (sci). see serial communications interface (sci) on page 195, serial peripheral interface (spi) on page 235, timer interface module a (tima) on page 331, and input/output ports on page 303. 1.5.14 port f i/o pins (ptf3 ? ptf0/tach2) port f is a 4-bit special function port that shares four of its pins with the timer interface module a (tima-6). see timer interface module a (tima) on page 331, and input/output ports on page 303. 1.5.15 bdlc transmit pin (bdtxd) this pin is the digital output from the bdlc module (bdtxd). see electrical specification on page 419. 1.5.16 bdlc receive pin (bdrxd) this pin is the digital input to the can module (bdrxd). see electrical specification on page 419. table 1-1. external pins summary pin name function driver type hysteresis (1) reset state pta7 ? pta0 general-purpose i/o dual state no input hi-z ptb7/atd7 ? ptb0/atd0 general-purpose i/o adc channel dual state no input hi-z ptc4 ? ptc0 general-purpose i/o dual state no input hi-z ptd6/atd14/taclk adc channel general-purpose i/o adc channel/timer external input clock dual state no input hi-z ptd5/atd13 adc channel general-purpose i/o adc channel dual state no input hi-z ptd4/atd12/tbclk adc channel general-purpose i/o adc channel/timer external input clock dual state no input hi-z ptd3/atd11 ? ptd0/atd8 adc channels general-purpose i/o adc channel dual state no input hi-z pte7/spsck general-purpose i/o spi clock dual state open drain yes input hi-z f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description advance information mc68HC908AS32A ? rev 0.0 34 general description motorola pte6/mosi general-purpose i/o spi data path dual state open drain yes input hi-z pte5/miso general-purpose i/o spi data path dual state open drain yes input hi-z pte4/ss general-purpose i/o spi slave select dual state yes input hi-z pte3/tach1 general-purpose i/o timer a channel 1 dual state yes input hi-z pte2/tach0 general-purpose i/o timer a channel 0 dual state yes input hi-z pte1/rxd general-purpose i/o sci receive data dual state yes input hi-z pte0/txd general-purpose i/o sci transmit data dual state no input hi-z ptf3/tach5 general-purpose i/o timer a channel 5 dual state yes input hi-z ptf2/tach4 general-purpose i/o timer a channel 4 dual state yes input hi-z ptf1/tach3 general-purpose i/o timer a channel 3 dual state yes input hi-z ptf0/tach2 general-purpose i/o timer a channel 2 dual state yes input hi-z v dd chip power supply n/a n/a n/a v ss chip ground n/a n/a n/a v dda/ v ddaref adc analog power supply cgm analog power supply n/a n/a n/a v ssa /v refl adc ground/adc reference low voltage cgm analog ground n/a n/a n/a v refh a/d reference high voltage n/a n/a n/a osc1 external clock in n/a n/a input hi-z osc2 external clock out n/a n/a output cgmxfc pll loop filter cap n/a n/a n/a irq external interrupt request n/a n/a input hi-z rst reset n/a n/a output low bdrxd bdlc serial input n/a yes input hi-z bdtxd bdlc serial output output no output 1. hysteresis is not 100% tested but is typically a minimum of 300mv. table 1-1. external pins summary (continued) pin name function driver type hysteresis (1) reset state f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description pin assignments mc68HC908AS32A ? rev 0.0 advance information motorola general description 35 table 1-2. clock signal naming conventions clock signal name description cgmxclk buffered version of osc1 from clock generation module (cgm) cgmout pll-based or osc1-based clock output from clock generator module (cgm) bus clock cgmout divided by two spsck spi serial clock taclk external clock input for tima table 1-3. clock source summary module clock source adc cgmxclk or bus clock can cgmxclk or cgmout cop cgmxclk cpu bus clock flash bus clock eeprom cgmxclk or bus clock ram bus clock spi bus clock/spsck sci cgmxclk tima bus clock or ptd6/atd14/taclk pit bus clock sim cgmout and cgmxclk irq bus clock brk bus clock lvi bus clock cgm osc1 and osc2 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . general description advance information mc68HC908AS32A ? rev 0.0 36 general description motorola 1.6 ordering information this section contains instructions for ordering the mc68HC908AS32A. 1.6.1 mc order numbers table 1-4. mc order numbers mc order number operating temperature range mc68HC908AS32Acfn (52-pin plcc) ? 40c to + 85c mc68HC908AS32Avfn (52-pin plcc) ? 40c to + 105c mc68HC908AS32Amfn (52-pin plcc) ? 40c to + 125c f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola memory map 37 technical data ? mc68HC908AS32A section 2. memory map 2.1 contents 2.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.3 i/o section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.4 additional status and control registers . . . . . . . . . . . . . . . 45 2.5 vector addresses and priority . . . . . . . . . . . . . . . . . . . . . . . 46 2.2 introduction the cpu08 can address 64k bytes of memory space. the memory map, shown in figure 2-1 , includes: 32,256 bytes of flash eeprom 1024 bytes of ram 512 bytes of eeprom with protect option 52 bytes of user-defined vectors 256 bytes of monitor rom the following definitions apply to the memory map representation of reserved and unimplemented locations. reserved ? accessing a reserved location can have unpredictable effects on mcu operation. unused ? these locations are reserved in the memory map for future use, accessing an unused location can have unpredictable effects on mcu operation. unimplemented ? accessing an unimplemented location can cause an illegal address reset (within the constraints as outlined in the memory map ). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map advance information mc68HC908AS32A ? rev 0.0 38 memory map motorola mc68HC908AS32A $0000 i/o registers (80 bytes) $0000 $004f $004f $0050 ram (1024 bytes) $0050 $044f $044f $0450 unimplemented (944 bytes) $0450 $07ff $07ff $0800 eeprom (512 bytes) $0800 $09ff $09ff $0a00 unimplemented (1536 bytes) $0a00 $0fff $0fff $1000 unimplemented (28,672 bytes) $1000 $7fff $7fff $8000 flash (32,256 bytes) $8000 $fdff $fdff $fe00 sim break status register (sbsr) $fe00 $fe01 sim reset status register (srsr) $fe01 $fe02 reserved $fe02 $fe03 sim break flag control register (sbfcr) $fe03 $fe04 $fe08 reserved $fe04 $fe08 $fe09 configuration write-once regiser 2 (config-2) $fe09 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map introduction mc68HC908AS32A ? rev 0.0 advance information motorola memory map 39 $fe0a reserved $fe0a $fe0b reserved $fe0b $fe0c break address register high (brkh) $fe0c $fe0d break address register low (brkl) $fe0d $fe0e break status and control register (bscr) $fe0e $fe0f lvi status register (lvisr) $fe0f $fe10 eeprom eedivh non-volatile register (eedivhnvr) $fe10 $fe11 eeprom eedivl non-volatile register (eedivlnvr) $fe11 $fe12 $fe19 reserved $fe12 $fe19 $fe1a eeprom ee divider high register (eedivh) $fe1a $fe1b eeprom ee divider low register (eedivl) $fe1b $fe1c eeprom non-volatile register (eenvr) $fe1c $fe1d eeprom control register (eecr) $fe1d $fe1e reserved $fe1e $fe1f eeprom array configuration register (eeacr) $fe1f $fe20 monitor rom (256 bytes) $fe20 $ff1f $ff1f $ff20 $ff7f unimplemented (80 bytes) $ff20 $ff7f $ff80 flash block protect register (flbpr) $ff80 $ff81 reserved (7 bytes) $ff82 $ff87 $ff87 $ff88 flash control register (flcr) $ff88 $ff89 reserved $ff89 $ff8a reserved $ff8a f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map advance information mc68HC908AS32A ? rev 0.0 40 memory map motorola $ff8b reserved (4 bytes) $ff8b $ff8f $ff8f $ff90 unimplemented (48 bytes) $ff90 $ffbf $ffbf $ffc0 reserved (26 bytes) $ffc0 $ffd9 $ffd9 $ffda $ffda vectors (38 bytes) see memory map on page 37 $ffff $ffff figure 2-1. memory map (continued) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map i/o section mc68HC908AS32A ? rev 0.0 advance information motorola memory map 41 2.3 i/o section addresses $0000 ? $004f, shown in figure 2-2 , contain the i/o data, status and control registers. addr.register name bit 7654321bit 0 $0000 port a data register (pta) read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: $0001 port b data register (ptb) read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: $0002 port c data register (ptc) read: 0 0 0 ptc4 ptc3 ptc2 ptc1 ptc0 write: $0003 port d data register (ptd) read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: $0004 data direction register a (ddra) read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: $0005 data direction register b (ddrb) read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: $0006 data direction register c (ddrc) read: mclken 00 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: $0007 data direction register d (ddrd) read: 0 ddrd6 ddrd5 ddrd4 ddrd3 ddr2 ddrd1 ddrd0 write: $0008 port e data register (pte) read: pte7 pte6 pte5 pte4 pte3 pte2 pte1 pte0 write: $0009 port f data register (ptf) read: 0000 ptf3 ptf2 ptf1 ptf0 write: $000c data direction register e (ddre) read: ddre7 ddre6 ddre5 ddre4 ddre3 ddre2 ddre1 ddre0 write: $000d data direction register f (ddrf) read: 0000 ddrf3 ddrf2 ddrf1 ddrf0 write: $0010 spi control register (spcr) read: sprie r spmstr cpol cpha spwom spe sptie write: $0011 spi status and control register (spscr) read: sprf 0 ovrf modf spte 0 spr1 spr0 write: $0012 spi data register (spdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 $0013 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: figure 2-2. i/o data, status and control registers (sheet 1 of 4) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map advance information mc68HC908AS32A ? rev 0.0 42 memory map motorola $0014 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: $0015 sci control register 3 (scc3) read: r8 t8 r r orie neie feie peie write: $0016 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: $0017 sci status register 2 (scs2) read: 000000bkfrpf write: $0018 sci data register (scdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 $0019 sci baud rate register (scbr) read: 0 0 scp1 scp0 0 scr2 scr1 scr0 write: $001a irq status and control register (iscr) read: 0000irqf0 imask mode write: ack $001c pll control register (pctl) read: pllie pllf pllon bcs 1111 write: $001d pll bandwidth control register (pbwc) read: auto lock acq xld 0000 write: $001e pll programming register (ppg) read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: $001f configuration write-once register (config-1) read: lvistop r lvirst lvipwr ssrec copl stop copd write: $0020 timer a status and control register (tasc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst $0022 timer a counter register high (tacnth) read: bit 15 14 13 12 11 10 9 bit 8 write: $0023 timer a counter register low (tacntl) read: bit 7 654321bit 0 write: $0024 timer a modulo register high (tamodh) read: bit 15 14 13 12 11 10 9 bit 8 write: $0025 timer a modulo register low (tamodl) read: bit 7654321bit 0 write: $0026 timer a channel 0 status and control register (tasc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 $0027 timer a channel 0 register high (tach0h) read: bit 15 14 13 12 11 10 9 bit 8 write: addr.register name bit 7654321bit 0 figure 2-2. i/o data, status and control registers (sheet 2 of 4) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map i/o section mc68HC908AS32A ? rev 0.0 advance information motorola memory map 43 $0028 timer a channel 0 register low (tach0l) read: bit 7654321bit 0 write: $0029 timer a channel 1 status and control register (tasc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 $002a timer a channel 1 register high (tach1h) read: bit 15 14 13 12 11 10 9 bit 8 write: $002b timer a channel 1 register low (tach1l) read: bit 7654321bit 0 write: $002c timer a channel 2 status and control register (tasc2) read: ch2f ch2ie ms2b ms2a els2b els2a tov2 ch2max write: 0 $002d timer a channel 2 register high (tach2h) read: bit 15 14 13 12 11 10 9 bit 8 write: $002e timer a channel 2 register low (tach2l) read: bit 7654321bit 0 write: $002f timer a channel 3 status and control register (tasc3) read: ch3f ch3ie 0 ms3a els3b els3a tov3 ch3max write: 0 $0030 timer a channel 3 register high (tach3h) read: bit 15 14 13 12 11 10 9 bit 8 write: $0031 timer a channel 3 register low (tach3l) read: bit 7654321bit 0 write: $0032 timer a channel 4 status and control register (tasc4) read: ch4f ch4ie ms4b ms4a els4b els4a tov4 ch4max write: 0 $0033 timer a channel 4 register high (tach4h) read: bit 15 14 13 12 11 10 9 bit 8 write: $0034 timer a channel 4 register low (tach4l) read: bit 7654321bit 0 write: $0035 timer a channel 5 status and control register (tasc5) read: ch5f ch5ie 0 ms5a els5b els5a tov5 ch5max write: 0 $0036 timer a channel 5 register high (tach5h) read: bit 15 14 13 12 11 10 9 bit 8 write: $0037 timer a channel 5 register low (tach5l) read: bit 7654321bit 0 write: $0038 analog-to-digital status and control register (adscr) read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: r $0039 analog-to-digital data register (adr) read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write: addr.register name bit 7654321bit 0 figure 2-2. i/o data, status and control registers (sheet 3 of 4) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map advance information mc68HC908AS32A ? rev 0.0 44 memory map motorola $003a analog-to-digital input clock register (adiclk) read: adiv2 adiv1 adiv0 adiclk 0000 write: $003b bdlc analog and roundtrip delay register (bard) read: ate rxpol 00 bo3 bo2 bo1 bo0 write: r r $003c bdlc control register 1 (bcr1) read: imsg clks r1 r0 00 ie wcm write: r r $003d bdlc control register 2 (bcr2) read: aloop dloop rx4xe nbfs teod tsifr tmifr1 tmifr0 write: $003e bdlc state vector register (bsvr) read: 0 0 i3 i2 i1 i0 0 0 write:rrrrrrrr $003f bdlc data register (bdr) read: bd7 bd6 bd5 bd4 bd3 bd2 bd1 bd0 write: $004b pit status and control register (psc) read: pof pie pstop 00 pps2 pps1 pps0 write: 0 prst $004c pit counter register high (pcnth) read: bit 15 14 13 12 11 10 9 bit 8 write: $004d pit counter register low (pcntl) read: bit 7 654321bit 0 write: $004e pit modul o register high (pmodh) read: bit 15 14 13 12 11 10 9 bit 8 write: $004f pit modulo register low (pmodl) read: bit 7654321bit 0 write: = unimplemented r = reserved addr.register name bit 7654321bit 0 figure 2-2. i/o data, status and control registers (sheet 4 of 4) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map additional status and control registers mc68HC908AS32A ? rev 0.0 advance information motorola memory map 45 2.4 additional status and control registers selected addresses in the range $fe00 to $ff88 contain additional status and control registers as shown in figure 2-3 . a noted exception is the cop control register (copctl at address $ffff. addr. register name bit 7 6 5 4 3 2 1 bit 0 $fe00 sim break status register (sbsr) read: rrrrrrbwr write: $fe01 sim reset status register (srsr) read: por pin cop ilop ilad 0 lvi 0 write: $fe03 sim break flag control register (sbfcr) read: bcferrrrrrr write: $fe09 configuration write-once register (config-2) read: eedivclk rrras32arrr write: $fe0c break address register high (brkh) read: bit 15 14 13 12 11 10 9 bit 8 write: $fe0d break address register low (brkl) read: bit 7 6 5 4 3 2 1 bit 0 write: $fe0e break status and control register (brkscr) read: brke brka 000000 write: $fe0f lvi status register (lvisr) read: lviout 0 0 0 0000 write: $fe10 eediv hi non-volatile register (eedivhnvr) read: write: eedivsecd eediv10 eediv9 eediv8 $fe11 eediv lo non-volatile register read: write: eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 (eedivlnvr) $fe1a eediv divider high register read: write: eedivsecd eediv10 eediv9 eediv8 (eedivh) $fe1b eediv divider low register read: write: eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 (eedivl) $fe1c eeprom nonvolatile register (eenvr) read: eeprtct eebp3 eebp2 eebp1 eebp0 write: $fe1d eeprom control register (eecr) read: 0 eeoff eeras1 eeras0 eelat auto eepgm write: $fe1f eeprom array configuration register (eeacr) read: eeprtct eebp3 eebp2 eebp1 eebp0 write: figure 2-3. additional status and control registers (sheet 1 of 2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map advance information mc68HC908AS32A ? rev 0.0 46 memory map motorola 2.5 vector addresses and priority addresses in the range $ffda to $ffff contain the user-specified vector locations. the vector addresses are shown in table 2-1 . it is recommended that all vector addresses are defined. $ff80 flash block protect register (flbpr) read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: $ff88 flash control register (flcr) read: 0 0 0 0 hven verf erase pgm write: $ffff cop control register (copctl) read: low byte of reset vector write: writing to $ffff clears cop counter = unimplemented r = reserved addr. register name bit 7 6 5 4 3 2 1 bit 0 figure 2-3. additional status and control registers (sheet 2 of 2) table 2-1. vector addresses vector address mc68HC908AS32A lowest priority $ffda pit vector (high) $ffdb pit vector (low) $ffdc bdlc vector (high) $ffdd bdlc vector (low) $ffde adc vector (high) $ffdf adc vector (low) $ffe0 sci transmit vector (high) $ffe1 sci transmit vector (low) $ffe2 sci receive vector (high) $ffe3 sci receive vector (low) $ffe4 sci error vector (high) $ffe5 sci error vector (low) $ffe6 spi transmit vector (high) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map vector addresses and priority mc68HC908AS32A ? rev 0.0 advance information motorola memory map 47 $ffe7 spi transmit vector (low) $ffe8 spi receive vector (high) $ffe9 spi receive vector (low) $ffea tima overflow vector (high) $ffeb tima overflow vector (low) $ffec tima channel 5 vector (high) $ffed tima channel 5 vector (low) $ffee tima channel 4 vector (high) $ffef tima channel 4 vector (low) $fff0 tima channel 3 vector (high) $fff1 tima channel 3 vector (low) $fff2 tima channel 2 vector (high) $fff3 tima channel 2 vector (low) $fff4 tima channel 1 vector (high) $fff5 tima channel 1 vector (low) $fff6 tima channel 0 vector (high) $fff7 tima channel 0 vector (low) $fff8 pll vector (high) $fff9 pll vector (low) $fffa irq1 vector (high) $fffb irq1 vector (low) $fffc swi vector (high) $fffd swi vector (low) $fffe reset vector (high) highest priority $ffff reset vector (low) table 2-1. vector addresses vector address mc68HC908AS32A f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . memory map advance information mc68HC908AS32A ? rev 0.0 48 memory map motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola ram 49 technical data ? mc68HC908AS32A section 3. ram 3.1 contents 3.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2 introduction this section describes the 1024 bytes of random-access memory (ram). 3.3 functional description address $0050 through $044f is the ram location. the 16-bit stack pointer allows the stack ram to be anywhere in the 64k-byte memory space. note: for correct operation, the stack pointer must point only to ram locations. within page zero are 176 bytes of ram. because the location of the stack ram is programmable, all page zero ram locations can be used for input/output (i/o) control and user data or code. when the stack pointer is moved from its reset location at $00ff, direct addressing mode instructions can access all page zero ram locations efficiently. page zero ram, therefore, provides ideal locations for frequently accessed global variables. before processing an interrupt, the cpu uses five bytes of the stack to save the contents of the cpu registers. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . ram advance information mc68HC908AS32A ? rev 0.0 50 ram motorola note: for m68hc05, m6805, and m146805 compatibility, the h register is not stacked. during a subroutine call, the cpu uses two bytes of the stack to store the return address. the stack pointer decrements during pushes and increments during pulls. note: be careful when using nested subroutines. the cpu could overwrite data in the ram during a subroutine or during the interrupt stacking operation. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola flash memory 51 technical data ? mc68HC908AS32A section 4. flash memory 4.1 contents 4.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.4 flash control and block protect registers . . . . . . . . . . . . 52 4.4.1 flash control register . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.4.2 flash block protect register . . . . . . . . . . . . . . . . . . . . . 54 4.5 flash block protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.6 flash mass erase operation . . . . . . . . . . . . . . . . . . . . . . . . 57 4.7 flash page erase operation . . . . . . . . . . . . . . . . . . . . . . . . 58 4.8 flash program operation . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.9 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.9.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.9.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.2 introduction this section describes the operation of the embedded flash memory. this memory can be read, programmed and erased from a single external supply. the program and erase operations are enabled through the use of an internal charge pump. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory advance information mc68HC908AS32A ? rev 0.0 52 flash memory motorola 4.3 functional description the flash memory is an array of 32,256 bytes with one byte of block protection and an additional 38 bytes of user vectors. an erased bit reads as a logic 1 and a programmed bit reads as a logic 0. memory in the flash array is organized into rows within pages. there are two rows of memory per page with 64 bytes per row. the minimum erase block size is a single page,128 bytes. programming is performed on a per-row basis, 64 bytes at a time. program and erase operations are facilitated through control bits in the flash control register (flcr). details for these operations appear later in this section. the flash memory map consists of: $8000 ? $fdff: user memory (32,256 bytes) $ff80: flash block protect register (flbpr) $ff88: flash control register (flcr) $ffcc ? $ffff: these locations are reserved for user-defined interrupt and reset vectors (please see vector addresses and priority on page 46 for details) programming tools are available from motorola. contact your local motorola representative for more information. note: a security feature prevents viewing of the flash contents. (1) 4.4 flash control and block protect registers the flash array has two registers that control its operation, the flash control register (flcr) and the flash block protect register (flbpr). 1. no security feature is absolutely secure. however, motorola ? s strategy is to make reading or copying the flash difficult for unauthorized users. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory flash control and block protect registers mc68HC908AS32A ? rev 0.0 advance information motorola flash memory 53 4.4.1 flash control register the flash control register (flcr) controls flash program and erase operations. hven ? high-voltage enable bit this read/write bit enables the charge pump to drive high voltages for program and erase operations in the array. hven can only be set if either pgm = 1 or erase = 1 and the proper sequence for program or erase is followed. 1 = high voltage enabled to array and charge pump on 0 = high voltage disabled to array and charge pump off mass ? mass erase control bit setting this read/write bit configures the flash array for mass or page erase operation. 1 = mass erase operation selected 0 = page erase operation selected erase ? erase control bit this read/write bit configures the memory for erase operation. erase is interlocked with the pgm bit such that both bits cannot be set at the same time. 1 = erase operation selected 0 = erase operation unselected address: $ff88 bit 7654321bit 0 read: 0000 hven mass erase pgm write: reset:00000000 figure 4-1. flash control register (flcr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory advance information mc68HC908AS32A ? rev 0.0 54 flash memory motorola pgm ? program control bit this read/write bit configures the memory for program operation. pgm is interlocked with the erase bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = program operation selected 0 = program operation unselected 4.4.2 flash block protect register the flash block protect register (flbpr) is implemented as a byte within the flash memory and therefore can only be written during a flash programming sequence. the value in this register determines the starting location of the protected range within the flash memory. flbpr[7:0] ? block protect register bit7 to bit0 these eight bits represent bits [14:7] of a 16-bit memory address. bit- 15 is logic 1 and bits [6:0] are logic 0s. the resultant 16-bit address is used for specifying the start address of the flash memory for block protection. flash is protected from this start address to the end of flash memory at $ffff. with this mechanism, the protect start address can be $xx00 and $xx80 (128 byte page boundaries) within the flash array. figure 4-3. flash block protect start address address: $ff80 bit 7654321bit 0 read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: figure 4-2. flash block protect register (flbpr) 1 flbpr value 16-bit memory address 0000000 start address of flash block protect f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory flash control and block protect registers mc68HC908AS32A ? rev 0.0 advance information motorola flash memory 55 flash protected ranges: decreasing the value in flbpr by one increases the protected range by one page (128 bytes). however, programming the block protect register with $fe protects a range twice that size, 256 bytes, in the corresponding array. $fe means that locations $ff00 ? $ffff are protected in flash. the flash memory does not exist at some locations. the block protection range configuration is unaffected if flash memory does not exist in that range. refer to the memory map and make sure that the desired locations are protected. flbpr[7:0] protected range $ff no protection $fe $ff00 ? $ffff $fd $fe80 ? $ffff $0b $8580 ? $ffff $0a $8500 ? $ffff $09 $8480 ? $ffff $08 $8400 ? $ffff $04 $8200 ? $ffff $03 $8180 ? $ffff $02 $8100 ? $ffff $01 $8080 ? $ffff $00 $8000 ? $ffff f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory advance information mc68HC908AS32A ? rev 0.0 56 flash memory motorola 4.5 flash block protection due to the ability of the on-board charge pump to erase and program the flash memory in the target application, provision is made for protecting blocks of memory from unintentional erase or program operations due to system malfunction. this protection is done by using the flash block protection register (flbpr). flbpr determines the range of the flash memory which is to be protected. the range of the protected area starts from a location defined by flbpr and ends at the bottom of the flash memory ($ffff). when the memory is protected, the hven bit can not be set in either erase or program operations. note: in performing a program or erase operation, the flash block protect register must be read after setting the pgm or erase bit and before asserting the hven bit. when the flash block protect register is programmed with all 0 ? s, the entire memory is protected from being programmed and erased. when all the bits are erased (all 1 ? s), the entire memory is accessible for program and erase. when bits within flbpr are programmed (logic 0), they lock a block of memory address ranges as shown in flash block protect register on page 54. if flbpr is programmed with any value other than $ff, the protected block of flash memory can not be erased or programmed. note: the vector locations and the flash block protect registers are located in the same page. flbpr is not protected with special hardware or software; therefore, if this page is not protected by flbpr and the vector locations are erased by either a page or a mass erase operation, flbpr will also be erased. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory flash mass erase operation mc68HC908AS32A ? rev 0.0 advance information motorola flash memory 57 4.6 flash mass erase operation use this step-by-step procedure to erase the entire flash memory to read as logic 1: 1. set both the erase bit and the mass bit in the flash control register (flcr). 2. read the flash block protect register (flbpr). 3. write to any flash address within the flash array with any data. note: if the address written to in step 3 is within address space protected by the flash block protect register (flbpr), no erase will occur. 4. wait for a time, t nvs . 5. set the hven bit. 6. wait for a time, t merase . 7. clear the erase bit. 8. wait for a time, t nvhl . 9. clear the hven bit. 10. wait for a time, t rcv , after which the memory can be accessed in normal read mode. note: a. programming and erasing of flash locations can not be performed by code being executed from the same flash array. b. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. care must be taken however to ensure that these operations do not access any address within the flash array memory space such as the cop control register (copctl) at $ffff. c. it is highly recommended that interrupts be disabled during program/erase operations. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory advance information mc68HC908AS32A ? rev 0.0 58 flash memory motorola 4.7 flash page erase operation use this step-by-step procedure to erase a page (128 bytes) of flash memory to read as logic 1: 1. set the erase bit and clear the mass bit in the flash control register (flcr). 2. read the flash block protect register (flbpr). 3. write any data to any flash address within the address range of the page (128 byte block) to be erased. 4. wait for time, t nvs . 5. set the hven bit. 6. wait for time, t erase . 7. clear the erase bit. 8. wait for time, t nvh . 9. clear the hven bit. 10. wait for a time, t rcv , after which the memory can be accessed in normal read mode. note: a. programming and erasing of flash locations can not be performed by code being executed from the same flash array. b. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. care must be taken however to ensure that these operations do not access any address within the flash array memory space such as the cop control register (copctl) at $ffff. c. it is highly recommended that interrupts be disabled during program/erase operations. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory flash program operation mc68HC908AS32A ? rev 0.0 advance information motorola flash memory 59 4.8 flash program operation programming of the flash memory is done on a row basis. a row consists of 64 consecutive bytes with address ranges as follows: $xx00 to $xx3f $xx40 to $xx7f $xx80 to $xxbf $xxc0 to $xxff during the programming cycle, make sure that all addresses being written to fit within one of the ranges specified above. attempts to program addresses in different row ranges in one programming cycle will fail. use this step-by-step procedure to program a row of flash memory. note: in order to avoid program disturbs, the row must be erased before any byte on that row is programmed. 1. set the pgm bit in the flash control register (flcr). this configures the memory for program operation and enables the latching of address and data programming. 2. read the flash block protect register (flbpr). 3. write to any flash address within the row address range desired with any data. 4. wait for time, t nvs . 5. set the hven bit. 6. wait for time, t pgs . 7. write data byte to the flash address to be programmed. 8. wait for time, t prog . 9. repeat step 7 and 8 until all the bytes within the row are programmed. 10. clear the pgm bit. 11. wait for time, t nvh . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory advance information mc68HC908AS32A ? rev 0.0 60 flash memory motorola 12. clear the hven bit. 13. wait for a time, t rcv , after which the memory can be accessed in normal read mode. the flash programming algorithm flowchart is shown in figure 4-4 . note: a. programming and erasing of flash locations can not be performed by code being executed from the same flash array. b. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. care must be taken however to ensure that these operations do not access any address within the flash array memory space such as the cop control register (copctl) at $ffff. c. it is highly recommended that interrupts be disabled during program/erase operations. d. do not exceed t prog maximum or t hv maximum. t hv is defined as the cumulative high voltage programming time to the same row before next erase. t hv must satisfy this condition: t nvs + t nvh + t pgs + (t prog x 64) e t hv max. please also see flash memory characteristics on page 431. e. the time between each flash address change (step 7 to step 7), or the time between the last flash address programmed to clearing the pgm bit (step 7 to step 10) must not exceed the maximum programming time, t prog max. f. be cautious when programming the flash array to ensure that non- flash locations are not used as the address that is written to when selecting either the desired row address range in step 3 of the algorithm or the byte to be programmed in step 7 of the algorithm. this applies particularly to: $ffda-$ffff (38 bytes) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory flash program operation mc68HC908AS32A ? rev 0.0 advance information motorola flash memory 61 figure 4-4. flash programming algorithm flowchart set hven bit read the flash block protect register write any data to any flash address within the row address range desired wait for a time, t nvs set pgm bit wait for a time, t pgs write data to the flash address to be programmed wait for a time, t prog clear pgm bit wait for a time, t nvh clear hven bit wait for a time, t rcv completed programming this row? y n end of programming the time between each flash address change (step 7 to step 7), or must not exceed the maximum programming time, t prog max. the time between the last flash address programmed to clearing pgm bit (step 7 to step 10) note: 1 2 3 4 5 6 7 8 10 11 12 13 algorithm for programming a row (64 bytes) of flash memory this row program algorithm assumes the row/s to be programmed are initially erased. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . flash memory advance information mc68HC908AS32A ? rev 0.0 62 flash memory motorola 4.9 low-power modes the wait and stop instructions will place the mcu in low power consumption standby modes. 4.9.1 wait mode putting the mcu into wait mode while the flash is in read mode does not affect the operation of the flash memory directly; however, no memory activity will take place since the cpu is inactive. the wait instruction should not be executed while performing a program or erase operation on the flash. wait mode will suspend any flash program/erase operations and leave the memory in a standby mode. 4.9.2 stop mode putting the mcu into stop mode while the flash is in read mode does not affect the operation of the flash memory directly; however, no memory activity will take place since the cpu is inactive. the stop instruction should not be executed while performing a program or erase operation on the flash. stop mode will suspend any flash program/erase operations and leave the memory in a standby mode. note: standby mode is the power saving mode of the flash module, in which all internal control signals to the flash are inactive and the current consumption of the flash is minimum. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 63 technical data ? mc68HC908AS32A section 5. eeprom memory 5.1 contents 5.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.4 eeprom register summary . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.5.1 eeprom configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.5.2 eeprom timebase requirements . . . . . . . . . . . . . . . . . . 67 5.5.3 eeprom program/erase protection . . . . . . . . . . . . . . . . 67 5.5.4 eeprom block protection . . . . . . . . . . . . . . . . . . . . . . . . 68 5.5.5 eeprom programming and erasing . . . . . . . . . . . . . . . . 69 5.6 eeprom register descriptions . . . . . . . . . . . . . . . . . . . . . . 73 5.6.1 eeprom control register . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.6.2 eeprom array configuration register . . . . . . . . . . . . . . 75 5.6.3 eeprom nonvolatile register . . . . . . . . . . . . . . . . . . . . . 77 5.6.4 eeprom timebase divider register . . . . . . . . . . . . . . . . 78 5.6.5 eeprom timebase divider non-volatile register . . . . . 80 5.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.7.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 5.7.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 64 eeprom memory motorola 5.2 introduction this section describes the 512 bytes of electrically erasable programmable read-only memory (eeprom) residing at address range $0800 to $09ff. 5.3 features features of the eeprom include the following: 512 bytes non-volatile memory byte, block, or bulk erasable non-volatile eeprom configuration and block protection options on-chip charge pump for programming/erasing security option auto bit driven programming/erasing time feature f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory eeprom register summary mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 65 5.4 eeprom register summary the eeprom register summary is shown in figure 5-1 . addr.register name bit 7654321bit 0 $fe10 eediv non-volatile register high (eedivhnvr)* read: eedivsecd rrrreediv10eediv9eediv8 write: reset: unaffected by reset; $ff when blank $fe11 eediv non-volatile register low (eedivlnvr)* read: eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 write: reset: unaffected by reset; $ff when blank $fe1a ee divider register high (eedivh) read: eedivsecd 0000 eediv10 eediv9 eediv8 write: reset: contents of eedivhnvr ($fe10), bits [6:3] = 0 $fe1b ee divider register low (eedivl) read: eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 write: reset: contents of eedivlnvr ($fe11) $fe1c eeprom non-volatile register (eenvr)* read: unused unused unused eeprtct eebp3 eebp2 eebp1 eebp0 write: reset: unaffected by reset; $ff when blank; factory programmed $f0 $fe1d eeprom control register (eecr) read: unused 0 eeoff eeras1 eeras0 eelat auto eepgm write: reset:00000000 $fe1f eeprom array configuration register (eeacr) read: unused unused unused eeprtct eebp3 eebp2 eebp1 eebp0 write: reset: contents of eenvr ($fe1c) * non-volatile eeprom register; write by programming. = unimplemented r = reserved unused = unused figure 5-1. eeprom register summary f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 66 eeprom memory motorola 5.5 functional description the 512 bytes of eeprom are located at $0800-$09ff and can be programmed or erased without an additional external high voltage supply. the program and erase operations are enabled through the use of an internal charge pump. for each byte of eeprom, the write/erase endurance is 10,000 cycles. 5.5.1 eeprom configuration the 8-bit eeprom non-volatile register (eenvr) and the 16-bit eeprom timebase divider non-volatile register (eedivnvr) contain the default settings for the following eeprom configurations: eeprom timebase reference eeprom security option eeprom block protection eenvr and eedivnvr are non-volatile eeprom registers. they are programmed and erased in the same way as eeprom bytes. the contents of these registers are loaded into their respective volatile registers during a mcu reset. the values in these read/write volatile registers define the eeprom configurations. for eenvr, the corresponding volatile register is the eeprom array configuration register (eeacr). for the eedivncr (two 8-bit registers: eedivhnvr and eedivlnvr), the corresponding volatile register is the eeprom divider register (eediv: eedivh and ee divl). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory functional description mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 67 5.5.2 eeprom timebase requirements a 35 s timebase is required by the eeprom control circuit for program and erase of eeprom content. this timebase is derived from dividing the cgmxclk or bus clock (selected by eedivclk bit in config-2 register) using a timebase divider circuit controlled by the 16-bit eeprom timebase divider eediv register (eedivh and eedivl). as the cgmxclk or bus clock is user selected, the eeprom timebase divider register must be configured with the appropriate value to obtain the 35 s. the timebase divider value is calculated by using the following formula: eediv= int[reference frequency(hz) x 35 x10 -6 +0.5] this value is written to the eeprom timebase divider register (eedivh and eedivl) or programmed into the eeprom timebase divider non-volatile register prior to any eeprom program or erase operations(see eeprom configuration on page 66 and eeprom timebase requirements on page 67). 5.5.3 eeprom program/erase protection the eeprom has a special feature that designates the 16 bytes of addresses from $08f0 to $08ff to be permanently secured. this program/erase protect option is enabled by programming the eeprtct bit in the eeprom non-volatile register (eenvr) to a logic zero. once the eeprtct bit is programmed to 0 for the first time: programming and erasing of secured locations $08f0 to $08ff is permanently disabled. secured locations $08f0 to $08ff can be read as normal. programming and erasing of eenvr is permanently disabled. bulk and block erase operations are disabled for the unprotected locations $0800-$08ef, $0900-$09ff. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 68 eeprom memory motorola single byte program and erase operations are still available for locations $0800-$08ef and $0900-$09ff for all bytes that are not protected by the eeprom block protect eebpx bits (see eeprom block protection on page 68 and eeprom array configuration register on page 75) note: once armed, the protect option is permanently enabled. as a consequence, all functions in the eenvr will remain in the state they were in immediately before the security was enabled. 5.5.4 eeprom block protection the 512 bytes of eeprom are divided into four 128-byte blocks. each of these blocks can be protected from erase/program operations by setting the eebpx bit in the eenvr. table 5-1 shows the address ranges for the blocks. these bits are effective after a reset or a upon read of the eenvr register. the block protect configuration can be modified by erasing/programming the corresponding bits in the eenvr register and then reading the eenvr register. please see eeprom array configuration register on page 75 for more information. note: once eedivsecd in the eedivhnvr is programmed to 0 and after a system reset, the eediv security feature is permanently enabled because the eedivsecd bit in the eedivh is always loaded with 0 thereafter. once this security feature is armed, erase and program mode are disabled for eedivhnvr and eedivlnvr. modifications to the eedivh and eedivl registers are also disabled. therefore, be cautious on programming a value into the eedivhnvr. table 5-1. eeprom array address blocks block number (eebpx) address range eebp0 $0800 ? $087f eebp1 $0880 ? $08ff eebp2 $0900 ? $097f eebp3 $0980 ? $09ff f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory functional description mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 69 5.5.5 eeprom programming and erasing the unprogrammed or erase state of an eeprom bit is a logic 1. the factory default for all bytes within the eeprom array is $ff. the programming operation changes an eeprom bit from logic 1 to logic 0 (programming cannot change a bit from logic 0 to a logic 1). in a single programming operation, the minimum eeprom programming size is one bit; the maximum is eight bits (one byte). the erase operation changes an eeprom bit from logic 0 to logic 1. in a single erase operation, the minimum eeprom erase size is one byte; the maximum is the entire eeprom array. the eeprom can be programmed such that one or multiple bits are programmed (written to a logic 0) at a time. however, the user may never program the same bit location more than once before erasing the entire byte. in other words, the user is not allowed to program a logic 0 to a bit that is already programmed (bit state is already logic 0). for some applications it might be advantageous to track more than 10k events with a single byte of eeprom by programming one bit at a time. for that purpose, a special selective bit programming technique is available. an example of this technique is illustrated in table 5-2 . note that none of the bit locations are actually programmed more than once although the byte was programmed eight times. table 5-2. example selective bit programming description description program data in binary result in binary original state of byte (erased) n/a 1111:1111 first event is recorded by programming bit position 0 1111:1110 1111:1110 second event is recorded by programming bit position 1 1111:1101 1111:1100 third event is recorded by programming bit position 2 1111:1011 1111:1000 fourth event is recorded by programming bit position 3 1111:0111 1111:0000 events five through eight are recorded in a similar fashion f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 70 eeprom memory motorola when this technique is utilized, a program/erase cycle is defined as multiple program sequences (up to eight) to a unique location followed by a single erase operation. program/erase using auto bit an additional feature available for eeprom program and erase operations is the auto mode. when enabled, auto mode will activate an internal timer that will automatically terminate the program/erase cycle and clear the eepgm bit. please see eeprom programming on page 70, eeprom erasing on page 71 and eeprom control register on page 73 for more information. eeprom programming the unprogrammed or erase state of an eeprom bit is a logic 1. programming changes the state to a logic 0. only eeprom bytes in the non-protected blocks and the eenvr register can be programmed. use the following procedure to program a byte of eeprom: 1. clear eeras1 and eeras0 and set eelat in the eecr. (a) note: if using the auto mode, also set the auto bit during step 1. 2. write the desired data to the desired eeprom address. (b) 3. set the eepgm bit. (c) go to step 7 if auto is set. 4. wait for time, t eepgm , to program the byte. 5. clear eepgm bit. 6. wait for time, t eefpv , for the programming voltage to fall. go to step 8. 7. poll the eepgm bit until it is cleared by the internal timer. (d) 8. clear eelat bits. (e) note: a. eeras1 and eeras0 must be cleared for programming. setting the eelat bit configures the address and data buses to latch data for programming the array. only data with a valid eeprom address will be latched. if eelat is set, other writes to the eecr will be allowed after a valid eeprom write. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory functional description mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 71 b. if more than one valid eeprom write occurs, the last address and data will be latched overriding the previous address and data. once data is written to the desired address, do not read eeprom locations other than the written location. (reading an eeprom location returns the latched data and causes the read address to be latched). c. the eepgm bit cannot be set if the eelat bit is cleared or a non- valid eeprom address is latched. this is to ensure proper programming sequence. once eepgm is set, do not read any eeprom locations; otherwise, the current program cycle will be unsuccessful. when eepgm is set, the on-board programming sequence will be activated. d. the delay time for the eepgm bit to be cleared in auto mode is less than t eepgm . however, on other mcus, this delay time may be different. for forward compatibility, software should not make any dependency on this delay time. e. any attempt to clear both eepgm and eelat bits with a single instruction will only clear eepgm. this is to allow time for removal of high voltage from the eeprom array. eeprom erasing the programmed state of an eeprom bit is logic 0. erasing changes the state to a logic 1. only eeprom bytes in the non-protected blocks and the eenvr register can be erased. use the following procedure to erase a byte, block or the entire eeprom array: 1. configure eeras1 and eeras0 for byte, block or bulk erase; set eelat in eecr. (a) note: if using the auto mode, also set the auto bit in step 1. 2. byte erase: write any data to the desired address. (b) block erase: write any data to an address within the desired block. (b) bulk erase: write any data to an address within the array. (b) 3. set the eepgm bit. (c) go to step 7 if auto is set. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 72 eeprom memory motorola 4. wait for a time: t eebyte for byte erase; t eeblock for block erase; t eebulk. for bulk erase. 5. clear eepgm bit. 6. wait for a time, t eefpv , for the erasing voltage to fall. go to step 8. 7. poll the eepgm bit until it is cleared by the internal timer. (d) 8. clear eelat bits. (e) note: a. setting the eelat bit configures the address and data buses to latch data for erasing the array. only valid eeprom addresses will be latched. if eelat is set, other writes to the eecr will be allowed after a valid eeprom write. b. if more than one valid eeprom write occurs, the last address and data will be latched overriding the previous address and data. once data is written to the desired address, do not read eeprom locations other than the written location. (reading an eeprom location returns the latched data and causes the read address to be latched). c. the eepgm bit cannot be set if the eelat bit is cleared or a non- valid eeprom address is latched. this is to ensure proper programming sequence. once eepgm is set, do not read any eeprom locations; otherwise, the current program cycle will be unsuccessful. when eepgm is set, the on-board programming sequence will be activated. d. the delay time for the eepgm bit to be cleared in auto mode is less than t eebyte /t eeblock /t eebulk . however, on other mcus, this delay time may be different. for forward compatibility, software should not make any dependency on this delay time. e. any attempt to clear both eepgm and eelat bits with a single instruction will only clear eepgm. this is to allow time for removal of high voltage from the eeprom array. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory eeprom register descriptions mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 73 5.6 eeprom register descriptions four i/o registers and three non-volatile registers control program, erase and options of the eeprom array. 5.6.1 eeprom control register this read/write register controls programming/erasing of the array. bit 7 ? unused bit this read/write bit is software programmable but has no functionality. eeoff ? eeprom power down this read/write bit disables the eeprom module for lower power consumption. any attempts to access the array will give unpredictable results. reset clears this bit. 1 = disable eeprom array 0 = enable eeprom array eeras1 and eeras0 ? erase/program mode select bits these read/write bits set the erase modes. reset clears these bits. address: $fe1d bit 7654321bit 0 read: unused 0 eeoff eeras1 eeras0 eelat auto eepgm write: reset:00000000 = unimplemented figure 5-2. eeprom control register (eecr) table 5-3. eeprom program/erase mode select eebpx eeras1 eeras0 mode 000byte program 001byte erase 010block erase 0 1 1 bulk erase 1 x x no erase/program x = don ? t care f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 74 eeprom memory motorola eelat ? eeprom latch control this read/write bit latches the address and data buses for programming the eeprom array. eelat cannot be cleared if eepgm is still set. reset clears this bit. 1 = buses configured for eeprom programming or erase operation 0 = buses configured for normal operation auto ? automatic termination of program/erase cycle when auto is set, eepgm is cleared automatically after the program/erase cycle is terminated by the internal timer. (see note d for eeprom programming on page 70, eeprom erasing on page 71 and eeprom memory characteristics on page 430) 1 = automatic clear of eepgm is enabled 0 = automatic clear of eepgm is disabled eepgm ? eeprom program/erase enable this read/write bit enables the internal charge pump and applies the programming/erasing voltage to the eeprom array if the eelat bit is set and a write to a valid eeprom location has occurred. reset clears the eepgm bit. 1 = eeprom programming/erasing power switched on 0 = eeprom programming/erasing power switched off note: writing logic 0s to both the eelat and eepgm bits with a single instruction will clear eepgm only to allow time for the removal of high voltage. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory eeprom register descriptions mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 75 5.6.2 eeprom array configuration register the eeprom array configuration register configures eeprom security and eeprom block protection. this read-only register is loaded with the contents of the eeprom non- volatile register (eenvr) after a reset. bit 7:5 ? unused bits these read/write bits are software programmable but have no functionality. eeprtct ? eeprom protection bit the eeprtct bit is used to enable the security feature in the eeprom (see eeprom program/erase protection ). 1 = eeprom security disabled 0 = eeprom security enabled this feature is a write-once feature. once the protection is enabled it may not be disabled. address: $fe1f bit 7 6 5 4 3 2 1 bit 0 read: unused unused unused eeprtct eebp3 eebp2 eebp1 eebp0 write: reset: contents of eenvr ($fe1c) figure 5-3. eeprom array configuration register (eeacr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 76 eeprom memory motorola eebp[3:0] ? eeprom block protection bits these bits prevent blocks of eeprom array from being programmed or erased. 1 = eeprom array block is protected 0 = eeprom array block is unprotected block number (eebpx) address range eebp0 $0800 ? $087f eebp1 $0880 ? $08ff eebp2 $0900 ? $097f eebp3 $0980 ? $09ff table 5-4. eeprom block protect and security summary address range eebpx eeprtct = 1 eeprtct = 0 $0800 - $087f eebp0 = 0 byte programming available bulk, block and byte erasing available byte programming available only byte erasing available eebp0 = 1 protected protected $0880 - $08ef eebp1 = 0 byte programming available bulk, block and byte erasing available byte programming available only byte erasing available eebp1 = 1 protected protected $08f0 - $08ff eebp1 = 0 byte programming available bulk, block and byte erasing available secured (no programming or erasing) eebp1 = 1 protected $0900 - $097f eebp2 = 0 byte programming available bulk, block and byte erasing available byte programming available only byte erasing available eebp2 = 1 protected protected $0980 - $09ff eebp3 = 0 byte programming available bulk, block and byte available byte programming available only byte erasing available eebp3 = 1 protected protected f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory eeprom register descriptions mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 77 5.6.3 eeprom nonvolatile register the contents of this register is loaded into the eeprom array configuration register (eeacr) after a reset. this register is erased and programmed in the same way as an eeprom byte. (see eeprom control register on page 73 for individual bit descriptions). note: the eenvr will leave the factory programmed with $f0 such that the full array is available and unprotected. address: $fe1c bit 7 6 5 4 3 2 1 bit 0 read: unused unused unused eeprtct eebp3 eebp2 eebp1 eebp0 write: reset: pv = unimplemented pv = programmed value or 1 in the erased state. figure 5-4. eeprom nonvolatile register (eenvr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 78 eeprom memory motorola 5.6.4 eeprom timebase divider register the 16-bit eeprom timebase divider register consists of two 8-bit registers: eedivh and eedivl. the 11-bit value in this register is used to configure the timebase divider circuit to obtain the 35 s timebase for eeprom control. these two read/write registers are respectively loaded with the contents of the eeprom timebase divider on-volatile registers (eedivhnvr and eedivlnvr) after a reset. address: $fe1a bit 7 6 5 4 3 2 1 bit 0 read: eedivsecd 0000 eediv10 eediv9 eediv8 write: reset: contents of eedivhnvr ($fe10), bits [6:3] = 0 = unimplemented figure 5-5. eediv divider high register (eedivh) address: $fe1b bit 7 6 5 4 3 2 1 bit 0 read: eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 write: reset: contents of eedivlnvr ($fe11) figure 5-6. eediv divider low register (eedivl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory eeprom register descriptions mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 79 eedivsecd ? eeprom divider security disable this bit enables/disables the security feature of the eediv registers. when eediv security feature is enabled, the state of the registers eedivh and eedivl are locked (including eedivsecd bit). the eedivhnvr and eedivlnvr non-volatile memory registers are also protected from being erased/programmed. 1 = eediv security feature disabled 0 = eediv security feature enabled eediv[10:0] ? eeprom timebase prescaler these prescaler bits store the value of eediv which is used as the divisor to derive a timebase of 35 s from the selected reference clock source (cgmxclk or bus block in the config-2 register) for the eeprom related internal timer and circuits. eediv[10:0] bits are readable at any time. they are writable when eelat = 0 and eedivsecd = 1. the eediv value is calculated by the following formula: eediv= int[reference frequency(hz) x 35 x10 -6 +0.5] where the result inside the bracket is rounded down to the nearest integer value for example, if the reference frequency is 4.9152mhz, the eediv value is 172 note: programming/erasing the eeprom with an improper eediv value may result in data lost and reduce endurance of the eeprom device. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 80 eeprom memory motorola 5.6.5 eeprom timebase divider non-volatile register the 16-bit eeprom timebase divider non-volatile register consists of two 8-bit registers: eedivhnvr and eedivlnvr. the contents of these two registers are respectively loaded into the eeprom timebase divider registers, eedivh and eedivl, after a reset. these two registers are erased and programmed in the same way as an eeprom byte. these two registers are protected from erase and program operations if the eedivsecd is set to logic 1 in the eedivh (see eeprom timebase divider register ) or programmed to a logic 1 in the eedivhnvr. note: once eedivsecd in the eedivhnvr is programmed to 0 and after a system reset, the eediv security feature is permanently enabled because the eedivsecd bit in the eedivh is always loaded with 0 address: $fe10 bit 7 6 5 4 3 2 1 bit 0 read: eedivsecd r r r r eediv10 eediv9 eediv8 write: reset: unaffected by reset; $ff when blank r=reserved figure 5-7. eeprom divider non-volatile register high (eedivhnvr)) address: $fe11 bit 7 6 5 4 3 2 1 bit 0 read: eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 write: reset: unaffected by reset; $ff when blank figure 5-8. eeprom divider non-volatile register low (eedivlnvr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola eeprom memory 81 thereafter. once this security feature is armed, erase and program mode are disabled for eedivhnvr and eedivlnvr. modifications to the eedivh and eedivl registers are also disabled. therefore, care should be taken before programming a value into the eedivhnvr. 5.7 low-power modes the wait and stop instructions can put the mcu in low power- consumption standby modes. 5.7.1 wait mode the wait instruction does not affect the eeprom. it is possible to start the program or erase sequence on the eeprom and put the mcu in wait mode. 5.7.2 stop mode the stop instruction reduces the eeprom power consumption to a minimum. the stop instruction should not be executed while a programming or erasing sequence is in progress. if stop mode is entered while eelat and eepgm are set, the programming sequence will be stopped and the programming voltage to the eeprom array removed. the programming sequence will be restarted after leaving stop mode; access to the eeprom is only possible after the programming sequence has completed. if stop mode is entered while eelat and eepgm is cleared, the programming sequence will be terminated abruptly. in either case, the data integrity of the eeprom is not guaranteed. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . eeprom memory advance information mc68HC908AS32A ? rev 0.0 82 eeprom memory motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 83 technical data ? mc68HC908AS32A section 6. central processor unit (cpu) 6.1 contents 6.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.4 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.4.1 accumulator (a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6.4.2 index register (h:x) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 6.4.3 stack pointer (sp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.4.4 program counter (pc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.4.5 condition code register (ccr) . . . . . . . . . . . . . . . . . . . . . 87 6.5 arithmetic/logic unit (alu) . . . . . . . . . . . . . . . . . . . . . . . . . . 89 6.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.7 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 90 6.8 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.9 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 6.2 introduction this section describes the central processor unit (cpu8). the m68hc08 cpu is an enhanced and fully object-code-compatible version of the m68hc05 cpu. the cpu08 reference manual (motorola document number cpu08rm/ad) contains a description of the cpu instruction set, addressing modes, and architecture. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 84 central processor unit (cpu) motorola 6.3 features features of the cpu include the following: full upward, object-code compatibility with m68hc05 family 16-bit stack pointer with stack manipulation instructions 16-bit index register with x-register manipulation instructions 8.4mhz cpu internal bus frequency 64k byte program/data memory space 16 addressing modes memory-to-memory data moves without using accumulator fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions enhanced binary-coded decimal (bcd) data handling low-power stop and wait modes 6.4 cpu registers figure 6-1 shows the five cpu registers. cpu registers are not part of the memory map. figure 6-1. cpu registers accumulator (a) index register (h:x) stack pointer (sp) program counter (pc) condition code register (ccr) carry/borrow flag zero flag negative flag interrupt mask half-carry flag two ? s complement overflow flag v11h i nzc h x 0 0 0 0 7 15 15 15 70 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) cpu registers mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 85 6.4.1 accumulator (a) the accumulator is a general-purpose 8-bit register. the cpu uses the accumulator to hold operands and the results of arithmetic/logic operations. 6.4.2 index register (h:x) the 16-bit index register allows indexed addressing of a 64k byte memory space. h is the upper byte of the index register and x is the lower byte. h:x is the concatenated 16-bit index register. in the indexed addressing modes, the cpu uses the contents of the index register to determine the conditional address of the operand. the index register can also be used as a temporary data storage location. bit 7654321bit 0 a read: write: reset: unaffected by reset figure 6-2. accumulator (a) bit 151413121110987654321 bit 0 h:x read: write: reset:00000000 xxxxxxxx x = indeterminate figure 6-3. index register (h:x) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 86 central processor unit (cpu) motorola 6.4.3 stack pointer (sp) the stack pointer is a 16-bit register that contains the address of the next location on the stack. during a reset, the stack pointer is preset to $00ff. the reset stack pointer (rsp) instruction sets the least significant byte to $ff and does not affect the most significant byte. the stack pointer decrements as data is pushed onto the stack and increments as data is pulled from the stack. in the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an index register to access data on the stack. the cpu uses the contents of the stack pointer to determine the conditional address of the operand. note: the location of the stack is arbitrary and may be relocated anywhere in ram. moving the sp out of page zero ($0000 to $00ff) frees direct address (page zero) space. for correct operation, the stack pointer must point only to ram locations. 6.4.4 program counter (pc) the program counter is a 16-bit register that contains the address of the next instruction or operand to be fetched. normally, the program counter automatically increments to the next sequential memory location every time an instruction or operand is fetched. jump, branch, and interrupt operations load the program counter with an address other than that of the next sequential location. bit 151413121110987654321 bit 0 sp read: write: reset:0000000011111111 figure 6-4. stack pointer (sp) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) cpu registers mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 87 during reset, the program counter is loaded with the reset vector address located at $fffe and $ffff. the vector address is the address of the first instruction to be executed after exiting the reset state. 6.4.5 condition code register (ccr) the 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the instruction just executed. bits 6 and 5 are set permanently to ? 1 ? . the following paragraphs describe the functions of the condition code register. v ? overflow flag the cpu sets the overflow flag when a two's complement overflow occurs. the signed branch instructions bgt, bge, ble, and blt use the overflow flag. 1 = overflow 0 = no overflow bit 151413121110987654321 bit 0 pc read: write: reset: loaded with vector from $fffe and $ffff figure 6-5. program counter (pc) bit 7654321bit 0 ccr read: v11h i nzc write: reset:x11x1xxx x = indeterminate figure 6-6. condition code register (ccr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 88 central processor unit (cpu) motorola h ? half-carry flag the cpu sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an add or adc operation. the half- carry flag is required for binary-coded decimal (bcd) arithmetic operations. the daa instruction uses the states of the h and c flags to determine the appropriate correction factor. 1 = carry between bits 3 and 4 0 = no carry between bits 3 and 4 i ? interrupt mask when the interrupt mask is set, all maskable cpu interrupts are disabled. cpu interrupts are enabled when the interrupt mask is cleared. when a cpu interrupt occurs, the interrupt mask is set automatically after the cpu registers are saved on the stack, but before the interrupt vector is fetched. 1 = interrupts disabled 0 = interrupts enabled note: to maintain m6805 compatibility, the upper byte of the index register (h) is not stacked automatically. if the interrupt service routine modifies h, then the user must stack and unstack h using the pshh and pulh instructions. after the i bit is cleared, the highest-priority interrupt request is serviced first. a return from interrupt (rti) instruction pulls the cpu registers from the stack and restores the interrupt mask from the stack. after any reset, the interrupt mask is set and can only be cleared by the clear interrupt mask software instruction (cli). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) arithmetic/logic unit (alu) mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 89 n ? negative flag the cpu sets the negative flag when an arithmetic operation, logic operation, or data manipulation produces a negative result, setting bit 7 of the result. 1 = negative result 0 = non-negative result z ? zero flag the cpu sets the zero flag when an arithmetic operation, logic operation, or data manipulation produces a result of $00. 1 = zero result 0 = non-zero result c ? carry/borrow flag the cpu sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the accumulator or when a subtraction operation requires a borrow. some instructions - such as bit test and branch, shift, and rotate - also clear or set the carry/borrow flag. 1 = carry out of bit 7 0 = no carry out of bit 7 6.5 arithmetic/logic unit (alu) the alu performs the arithmetic and logic operations defined by the instruction set. refer to the cpu08 reference manual (motorola document number cpu08rm/ad) for a description of the instructions and addressing modes and more detail about cpu architecture. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 90 central processor unit (cpu) motorola 6.6 low-power modes the wait and stop instructions put the mcu in low--power consumption standby modes. 6.6.1 wait mode the wait instruction: clears the interrupt mask (i bit) in the condition code register, enabling interrupts. after exit from wait mode by interrupt, the i bit remains clear. after exit by reset, the i bit is set. disables the cpu clock 6.6.2 stop mode the stop instruction: clears the interrupt mask (i bit) in the condition code register, enabling external interrupts. after exit from stop mode by external interrupt, the i bit remains clear. after exit by reset, the i bit is set. disables the cpu clock after exiting stop mode, the cpu clock begins running after the oscillator stabilization delay. 6.7 cpu during break interrupts if the break module is enabled, a break interrupt causes the cpu to execute the software interrupt instruction (swi) at the completion of the current cpu instruction. see break module (brk) . the program counter vectors to $fffc ? $fffd ($fefc ? $fefd in monitor mode). a return-from-interrupt instruction (rti) in the break routine ends the break interrupt and returns the mcu to normal operation if the break interrupt has been deasserted. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) instruction set summary mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 91 6.8 instruction set summary table 6-1 provides a summary of the m68hc08 instruction set. table 6-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vhi nzc adc # opr adc opr adc opr adc opr ,x adc opr ,x adc ,x adc opr ,sp adc opr ,sp add with carry a (a) + (m) + (c) ?? ? ??? imm dir ext ix2 ix1 ix sp1 sp2 a9 b9 c9 d9 e9 f9 9e e9 9e d9 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 add # opr add opr add opr add opr ,x add opr ,x add ,x add opr ,sp add opr ,sp add without carry a (a) + (m) ?? ? ??? imm dir ext ix2 ix1 ix sp1 sp2 ab bb cb db eb fb 9e eb 9e db ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ais # opr add immediate value (signed) to sp sp (sp) + (16 ? m) ?????? imm a7 ii 2 aix # opr add immediate value (signed) to h:x h:x (h:x) + (16 ? m) ?????? imm af ii 2 and # opr and opr and opr and opr ,x and opr ,x and ,x and opr ,sp and opr ,sp logical and a (a) & (m) 0 ?? ?? ? imm dir ext ix2 ix1 ix sp1 sp2 a4 b4 c4 d4 e4 f4 9e e4 9e d4 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 asl opr asla aslx asl opr ,x asl ,x asl opr ,sp arithmetic shift left (same as lsl) ? ?? ??? dir inh inh ix1 ix sp1 38 48 58 68 78 9e 68 dd ff ff 4 1 1 4 3 5 asr opr asra asrx asr opr ,x asr opr ,x asr opr ,sp arithmetic shift right ? ?? ??? dir inh inh ix1 ix sp1 37 47 57 67 77 9e 67 dd ff ff 4 1 1 4 3 5 c b0 b7 0 b0 b7 c f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 92 central processor unit (cpu) motorola bcc rel branch if carry bit clear pc (pc) + 2 + rel ? (c) = 0 ?????? rel 24 rr 3 bclr n , opr clear bit n in m mn 0 ?????? dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 11 13 15 17 19 1b 1d 1f dd dd dd dd dd dd dd dd 4 4 4 4 4 4 4 4 bcs rel branch if carry bit set (same as blo) pc (pc) + 2 + rel ? (c) = 1 ?????? rel 25 rr 3 beq rel branch if equal pc (pc) + 2 + rel ? (z) = 1 ?????? rel 27 rr 3 bge opr branch if greater than or equal to (signed operands) pc (pc) + 2 + rel ? (n v ) = 0 ?????? rel 90 rr 3 bgt opr branch if greater than (signed operands) pc (pc) + 2 + rel ? (z) | (n v ) = 0 ?????? rel 92 rr 3 bhcc rel branch if half carry bit clear pc (pc) + 2 + rel ? (h) = 0 ?????? rel 28 rr 3 bhcs rel branch if half carry bit set pc (pc) + 2 + rel ? (h) = 1 ?????? rel 29 rr 3 bhi rel branch if higher pc (pc) + 2 + rel ? (c) | (z) = 0 ?????? rel 22 rr 3 bhs rel branch if higher or same (same as bcc) pc (pc) + 2 + rel ? (c) = 0 ?????? rel 24 rr 3 bih rel branch if irq pin high pc (pc) + 2 + rel ? irq = 1 ?????? rel 2f rr 3 bil rel branch if irq pin low pc (pc) + 2 + rel ? irq = 0 ?????? rel 2e rr 3 bit # opr bit opr bit opr bit opr ,x bit opr ,x bit ,x bit opr ,sp bit opr ,sp bit test (a) & (m) 0 ?? ?? ? imm dir ext ix2 ix1 ix sp1 sp2 a5 b5 c5 d5 e5 f5 9e e5 9e d5 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ble opr branch if less than or equal to (signed operands) pc (pc) + 2 + rel ? (z) | (n v ) = 1 ?????? rel 93 rr 3 blo rel branch if lower (same as bcs) pc (pc) + 2 + rel ? (c) = 1 ?????? rel 25 rr 3 bls rel branch if lower or same pc (pc) + 2 + rel ? (c) | (z) = 1 ?????? rel 23 rr 3 blt opr branch if less than (signed operands) pc (pc) + 2 + rel ? (n v ) = 1 ?????? rel 91 rr 3 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) instruction set summary mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 93 bmc rel branch if interrupt mask clear pc (pc) + 2 + rel ? (i) = 0 ?????? rel 2c rr 3 bmi rel branch if minus pc (pc) + 2 + rel ? (n) = 1 ?????? rel 2b rr 3 bms rel branch if interrupt mask set pc (pc) + 2 + rel ? (i) = 1 ?????? rel 2d rr 3 bne rel branch if not equal pc (pc) + 2 + rel ? (z) = 0 ?????? rel 26 rr 3 bpl rel branch if plus pc (pc) + 2 + rel ? (n) = 0 ?????? rel 2a rr 3 bra rel branch always pc (pc) + 2 + rel ?????? rel 20 rr 3 brclr n , opr , rel branch if bit n in m clear pc (pc) + 3 + rel ? (mn) = 0 ????? ? dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 01 03 05 07 09 0b 0d 0f dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr 5 5 5 5 5 5 5 5 brn rel branch never pc (pc) + 2 ?????? rel 21 rr 3 brset n , opr , rel branch if bit n in m set pc (pc) + 3 + rel ? (mn) = 1 ????? ? dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 00 02 04 06 08 0a 0c 0e dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr 5 5 5 5 5 5 5 5 bset n , opr set bit n in m mn 1 ?????? dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 10 12 14 16 18 1a 1c 1e dd dd dd dd dd dd dd dd 4 4 4 4 4 4 4 4 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 94 central processor unit (cpu) motorola bsr rel branch to subroutine pc (pc) + 2; push (pcl) sp (sp) ? 1; push (pch) sp (sp) ? 1 pc (pc) + rel ?????? rel ad rr 4 cbeq opr,rel cbeqa # opr,rel cbeqx # opr,rel cbeq opr, x+ ,rel cbeq x+ ,rel cbeq opr, sp ,rel compare and branch if equal pc (pc) + 3 + rel ? (a) ? (m) = $00 pc (pc) + 3 + rel ? (a) ? (m) = $00 pc (pc) + 3 + rel ? (x) ? (m) = $00 pc (pc) + 3 + rel ? (a) ? (m) = $00 pc (pc) + 2 + rel ? (a) ? (m) = $00 pc (pc) + 4 + rel ? (a) ? (m) = $00 ?????? dir imm imm ix1+ ix+ sp1 31 41 51 61 71 9e 61 dd rr ii rr ii rr ff rr rr ff rr 5 4 4 5 4 6 clc clear carry bit c 0 ????? 0inh 98 1 cli clear interrupt mask i 0 ?? 0 ??? inh 9a 2 clr opr clra clrx clrh clr opr ,x clr ,x clr opr ,sp clear m $00 a $00 x $00 h $00 m $00 m $00 m $00 0 ?? 01 ? dir inh inh inh ix1 ix sp1 3f 4f 5f 8c 6f 7f 9e 6f dd ff ff 3 1 1 1 3 2 4 cmp # opr cmp opr cmp opr cmp opr ,x cmp opr ,x cmp ,x cmp opr ,sp cmp opr ,sp compare a with m (a) ? (m) ? ?? ??? imm dir ext ix2 ix1 ix sp1 sp2 a1 b1 c1 d1 e1 f1 9e e1 9e d1 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 com opr coma comx com opr ,x com ,x com opr ,sp complement (one ? s complement) m (m ) = $ff ? (m) a (a ) = $ff ? (m) x (x ) = $ff ? (m) m (m ) = $ff ? (m) m (m ) = $ff ? (m) m (m ) = $ff ? (m) 0 ?? ?? 1 dir inh inh ix1 ix sp1 33 43 53 63 73 9e 63 dd ff ff 4 1 1 4 3 5 cphx # opr cphx opr compare h:x with m (h:x) ? (m:m + 1) ? ?? ??? imm dir 65 75 ii ii+1 dd 3 4 cpx # opr cpx opr cpx opr cpx ,x cpx opr ,x cpx opr ,x cpx opr ,sp cpx opr ,sp compare x with m (x) ? (m) ? ?? ??? imm dir ext ix2 ix1 ix sp1 sp2 a3 b3 c3 d3 e3 f3 9e e3 9e d3 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) instruction set summary mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 95 daa decimal adjust a (a) 10 u ?? ??? inh 72 2 dbnz opr,rel dbnza rel dbnzx rel dbnz opr, x ,rel dbnz x ,rel dbnz opr, sp ,rel decrement and branch if not zero a (a) ? 1 or m (m) ? 1 or x (x) ? 1 pc (pc) + 3 + rel ? (result) 0 pc (pc) + 2 + rel ? (result) 0 pc (pc) + 2 + rel ? (result) 0 pc (pc) + 3 + rel ? (result) 0 pc (pc) + 2 + rel ? (result) 0 pc (pc) + 4 + rel ? (result) 0 ?????? dir inh inh ix1 ix sp1 3b 4b 5b 6b 7b 9e 6b dd rr rr rr ff rr rr ff rr 5 3 3 5 4 6 dec opr deca decx dec opr ,x dec ,x dec opr ,sp decrement m (m) ? 1 a (a) ? 1 x (x) ? 1 m (m) ? 1 m (m) ? 1 m (m) ? 1 ? ?? ?? ? dir inh inh ix1 ix sp1 3a 4a 5a 6a 7a 9e 6a dd ff ff 4 1 1 4 3 5 div divide a (h:a)/(x) h remainder ???? ?? inh 52 7 eor # opr eor opr eor opr eor opr ,x eor opr ,x eor ,x eor opr ,sp eor opr ,sp exclusive or m with a a (a m) 0 ?? ?? ? imm dir ext ix2 ix1 ix sp1 sp2 a8 b8 c8 d8 e8 f8 9e e8 9e d8 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 inc opr inca incx inc opr ,x inc ,x inc opr ,sp increment m (m) + 1 a (a) + 1 x (x) + 1 m (m) + 1 m (m) + 1 m (m) + 1 ? ?? ?? ? dir inh inh ix1 ix sp1 3c 4c 5c 6c 7c 9e 6c dd ff ff 4 1 1 4 3 5 jmp opr jmp opr jmp opr ,x jmp opr ,x jmp ,x jump pc jump address ?????? dir ext ix2 ix1 ix bc cc dc ec fc dd hh ll ee ff ff 2 3 4 3 2 jsr opr jsr opr jsr opr ,x jsr opr ,x jsr ,x jump to subroutine pc (pc) + n ( n = 1, 2, or 3) push (pcl); sp (sp) ? 1 push (pch); sp (sp) ? 1 pc unconditional address ?????? dir ext ix2 ix1 ix bd cd dd ed fd dd hh ll ee ff ff 4 5 6 5 4 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 96 central processor unit (cpu) motorola lda # opr lda opr lda opr lda opr ,x lda opr ,x lda ,x lda opr ,sp lda opr ,sp load a from m a (m) 0 ?? ?? ? imm dir ext ix2 ix1 ix sp1 sp2 a6 b6 c6 d6 e6 f6 9e e6 9e d6 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ldhx # opr ldhx opr load h:x from m h:x ( m:m + 1 ) 0 ?? ?? ? imm dir 45 55 ii jj dd 3 4 ldx # opr ldx opr ldx opr ldx opr ,x ldx opr ,x ldx ,x ldx opr ,sp ldx opr ,sp load x from m x (m) 0 ?? ?? ? imm dir ext ix2 ix1 ix sp1 sp2 ae be ce de ee fe 9e ee 9e de ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 lsl opr lsla lslx lsl opr ,x lsl ,x lsl opr ,sp logical shift left (same as asl) ? ?? ??? dir inh inh ix1 ix sp1 38 48 58 68 78 9e 68 dd ff ff 4 1 1 4 3 5 lsr opr lsra lsr x lsr opr ,x lsr ,x lsr opr ,sp logical shift right ? ?? 0 ?? dir inh inh ix1 ix sp1 34 44 54 64 74 9e 64 dd ff ff 4 1 1 4 3 5 mov opr,opr mov opr, x+ mov # opr,opr mov x+ ,opr move (m) destination (m) source h:x (h:x) + 1 (ix+d, dix+) 0 ?? ?? ? dd dix+ imd ix+d 4e 5e 6e 7e dd dd dd ii dd dd 5 4 4 4 mul unsigned multiply x:a (x) (a) ? 0 ??? 0inh 42 5 neg opr nega negx neg opr ,x neg ,x neg opr ,sp negate (two ? s complement) m ? (m) = $00 ? (m) a ? (a) = $00 ? (a) x ? (x) = $00 ? (x) m ? (m) = $00 ? (m) m ? (m) = $00 ? (m) ? ?? ??? dir inh inh ix1 ix sp1 30 40 50 60 70 9e 60 dd ff ff 4 1 1 4 3 5 nop no operation none ?????? inh 9d 1 nsa nibble swap a a (a[3:0]:a[7:4]) ?????? inh 62 3 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc c b0 b7 0 b0 b7 c 0 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) instruction set summary mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 97 ora # opr ora opr ora opr ora opr ,x ora opr ,x ora ,x ora opr ,sp ora opr ,sp inclusive or a and m a (a) | (m) 0 ?? ?? ? imm dir ext ix2 ix1 ix sp1 sp2 aa ba ca da ea fa 9e ea 9e da ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 psha push a onto stack push (a); sp (sp ) ? 1 ?????? inh 87 2 pshh push h onto stack push (h) ; sp (sp ) ? 1 ?????? inh 8b 2 pshx push x onto stack push (x) ; sp (sp ) ? 1 ?????? inh 89 2 pula pull a from stack sp (sp + 1); pull ( a ) ?????? inh 86 2 pulh pull h from stack sp (sp + 1); pull ( h ) ?????? inh 8a 2 pulx pull x from stack sp (sp + 1); pull ( x ) ?????? inh 88 2 rol opr rola rolx rol opr ,x rol ,x rol opr ,sp rotate left through carry ? ?? ??? dir inh inh ix1 ix sp1 39 49 59 69 79 9e 69 dd ff ff 4 1 1 4 3 5 ror opr rora rorx ror opr ,x ror ,x ror opr ,sp rotate right through carry ? ?? ??? dir inh inh ix1 ix sp1 36 46 56 66 76 9e 66 dd ff ff 4 1 1 4 3 5 rsp reset stack pointer sp $ff ?????? inh 9c 1 rti return from interrupt sp (sp) + 1; pull (ccr) sp (sp) + 1; pull (a) sp (sp) + 1; pull (x) sp (sp) + 1; pull (pch) sp (sp) + 1; pull (pcl) ?????? inh 80 7 rts return from subroutine sp sp + 1 ; pull ( pch) sp sp + 1; pull (pcl) ?????? inh 81 4 sbc # opr sbc opr sbc opr sbc opr ,x sbc opr ,x sbc ,x sbc opr ,sp sbc opr ,sp subtract with carry a (a) ? (m) ? (c) ? ?? ??? imm dir ext ix2 ix1 ix sp1 sp2 a2 b2 c2 d2 e2 f2 9e e2 9e d2 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 sec set carry bit c 1 ????? 1inh 99 1 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc c b0 b7 b0 b7 c f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) advance information mc68HC908AS32A ? rev 0.0 98 central processor unit (cpu) motorola sei set interrupt mask i 1 ?? 1 ??? inh 9b 2 sta opr sta opr sta opr ,x sta opr ,x sta ,x sta opr ,sp sta opr ,sp store a in m m (a) 0 ?? ?? ? dir ext ix2 ix1 ix sp1 sp2 b7 c7 d7 e7 f7 9e e7 9e d7 dd hh ll ee ff ff ff ee ff 3 4 4 3 2 4 5 sthx opr store h:x in m (m:m + 1) (h:x) 0 ?? ?? ? dir 35 dd 4 stop enable irq pin; stop oscillator i 0; stop oscillator ?? 0 ??? inh 8e 1 stx opr stx opr stx opr ,x stx opr ,x stx ,x stx opr ,sp stx opr ,sp store x in m m (x) 0 ?? ?? ? dir ext ix2 ix1 ix sp1 sp2 bf cf df ef ff 9e ef 9e df dd hh ll ee ff ff ff ee ff 3 4 4 3 2 4 5 sub # opr sub opr sub opr sub opr ,x sub opr ,x sub ,x sub opr ,sp sub opr ,sp subtract a (a) ? (m) ? ?? ??? imm dir ext ix2 ix1 ix sp1 sp2 a0 b0 c0 d0 e0 f0 9e e0 9e d0 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 swi software interrupt pc (pc) + 1; push (pcl) sp (sp) ? 1; push (pch) sp (sp) ? 1; push (x) sp (sp) ? 1; push (a) sp (sp) ? 1; push (ccr) sp (sp) ? 1; i 1 pch interrupt vector high byte pcl interrupt vector low byte ?? 1 ??? inh 83 9 tap transfer a to ccr ccr (a) ?????? inh 84 2 tax transfer a to x x (a) ?????? inh 97 1 tpa transfer ccr to a a (ccr) ?????? inh 85 1 tst opr tsta tstx tst opr ,x tst ,x tst opr ,sp test for negative or zero (a) ? $00 or (x) ? $00 or (m) ? $00 0 ?? ?? ? dir inh inh ix1 ix sp1 3d 4d 5d 6d 7d 9e 6d dd ff ff 3 1 1 3 2 4 tsx transfer sp to h:x h:x (sp) + 1 ?????? inh 95 2 table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . central processor unit (cpu) opcode map mc68HC908AS32A ? rev 0.0 advance information motorola central processor unit (cpu) 99 6.9 opcode map the opcode map is provided in table 6-2 . txa transfer x to a a (x) ?????? inh 9f 1 txs transfer h:x to sp (sp) (h:x) ? 1 ?????? inh 94 2 a accumulator n any bit c carry/borrow bit opr operand (one or two bytes) ccrcondition code registerpc program counter dddirect address of operandpch program counter high byte dd rrdirect address of operand and relative offset of branch instructionpcl program counter low byte dddirect to direct addressing moderel relative addressing mode dirdirect addressing mode rel relative program counter offset byte dix+direct to indexed with post increment addressing moderr relative program counter offset byte ee ffhigh and low bytes of offset in indexed, 16-bit offset addressingsp1 stack pointer, 8-bit offset addressing mode extextended addressing modesp2 stack pointer 16-bit offset addressing mode ff offset byte in indexed, 8-bit offset addressingsp stack pointer h half-carry bitu undefined h index register high bytev overflow bit hh llhigh and low bytes of operand address in extended addressingx index register low byte i interrupt maskz zero bit ii immediate operand byte& logical and imdimmediate source to direct destination addressing mode| logical or immimmediate addressing mode logical exclusive or inhinherent addressing mode( ) contents of ixindexed, no offset addressing mode ? ( ) negation (two ? s complement) ix+indexed, no offset, post increment addressing mode# immediate value ix+dindexed with post increment to direct addressing mode ? sign extend ix1indexed, 8-bit offset addressing mode loaded with ix1+indexed, 8-bit offset, post increment addressing mode? if ix2indexed, 16-bit offset addressing mode: concatenated with mmemory location ? set or cleared n negative bit ? not affected table 6-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vhi nzc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . advance information mc68HC908AS32A ? rev 0.0 100 central processor unit (cpu) motorola central processor unit (cpu) table 6-2. opcode map 0 1 2 3 4 5 6 7 8 9 a b c d e f bit manipulation branch read-modify-write control register/memory dir dir rel dir inh inh ix1 sp1 ix inh inh imm dir ext ix2 sp2 ix1 sp1 ix 0 12 3 4 5 69e67 8 9abcd9ede9eef 5 brset0 3dir 4 bset0 2dir 3 bra 2rel 4 neg 2dir 1 nega 1inh 1 negx 1inh 4 neg 2ix1 5 neg 3 sp1 3 neg 1ix 7 rti 1inh 3 bge 2rel 2 sub 2imm 3 sub 2dir 4 sub 3ext 4 sub 3ix2 5 sub 4 sp2 3 sub 2ix1 4 sub 3 sp1 2 sub 1ix 5 brclr0 3dir 4 bclr0 2dir 3 brn 2rel 5 cbeq 3dir 4 cbeqa 3imm 4 cbeqx 3imm 5 cbeq 3ix1+ 6 cbeq 4 sp1 4 cbeq 2ix+ 4 rts 1inh 3 blt 2rel 2 cmp 2imm 3 cmp 2dir 4 cmp 3ext 4 cmp 3ix2 5 cmp 4 sp2 3 cmp 2ix1 4 cmp 3 sp1 2 cmp 1ix 5 brset1 3dir 4 bset1 2dir 3 bhi 2rel 5 mul 1inh 7 div 1inh 3 nsa 1inh 2 daa 1inh 3 bgt 2rel 2 sbc 2imm 3 sbc 2dir 4 sbc 3ext 4 sbc 3ix2 5 sbc 4 sp2 3 sbc 2ix1 4 sbc 3 sp1 2 sbc 1ix 5 brclr1 3dir 4 bclr1 2dir 3 bls 2rel 4 com 2dir 1 coma 1inh 1 comx 1inh 4 com 2ix1 5 com 3 sp1 3 com 1ix 9 swi 1inh 3 ble 2rel 2 cpx 2imm 3 cpx 2dir 4 cpx 3ext 4 cpx 3ix2 5 cpx 4 sp2 3 cpx 2ix1 4 cpx 3 sp1 2 cpx 1ix 5 brset2 3dir 4 bset2 2dir 3 bcc 2rel 4 lsr 2dir 1 lsra 1inh 1 lsrx 1inh 4 lsr 2ix1 5 lsr 3 sp1 3 lsr 1ix 2 tap 1inh 2 txs 1inh 2 and 2imm 3 and 2dir 4 and 3ext 4 and 3ix2 5 and 4 sp2 3 and 2ix1 4 and 3 sp1 2 and 1ix 5 brclr2 3dir 4 bclr2 2dir 3 bcs 2rel 4 sthx 2dir 3 ldhx 3imm 4 ldhx 2dir 3 cphx 3imm 4 cphx 2dir 1 tpa 1inh 2 tsx 1inh 2 bit 2imm 3 bit 2dir 4 bit 3ext 4 bit 3ix2 5 bit 4 sp2 3 bit 2ix1 4 bit 3 sp1 2 bit 1ix 5 brset3 3dir 4 bset3 2dir 3 bne 2rel 4 ror 2dir 1 rora 1inh 1 rorx 1inh 4 ror 2ix1 5 ror 3 sp1 3 ror 1ix 2 pula 1inh 2 lda 2imm 3 lda 2dir 4 lda 3ext 4 lda 3ix2 5 lda 4 sp2 3 lda 2ix1 4 lda 3 sp1 2 lda 1ix 5 brclr3 3dir 4 bclr3 2dir 3 beq 2rel 4 asr 2dir 1 asra 1inh 1 asrx 1inh 4 asr 2ix1 5 asr 3 sp1 3 asr 1ix 2 psha 1inh 1 tax 1inh 2 ais 2imm 3 sta 2dir 4 sta 3ext 4 sta 3ix2 5 sta 4 sp2 3 sta 2ix1 4 sta 3 sp1 2 sta 1ix 5 brset4 3dir 4 bset4 2dir 3 bhcc 2rel 4 lsl 2dir 1 lsla 1inh 1 lslx 1inh 4 lsl 2ix1 5 lsl 3 sp1 3 lsl 1ix 2 pulx 1inh 1 clc 1inh 2 eor 2imm 3 eor 2dir 4 eor 3ext 4 eor 3ix2 5 eor 4 sp2 3 eor 2ix1 4 eor 3 sp1 2 eor 1ix 5 brclr4 3dir 4 bclr4 2dir 3 bhcs 2rel 4 rol 2dir 1 rola 1inh 1 rolx 1inh 4 rol 2ix1 5 rol 3 sp1 3 rol 1ix 2 pshx 1inh 1 sec 1inh 2 adc 2imm 3 adc 2dir 4 adc 3ext 4 adc 3ix2 5 adc 4 sp2 3 adc 2ix1 4 adc 3 sp1 2 adc 1ix 5 brset5 3dir 4 bset5 2dir 3 bpl 2rel 4 dec 2dir 1 deca 1inh 1 decx 1inh 4 dec 2ix1 5 dec 3 sp1 3 dec 1ix 2 pulh 1inh 2 cli 1inh 2 ora 2imm 3 ora 2dir 4 ora 3ext 4 ora 3ix2 5 ora 4 sp2 3 ora 2ix1 4 ora 3 sp1 2 ora 1ix 5 brclr5 3dir 4 bclr5 2dir 3 bmi 2rel 5 dbnz 3dir 3 dbnza 2inh 3 dbnzx 2inh 5 dbnz 3ix1 6 dbnz 4 sp1 4 dbnz 2ix 2 pshh 1inh 2 sei 1inh 2 add 2imm 3 add 2dir 4 add 3ext 4 add 3ix2 5 add 4 sp2 3 add 2ix1 4 add 3 sp1 2 add 1ix 5 brset6 3dir 4 bset6 2dir 3 bmc 2rel 4 inc 2dir 1 inca 1inh 1 incx 1inh 4 inc 2ix1 5 inc 3 sp1 3 inc 1ix 1 clrh 1inh 1 rsp 1inh 2 jmp 2dir 3 jmp 3ext 4 jmp 3ix2 3 jmp 2ix1 2 jmp 1ix 5 brclr6 3dir 4 bclr6 2dir 3 bms 2rel 3 tst 2dir 1 tsta 1inh 1 tstx 1inh 3 tst 2ix1 4 tst 3 sp1 2 tst 1ix 1 nop 1inh 4 bsr 2rel 4 jsr 2dir 5 jsr 3ext 6 jsr 3ix2 5 jsr 2ix1 4 jsr 1ix 5 brset7 3dir 4 bset7 2dir 3 bil 2rel 5 mov 3dd 4 mov 2dix+ 4 mov 3imd 4 mov 2ix+d 1 stop 1inh * 2 ldx 2imm 3 ldx 2dir 4 ldx 3ext 4 ldx 3ix2 5 ldx 4 sp2 3 ldx 2ix1 4 ldx 3 sp1 2 ldx 1ix 5 brclr7 3dir 4 bclr7 2dir 3 bih 2rel 3 clr 2dir 1 clra 1inh 1 clrx 1inh 3 clr 2ix1 4 clr 3 sp1 2 clr 1ix 1 wait 1inh 1 txa 1inh 2 aix 2imm 3 stx 2dir 4 stx 3ext 4 stx 3ix2 5 stx 4 sp2 3 stx 2ix1 4 stx 3 sp1 2 stx 1ix inh inherent rel relative sp1 stack pointer, 8-bit offset imm immediate ix indexed, no offset sp2 stack pointer, 16-bit offset dir direct ix1 indexed, 8-bit offset ix+ indexed, no offset with ext extended ix2 indexed, 16-bit offset post increment dd direct-direct imd immediate-direct ix1+ indexed, 1-byte offset with ix+d indexed-direct dix+ direct-indexed post increment * pre-byte for stack pointer indexed instructions 0 high byte of opcode in hexadecimal low byte of opcode in hexadecimal 0 5 brset0 3dir cycles opcode mnemonic number of bytes / addressing mode msb lsb msb lsb f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 101 technical data ? mc68HC908AS32A section 7. system integration module (sim) 7.1 contents 7.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.3 sim bus clock control and generation . . . . . . . . . . . . . . . 104 7.3.1 bus timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.3.2 clock startup from por or lvi reset . . . . . . . . . . . . . . 105 7.3.3 clocks in stop mode and wait mode . . . . . . . . . . . . . . . 105 7.4 reset and system initialization . . . . . . . . . . . . . . . . . . . . . . 106 7.4.1 external pin reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7.4.2 active resets from internal sources . . . . . . . . . . . . . . . 107 7.4.2.1 power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 7.4.2.2 computer operating properly (cop) reset . . . . . . . . 109 7.4.2.3 illegal opcode reset . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.4.2.4 illegal address reset . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.4.2.5 low-voltage inhibit (lvi) reset . . . . . . . . . . . . . . . . . 110 7.5 sim counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 7.5.1 sim counter during power-on reset . . . . . . . . . . . . . . . 110 7.5.2 sim counter during stop mode recovery . . . . . . . . . . . 111 7.5.3 sim counter and reset states . . . . . . . . . . . . . . . . . . . . 111 7.6 program exception control . . . . . . . . . . . . . . . . . . . . . . . . . 111 7.6.1 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 7.6.2 reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 7.6.3 break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 7.6.4 status flag protection in break mode . . . . . . . . . . . . . . 116 7.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 7.7.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 7.7.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 7.8 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 7.8.1 sim break status register . . . . . . . . . . . . . . . . . . . . . . . . 120 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 102 system integration module (sim) motorola 7.8.2 sim reset status register . . . . . . . . . . . . . . . . . . . . . . . . 121 7.8.3 sim break flag control register . . . . . . . . . . . . . . . . . . 122 7.2 introduction this section describes the system integration module (sim), which supports up to 32 external and/or internal interrupts. together with the central processor unit (cpu), the sim controls all mcu activities. a block diagram of the sim is shown in figure 7-1 . figure 7-2 is a summary of the sim input/output (i/o) registers. the sim is a system state controller that coordinates cpu and exception timing. the sim is responsible for: bus clock generation and control for cpu and peripherals ? stop/wait/reset/break entry and recovery ? internal clock control master reset control, including power-on reset (por) and computer operating properly (cop) timeout interrupt control: ? acknowledge timing ? arbitration control timing ? vector address generation cpu enable/disable timing f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) introduction mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 103 figure 7-1. sim block diagram register name bit 7 6 5 4 3 2 1 bit 0 sim break status register (sbsr) r r r r r r bw r sim reset status register (srsr) por pin cop ilop ilad 0 lvi 0 sim break flag control register (sbfcr) bcfe r r r r r r r r=reserved figure 7-2. sim i/o register summary stop/wait clock control clock generators por control reset pin control sim reset status register interrupt control and priority decode module stop module wait cpu stop (from cpu) cpu wait (from cpu) simoscen (to cgm) cgmout (from cgm) internal clocks master reset control reset pin logic lvi (from lvi module) illegal opcode (from cpu) illegal address (from address map decoders) cop (from cop module) interrupt sources cpu interface reset control sim counter cop clock cgmxclk (from cgm) 2 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 104 system integration module (sim) motorola table 7-2 shows the internal signal names used in this section. 7.3 sim bus clock control and generation the bus clock generator provides system clock signals for the cpu and peripherals on the mcu. the system clocks are generated from an incoming clock, cgmout, as shown in figure 7-3 . this clock can come from either an external oscillator or from the on-chip pll. (see clock generator module (cgm) on page 123). 7.3.1 bus timing in user mode , the internal bus frequency is either the crystal oscillator output (cgmxclk) divided by four or the pll output (cgmvclk) divided by four. (see clock generator module (cgm) on page 123). table 7-1. i/o register address summary register sbsr srsr sbfcr address $fe00 $fe01 $fe03 table 7-2. signal name conventions signal name description cgmxclk buffered version of osc1 from clock generator module (cgm) cgmvclk pll output cgmout pll-based or osc1-based clock output from cgm module (bus clock = cgmout divided by two) iab internal address bus idb internal data bus porrst signal from the power-on reset module to the sim irst internal reset signal r/w read/write signal f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) sim bus clock control and generation mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 105 7.3.2 clock startup from por or lvi reset when the power-on reset module or the low-voltage inhibit module generates a reset, the clocks to the cpu and peripherals are inactive and held in an inactive phase until after 4096 cgmxclk cycles. the rst pin is driven low by the sim during this entire period. the bus clocks start upon completion of the timeout. figure 7-3. cgm clock signals 7.3.3 clocks in stop mode and wait mode upon exit from stop mode by an interrupt, break, or reset, the sim allows cgmxclk to clock the sim counter. the cpu and peripheral clocks do not become active until after the stop delay timeout. this timeout is selectable as 4096 or 32 cgmxclk cycles. see stop mode on page 118. in wait mode, the cpu clocks are inactive. refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. some modules can be programmed to be active in wait mode. pll osc1 cgmxclk 2 bus clock generators sim cgm sim counter ptc3 monitor mode clock select circuit cgmvclk bcs 2 a b s* cgmout *when s = 1, cgmout = b user mode f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 106 system integration module (sim) motorola 7.4 reset and system initialization the mcu has these reset sources: power-on reset module (por) external reset pin (rst ) computer operating properly module (cop) low-voltage inhibit module (lvi) illegal opcode illegal address all of these resets produce the vector $fffe ? ffff ($fefe ? feff in monitor mode) and assert the internal reset signal (irst). irst causes all registers to be returned to their default values and all modules to be returned to their reset states. an internal reset clears the sim counter (see sim counter on page 110), but an external reset does not. each of the resets sets a corresponding bit in the sim reset status register (srsr) (see sim registers on page 119). 7.4.1 external pin reset pulling the asynchronous rst pin low halts all processing. the pin bit of the sim reset status register (srsr) is set as long as rst is held low for a minimum of 67 cgmxclk cycles, assuming that neither the por nor the lvi was the source of the reset. see table 7-3 for details. figure 7-4 shows the relative timing. table 7-3. pin bit set timing reset type number of cycles required to set pin por/lvi 4163 (4096 + 64 + 3) all others 67 (64 + 3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) reset and system initialization mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 107 figure 7-4. external reset timing 7.4.2 active resets from internal sources all internal reset sources actively pull the rst pin low for 32 cgmxclk cycles to allow resetting of external peripherals. the internal reset signal irst continues to be asserted for an additional 32 cycles (see figure 7- 5 ). an internal reset can be caused by an illegal address, illegal opcode, cop timeout, lvi, or por (see figure 7-6 ). note that for lvi or por resets, the sim cycles through 4096 cgmxclk cycles during which the sim forces the rst pin low. the internal reset signal then follows the sequence from the falling edge of rst shown in figure 7-5 . the cop reset is asynchronous to the bus clock. the active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the mcu. figure 7-5. internal reset timing rst iab pc vect h vect l cgmout irst rst rst pulled low by mcu iab 32 cycles 32 cycles vector high cgmxclk f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 108 system integration module (sim) motorola figure 7-6. sources of internal reset 7.4.2.1 power-on reset when power is first applied to the mcu, the power-on reset module (por) generates a pulse to indicate that power-on has occurred. the external reset pin (rst ) is held low while the sim counter counts out 4096 cgmxclk cycles. another sixty-four cgmxclk cycles later, the cpu and memories are released from reset to allow the reset vector sequence to occur. at power-on, the following events occur: a por pulse is generated. the internal reset signal is asserted. the sim enables cgmout. internal clocks to the cpu and modules are held inactive for 4096 cgmxclk cycles to allow stabilization of the oscillator. the rst pin is driven low during the oscillator stabilization time. the por bit of the sim reset status register (srsr) is set and all other bits in the register are cleared. illegal address rst illegal opcode rst coprst lvi por internal reset f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) reset and system initialization mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 109 figure 7-7. por recovery 7.4.2.2 computer operating properly (cop) reset the overflow of the cop counter causes an internal reset and sets the cop bit in the sim reset status register (srsr) if the copd bit in the config-1 register is at logic zero. see computer operating properly (cop) on page 175. 7.4.2.3 illegal opcode reset the sim decodes signals from the cpu to detect illegal instructions. an illegal instruction sets the ilop bit in the sim reset status register (srsr) and causes a reset. if the stop enable bit, stop, in the config-1 register is logic zero, the sim treats the stop instruction as an illegal opcode and causes an illegal opcode reset. 7.4.2.4 illegal address reset an opcode fetch from an unmapped address generates an illegal address reset. the sim verifies that the cpu is fetching an opcode prior to asserting the ilad bit in the sim reset status register srsr) and porrst osc1 cgmxclk cgmout rst iab 4096 cycles 32 cycles 32 cycles $fffe $ffff f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 110 system integration module (sim) motorola resetting the mcu. a data fetch from an unmapped address does not generate a reset. the sim actively pulls down the rst pin for all internal reset sources. note: extra care should be exercised if code in this part has been migrated from older hc08 devices since the illegal address reset specification may be different. also, extra care should be exercised when using this emulation part for development of code to be run in rom az, ab or as family parts with a smaller memory size since some legal addresses will become illegal addresses on the smaller rom memory map device and may as a result generate unwanted resets. 7.4.2.5 low-voltage inhibit (lvi) reset the low-voltage inhibit module (lvi) asserts its output to the sim when the v dd voltage falls to the v lvii voltage. the lvi bit in the sim reset status register (srsr) is set and a chip reset is asserted if the lvipwrd and lvirstd bits in the config-1 register are at logic zero. the rst pin will be held low until the sim counts 4096 cgmxclk cycles after v dd rises above v lvir . another sixty-four cgmxclk cycles later, the cpu is released from reset to allow the reset vector sequence to occur. see low voltage inhibit (lvi) on page 181. 7.5 sim counter the sim counter is used by the power-on reset module (por) and in stop mode recovery to allow the oscillator time to stabilize before enabling the internal bus (ibus) clocks. the sim counter also serves as a prescaler for the computer operating properly module (cop). the sim counter overflow supplies the clock for the cop module. the sim counter is 12 bits long and is clocked by the falling edge of cgmxclk. 7.5.1 sim counter during power-on reset the power-on reset module (por) detects power applied to the mcu. at power-on, the por circuit asserts the signal porrst. once the sim f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) program exception control mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 111 is initialized, it enables the clock generation module (cgm) to drive the bus clock state machine. 7.5.2 sim counter during stop mode recovery the sim counter also is used for stop mode recovery. the stop instruction clears the sim counter. after an interrupt or reset, the sim senses the state of the short stop recovery bit, ssrec, in the config- 1 register. if the ssrec bit is a logic one, then the stop recovery is reduced from the normal delay of 4096 cgmxclk cycles down to 32 cgmxclk cycles. this is ideal for applications using canned oscillators that do not require long start-up times from stop mode. external crystal applications should use the full stop recovery time, that is, with ssrec cleared. 7.5.3 sim counter and reset states external reset has no effect on the sim counter. see stop mode on page 118 for details. the sim counter is free-running after all reset states. see active resets from internal sources on page 107 for counter control and internal reset recovery sequences. 7.6 program exception control normal, sequential program execution can be changed in three different ways: interrupts ? maskable hardware cpu interrupts ? non-maskable software interrupt instruction (swi) reset break interrupts f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 112 system integration module (sim) motorola 7.6.1 interrupts at the beginning of an interrupt, the cpu saves the cpu register contents on the stack and sets the interrupt mask (i bit) to prevent additional interrupts. at the end of an interrupt, the rti instruction recovers the cpu register contents from the stack so that normal processing can resume. figure 7-8 shows interrupt entry timing. figure 7-10 shows interrupt recovery timing. interrupts are latched, and arbitration is performed in the sim at the start of interrupt processing. the arbitration result is a constant that the cpu uses to determine which vector to fetch. once an interrupt is latched by the sim, no other interrupt can take precedence, regardless of priority, until the latched interrupt is serviced (or the i bit is cleared), see figure 7-9 . figure 7-8 . interrupt entry module idb r/w interrupt dummy sp sp ? 1 sp ? 2 sp ? 3 sp ? 4 vect h vect l start addr iab dummy pc ? 1[7:0] pc ? 1[15:8] x a ccr v data h v data l opcode i bit f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) program exception control mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 113 figure 7-9. interrupt processing no no no yes no no yes yes (as many interrupts i bit set? from reset break interrupt? i bit set? irq1 interrupt? swi instruction? rti instruction? fetch next instruction. unstack cpu registers. stack cpu registers. set i bit. load pc with interrupt vector. execute instruction. yes yes as exist on chip) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 114 system integration module (sim) motorola figure 7-10. interrupt recovery hardware interrupts a hardware interrupt does not stop the current instruction. processing of a hardware interrupt begins after completion of the current instruction. when the current instruction is complete, the sim checks all pending hardware interrupts. if interrupts are not masked (i bit clear in the condition code register), and if the corresponding interrupt enable bit is set, the sim proceeds with interrupt processing; otherwise, the next instruction is fetched and executed. if more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is serviced first. figure 7-11 demonstrates what happens when two interrupts are pending. if an interrupt is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the lda instruction is executed. the lda opcode is prefetched by both the int1 and int2 rti instructions. however, in the case of the int1 rti prefetch, this is a redundant operation. note: to maintain compatibility with the m68hc05, m6805 and m146805 families the h register is not pushed on the stack during interrupt entry. if the interrupt service routine modifies the h register or uses the indexed addressing mode, software should save the h register and then restore it prior to exiting the routine. module idb r/w interrupt sp ? 4 sp ? 3 sp ? 2 sp ? 1 sp pc pc + 1 iab ccr a x pc ? 1 [7:0] pc ? 1 [15:8] opcode operand i bit f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) program exception control mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 115 figure 7-11 . interrupt recognition example swi instruction the swi instruction is a non-maskable instruction that causes an interrupt regardless of the state of the interrupt mask (i bit) in the condition code register. note: a software interrupt pushes pc onto the stack. a software interrupt does not push pc ? 1, as a hardware interrupt does. 7.6.2 reset all reset sources always have higher priority than interrupts and cannot be arbitrated. cli lda int1 pulh rti int2 background #$ff pshh int1 interrupt service routine pulh rti pshh int2 interrupt service routine routine f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 116 system integration module (sim) motorola 7.6.3 break interrupts the break module can stop normal program flow at a software- programmable break point by asserting its break interrupt output. see break module (brk) on page 157. the sim puts the cpu into the break state by forcing it to the swi vector location. refer to the break interrupt subsection of each module to see how each module is affected by the break state. 7.6.4 status flag protection in break mode the sim controls whether status flags contained in other modules can be cleared during break mode. the user can select whether flags are protected from being cleared by properly initializing the break clear flag enable bit (bcfe) in the sim break flag control register (sbfcr). protecting flags in break mode ensures that set flags will not be cleared while in break mode. this protection allows registers to be freely read and written during break mode without losing status flag information. setting the bcfe bit enables the clearing mechanisms. once cleared in break mode, a flag remains cleared even when break mode is exited. status flags with a two-step clearing mechanism ? for example, a read of one register followed by the read or write of another ? are protected, even when the first step is accomplished prior to entering break mode. upon leaving break mode, execution of the second step will clear the flag as normal. 7.7 low-power modes executing the wait or stop instruction puts the mcu in a low power- consumption mode for standby situations. the sim holds the cpu in a non-clocked state. the operation of each of these modes is described below. both stop and wait clear the interrupt mask (i) in the condition code register, allowing interrupts to occur. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 117 7.7.1 wait mode in wait mode, the cpu clocks are inactive while one set of peripheral clocks continue to run. figure 7-12 shows the timing for wait mode entry. a module that is active during wait mode can wake up the cpu with an interrupt if the interrupt is enabled. stacking for the interrupt begins one cycle after the wait instruction during which the interrupt occurred. refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. some modules can be programmed to be active in wait mode. wait mode can also be exited by a reset or break. a break interrupt during wait mode sets the sim break wait bit, bw, in the sim break status register (sbsr). if the cop disable bit, copd, in the configuration register is logic 0, then the computer operating properly module (cop) is enabled and remains active in wait mode. figure 7-12. wait mode entry timing figure 7-13. wait recovery from interrupt or break wait addr + 1 same same iab idb previous data next opcode same wait addr same r/w note: previous data can be operand data or the wait opcode, depending on the last instruction. $6e0c $6e0b $00ff $00fe $00fd $00fc $a6 $a6 $01 $0b $6e $a6 iab idb exitstopwait note: exitstopwait = rst pin or cpu interrupt or break interrupt f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 118 system integration module (sim) motorola figure 7-14. wait recovery from internal reset 7.7.2 stop mode in stop mode, the sim counter is reset and the system clocks are disabled. an interrupt request from a module can cause an exit from stop mode. stacking for interrupts begins after the selected stop recovery time has elapsed. reset also causes an exit from stop mode. the sim disables the clock generator module outputs (cgmout and cgmxclk) in stop mode, stopping the cpu and peripherals. stop recovery time is selectable using the ssrec bit in the configuration register (config-1). if ssrec is set, stop recovery is reduced from the normal delay of 4096 cgmxclk cycles down to 32. this is ideal for applications using canned oscillators that do not require long startup times from stop mode. note: external crystal applications should use the full stop recovery time by clearing the ssrec bit. the break module is inactive in stop mode. the stop instruction does not affect break module register states. the sim counter is held in reset from the execution of the stop instruction until the beginning of stop recovery. it is then used to time the recovery period. figure 7-15 shows stop mode entry timing. iab idb rst $a6 $a6 $6e0b rst vct h rst vct l $a6 cgmxclk 32 cycles 32 cycles f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) sim registers mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 119 figure 7-15. stop mode entry timing figure 7-16. stop mode recovery from interrupt or break 7.8 sim registers the sim has three memory mapped registers. stop addr + 1 same same iab idb previous data next opcode same stop addr same r/w cpustop note: previous data can be operand data or the stop opcode, depending on the last instruction . cgmxclk int/break iab stop + 2 stop + 2 sp sp ? 1 sp ? 2 sp ? 3 stop +1 stop recovery period f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 120 system integration module (sim) motorola 7.8.1 sim break status register the sim break status register contains a flag to indicate that a break caused an exit from wait mode. bw ? sim break wait this status bit is useful in applications requiring a return to wait mode after exiting from a break interrupt. clear bw by writing a logic 0 to it. reset clears bw. 1 = wait mode was exited by break interrupt 0 = wait mode was not exited by break interrupt bw can be read within the break state swi routine. the user can modify the return address on the stack by subtracting one from it. the following code is an example of this. writing zero to the bw bit clears it. address: $fe00 bit 7654321bit 0 read: rrrrrr bw r write: see note reset: 0 r = reserved note: writing a logic 0 clears bw figure 7-17. sim break status register (sbsr) ; ; ; this code works if the h register has been pushed onto the stack in the break service routine software. this code should be executed at the end of the break service routine software. hibyte equ 5 lobyte equ 6 ; if not bw, do rti brclr bw,sbsr, return ; ; see if wait mode was exited by break. tst lobyte,sp ; if returnlo is not zero, bne dolo ; then just decrement low byte. dec hibyte,sp ; else deal with high byte, too. dolo dec lobyte,sp ; point to wait/stop opcode. return pulh rti ; restore h register. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) sim registers mc68HC908AS32A ? rev 0.0 advance information motorola system integration module (sim) 121 7.8.2 sim reset status register this register contains six flags that show the source of the last reset. the status register will automatically clear after reading it. a power-on reset sets the por bit and clears all other bits in the register. por ? power-on reset bit 1 = last reset caused by por circuit 0 = read of srsr pin ? external reset bit 1 = last reset caused by external reset pin (rst ) 0 = por or read of srsr cop ? computer operating properly reset bit 1 = last reset caused by cop counter 0 = por or read of srsr ilop ? illegal opcode reset bit 1 = last reset caused by an illegal opcode 0 = por or read of srsr ilad ? illegal address reset bit (opcode fetches only) 1 = last reset caused by an opcode fetch from an illegal address 0 = por or read of srsr lvi ? low-voltage inhibit reset bit 1 = last reset was caused by the lvi circuit 0 = por or read of srsr address: $fe01 bit 7654321bit 0 read: por pin cop ilop ilad 0 lvi 0 write: por:10000000 = unimplemented figure 7-18. sim reset status register (srsr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . system integration module (sim) advance information mc68HC908AS32A ? rev 0.0 122 system integration module (sim) motorola 7.8.3 sim break flag control register the sim break control register contains a bit that enables software to clear status bits while the mcu is in a break state. bcfe ? break clear flag enable bit this read/write bit enables software to clear status bits by accessing status registers while the mcu is in a break state. to clear status bits during the break state, the bcfe bit must be set. 1 = status bits clearable during break 0 = status bits not clearable during break address: $fe03 bit 7654321bit 0 read: bcferrrrrrr write: reset: 0 0 r= reserved figure 7-19. sim break flag control register (sbfcr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 123 technical data ? mc68HC908AS32A section 8. clock generator module (cgm) 8.1 contents 8.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 8.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 8.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.4.1 crystal oscillator circuit . . . . . . . . . . . . . . . . . . . . . . . . . 125 8.4.2 phase-locked loop circuit (pll) . . . . . . . . . . . . . . . . . . 127 8.4.2.1 circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 8.4.2.2 acquisition and tracking modes . . . . . . . . . . . . . . . . 129 8.4.2.3 manual and automatic pll bandwidth modes . . . . . 129 8.4.2.4 programming the pll . . . . . . . . . . . . . . . . . . . . . . . . . 131 8.4.2.5 special programming exceptions . . . . . . . . . . . . . . . 133 8.4.3 base clock selector circuit . . . . . . . . . . . . . . . . . . . . . . 133 8.4.4 cgm external connections . . . . . . . . . . . . . . . . . . . . . . . 134 8.5 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 8.5.1 crystal amplifier input pin (osc1) . . . . . . . . . . . . . . . . . 135 8.5.2 crystal amplifier output pin (osc2) . . . . . . . . . . . . . . . 135 8.5.3 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . 135 8.5.4 analog power pin (v dda ) . . . . . . . . . . . . . . . . . . . . . . . . . 136 8.5.5 oscillator enable signal (simoscen) . . . . . . . . . . . . . . 136 8.5.6 crystal output frequency signal (cgmxclk) . . . . . . . 136 8.5.7 cgm base clock output (cgmout) . . . . . . . . . . . . . . . 136 8.5.8 cgm cpu interrupt (cgmint) . . . . . . . . . . . . . . . . . . . . . 136 8.6 cgm registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 8.6.1 pll control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 8.6.2 pll bandwidth control register . . . . . . . . . . . . . . . . . . 139 8.6.3 pll programming register . . . . . . . . . . . . . . . . . . . . . . . 141 8.7 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 8.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 124 clock generator module (cgm) motorola 8.8.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 8.8.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 8.9 cgm during break interrupts . . . . . . . . . . . . . . . . . . . . . . . 144 8.10 acquisition/lock time specifications . . . . . . . . . . . . . . . . 144 8.10.1 acquisition/lock time definitions . . . . . . . . . . . . . . . . . 144 8.10.2 parametric influences on reaction time . . . . . . . . . . . . 146 8.10.3 choosing a filter capacitor . . . . . . . . . . . . . . . . . . . . . . 147 8.10.4 reaction time calculation . . . . . . . . . . . . . . . . . . . . . . . 147 8.2 introduction the cgm generates the crystal clock signal, cgmxclk, which operates at the frequency of the crystal. the cgm also generates the base clock signal, cgmout, from which the system clocks are derived. cgmout is based on either the crystal clock divided by two or the phase-locked loop (pll) clock, cgmvclk, divided by two. the pll is a frequency generator designed for use with 1-mhz to 8-mhz crystals or ceramic resonators. the pll can generate an 8-mhz bus frequency without using high frequency crystals. 8.3 features features of the cgm include: phase-locked loop with output frequency in integer multiples of the crystal reference programmable hardware voltage-controlled oscillator (vco) for low-jitter operation automatic bandwidth control mode for low-jitter operation automatic frequency lock detector cpu interrupt on entry or exit from locked condition f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) functional description mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 125 8.4 functional description the cgm consists of three major submodules: crystal oscillator circuit ? the crystal oscillator circuit generates the constant crystal frequency clock, cgmxclk. phase-locked loop (pll) ? the pll generates the programmable vco frequency clock cgmvclk. base clock selector circuit ? this software-controlled circuit selects either cgmxclk divided by two or the vco clock, cgmvclk, divided by two as the base clock, cgmout. the system clocks are derived from cgmout. figure 8-1 shows the structure of the cgm. 8.4.1 crystal oscillator circuit the crystal oscillator circuit consists of an inverting amplifier and an external crystal. the osc1 pin is the input to the amplifier and the osc2 pin is the output. the simoscen signal enables the crystal oscillator circuit. the cgmxclk signal is the output of the crystal oscillator circuit and runs at a rate equal to the crystal frequency. cgmxclk is then buffered to produce cgmrclk, the pll reference clock. cgmxclk can be used by other modules which require precise timing for operation. the duty cycle of cgmxclk is not guaranteed to be 50% and depends on external factors, including the crystal and related external components. an externally generated clock also can feed the osc1 pin of the crystal oscillator circuit. connect the external clock to the osc1 pin and let the osc2 pin float. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 126 clock generator module (cgm) motorola figure 8-1. cgm block diagram phase detector loop filter frequency divider voltage controlled oscillator bandwidth control lock detector clock cgmvdv cgmvclk interrupt control cgmint cgmrdv pll analog cgmrclk select circuit lock auto acq vrs7 ? vrs4 pllie pllf mul7 ? mul4 v dda cgmxfc v ss osc1 cgmxclk ptc3 monitor mode bcs 2 a b s* cgmout *when s = 1, cgmout = b user mode f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) functional description mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 127 8.4.2 phase-locked loop circuit (pll) the pll is a frequency generator that can operate in either acquisition mode or tracking mode, depending on the accuracy of the output frequency. the pll can change between acquisition and tracking modes either automatically or manually. 8.4.2.1 circuits the pll consists of these circuits: voltage-controlled oscillator (vco) modulo vco frequency divider phase detector register name bit 7654321bit 0 pll control register (pctl) read: pllie pllf pllon bcs 1111 write: reset:00101111 pll bandwidth control register (pbwc) read: auto lock acq xld 0000 write: reset:00000000 pll programming register (ppg) read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: reset:01100110 = unimplemented figure 8-2. i/o register summary table 8-1. i/o register address summary register pctl pbwc ppg address $001c $001d $001e f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 128 clock generator module (cgm) motorola loop filter lock detector the operating range of the vco is programmable for a wide range of frequencies and for maximum immunity to external noise, including supply and cgmxfc noise. the vco frequency is bound to a range from roughly one-half to twice the center-of-range frequency, f cgmvrs . modulating the voltage on the cgmxfc pin changes the frequency within this range. by design, f cgmvrs is equal to the nominal center-of- range frequency, f nom , (4.9152 mhz) times a linear factor l or (l)f nom . cgmrclk is the pll reference clock, a buffered version of cgmxclk. cgmrclk runs at a frequency, f cgmrclk , and is fed to the pll through a buffer. the buffer output is the final reference clock, cgmrdv, running at a frequency f cgmrdv =f cgmrclk . the vco ? s output clock, cgmvclk, running at a frequency f cgmvclk , is fed back through a programmable modulo divider. the modulo divider reduces the vco clock by a factor, n. the divider ? s output is the vco feedback clock, cgmvdv, running at a frequency f cgmvdv =f cgmvclk /n. see programming the pll for more information. the phase detector then compares the vco feedback clock, cgmvdv, with the final reference clock, cgmrdv. a correction pulse is generated based on the phase difference between the two signals. the loop filter then slightly alters the dc voltage on the external capacitor connected to cgmxfc based on the width and direction of the correction pulse. the filter can make fast or slow corrections depending on its mode, as described in acquisition and tracking modes on page 129. the value of the external capacitor and the reference frequency determines the speed of the corrections and the stability of the pll. the lock detector compares the frequencies of the vco feedback clock, cgmvdv, and the final reference clock, cgmrdv. therefore, the speed of the lock detector is directly proportional to the final reference frequency, f cgmrdv . the circuit determines the mode of the pll and the lock condition based on this comparison. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) functional description mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 129 8.4.2.2 acquisition and tracking modes the pll filter is manually or automatically configurable into one of two operating modes: acquisition mode ? in acquisition mode, the filter can make large frequency corrections to the vco. this mode is used at pll startup or when the pll has suffered a severe noise hit and the vco frequency is far off the desired frequency. when in acquisition mode, the acq bit is clear in the pll bandwidth control register. see pll bandwidth control register on page 139. tracking mode ? in tracking mode, the filter makes only small corrections to the frequency of the vco. pll jitter is much lower in tracking mode, but the response to noise is also slower. the pll enters tracking mode when the vco frequency is nearly correct, such as when the pll is selected as the base clock source. see base clock selector circuit on page 133. the pll is automatically in tracking mode when it ? s not in acquisition mode or when the acq bit is set. 8.4.2.3 manual and automatic pll bandwidth modes the pll can change the bandwidth or operational mode of the loop filter manually or automatically. in automatic bandwidth control mode (auto = 1), the lock detector automatically switches between acquisition and tracking modes. automatic bandwidth control mode also is used to determine when the vco clock, cgmvclk, is safe to use as the source for the base clock, cgmout. see pll bandwidth control register on page 139. if pll cpu interrupt requests are enabled, the software can wait for a pll cpu interrupt request and then check the lock bit. if cpu interrupts are disabled, software can poll the lock bit continuously (during pll startup, usually) or at periodic intervals. in either case, when the lock bit is set, the vco clock is safe to use as the source for the base clock. see base clock selector circuit on page 133. if the vco is selected as the source for the base clock and the lock bit is clear, the pll has suffered a severe noise hit and the software must take appropriate action, depending on the application. see interrupts on page 143. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 130 clock generator module (cgm) motorola these conditions apply when the pll is in automatic bandwidth control mode: the acq bit (see 8.6.2 pll bandwidth control register .) is a read-only indicator of the mode of the filter. see acquisition and tracking modes on page 129. the acq bit is set when the vco frequency is within a certain tolerance, ? trk , and is cleared when the vco frequency is out of a certain tolerance, ? unt . see electrical specifications on page 420. the lock bit is a read-only indicator of the locked state of the pll. the lock bit is set when the vco frequency is within a certain tolerance, ? lock , and is cleared when the vco frequency is out of a certain tolerance, ? unl . see electrical specifications on page 420. cpu interrupts can occur if enabled (pllie = 1) when the pll ? s lock condition changes, toggling the lock bit. see pll control register on page 137. the pll also can operate in manual mode (auto = 0). manual mode is used by systems that do not require an indicator of the lock condition for proper operation. such systems typically operate well below f busmax and require fast startup. the following conditions apply when in manual mode: acq is a writable control bit that controls the mode of the filter. before turning on the pll in manual mode, the acq bit must be clear. before entering tracking mode (acq = 1), software must wait a given time, t acq (see electrical specifications on page 420), after turning on the pll by setting pllon in the pll control register (pctl). software must wait a given time, t al , after entering tracking mode before selecting the pll as the clock source to cgmout (bcs = 1). the lock bit is disabled. cpu interrupts from the cgm are disabled. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) functional description mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 131 8.4.2.4 programming the pll use this 9-step procedure to program the pll. the table below lists the variables used and their meaning (please also reference figure 8-1 on page 126). 1. choose the desired bus frequency, f busdes . example: f busdes = 8 mhz 2. calculate the desired vco frequency, f vclkdes . f vclkdes = 4 f busdes example: f vclkdes = 4 8 mhz = 32 mhz 3. using a reference frequency, f rclk , equal to the crystal frequency, calculate the vco frequency multiplier, n. round the result to the nearest integer. example: 4. calculate the vco frequency, f cgmvclk . example: f cgmvclk = 8 4 mhz = 32 mhz table 8-2. variable definitions variable definition f busdes desired bus clock frequency f vclkdes desired vco clock frequency f cgmrclk chosen reference crystal frequency f cgmvclk calculated vco clock frequency f bus calculated bus clock frequency f nom nominal vco center frequency f cgmvrs shifted vco center frequency n f vclkdes f cgmrclk ------------------------- = n 32 mhz 4 mhz -------------------- =8 = f cgmvclk nf cgmrclk = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 132 clock generator module (cgm) motorola 5. calculate the bus frequency, f bus , and compare f bus with f busdes . example: 6. if the calculated f bus is not within the tolerance limits of your application, select another f busdes or another f rclk . 7. using the value 4.9152 mhz for f nom , calculate the vco linear range multiplier, l. the linear range multiplier controls the frequency range of the pll. example: 8. calculate the vco center-of-range frequency, f cgmvrs . the center-of-range frequency is the midpoint between the minimum and maximum frequencies attainable by the pll. f cgmvrs = l f nom example: f cgmvrs = 7 4.9152 mhz = 34.4 mhz note: for proper operation, . exceeding the recommended maximum bus frequency or vco frequency can crash the mcu. 9. program the pll registers accordingly: a. in the upper four bits of the pll programming register (ppg), program the binary equivalent of n. b. in the lower four bits of the pll programming register (ppg), program the binary equivalent of l. f bus f cgmvclk 4 ----------------------- - = f bus 32 mhz 4 -------------------- =8 mhz = l round f cgmvclk f nom ----------------------- - ?? ?? = l 32 mhz 4.9152 mhz ------------------------------- - = 7 = f cgmvrs f cgmvclk ? f nom 2 ---------------- f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) functional description mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 133 8.4.2.5 special programming exceptions the programming method described in programming the pll on page 131, does not account for two possible exceptions. a value of 0 for n or l is meaningless when used in the equations given. to account for these exceptions: a 0 value for n is interpreted the same as a value of 1. a 0 value for l disables the pll and prevents its selection as the source for the base clock. see base clock selector circuit on page 133. 8.4.3 base clock selector circuit this circuit is used to select either the crystal clock, cgmxclk, or the vco clock, cgmvclk, as the source of the base clock, cgmout. the two input clocks go through a transition control circuit that waits up to three cgmxclk cycles and three cgmvclk cycles to change from one clock source to the other. during this time, cgmout is held in stasis. the output of the transition control circuit is then divided by two to correct the duty cycle. therefore, the bus clock frequency, which is one-half of the base clock frequency, is one-fourth the frequency of the selected clock (cgmxclk or cgmvclk). the bcs bit in the pll control register (pctl) selects which clock drives cgmout. the vco clock cannot be selected as the base clock source if the pll is not turned on. the pll cannot be turned off if the vco clock is selected. the pll cannot be turned on or off simultaneously with the selection or deselection of the vco clock. the vco clock also cannot be selected as the base clock source if the factor l is programmed to a 0. this value would set up a condition inconsistent with the operation of the pll, so that the pll would be disabled and the crystal clock would be forced as the source of the base clock. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 134 clock generator module (cgm) motorola 8.4.4 cgm external connections in its typical configuration, the cgm requires seven external components. five of these are for the crystal oscillator and two are for the pll. the crystal oscillator is normally connected in a pierce oscillator configuration, as shown in figure 8-3 . figure 8-3 shows only the logical representation of the internal components and may not represent actual circuitry. the oscillator configuration uses five components: crystal, x 1 fixed capacitor, c 1 tuning capacitor, c 2 (can also be a fixed capacitor) feedback resistor, r b series resistor, r s (optional) the series resistor (r s ) may not be required for all ranges of operation, especially with high-frequency crystals. refer to the crystal manufacturer ? s data for more information. figure 8-3 also shows the external components for the pll: bypass capacitor, c byp filter capacitor, c f routing should be done with great care to minimize signal cross talk and noise. (see acquisition/lock time specifications on page 144 for routing information and more information on the filter capacitor ? s value and its effects on pll performance). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) i/o signals mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 135 figure 8-3. cgm external connections 8.5 i/o signals the following paragraphs describe the cgm input/output (i/o) signals. 8.5.1 crystal amplifier input pin (osc1) the osc1 pin is an input to the crystal oscillator amplifier. 8.5.2 crystal amplifier output pin (osc2) the osc2 pin is the output of the crystal oscillator inverting amplifier. 8.5.3 external filter capacitor pin (cgmxfc) the cgmxfc pin is required by the loop filter to filter out phase corrections. a small external capacitor is connected to this pin. note: to prevent noise problems, c f should be placed as close to the cgmxfc pin as possible with minimum routing distances and no routing of other signals across the c f connection. c 1 c 2 c f simoscen cgmxclk r b x 1 r s * c byp *r s can be 0 (shorted) when used with higher-frequency crystals. refer to manufacturer ? s data. osc1 osc2 v ss cgmxfc v dd v dda f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 136 clock generator module (cgm) motorola 8.5.4 analog power pin (v dda ) v dda is a power pin used by the analog portions of the pll. connect the v dda pin to the same voltage potential as the v dd pin. note: route v dda carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. 8.5.5 oscillator enable signal (simoscen) the simoscen signal enables the oscillator and pll. 8.5.6 crystal output frequency signal (cgmxclk) cgmxclk is the crystal oscillator output signal. it runs at the full speed of the crystal (f cgmxclk ) and comes directly from the crystal oscillator circuit. figure 8-3 shows only the logical relation of cgmxclk to osc1 and osc2 and may not represent the actual circuitry. the duty cycle of cgmxclk is unknown and may depend on the crystal and other external factors. also, the frequency and amplitude of cgmxclk can be unstable at startup. 8.5.7 cgm base clock output (cgmout) cgmout is the clock output of the cgm. this signal is used to generate the mcu clocks. cgmout is a 50% duty cycle clock running at twice the bus frequency. cgmout is software programmable to be either the oscillator output, cgmxclk, divided by two or the vco clock, cgmvclk, divided by two. 8.5.8 cgm cpu interrupt (cgmint) cgmint is the cpu interrupt signal generated by the pll lock detector. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) cgm registers mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 137 8.6 cgm registers three registers control and monitor operation of the cgm: pll control register (pctl) pll bandwidth control register (pbwc) pll programming register (ppg) 8.6.1 pll control register the pll control register contains the interrupt enable and flag bits, the on/off switch, and the base clock selector bit. pllie ? pll interrupt enable bit this read/write bit enables the pll to generate a cpu interrupt request when the lock bit toggles, setting the pll flag, pllf. when the auto bit in the pll bandwidth control register (pbwc) is clear, pllie cannot be written and reads as logic 0. reset clears the pllie bit. 1 = pll cpu interrupt requests enabled 0 = pll cpu interrupt requests disabled address: $001c bit 7654321bit 0 read: pllie pllf pllon bcs 1111 write: reset:00101111 = unimplemented figure 8-4. pll control register (pctl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 138 clock generator module (cgm) motorola pllf ? pll flag bit this read-only bit is set whenever the lock bit toggles. pllf generates a cpu interrupt request if the pllie bit also is set. pllf always reads as logic 0 when the auto bit in the pll bandwidth control register (pbwc) is clear. clear the pllf bit by reading the pll control register. reset clears the pllf bit. 1 = change in lock condition 0 = no change in lock condition note: do not inadvertently clear the pllf bit. be aware that any read or read- modify-write operation on the pll control register clears the pllf bit. pllon ? pll on bit this read/write bit activates the pll and enables the vco clock, cgmvclk. pllon cannot be cleared if the vco clock is driving the base clock, cgmout (bcs = 1). see base clock selector circuit on page 133. reset sets this bit so that the loop can stabilize as the mcu is powering up. 1 = pll on 0 = pll off bcs ? base clock select bit this read/write bit selects either the crystal oscillator output, cgmxclk, or the vco clock, cgmvclk, as the source of the cgm output, cgmout. cgmout frequency is one-half the frequency of the selected clock. bcs cannot be set while the pllon bit is clear. after toggling bcs, it may take up to three cgmxclk and three cgmvclk cycles to complete the transition from one source clock to the other. during the transition, cgmout is held in stasis. see base clock selector circuit on page 133. reset and the stop instruction clear the bcs bit. 1 = cgmvclk divided by two drives cgmout 0 = cgmxclk divided by two drives cgmout note: pllon and bcs have built-in protection that prevents the base clock selector circuit from selecting the vco clock as the source of the base clock if the pll is off. therefore, pllon cannot be cleared when bcs is set, and bcs cannot be set when pllon is clear. if the pll is off f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) cgm registers mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 139 (pllon = 0), selecting cgmvclk requires two writes to the pll control register. see base clock selector circuit on page 133. pctl3 ? pctl0 ? unimplemented these bits provide no function and always read as logic 1s. 8.6.2 pll bandwidth control register the pll bandwidth control register: selects automatic or manual (software-controlled) bandwidth control mode indicates when the pll is locked in automatic bandwidth control mode, indicates when the pll is in acquisition or tracking mode in manual operation, forces the pll into acquisition or tracking mode address: $001d bit 7654321bit 0 read: auto lock acq xld 0000 write: reset:00000000 = unimplemented figure 8-5. pll bandwidth control register (pbwc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 140 clock generator module (cgm) motorola auto ? automatic bandwidth control bit this read/write bit selects automatic or manual bandwidth control. when initializing the pll for manual operation (auto = 0), clear the acq bit before turning on the pll. reset clears the auto bit. 1 = automatic bandwidth control 0 = manual bandwidth control lock ? lock indicator bit when the auto bit is set, lock is a read-only bit that becomes set when the vco clock, cgmvclk, is locked (running at the programmed frequency). when the auto bit is clear, lock reads as logic 0 and has no meaning. reset clears the lock bit. 1 = vco frequency correct or locked 0 = vco frequency incorrect or unlocked acq ? acquisition mode bit when the auto bit is set, acq is a read-only bit that indicates whether the pll is in acquisition mode or tracking mode. when the auto bit is clear, acq is a read/write bit that controls whether the pll is in acquisition or tracking mode. in automatic bandwidth control mode (auto = 1), the last-written value from manual operation is stored in a temporary location and is recovered when manual operation resumes. reset clears this bit, enabling acquisition mode. 1 = tracking mode 0 = acquisition mode xld ? crystal loss detect bit when the vco output, cgmvclk, is driving cgmout, this read/write bit can indicate whether the crystal reference frequency is active or not. 1 = crystal reference not active 0 = crystal reference active f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) cgm registers mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 141 to check the status of the crystal reference, do the following: 1. write a logic 1 to xld. 2. wait n 4 cycles. n is the vco frequency multiplier. 3. read xld. the crystal loss detect function works only when the bcs bit is set, selecting cgmvclk to drive cgmout. when bcs is clear, xld always reads as logic 0. bits 3 ? 0 ? reserved for test these bits enable test functions not available in user mode. to ensure software portability from development systems to user applications, software should write 0s to bits 3 ? 0 when writing to pbwc. 8.6.3 pll programming register the pll programming register contains the programming information for the modulo feedback divider and the programming information for the hardware configuration of the vco. mul7 ? mul4 ? multiplier select bits these read/write bits control the modulo feedback divider that selects the vco frequency multiplier, n. (see circuits on page 127 and programming the pll on page 131). a value of $0 in the multiplier select bits configures the modulo feedback divider the same as a value of $1. reset initializes these bits to $6 to give a default multiply value of 6. address: $001e bit 7654321bit 0 read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: reset:01100110 figure 8-6. pll programming register (ppg) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 142 clock generator module (cgm) motorola note: the multiplier select bits have built-in protection that prevents them from being written when the pll is on (pllon = 1). vrs7 ? vrs4 ? vco range select bits these read/write bits control the hardware center-of-range linear multiplier l, which controls the hardware center-of-range frequency, f vrs . (see circuits on page 127, programming the pll on page 131, and pll control register on page 137.) vrs7 ? vrs4 cannot be written when the pllon bit in the pll control register (pctl) is set. see special programming exceptions on page 133. a value of $0 in the vco range select bits disables the pll and clears the bcs bit in the pctl. (see base clock selector circuit on page 133 and special programming exceptions on page 133 for more information.) reset initializes the bits to $6 to give a default range multiply value of 6. note: the vco range select bits have built-in protection that prevents them from being written when the pll is on (pllon = 1) and prevents selection of the vco clock as the source of the base clock (bcs = 1) if the vco range select bits are all clear. the vco range select bits must be programmed correctly. incorrect programming can result in failure of the pll to achieve lock. table 8-3. vco frequency multiplier (n) selection mul7:mul6:mul5:mul4 vco frequency multiplier (n) 0000 1 0001 1 0010 2 0011 3 1101 13 1110 14 1111 15 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) interrupts mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 143 8.7 interrupts when the auto bit is set in the pll bandwidth control register (pbwc), the pll can generate a cpu interrupt request every time the lock bit changes state. the pllie bit in the pll control register (pctl) enables cpu interrupt requests from the pll. pllf, the interrupt flag in the pctl, becomes set whether cpu interrupt requests are enabled or not. when the auto bit is clear, cpu interrupt requests from the pll are disabled and pllf reads as logic 0. software should read the lock bit after a pll cpu interrupt request to see if the request was due to an entry into lock or an exit from lock. when the pll enters lock, the vco clock, cgmvclk, divided by two can be selected as the cgmout source by setting bcs in the pctl. when the pll exits lock, the vco clock frequency is corrupt, and appropriate precautions should be taken. if the application is not frequency sensitive, cpu interrupt requests should be disabled to prevent pll interrupt service routines from impeding software performance or from exceeding stack limitations. note: software can select the cgmvclk divided by two as the cgmout source even if the pll is not locked (lock = 0). therefore, software should make sure the pll is locked before setting the bcs bit. 8.8 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 8.8.1 wait mode the cgm remains active in wait mode. before entering wait mode, software can disengage and turn off the pll by clearing the bcs and pllon bits in the pll control register (pctl). less power-sensitive applications can disengage the pll without turning it off. applications that require the pll to wake the mcu from wait mode also can deselect the pll output without turning off the pll. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 144 clock generator module (cgm) motorola 8.8.2 stop mode the stop instruction disables the cgm and holds low all cgm outputs (cgmxclk, cgmout, and cgmint). if cgmout is being driven by cgmvclk and a stop instruction is executed; the pll will clear the bcs bit in the pll control register, causing cgmout to be driven by cgmxclk. when the mcu recovers from stop, the crystal clock divided by two drives cgmout and bcs remains clear. 8.9 cgm during break interrupts the bcfe bit in the break flag control register (bfcr) enables software to clear status bits during the break state. see break module (brk) on page 157. to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect the pllf bit during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write the pll control register during the break state without affecting the pllf bit. 8.10 acquisition/lock time specifications the acquisition and lock times of the pll are, in many applications, the most critical pll design parameters. proper design and use of the pll ensures the highest stability and lowest acquisition/lock times. 8.10.1 acquisition/lock time definitions typical control systems refer to the acquisition time or lock time as the reaction time, within specified tolerances, of the system to a step input. in a pll, the step input occurs when the pll is turned on or when it suffers a noise hit. the tolerance is usually specified as a percent of the f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) acquisition/lock time specifications mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 145 step input or when the output settles to the desired value plus or minus a percent of the frequency change. therefore, the reaction time is constant in this definition, regardless of the size of the step input. for example, consider a system with a 5% acquisition time tolerance. if a command instructs the system to change from 0 hz to 1 mhz, the acquisition time is the time taken for the frequency to reach 1mhz 50 khz. fifty khz = 5% of the 1-mhz step input. if the system is operating at 1 mhz and suffers a ? 100 khz noise hit, the acquisition time is the time taken to return from 900 khz to 1 mhz 5 khz. five khz = 5% of the 100-khz step input. other systems refer to acquisition and lock times as the time the system takes to reduce the error between the actual output and the desired output to within specified tolerances. therefore, the acquisition or lock time varies according to the original error in the output. minor errors may not even be registered. typical pll applications prefer to use this definition because the system requires the output frequency to be within a certain tolerance of the desired frequency regardless of the size of the initial error. the discrepancy in these definitions makes it difficult to specify an acquisition or lock time for a typical pll. therefore, the definitions for acquisition and lock times for this module are: acquisition time, t acq , is the time the pll takes to reduce the error between the actual output frequency and the desired output frequency to less than the tracking mode entry tolerance, ? trk . acquisition time is based on an initial frequency error, (f des ? f orig )/f des , of not more than 100%. in automatic bandwidth control mode (see manual and automatic pll bandwidth modes on page 129), acquisition time expires when the acq bit becomes set in the pll bandwidth control register (pbwc). lock time, t lock , is the time the pll takes to reduce the error between the actual output frequency and the desired output frequency to less than the lock mode entry tolerance, ? lock . lock time is based on an initial frequency error, (f des ? f orig )/f des , of not more than 100%. in automatic bandwidth control mode, lock time f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 146 clock generator module (cgm) motorola expires when the lock bit becomes set in the pll bandwidth control register (pbwc). (see manual and automatic pll bandwidth modes on page 129). obviously, the acquisition and lock times can vary according to how large the frequency error is and may be shorter or longer in many cases. 8.10.2 parametric influences on reaction time acquisition and lock times are designed to be as short as possible while still providing the highest possible stability. these reaction times are not constant, however. many factors directly and indirectly affect the acquisition time. the most critical parameter which affects the reaction times of the pll is the reference frequency, f cgmrdv (please reference figure 8-1 ). this frequency is the input to the phase detector and controls how often the pll makes corrections. for stability, the corrections must be small compared to the desired frequency, so several corrections are required to reduce the frequency error. therefore, the slower the reference the longer it takes to make these corrections. this parameter is also under user control via the choice of crystal frequency f cgmxclk . another critical parameter is the external filter capacitor. the pll modifies the voltage on the vco by adding or subtracting charge from this capacitor. therefore, the rate at which the voltage changes for a given frequency error (thus a change in charge) is proportional to the capacitor size. the size of the capacitor also is related to the stability of the pll. if the capacitor is too small, the pll cannot make small enough adjustments to the voltage and the system cannot lock. if the capacitor is too large, the pll may not be able to adjust the voltage in a reasonable time. see choosing a filter capacitor on page 147. also important is the operating voltage potential applied to v dda . the power supply potential alters the characteristics of the pll. a fixed value is best. variable supplies, such as batteries, are acceptable if they vary within a known range at very slow speeds. noise on the power supply is not acceptable, because it causes small frequency errors which continually change the acquisition time of the pll. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) acquisition/lock time specifications mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 147 temperature and processing also can affect acquisition time because the electrical characteristics of the pll change. the part operates as specified as long as these influences stay within the specified limits. external factors, however, can cause drastic changes in the operation of the pll. these factors include noise injected into the pll through the filter capacitor, filter capacitor leakage, stray impedances on the circuit board, and even humidity or circuit board contamination. 8.10.3 choosing a filter capacitor as described in parametric influences on reaction time on page 146, the external filter capacitor, c f , is critical to the stability and reaction time of the pll. the pll is also dependent on reference frequency and supply voltage. the value of the capacitor must, therefore, be chosen with supply potential and reference frequency in mind. for proper operation, the external filter capacitor must be chosen according to this equation: for acceptable values of c fact , (see electrical specifications on page 420). for the value of v dda , choose the voltage potential at which the mcu is operating. if the power supply is variable, choose a value near the middle of the range of possible supply values. this equation does not always yield a commonly available capacitor size, so round to the nearest available size. if the value is between two different sizes, choose the higher value for better stability. choosing the lower size may seem attractive for acquisition time improvement, but the pll may become unstable. also, always choose a capacitor with a tight tolerance ( 20% or better) and low dissipation. 8.10.4 reaction time calculation the actual acquisition and lock times can be calculated using the equations below. these equations yield nominal values under the following conditions: c f c fact v dda f cgmrdv ------------------ - ?? ?? = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 148 clock generator module (cgm) motorola correct selection of filter capacitor, c f (see choosing a filter capacitor on page 147). room temperature operation negligible external leakage on cgmxfc negligible noise the k factor in the equations is derived from internal pll parameters. k acq is the k factor when the pll is configured in acquisition mode, and k trk is the k factor when the pll is configured in tracking mode. (see acquisition and tracking modes on page 129). note the inverse proportionality between the lock time and the reference frequency. in automatic bandwidth control mode, the acquisition and lock times are quantized into units based on the reference frequency. (see manual and automatic pll bandwidth modes on page 129). a certain number of clock cycles, n acq , is required to ascertain that the pll is within the tracking mode entry tolerance, ? trk , before exiting acquisition mode. a certain number of clock cycles, n trk , is required to ascertain that the pll is within the lock mode entry tolerance, ? lock . therefore, the acquisition time, t acq , is an integer multiple of n acq /f cgmrdv , and the acquisition to lock time, t al , is an integer multiple of n trk /f cgmrdv . also, since the average frequency over the entire measurement period must be within the specified tolerance, the total time usually is longer than t lock as calculated above. t acq v dda f cgmrdv ------------------- - ?? ?? 8 k acq ------------ - ?? ?? = t al v dda f cgmrdv ------------------- - ?? ?? 4 k trk ----------- - ?? ?? = t lock t acq t al + = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) acquisition/lock time specifications mc68HC908AS32A ? rev 0.0 advance information motorola clock generator module (cgm) 149 in manual mode, it is usually necessary to wait considerably longer than t lock before selecting the pll clock (see base clock selector circuit on page 133), because the factors described in parametric influences on reaction time on page 146, may slow the lock time considerably. when defining a limit in software for the maximum lock time, the value must allow for variation due to all of the factors mentioned in this section, especially due to the c f capacitor and application specific influences. the calculated lock time is only an indication and it is the customer ? s responsibility to allow enough of a guard band for their application. prior to finalizing any software and while determining the maximum lock time, take into account all device to device differences. typically, applications set the maximum lock time as an order of magnitude higher than the measured value. this is considered sufficient for all such device to device variation. motorola recommends measuring the lock time of the application system by utilizing dedicated software, running in flash, eeprom or ram. this should toggle a port pin when the pll is first configured and switched on, then again when it goes from acquisition to lock mode and finally again when the pll lock bit is set. the resultant waveform can be captured on an oscilloscope and used to determine the typical lock time for the microcontroller and the associated external application circuit. e.g. note: the filter capacitor should be fully discharged prior to making any measurements. t lock t acq t al t trk complete and lock set init. low signal on port pin t acq complete pll configured and switched on f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . clock generator module (cgm) advance information mc68HC908AS32A ? rev 0.0 150 clock generator module (cgm) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola configuration register (config-1) 151 technical data ? mc68HC908AS32A section 9. configuration register (config-1) 9.1 contents 9.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 9.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 9.2 introduction this section describes the configuration register (config-1), which contains bits that configure these options: resets caused by the lvi module power to the lvi module lvi enabled during stop mode stop mode recovery time (32 cgmxclk cycles or 4096 cgmxclk cycles) computer operating properly module (cop) stop instruction enable/disable. 9.3 functional description the configuration register is a write-once register. out of reset, the configuration register will read the default value. once the register is written, further writes will have no effect until a reset occurs. note: if the lvi module and the lvi reset signal are enabled, a reset occurs when v dd falls to a voltage, lvi tripf , and remains at or below that level f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . configuration register (config-1) advance information mc68HC908AS32A ? rev 0.0 152 configuration register (config-1) motorola for at least nine consecutive cpu cycles. once an lvi reset occurs, the mcu remains in reset until v dd rises to a voltage, lvi tripr . lvistop ? lvi stop mode enable bit lvistop enables the lvi module in stop mode. (see low voltage inhibit (lvi) on page 181). 1 = lvi enabled during stop mode 0 = lvi disabled during stop mode note: to have the lvi enabled in stop mode, the lvipwr must be at a logic 1 and the lvistop bit must be at a logic 1. take note that by enabling the lvi in stop mode, the stop i dd current will be higher. lvirst ? lvi reset enable bit lvirst enables the reset signal from the lvi module. (see low voltage inhibit (lvi) on page 181). 1 = lvi module resets enabled 0 = lvi module resets disabled address: $001f bit 7654321bit 0 read: lvistop r lvirst lvipwr ssrec copl stop copd write: reset:01110000 r=reserved figure 9-1. configuration register (config-1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . configuration register (config-1) functional description mc68HC908AS32A ? rev 0.0 advance information motorola configuration register (config-1) 153 lvipwr ? lvi power enable bit lvipwr enables the lvi module. (see low voltage inhibit (lvi) on page 181). 1 = lvi module power enabled 0 = lvi module power disabled ssrec ? short stop recovery bit ssrec enables the cpu to exit stop mode with a delay of 32 cgmxclk cycles instead of a 4096-cgmxclk cycle delay. (see system integration module (sim) on page 101). 1 = stop mode recovery after 32 cgmxclk cycles 0 = stop mode recovery after 4096 cgmxclk cycles note: if using an external crystal oscillator, do not set the ssrec bit. copl ? cop long timeout copl enables the shorter cop timeout period. (see computer operating properly (cop) on page 175). 1 = cop timeout period is 2 13 ? 2 4 cgmxclk cycles 0 = cop timeout period is 2 18 ? 2 4 cgmxclk cycles stop ? stop instruction enable bit stop enables the stop instruction. 1 = stop instruction enabled 0 = stop instruction treated as illegal opcode copd ? cop disable bit copd disables the cop module. (see computer operating properly (cop) on page 175). 1 = cop module disabled 0 = cop module enabled f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . configuration register (config-1) advance information mc68HC908AS32A ? rev 0.0 154 configuration register (config-1) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola configuration register (config-2) 155 technical data ? mc68HC908AS32A section 10. configuration register (config-2) 10.1 contents 10.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 10.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 10.2 introduction this section describes the configuration register (config-2). this register contains bits that configure these options: configures the device to either the mc68hc08azxx emulator or the mc68hc08asxx emulator 10.3 functional description the configuration register is a write-once register. out of reset, the configuration register will read the default. once the register is written, further writes will have no effect until a reset occurs. address: $fe09 bit 7654321bit 0 read: eediv clk rrras32arrr write: reset:00011000 figure 10-1. configuration register (config-2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . configuration register (config-2) advance information mc68HC908AS32A ? rev 0.0 156 configuration register (config-2) motorola eedivclk ? eeprom timebase divider clock select bit this bit selects the reference clock source for the eeprom timebase divider module. 1 = eexdiv clock input is driven by internal bus clock 0 = eexdiv clock input is driven by cgmxclk as32a ? device indicator bit this bit is used to distinguish mc68hc908as60a from older non- ? a ? suffix versions. 1 = ? a ? version 0 = non- ? a ? version f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola break module (brk) 157 technical data ? mc68HC908AS32A section 11. break module (brk) 11.1 contents 11.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 11.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 11.4.1 flag protection during break interrupts . . . . . . . . . . . . 159 11.4.2 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . 160 11.4.3 tim during break interrupts . . . . . . . . . . . . . . . . . . . . . . 160 11.4.4 cop during break interrupts . . . . . . . . . . . . . . . . . . . . . 160 11.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 11.5.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 11.5.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 11.6 break module registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 11.6.1 break status and control register . . . . . . . . . . . . . . . . . 161 11.6.2 break address registers . . . . . . . . . . . . . . . . . . . . . . . . . 162 11.2 introduction the break module can generate a break interrupt that stops normal program flow at a defined address to enter a background program. 11.3 features accessible i/o registers during break interrupts cpu-generated break interrupts software-generated break interrupts cop disabling during break interrupts f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . break module (brk) advance information mc68HC908AS32A ? rev 0.0 158 break module (brk) motorola 11.4 functional description when the internal address bus matches the value written in the break address registers, the break module issues a breakpoint signal to the cpu. the cpu then loads the instruction register with a software interrupt instruction (swi) after completion of the current cpu instruction. the program counter vectors to $fffc and $fffd ($fefc and $fefd in monitor mode). the following events can cause a break interrupt to occur: a cpu-generated address (the address in the program counter) matches the contents of the break address registers. software writes a logic 1 to the brka bit in the break status and control register. when a cpu-generated address matches the contents of the break address registers, the break interrupt begins after the cpu completes its current instruction. a return-from-interrupt instruction (rti) in the break routine ends the break interrupt and returns the mcu to normal operation. figure 11-1 shows the structure of the break module. figure 11-1. break module block diagram iab[15:8] iab[7:0] 8-bit comparator 8-bit comparator control break address register low break address register high iab[15:0] break f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . break module (brk) functional description mc68HC908AS32A ? rev 0.0 advance information motorola break module (brk) 159 11.4.1 flag protection during break interrupts the bcfe bit in the break flag control register (bfcr) enables software to clear status bits during the break state. register name bit 7654321bit 0 break address register high (brkh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 break address register low (brkl) read: bit 7654321bit 0 write: reset:00000000 break status and control register (bscr) read: brke brka 000000 write: reset:00000000 = unimplemented r = reserved figure 11-2. i/o register summary table 11-1. i/o register address summary register brkh brkl bscr address $fe0c $fe0d $fe0e f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . break module (brk) advance information mc68HC908AS32A ? rev 0.0 160 break module (brk) motorola 11.4.2 cpu during break interrupts the cpu starts a break interrupt by: loading the instruction register with the swi instruction loading the program counter with $fffc:$fffd ($fefc:$fefd in monitor mode) the break interrupt begins after completion of the cpu instruction in progress. if the break address register match occurs on the last cycle of a cpu instruction, the break interrupt begins immediately. 11.4.3 tim during break interrupts a break interrupt stops the timer counter. 11.4.4 cop during break interrupts the cop is disabled during a break interrupt when v hi is present on the rst pin. 11.5 low-power modes the wait and stop instructions put the mcu in low power-consump- tion standby modes. 11.5.1 wait mode if enabled, the break module is active in wait mode. the sim break wait bit (bw) in the sim break status register indicates whether wait was exited by a break interrupt. if so, the user can modify the return address on the stack by subtracting one from it. (see sim break status register on page 120). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . break module (brk) break module registers mc68HC908AS32A ? rev 0.0 advance information motorola break module (brk) 161 11.5.2 stop mode the break module is inactive in stop mode. the stop instruction does not affect break module register states. 11.6 break module registers these registers control and monitor operation of the break module: break address register high (brkh) break address register low (brkl) break status and control register (bscr) 11.6.1 break status and control register the break status and control register contains break module enable and status bits. brke ? break enable bit this read/write bit enables breaks on break address register matches. clear brke by writing a logic 0 to bit 7. reset clears the brke bit. 1 = breaks enabled on 16-bit address match 0 = breaks disabled on 16-bit address match address: $fe0e bit 7654321bit 0 read: brke brka 000000 write: reset:00000000 = unimplemented figure 11-3. break status and control register (bscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . break module (brk) advance information mc68HC908AS32A ? rev 0.0 162 break module (brk) motorola brka ? break active bit this read/write status and control bit is set when a break address match occurs. writing a logic 1 to brka generates a break interrupt. clear brka by writing a logic 0 to it before exiting the break routine. reset clears the brka bit. 1 = (when read) break address match 0 = (when read) no break address match 11.6.2 break address registers the break address registers contain the high and low bytes of the desired breakpoint address. reset clears the break address registers. register: brkh brkl address: $fe0c $fe0d bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 read: bit 7654321bit 0 write: reset:00000000 figure 11-4. break address registers (brkh and brkl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola monitor rom (mon) 163 technical data ? mc68HC908AS32A section 12. monitor rom (mon) 12.1 contents 12.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 12.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 12.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 12.4.1 entering monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . 166 12.4.2 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 12.4.3 echoing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12.4.4 break signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12.4.5 commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12.4.6 mc68hc908as60a baud rate . . . . . . . . . . . . . . . . . . . . 172 12.4.7 security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 12.2 introduction this section describes the monitor rom (mon). the monitor rom allows complete testing of the mcu through a single-wire interface with a host computer. 12.3 features features of the monitor rom include: normal user-mode pin functionality one pin dedicated to serial communication between monitor rom and host computer standard mark/space non-return-to-zero (nrz) communication with host computer f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) advance information mc68HC908AS32A ? rev 0.0 164 monitor rom (mon) motorola up to 28.8 kbaud communication with host computer execution of code in ram or flash flash security flash programming 12.4 functional description monitor rom receives and executes commands from a host computer. figure 12-1 shows a sample circuit used to enter monitor mode and communicate with a host computer via a standard rs-232 interface. while simple monitor commands can access any memory address, the mc68hc908as60a has a flash security feature to prevent external viewing of the contents of flash. proper procedures must be followed to verify flash content. access to the flash is denied to unauthorized users of customer specified software (see security on page 173). in monitor mode, the mcu can execute host-computer code in ram while all mcu pins except pta0 retain normal operating mode functions. all communication between the host computer and the mcu is through the pta0 pin. a level-shifting and multiplexing interface is required between pta0 and the host computer. pta0 is used in a wired-or configuration and requires a pullup resistor. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) functional description mc68HC908AS32A ? rev 0.0 advance information motorola monitor rom (mon) 165 figure 12-1. monitor mode circuit + + + 10 m ? x1 v dd v dda v hi mc145407 mc74hc125 68hc08 rst irq v dda /v ddaref cgmxfc osc1 osc2 v ss v dd pta0 v dd 10 k ? 0.1 f 0.1 f 1 k ? 6 5 2 4 3 1 db-25 2 3 7 20 18 17 19 16 15 v dd v dd v dd 20 pf 20 pf 10 f 10 f 10 f 10 f 1 2 4 7 14 3 0.1 f 4.9152 mhz 10 k ? ptc3 v dd 10 k ? b a note: position a ? bus clock = cgmxclk 4 or cgmvclk 4 position b ? bus clock = cgmxclk 2 (see note.) 5 6 + ptc0 ptc1 v dd 10 k ? v ssa * * = refer to table 12-9 for correct value. 9.1v f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) advance information mc68HC908AS32A ? rev 0.0 166 monitor rom (mon) motorola 12.4.1 entering monitor mode table 12-1 shows the pin conditions for entering monitor mode. enter monitor mode by either executing a software interrupt instruction (swi) or applying a logic 0 and then a logic 1 to the rst pin. once out of reset, the mcu waits for the host to send eight security bytes (see security on page 173). after the security bytes, the mcu sends a break signal (10 consecutive logic 0s) to the host computer, indicating that it is ready to receive a command. monitor mode uses alternate vectors for reset, swi, and break interrupt. the alternate vectors are in the $fe page instead of the $ff page and allow code execution from the internal monitor firmware instead of user code. the cop module is disabled in monitor mode as long as v hi (see 5.0 volt dc electrical characteristics on page 422), is applied to either the irq pin or the reset pin. (see system integration module (sim) on page 101 for more information on modes of operation). note: holding the ptc3 pin low when entering monitor mode causes a bypass of a divide-by-two stage at the oscillator. the cgmout frequency is equal to the cgmxclk frequency, and the osc1 input directly generates internal bus clocks. in this case, the osc1 signal must have a 50% duty cycle at maximum bus frequency. table 12-1. mode selection irq pin ptc0 pin ptc1 pin pta0 pin ptc3 pin mode cgmout bus frequency v hi (1) 1011monitor or v hi (1) 1010monitor cgmxclk 1. for v hi , 5.0 volt dc electrical characteristics on page 422, and maximum ratings on page 420. cgmxclk 2 ----------------------------- cgmvclk 2 ----------------------------- cgmout 2 -------------------------- cgmout 2 -------------------------- f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) functional description mc68HC908AS32A ? rev 0.0 advance information motorola monitor rom (mon) 167 table 12-2 is a summary of the differences between user mode and monitor mode. 12.4.2 data format communication with the monitor rom is in standard non-return-to-zero (nrz) mark/space data format. (see figure 12-2 and figure 12-3 .) the data transmit and receive rate can be anywhereup to 28.8 kbaud. transmit and receive baud rates must be identical. figure 12-2. monitor data format figure 12-3. sample monitor waveforms table 12-2. mode differences modes functions cop reset vector high reset vector low break vector high break vector low swi vector high swi vector low user enabled $fffe $ffff $fffc $fffd $fffc $fffd monitor disabled (1) 1. if the high voltage (v hi ) is removed from the irq pin while in monitor mode, the sim asserts its cop enable output. the cop is a mask option enabled or disabled by the copd bit in the configuration register. (see 5.0 volt dc electrical characteristics on page 422). $fefe $feff $fefc $fefd $fefc $fefd bit 5 start bit bit 0 bit 1 next stop bit start bit bit 2 bit 3 bit 4 bit 6 bit 7 bit 5 start bit bit 0 bit 1 next stop bit start bit bit 2 bit 3 bit 4 bit 6 bit 7 start bit bit 0 bit 1 next stop bit start bit bit 2 $a5 break bit 3bit 4bit 5bit 6bit 7 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) advance information mc68HC908AS32A ? rev 0.0 168 monitor rom (mon) motorola 12.4.3 echoing as shown in figure 12-4 , the monitor rom immediately echoes each received byte back to the pta0 pin for error checking. any result of a command appears after the echo of the last byte of the command. figure 12-4. read transaction 12.4.4 break signal a start bit followed by nine low bits is a break signal. (see figure 12-5 ). when the monitor receives a break signal, it drives the pta0 pin high for the duration of two bits before echoing the break signal. figure 12-5. break transaction 12.4.5 commands the monitor rom uses these commands: addr. high read read addr. high addr. low addr. low data echo sent to monitor result 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 missing stop bit two-stop-bit delay before zero echo f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) functional description mc68HC908AS32A ? rev 0.0 advance information motorola monitor rom (mon) 169 read, read memory write, write memory iread, indexed read iwrite, indexed write readsp, read stack pointer run, run user program a sequence of iread or iwrite commands can access a block of memory sequentially over the full 64-kbyte memory map. table 12-3. read (read memory) command description read byte from memory operand specifies 2-byte address in high byte:low byte order data returned returns contents of specified address opcode $4a command sequence addr. high read read addr. high addr. low addr. low data echo sent to monitor result f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) advance information mc68HC908AS32A ? rev 0.0 170 monitor rom (mon) motorola table 12-4. write (write memory) command description write byte to memory operand specifies 2-byte address in high byte:low byte order; low byte followed by data byte data returned none opcode $49 command sequence addr. high write write addr. high addr. low addr. low data echo sent to monitor data table 12-5. iread (indexed read) command description read next 2 bytes in memory from last address accessed operand specifies 2-byte address in high byte:low byte order data returned returns contents of next two addresses opcode $1a command sequence data iread iread data echo sent to monitor result f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) functional description mc68HC908AS32A ? rev 0.0 advance information motorola monitor rom (mon) 171 table 12-6. iwrite (indexed write) command description write to last address accessed + 1 operand specifies single data byte data returned none opcode $19 command sequence data iwrite iwrite data echo sent to monitor table 12-7. readsp (read stack pointer) command description reads stack pointer operand none data returned returns stack pointer in high byte:low byte order opcode $0c command sequence sp high readsp readsp sp low echo sent to monitor result f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) advance information mc68HC908AS32A ? rev 0.0 172 monitor rom (mon) motorola 12.4.6 mc68hc908as60a baud rate with a 4.9152-mhz crystal and the ptc3 pin at logic 1 during reset, data is transferred between the monitor and host at 4800 baud. if the ptc3 pin is at logic 0 during reset, the monitor baud rate is 9600. when the cgm output, cgmout, is driven by the pll, the baud rate is determined by the mul[7:4] bits in the pll programming register (ppg). (see clock generator module (cgm) on page 123). care should be taken when setting the baud rate since incorrect baud rate setting can result in communications failure. table 12-8. run (run user program) command description executes rti instruction operand none data returned none opcode $28 command sequence run run echo sent to monitor table 12-9. mc68hc908as60a monitor baud rate selection monitor baud rate vco frequency multiplier (n) 123456 4.9152 mhz 4800 9600 14,400 19,200 24,000 28,800 4.194 mhz 4096 8192 12,288 16,384 20,480 24,576 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) functional description mc68HC908AS32A ? rev 0.0 advance information motorola monitor rom (mon) 173 12.4.7 security a security feature discourages unauthorized reading of flash locations while in monitor mode. the host can bypass the security feature at monitor mode entry by sending eight security bytes that match the bytes at locations $fff6 ? $fffd. locations $fff6 ? $fffd contain user- defined data. note: do not leave locations $fff6 ? $fffd blank. for security reasons, program locations $fff6 ? $fffd even if they are not used for vectors. if flash is unprogrammed, the eight security byte values to be sent are $ff, the unprogrammed state of flash. during monitor mode entry, the mcu waits after the power-on reset for the host to send the eight security bytes on pin pa0. figure 12-6. monitor mode entry timing if the received bytes match those at locations $fff6 ? $fffd, the host bypasses the security feature and can read all flash locations and execute code from flash. security remains bypassed until a power-on reset occurs. after the host bypasses security, any reset other than a byte 1 byte 1 echo byte 2 byte 2 echo byte 8 byte 8 echo command command echo pa0 pa7 rst v dd 4096 + 32 cgmxclk cycles 24 cgmxclk cycles 256 cgmxclk cycles (one bit time) 1 4 1 1 2 1 break note: 1 = echo delay (2 bit times) 2 = data return delay (2 bit times) 4 = wait 1 bit time before sending next byte. 4 from host from mcu f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) advance information mc68HC908AS32A ? rev 0.0 174 monitor rom (mon) motorola power-on reset requires the host to send another eight bytes. if the reset was not a power-on reset, the security remains bypassed regardless of the data that the host sends. if the received bytes do not match the data at locations $fff6 ? $fffd, the host fails to bypass the security feature. the mcu remains in monitor mode, but reading flash locations returns undefined data, and trying to execute code from flash causes an illegal address reset. after the host fails to bypass security, any reset other than a power-on reset causes an endless loop of illegal address resets. after receiving the eight security bytes from the host, the mcu transmits a break character signalling that it is ready to receive a command. note: the mcu does not transmit a break character until after the host sends the eight security bytes. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola computer operating properly (cop) 175 technical data ? mc68HC908AS32A section 13. computer operating properly (cop) 13.1 contents 13.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 13.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 13.4 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13.4.1 cgmxclk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13.4.2 stop instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13.4.3 copctl write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.4 power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.5 internal reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.6 reset vector fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.7 copd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.4.8 copl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 13.5 cop control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.6 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.7 monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.8.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 13.8.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 13.9 cop module during break interrupts . . . . . . . . . . . . . . . . . 180 13.2 introduction the cop module contains a free-running counter that generates a reset if allowed to overflow. the cop module helps software recover from runaway code. prevent a cop reset by periodically clearing the cop counter. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . computer operating properly (cop) advance information mc68HC908AS32A ? rev 0.0 176 computer operating properly (cop) motorola 13.3 functional description the cop counter is a free-running 6-bit counter preceded by a 12-bit prescaler. if not cleared by software, the cop counter overflows and generates an asynchronous reset after 2 13 ? 2 4 or 2 18 ? 2 4 cgmxclk cycles, depending on the state of the cop long timeout bit, copl, in the config-1. when copl = 0, a 4.9152-mhz crystal gives a cop timeout period of 53.3 ms. writing any value to location $ffff before an overflow occurs prevents a cop reset by clearing the cop counter and stages 4 ? 12 of the sim counter. note: service the cop immediately after reset and before entering or after exiting stop mode to guarantee the maximum time before the first cop counter overflow. a cop reset pulls the rst pin low for 32 cgmxclk cycles and sets the cop bit in the reset status register (rsr). in monitor mode, the cop is disabled if the rst pin or the irq pin is held at v hi . during the break state, v hi on the rst pin disables the cop. note: place cop clearing instructions in the main program and not in an interrupt subroutine. such an interrupt subroutine could keep the cop from generating a reset even while the main program is not working properly. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . computer operating properly (cop) i/o signals mc68HC908AS32A ? rev 0.0 advance information motorola computer operating properly (cop) 177 13.4 i/o signals the following paragraphs describe the signals shown in figure 13-1 . 13.4.1 cgmxclk cgmxclk is the crystal oscillator output signal. cgmxclk frequency is equal to the crystal frequency. 13.4.2 stop instruction the stop instruction clears the cop prescaler. figure 13-1. cop block diagram copctl write cgmxclk reset vector fetch reset reset status internal reset sources stop instruction clear stages 4 ? 12 clear all stages 6-bit cop counter copd from config-1 reset copctl write clear cop counter copl from config-1 12-bit cop prescaler register f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . computer operating properly (cop) advance information mc68HC908AS32A ? rev 0.0 178 computer operating properly (cop) motorola 13.4.3 copctl write writing any value to the cop control register (copctl) (see cop control register on page 179), clears the cop counter and clears stages 12 through 4 of the cop prescaler. reading the cop control register returns the reset vector. 13.4.4 power-on reset the power-on reset (por) circuit clears the cop prescaler 4096 cgmxclk cycles after power-up. 13.4.5 internal reset an internal reset clears the cop prescaler and the cop counter. 13.4.6 reset vector fetch a reset vector fetch occurs when the vector address appears on the data bus. a reset vector fetch clears the cop prescaler. 13.4.7 copd the copd signal reflects the state of the cop disable bit (copd) in the configuration register. (see configuration register (config-1) on page 151). 13.4.8 copl the copl signal reflects the state of the cop rate select bit. (copl) in the configuration register. (see configuration register (config-1) on page 151). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . computer operating properly (cop) cop control register mc68HC908AS32A ? rev 0.0 advance information motorola computer operating properly (cop) 179 13.5 cop control register the cop control register is located at address $ffff and overlaps the reset vector. writing any value to $ffff clears the cop counter and starts a new timeout period. reading location $ffff returns the low byte of the reset vector. 13.6 interrupts the cop does not generate cpu interrupt requests. 13.7 monitor mode the cop is disabled in monitor mode when v hi is present on the irq pin or on the rst pin. 13.8 low-power modes the wait and stop instructions put the mcu in low power-consump- tion standby modes. 13.8.1 wait mode the cop remains active in wait mode. to prevent a cop reset during wait mode, periodically clear the cop counter in a cpu interrupt routine. address: $ffff bit 7654321bit 0 read: low byte of reset vector write: clear cop counter reset: unaffected by reset figure 13-2. cop control register (copctl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . computer operating properly (cop) advance information mc68HC908AS32A ? rev 0.0 180 computer operating properly (cop) motorola 13.8.2 stop mode stop mode turns off the cgmxclk input to the cop and clears the cop prescaler. service the cop immediately before entering or after exiting stop mode to ensure a full cop timeout period after entering or exiting stop mode. the stop bit in the configuration register (config) enables the stop instruction. to prevent inadvertently turning off the cop with a stop instruction, disable the stop instruction by clearing the stop bit. 13.9 cop module during break interrupts the cop is disabled during a break interrupt when v hi is present on the rst pin. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola low voltage inhibit (lvi) 181 technical data ? mc68HC908AS32A section 14. low voltage inhibit (lvi) 14.1 contents 14.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 14.4.1 polled lvi operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.4.2 forced reset operation . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.4.3 false reset protection . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.5 lvi status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.6 lvi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 14.7.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 14.7.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 14.2 introduction this section describes the (tsmc .5u) low-voltage inhibit module (lvim26or43_tsmc_b10), which monitors the voltage on the v dd pin and can force a reset when the v dd voltage falls to the lvi trip voltage. 14.3 features features of the lvi module include: programmable lvi reset programmable power consumption f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . low voltage inhibit (lvi) advance information mc68HC908AS32A ? rev 0.0 182 low voltage inhibit (lvi) motorola note: if a low voltage interrupt (lvi) occurs during programming of eeprom or flash memory, then adequate programming time may not have been allowed to ensure the integrity and retention of the data. it is the responsibility of the user to ensure that in the event of an lvi any addresses being programmed receive specification programming conditions. 14.4 functional description figure 14-1 shows the structure of the lvi module. the lvi is enabled out of reset. the lvi module contains a bandgap reference circuit and comparator. the lvi power bit, lvipwr, enables the lvi to monitor v dd voltage. the lvi reset bit, lvirst, enables the lvi module to generate a reset when v dd falls below a voltage, lvi tripf , and remains at or below that level for nine or more consecutive cpu cycles. note that short v dd spikes may not trip the lvi. it is the user ? s responsibility to ensure a clean v dd signal within the specified operating voltage range if normal microcontroller operation is to be guaranteed. lvistop, enables the lvi module during stop mode. this will ensure when the stop instruction is implemented, the lvi will continue to monitor the voltage level on v dd . lvipwr, lvistop, and lvirst are in the configuration register, config-1 (see configuration register (config-1) on page 151). once an lvi reset occurs, the mcu remains in reset until v dd rises above a voltage, lvi tripr . v dd must be above lvi tripr for only one cpu cycle to bring the mcu out of reset (see forced reset operation on page 184). the output of the comparator controls the state of the lviout flag in the lvi status register (lvisr). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . low voltage inhibit (lvi) functional description mc68HC908AS32A ? rev 0.0 advance information motorola low voltage inhibit (lvi) 183 an lvi reset also drives the rst pin low to provide low-voltage protection to external peripheral devices. 14.4.1 polled lvi operation in applications that can operate at v dd levels below the lvi tripf level, software can monitor v dd by polling the lviout bit. in the configuration register, the lvipwr bit must be at logic 1 to enable the lvi module, and the lvirst bit must be at logic 0 to disable lvi resets. figure 14-1. lvi module block diagram figure 14-2. lvi i/o register summary addr. register name bit 7654321bit 0 $fe0f lvi status register (lvisr) lviout = unimplemented low v dd lvirst v dd > lvi trip = 0 v dd < lvi trip = 1 lviout lvipwr detector v dd lvi reset from config-1 from config-1 cpu clock anlgtrip stop mode filter bypass from config-1 lvistop f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . low voltage inhibit (lvi) advance information mc68HC908AS32A ? rev 0.0 184 low voltage inhibit (lvi) motorola 14.4.2 forced reset operation in applications that require v dd to remain above the lvi tripf level, enabling lvi resets allows the lvi module to reset the mcu when v dd falls to the lvi tripf level and remains at or below that level for nine or more consecutive cpu cycles. in the configuration register, the lvipwr and lvirst bits must be at logic 1 to enable the lvi module and to enable lvi resets. 14.4.3 false reset protection in order for the lvi module to reset the mcu,v dd must remain at or below the lvi tripf level for nine or more consecutive cpu cycles. v dd must be above lvi tripr for only one cpu cycle to bring the mcu out of reset. 14.5 lvi status register the lvi status register flags v dd voltages below the lvi tripf level . address: $fe0f bit 7654321bit 0 read: lviout 0000000 write: reset:00000000 = unimplemented figure 14-3. lvi status register (lvisr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . low voltage inhibit (lvi) lvi interrupts mc68HC908AS32A ? rev 0.0 advance information motorola low voltage inhibit (lvi) 185 lviout ? lvi output bit this read-only flag becomes set when the v dd voltage falls below the lvi tripf voltage for 32 to 40 cgmxclk cycles. (see table 14-1 ). reset clears the lviout bit. 14.6 lvi interrupts the lvi module does not generate interrupt requests. 14.7 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 14.7.1 wait mode with the lvipwr bit in the configuration register programmed to logic 1, the lvi module is active after a wait instruction. with the lvirst bit in the configuration register programmed to logic 1, the lvi module can generate a reset and bring the mcu out of wait mode. table 14-1. lviout bit indication v dd lviout at level: for number of cgmxclk cycles: v dd > lvi tripr any 0 v dd < lvi tripf < 32 cgmxclk cycles 0 v dd < lvi tripf between 32 and 40 cgmxclk cycles 0 or 1 v dd < lvi tripf > 40 cgmxclk cycles 1 lvi tripf < v dd < lvi tripr any previous value f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . low voltage inhibit (lvi) advance information mc68HC908AS32A ? rev 0.0 186 low voltage inhibit (lvi) motorola 14.7.2 stop mode with the lvistop and lvipwr bits in the configuration register programmed to a logic 1, the lvi module will be active after a stop instruction. because cpu clocks are disabled during stop mode, the lvi trip will generate a reset and bring the mcu out of stop. with the lvipwr bit in the configuration register programmed to logic 1 and the lvistop bit at a logic 0, the lvi module will be inactive after a stop instruction. note that the lvi feature is intended to provide the safe shutdown of the microcontroller and thus protection of related circuitry prior to any application v dd voltage collapsing completely to an unsafe level. it is not intended that users operate the microcontroller at lower than specified operating voltage v dd . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola external interrupt module (irq) 187 technical data ? mc68HC908AS32A section 15. external interrupt module (irq) 15.1 contents 15.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 15.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 15.5 irq pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 15.6 irq module during break interrupts . . . . . . . . . . . . . . . . . 192 15.7 irq status and control register . . . . . . . . . . . . . . . . . . . . . 192 15.2 introduction this section describes the nonmaskable external interrupt (irq) input. 15.3 features features include: dedicated external interrupt pin (irq ) hysteresis buffer programmable edge-only or edge- and level-interrupt sensitivity automatic interrupt acknowledge f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) advance information mc68HC908AS32A ? rev 0.0 188 external interrupt module (irq) motorola 15.4 functional description a logic 0 applied to the external interrupt pin can latch a cpu interrupt request. figure 15-1 shows the structure of the irq module. interrupt signals on the irq pin are latched into the irq latch. an interrupt latch remains set until one of the following actions occurs: vector fetch ? a vector fetch automatically generates an interrupt acknowledge signal that clears the latch that caused the vector fetch. software clear ? software can clear an interrupt latch by writing to the appropriate acknowledge bit in the interrupt status and control register (iscr). writing a logic 1 to the ack bit clears the irq latch. reset ? a reset automatically clears both interrupt latches. figure 15-1. irq block diagram ack imask dq ck clr irq high interrupt to mode select logic irq latch request irq v dd mode voltage detect synchro- nizer irqf to cpu for bil/bih instructions vector fetch decoder internal address bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) functional description mc68HC908AS32A ? rev 0.0 advance information motorola external interrupt module (irq) 189 the external interrupt pin is falling-edge triggered and is software- configurable to be both falling-edge and low-level triggered. the mode bit in the iscr controls the triggering sensitivity of the irq pin. when an interrupt pin is edge-triggered only, the interrupt latch remains set until a vector fetch, software clear, or reset occurs. when an interrupt pin is both falling-edge and low-level-triggered, the interrupt latch remains set until both of the following occur: vector fetch or software clear return of the interrupt pin to logic 1 the vector fetch or software clear may occur before or after the interrupt pin returns to logic 1. as long as the pin is low, the interrupt request remains pending. a reset will clear the latch and the mode1 control bit, thereby clearing the interrupt even if the pin stays low. when set, the imask bit in the iscr masks all external interrupt requests. a latched interrupt request is not presented to the interrupt priority logic unless the corresponding imask bit is clear. note: the interrupt mask (i) in the condition code register (ccr) masks all interrupt requests, including external interrupt requests. (see figure 15-2 ). table 15-1. irq i/o register summary addr. register name bit 7 6 5 4 3 2 1 bit 0 $001a irq status/control register (iscr) read: 0 0 0 0 irqf 0 imask mode write:rrrrrack r= reserved f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) advance information mc68HC908AS32A ? rev 0.0 190 external interrupt module (irq) motorola figure 15-2. irq interrupt flowchart from reset i bit set? fetch next yes no interrupt? instruction. swi instruction? rti instruction? no stack cpu registers. no set i bit. load pc with interrupt vector. no yes unstack cpu registers. execute instruction. yes yes f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) irq pin mc68HC908AS32A ? rev 0.0 advance information motorola external interrupt module (irq) 191 15.5 irq pin a logic 0 on the irq pin can latch an interrupt request into the irq latch. a vector fetch, software clear, or reset clears the irq latch. if the mode bit is set, the irq pin is both falling-edge sensitive and low- level sensitive. with mode set, both of the following actions must occur to clear the irq latch: vector fetch or software clear ? a vector fetch generates an interrupt acknowledge signal to clear the latch. software may generate the interrupt acknowledge signal by writing a logic 1 to the ack bit in the interrupt status and control register (iscr). the ack bit is useful in applications that poll the irq pin and require software to clear the irq latch. writing to the ack bit can also prevent spurious interrupts due to noise. setting ack does not affect subsequent transitions on the irq pin. a falling edge on irq that occurs after writing to the ack bit latches another interrupt request. if the irq mask bit, imask, is clear, the cpu loads the program counter with the vector address at locations $fffa and $fffb. return of the irq pin to logic 1 ? as long as the irq pin is at logic 0, the irq1 latch remains set. the vector fetch or software clear and the return of the irq pin to logic 1 can occur in any order. the interrupt request remains pending as long as the irq pin is at logic 0. a reset will clear the latch and the mode control bit, thereby clearing the interrupt even if the pin stays low. if the mode bit is clear, the irq pin is falling-edge sensitive only. with mode clear, a vector fetch or software clear immediately clears the irq latch. the irqf bit in the iscr register can be used to check for pending interrupts. the irqf bit is not affected by the imask bit, which makes it useful in applications where polling is preferred. use the bih or bil instruction to read the logic level on the irq pin. note: when using the level-sensitive interrupt trigger, avoid false interrupts by masking interrupt requests in the interrupt routine. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) advance information mc68HC908AS32A ? rev 0.0 192 external interrupt module (irq) motorola 15.6 irq module during break interrupts the system integration module (sim) controls whether the irq interrupt latch can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear the latches during the break state. (see sim break flag control register on page 122 to allow software to clear the irq latch during a break interrupt, write a logic 1 to the bcfe bit. if a latch is cleared during the break state, it remains cleared when the mcu exits the break state. to protect the latch during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), writing to the ack bit in the irq status and control register during the break state has no effect on the irq latch. 15.7 irq status and control register the irq status and control register (iscr) controls and monitors operation of the irq module. the iscr has these functions: shows the state of the irq interrupt flag clears the irq interrupt latch masks irq interrupt request controls triggering sensitivity of the irq interrupt pin address: $001a bit 7654321bit 0 read: 0000irqf0 imask mode write:rrrrrack reset:00000000 r= reserved figure 15-3. irq status and control register (iscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) irq status and control register mc68HC908AS32A ? rev 0.0 advance information motorola external interrupt module (irq) 193 irqf ? irq flag bit this read-only status bit is high when the irq interrupt is pending. 1 = irq interrupt pending 0 = irq interrupt not pending ack ? irq interrupt request acknowledge bit writing a logic 1 to this write-only bit clears the irq latch. ack always reads as logic 0. reset clears ack. imask ? irq interrupt mask bit writing a logic 1 to this read/write bit disables irq interrupt requests. reset clears imask. 1 = irq interrupt requests disabled 0 = irq interrupt requests enabled mode ? irq edge/level select bit this read/write bit controls the triggering sensitivity of the irq pin. reset clears mode. 1 = irq interrupt requests on falling edges and low levels 0 = irq interrupt requests on falling edges only f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . external interrupt module (irq) advance information mc68HC908AS32A ? rev 0.0 194 external interrupt module (irq) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 195 technical data ? mc68HC908AS32A section 16. serial communications interface (sci) 16.1 contents 16.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 16.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 16.4 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 16.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 16.5.1 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 16.5.2 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 16.5.2.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 16.5.2.2 character transmission . . . . . . . . . . . . . . . . . . . . . . . 200 16.5.2.3 break characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 16.5.2.4 idle characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 16.5.2.5 inversion of transmitted output . . . . . . . . . . . . . . . . 205 16.5.2.6 transmitter interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 205 16.5.3 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 16.5.3.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 16.5.3.2 character reception . . . . . . . . . . . . . . . . . . . . . . . . . . 208 16.5.3.3 data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 16.5.3.4 framing errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 16.5.3.5 baud rate tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . 211 16.5.3.6 receiver wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 16.5.3.7 receiver interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 16.5.3.8 error interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 16.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 16.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 16.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 16.7 sci during break module interrupts . . . . . . . . . . . . . . . . . . 216 16.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 16.8.1 pte0/sctxd (transmit data) . . . . . . . . . . . . . . . . . . . . . 217 16.8.2 pte1/scrxd (receive data) . . . . . . . . . . . . . . . . . . . . . . 217 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 196 serial communications interface (sci) motorola 16.9 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 16.9.1 sci control register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 16.9.2 sci control register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 16.9.3 sci control register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 16.9.4 sci status register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 16.9.5 sci status register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 16.9.6 sci data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 16.9.7 sci baud rate register . . . . . . . . . . . . . . . . . . . . . . . . . . 231 16.2 introduction the sci allows asynchronous communications with peripheral devices and other mcus. 16.3 features the sci module ? s features include: full duplex operation standard mark/space non-return-to-zero (nrz) format 32 programmable baud rates programmable 8-bit or 9-bit character length separately enabled transmitter and receiver separate receiver and transmitter cpu interrupt requests programmable transmitter output polarity two receiver wakeup methods: ? idle line wakeup ? address mark wakeup interrupt-driven operation with eight interrupt flags: ? transmitter empty ? transmission complete ? receiver full f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) pin name conventions mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 197 ? idle receiver input ? receiver overrun ? noise error ? framing error ? parity error receiver framing error detection hardware parity checking 1/16 bit-time noise detection 16.4 pin name conventions the generic names of the sci input/output (i/o) pins are: rxd (receive data) txd (transmit data) sci i/o lines are implemented by sharing parallel i/o port pins. the full name of an sci input or output reflects the name of the shared port pin. table 16-1 shows the full names and the generic names of the sci i/o pins.the generic pin names appear in the text of this section. 16.5 functional description figure 16-1 shows the structure of the sci module. the sci allows full- duplex, asynchronous, nrz serial communication between the mcu and remote devices, including other mcus. the transmitter and receiver of the sci operate independently, although they use the same baud rate generator. during normal operation, the cpu monitors the status of the sci, writes the data to be transmitted, and processes received data. table 16-1. pin name conventions generic pin names rxd txd full pin names pte1/scrxd pte0/sctxd f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 198 serial communications interface (sci) motorola figure 16-1. sci module block diagram scte tc scrf idle or nf fe pe sctie tcie scrie ilie te re rwu sbk r8 t8 orie feie peie bkf rpf sci data receive shift register sci data register transmit shift register neie m wake ilty flag control transmit control receive control data selection control wakeup pty pen register transmitter interrupt control receiver interrupt control error interrupt control control ensci loops ensci internal bus txinv loops 4 16 pre- scaler baud rate generator cgmxclk rxd txd f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 199 register name bit 7654321bit 0 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset:00000000 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 sci control register 3 (scc3) read: r8 t8 r r orie neie feie peie write: reset:uu000000 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 sci status register 2 (scs2) read: 000000bkfrpf write: reset:00000000 sci data register (scdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset sci baud rate register (scbr) read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented u = unaffected r = reserved figure 16-2. sci i/o register summary table 16-2. sci i/o register address summary register scc1 scc2 scc3 scs1 scs2 scdr scbr address $0013 $0014 $0015 $0016 $0017 $0018 $0019 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 200 serial communications interface (sci) motorola 16.5.1 data format the sci uses the standard non-return-to-zero mark/space data format illustrated in figure 16-3 . figure 16-3. sci data formats 16.5.2 transmitter figure 16-4 shows the structure of the sci transmitter. 16.5.2.1 character length the transmitter can accommodate either 8-bit or 9-bit data. the state of the m bit in sci control register 1 (scc1) determines character length. when transmitting 9-bit data, bit t8 in sci control register 3 (scc3) is the ninth bit (bit 8). 16.5.2.2 character transmission during an sci transmission, the transmit shift register shifts a character out to the txd pin. the sci data register (scdr) is the write-only buffer between the internal data bus and the transmit shift register. to initiate an sci transmission: 1. enable the sci by writing a logic 1 to the enable sci bit (ensci) in sci control register 1 (scc1). 2. enable the transmitter by writing a logic 1 to the transmitter enable bit (te) in sci control register 2 (scc2). 3. clear the sci transmitter empty bit (scte) by first reading sci bit 5 start bit bit 0 bit 1 next stop bit start bit 8-bit data format (bit m in scc1 clear) start bit bit 0 next stop bit start bit 9-bit data format (bit m in scc1 set) bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 bit 8 bit 2 bit 3 bit 4 bit 6 bit 7 parity or data bit parity or data bit f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 201 status register 1 (scs1) and then writing to the scdr. 4. repeat step 3 for each subsequent transmission. at the start of a transmission, transmitter control logic automatically loads the transmit shift register with a preamble of logic 1s. after the preamble shifts out, control logic transfers the scdr data into the transmit shift register. a logic 0 start bit automatically goes into the least significant bit position of the transmit shift register. a logic 1 stop bit goes into the most significant bit position. the sci transmitter empty bit, scte, in scs1 becomes set when the scdr transfers a byte to the transmit shift register. the scte bit indicates that the scdr can accept new data from the internal data bus. if the sci transmit interrupt enable bit, sctie, in scc2 is also set, the scte bit generates a transmitter cpu interrupt request. when the transmit shift register is not transmitting a character, the txd pin goes to the idle condition, logic 1. if at any time software clears the ensci bit in sci control register 1 (scc1), the transmitter and receiver relinquish control of the port e pins. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 202 serial communications interface (sci) motorola figure 16-4. sci transmitter pen pty h876543210l 11-bit transmit stop start t8 scte sctie tcie sbk tc cgmxclk parity generation msb sci data register load from scdr shift enable preamble (all ones) break (all zeros) transmitter control logic shift register tc sctie tcie scte transmitter cpu interrupt request m ensci loops te txinv internal bus 4 pre- scaler scp1 scp0 scr2 scr1 scr0 baud divider 16 txd f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 203 register name bit 7654321bit 0 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset:00000000 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 sci control register 3 (scc3) read: r8 t8 r r orie neie feie peie write: reset:uu000000 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 sci data register (scdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset sci baud rate register (scbr) read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented u = unaffected r = reserved figure 16-5. sci transmitter i/o register summary table 16-3. sci transmitter i/o address summary register scc1 scc2 scc3 scs1 scdr scbr address $0013 $0014 $0015 $0016 $0018 $0019 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 204 serial communications interface (sci) motorola 16.5.2.3 break characters writing a logic 1 to the send break bit, sbk, in scc2 loads the transmit shift register with a break character. a break character contains all logic 0s and has no start, stop, or parity bit. break character length depends on the m bit in scc1. as long as sbk is at logic 1, transmitter logic continuously loads break characters into the transmit shift register. after software clears the sbk bit, the shift register finishes transmitting the last break character and then transmits at least one logic 1. the automatic logic 1 at the end of a break character guarantees the recognition of the start bit of the next character. the sci recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a logic 0 where the stop bit should be. receiving a break character has the following effects on sci registers: sets the framing error bit (fe) in scs1 sets the sci receiver full bit (scrf) in scs1 clears the sci data register (scdr) clears the r8 bit in scc3 sets the break flag bit (bkf) in scs2 may set the overrun (or), noise flag (nf), parity error (pe), or reception in progress flag (rpf) bits 16.5.2.4 idle characters an idle character contains all logic 1s and has no start, stop, or parity bit. idle character length depends on the m bit in scc1. the preamble is a synchronizing idle character that begins every transmission. if the te bit is cleared during a transmission, the txd pin becomes idle after completion of the transmission in progress. clearing and then setting the te bit during a transmission queues an idle character to be sent after the character currently being transmitted. note: when a break sequence is followed immediately by an idle character, this sci design exhibits a condition in which the break character length is reduced by one half bit time. in this instance, the break sequence will f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 205 consist of a valid start bit, eight or nine data bits (as defined by the m bit in scc1) of logic 0 and one half data bit length of logic 0 in the stop bit position followed immediately by the idle character. to ensure a break character of the proper length is transmitted, always queue up a byte of data to be transmitted while the final break sequence is in progress. note: when queueing an idle character, return the te bit to logic 1 before the stop bit of the current character shifts out to the txd pin. setting te after the stop bit appears on txd causes data previously written to the scdr to be lost. a good time to toggle the te bit for a queued idle character is when the scte bit becomes set and just before writing the next byte to the scdr. 16.5.2.5 inversion of transmitted output the transmit inversion bit (txinv) in sci control register 1 (scc1) reverses the polarity of transmitted data. all transmitted values, including idle, break, start, and stop bits, are inverted when txinv is at logic 1. (see sci control register 1 .) 16.5.2.6 transmitter interrupts the following conditions can generate cpu interrupt requests from the sci transmitter: sci transmitter empty (scte) ? the scte bit in scs1 indicates that the scdr has transferred a character to the transmit shift register. scte can generate a transmitter cpu interrupt request. setting the sci transmit interrupt enable bit, sctie, in scc2 enables the scte bit to generate transmitter cpu interrupt requests. transmission complete (tc) ? the tc bit in scs1 indicates that the transmit shift register and the scdr are empty and that no break or idle character has been generated. the transmission complete interrupt enable bit, tcie, in scc2 enables the tc bit to generate transmitter cpu interrupt requests. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 206 serial communications interface (sci) motorola 16.5.3 receiver figure 16-6 shows the structure of the sci receiver. figure 16-6. sci receiver block diagram all ones all zeros m wake ilty pen pty bkf rpf h876543210l 11-bit receive shift register stop start data recovery or orie nf neie fe feie pe peie scrie scrf ilie idle wakeup logic parity checking msb error cpu interrupt request cpu interrupt request sci data register r8 orie neie feie peie scrie ilie rwu scrf idle or nf fe pe internal bus pre- scaler baud divider 4 16 scp1 scp0 scr2 scr1 scr0 cgmxclk rxd f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 207 register name bit 7654321bit 0 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset:00000000 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 sci control register 3 (scc3) read: r8 t8 r r orie neie feie peie write: reset:uu000000 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 sci status register 2 (scs2) read: 000000bkfrpf write: reset:00000000 sci data register (scdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset sci baud rate register (scbr) read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented u = unaffected r = reserved figure 16-7. sci i/o receiver register summary table 16-4. sci receiver i/o address summary register scc1 scc2 scc3 scs1 scs2 scdr scbr address $0013 $0014 $0015 $0016 $0017 $0018 $0019 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 208 serial communications interface (sci) motorola 16.5.3.1 character length the receiver can accommodate either 8-bit or 9-bit data. the state of the m bit in sci control register 1 (scc1) determines character length. when receiving 9-bit data, bit r8 in sci control register 2 (scc2) is the ninth bit (bit 8). when receiving 8-bit data, bit r8 is a copy of the eighth bit (bit 7). 16.5.3.2 character reception during an sci reception, the receive shift register shifts characters in from the rxd pin. the sci data register (scdr) is the read-only buffer between the internal data bus and the receive shift register. after a complete character shifts into the receive shift register, the data portion of the character transfers to the scdr. the sci receiver full bit, scrf, in sci status register 1 (scs1) becomes set, indicating that the received byte can be read. if the sci receive interrupt enable bit, scrie, in scc2 is also set, the scrf bit generates a receiver cpu interrupt request. 16.5.3.3 data sampling the receiver samples the rxd pin at the rt clock rate. the rt clock is an internal signal with a frequency 16 times the baud rate. to adjust for baud rate mismatch, the rt clock is resynchronized at the following times (see figure 16-8 ): after every start bit after the receiver detects a data bit change from logic 1 to logic 0 (after the majority of data bit samples at rt8, rt9, and rt10 returns a valid logic 1 and the majority of the next rt8, rt9, and rt10 samples returns a valid logic 0) to locate the start bit, data recovery logic does an asynchronous search for a logic 0 preceded by three logic 1s. when the falling edge of a possible start bit occurs, the rt clock begins to count to 16. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 209 figure 16-8. receiver data sampling to verify the start bit and to detect noise, data recovery logic takes samples at rt3, rt5, and rt7. table 16-5 summarizes the results of the start bit verification samples. if start bit verification is not successful, the rt clock is reset and a new search for a start bit begins. table 16-5. start bit verification rt3, rt5, and rt7 samples start bit verification noise flag 000 yes 0 001 yes 1 010 yes 1 011 no 0 100 yes 1 101 no 0 110 no 0 111 no 0 rt clock reset rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt2 rt3 rt4 rt5 rt8 rt7 rt6 rt11 rt10 rt9 rt15 rt14 rt13 rt12 rt16 rt1 rt2 rt3 rt4 start bit qualification start bit verification data sampling samples rt clock rt clock state start bit lsb rxd f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 210 serial communications interface (sci) motorola to determine the value of a data bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 16-6 summarizes the results of the data bit samples. note: the rt8, rt9, and rt10 samples do not affect start bit verification. if any or all of the rt8, rt9, and rt10 start bit samples are logic 1s following a successful start bit verification, the noise flag (nf) is set and the receiver assumes that the bit is a start bit. to verify a stop bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 16-7 summarizes the results of the stop bit samples. table 16-6. data bit recovery rt8, rt9, and rt10 samples data bit determination noise flag 000 0 0 001 0 1 010 0 1 011 1 1 100 0 1 101 1 1 110 1 1 111 1 0 table 16-7. stop bit recovery rt8, rt9, and rt10 samples framing error flag noise flag 000 1 0 001 1 1 010 1 1 011 0 1 100 1 1 101 0 1 110 0 1 111 0 0 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 211 16.5.3.4 framing errors if the data recovery logic does not detect a logic 1 where the stop bit should be in an incoming character, it sets the framing error bit, fe, in scs1. a break character also sets the fe bit because a break character has no stop bit. the fe bit is set at the same time that the scrf bit is set. 16.5.3.5 baud rate tolerance a transmitting device may be operating at a baud rate below or above the receiver baud rate. accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the actual stop bit. then a noise error occurs. if more than one of the samples is outside the stop bit, a framing error occurs. in most applications, the baud rate tolerance is much more than the degree of misalignment that is likely to occur. as the receiver samples an incoming character, it resynchronizes the rt clock on any valid falling edge within the character. resynchronization within characters corrects misalignments between transmitter bit times and receiver bit times. slow data tolerance figure 16-9 shows how much a slow received character can be misaligned without causing a noise error or a framing error. the slow stop bit begins at rt8 instead of rt1 but arrives in time for the stop bit data samples at rt8, rt9, and rt10. figure 16-9. slow data msb stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 212 serial communications interface (sci) motorola for an 8-bit character, data sampling of the stop bit takes the receiver 9bit times 16 rt cycles + 10 rt cycles = 154 rt cycles. with the misaligned character shown in figure 16-9 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 9 bit times 16 rt cycles + 3 rt cycles = 147 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is for a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times 16 rt cycles + 10 rt cycles = 170 rt cycles. with the misaligned character shown in figure 16-9 , the receiver counts 170 rt cycles at the point when the count of the transmitting device is 10 bit times 16 rt cycles + 3 rt cycles = 163 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is fast data tolerance figure 16-10 shows how much a fast received character can be misaligned without causing a noise error or a framing error. the fast stop bit ends at rt10 instead of rt16 but is still there for the stop bit data samples at rt8, rt9, and rt10. figure 16-10. fast data 154 147 ? 154 ------------------------- - 100 4.54% = 170 163 ? 170 ------------------------- - 100 4.12% = idle or next character stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 213 for an 8-bit character, data sampling of the stop bit takes the receiver 9bittimes 16 rt cycles + 10 rt cycles = 154 rt cycles. with the misaligned character shown in figure 16-10 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 10 bit times 16 rt cycles = 160 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is for a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times 16 rt cycles + 10 rt cycles = 170 rt cycles. with the misaligned character shown in figure 16-10 , the receiver counts 170 rt cycles at the point when the count of the transmitting device is 11 bit times 16 rt cycles = 176 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is 16.5.3.6 receiver wakeup so that the mcu can ignore transmissions intended only for other receivers in multiple-receiver systems, the receiver can be put into a standby state. setting the receiver wakeup bit, rwu, in scc2 puts the receiver into a standby state during which receiver interrupts are disabled. depending on the state of the wake bit in scc1, either of two conditions on the rxd pin can bring the receiver out of the standby state: address mark ? an address mark is a logic 1 in the most significant bit position of a received character. when the wake bit is set, an address mark wakes the receiver from the standby state by clearing the rwu bit. the address mark also sets the sci receiver full bit, scrf. software can then compare the character containing the address mark to the user-defined address of the receiver. if they are the same, the receiver remains awake and 154 160 ? 154 ------------------------- - 100 3.90%. = 170 176 ? 170 ------------------------- - 100 3.53%. = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 214 serial communications interface (sci) motorola processes the characters that follow. if they are not the same, software can set the rwu bit and put the receiver back into the standby state. idle input line condition ? when the wake bit is clear, an idle character on the rxd pin wakes the receiver from the standby state by clearing the rwu bit. the idle character that wakes the receiver does not set the receiver idle bit, idle, or the sci receiver full bit, scrf. the idle line type bit, ilty, determines whether the receiver begins counting logic 1s as idle character bits after the start bit or after the stop bit. note: with the wake bit clear, setting the rwu bit after the rxd pin has been idle may cause the receiver to wake up immediately. 16.5.3.7 receiver interrupts the following sources can generate cpu interrupt requests from the sci receiver: sci receiver full (scrf) ? the scrf bit in scs1 indicates that the receive shift register has transferred a character to the scdr. scrf can generate a receiver cpu interrupt request. setting the sci receive interrupt enable bit, scrie, in scc2 enables the scrf bit to generate receiver cpu interrupts. idle input (idle) ? the idle bit in scs1 indicates that 10 or 11 consecutive logic 1s shifted in from the rxd pin. the idle line interrupt enable bit, ilie, in scc2 enables the idle bit to generate cpu interrupt requests. 16.5.3.8 error interrupts the following receiver error flags in scs1 can generate cpu interrupt requests: receiver overrun (or) ? the or bit indicates that the receive shift register shifted in a new character before the previous character was read from the scdr. the previous character f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 215 remains in the scdr, and the new character is lost. the overrun interrupt enable bit, orie, in scc3 enables or to generate sci error cpu interrupt requests. noise flag (nf) ? the nf bit is set when the sci detects noise on incoming data or break characters, including start, data, and stop bits. the noise error interrupt enable bit, neie, in scc3 enables nf to generate sci error cpu interrupt requests. framing error (fe) ? the fe bit in scs1 is set when a logic 0 occurs where the receiver expects a stop bit. the framing error interrupt enable bit, feie, in scc3 enables fe to generate sci error cpu interrupt requests. parity error (pe) ? the pe bit in scs1 is set when the sci detects a parity error in incoming data. the parity error interrupt enable bit, peie, in scc3 enables pe to generate sci error cpu interrupt requests. 16.6 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 16.6.1 wait mode the sci module remains active in wait mode. any enabled cpu interrupt request from the sci module can bring the mcu out of wait mode. if sci module functions are not required during wait mode, reduce power consumption by disabling the module before executing the wait instruction. 16.6.2 stop mode the sci module is inactive in stop mode. the stop instruction does not affect sci register states. any enabled cpu interrupt request from the f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 216 serial communications interface (sci) motorola sci module does not bring the mcu out of stop mode. sci module operation resumes after the mcu exits stop mode. because the internal clock is inactive during stop mode, entering stop mode during an sci transmission or reception results in invalid data. 16.7 sci during break module interrupts the bcfe bit in the break flag control register (bfcr) enables software to clear status bits during the break state. (see break module (brk) on page 157). to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a two-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 16.8 i/o signals port e shares two of its pins with the sci module. the two sci i/o pins are: pte0/sctxd ? transmit data pte1/scrxd ? receive data f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 217 16.8.1 pte0/sctxd (transmit data) the pte0/sctxd pin is the serial data output from the sci transmitter. the sci shares the pte0/sctxd pin with port e. when the sci is enabled, the pte0/sctxd pin is an output regardless of the state of the ddre2 bit in data direction register e (ddre). 16.8.2 pte1/scrxd (receive data) the pte1/scrxd pin is the serial data input to the sci receiver. the sci shares the pte1/scrxd pin with port e. when the sci is enabled, the pte1/scrxd pin is an input regardless of the state of the ddre1 bit in data direction register e (ddre). 16.9 i/o registers the following i/o registers control and monitor sci operation: sci control register 1 (scc1) sci control register 2 (scc2) sci control register 3 (scc3) sci status register 1 (scs1) sci status register 2 (scs2) sci data register (scdr) sci baud rate register (scbr) 16.9.1 sci control register 1 sci control register 1: enables loop mode operation enables the sci controls output polarity controls character length controls sci wakeup method f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 218 serial communications interface (sci) motorola controls idle character detection enables parity function controls parity type loops ? loop mode select bit this read/write bit enables loop mode operation. in loop mode the rxd pin is disconnected from the sci, and the transmitter output goes into the receiver input. both the transmitter and the receiver must be enabled to use loop mode. reset clears the loops bit. 1 = loop mode enabled 0 = normal operation enabled ensci ? enable sci bit this read/write bit enables the sci and the sci baud rate generator. clearing ensci sets the scte and tc bits in sci status register 1 and disables transmitter interrupts. reset clears the ensci bit. 1 = sci enabled 0 = sci disabled txinv ? transmit inversion bit this read/write bit reverses the polarity of transmitted data. reset clears the txinv bit. 1 = transmitter output inverted 0 = transmitter output not inverted note: setting the txinv bit inverts all transmitted values, including idle, break, start, and stop bits. address: $0013 bit 7654321bit 0 read: loops ensci txinv m wake illty pen pty write: reset:00000000 figure 16-11. sci control register 1 (scc1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 219 m ? mode (character length) bit this read/write bit determines whether sci characters are eight or nine bits long. (see table 16-8 ).the ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. reset clears the m bit. 1 = 9-bit sci characters 0 = 8-bit sci characters wake ? wakeup condition bit this read/write bit determines which condition wakes up the sci: a logic 1 (address mark) in the most significant bit position of a received character or an idle condition on the rxd pin. reset clears the wake bit. 1 = address mark wakeup 0 = idle line wakeup ilty ? idle line type bit this read/write bit determines when the sci starts counting logic 1s as idle character bits. the counting begins either after the start bit or after the stop bit. if the count begins after the start bit, then a string of logic 1s preceding the stop bit may cause false recognition of an idle character. beginning the count after the stop bit avoids false idle character recognition, but requires properly synchronized transmissions. reset clears the ilty bit. 1 = idle character bit count begins after stop bit 0 = idle character bit count begins after start bit pen ? parity enable bit this read/write bit enables the sci parity function. (see table 16-8 ). when enabled, the parity function inserts a parity bit in the most significant bit position. (see table 16-7 ). reset clears the pen bit. 1 = parity function enabled 0 = parity function disabled f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 220 serial communications interface (sci) motorola pty ? parity bit this read/write bit determines whether the sci generates and checks for odd parity or even parity. (see table 16-8 ). reset clears the pty bit. 1 = odd parity 0 = even parity note: changing the pty bit in the middle of a transmission or reception can generate a parity error. 16.9.2 sci control register 2 sci control register 2: enables the following cpu interrupt requests: ? enables the scte bit to generate transmitter cpu interrupt requests ? enables the tc bit to generate transmitter cpu interrupt requests ? enables the scrf bit to generate receiver cpu interrupt requests ? enables the idle bit to generate receiver cpu interrupt requests table 16-8. character format selection control bits character format mpen:pty start bits data bits parity stop bits character length 0 0x 1 8 none 1 10 bits 1 0x 1 9 none 1 11 bits 0 10 1 7 even 1 10 bits 011 17odd110 bits 1 10 1 8 even 1 11 bits 111 18odd111 bits f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 221 enables the transmitter enables the receiver enables sci wakeup transmits sci break characters sctie ? sci transmit interrupt enable bit this read/write bit enables the scte bit to generate sci transmitter cpu interrupt requests. setting the sctie bit in scc3 enables the scte bit to generate cpu interrupt requests. reset clears the sctie bit. 1 = scte enabled to generate cpu interrupt 0 = scte not enabled to generate cpu interrupt tcie ? transmission complete interrupt enable bit this read/write bit enables the tc bit to generate sci transmitter cpu interrupt requests. reset clears the tcie bit. 1 = tc enabled to generate cpu interrupt requests 0 = tc not enabled to generate cpu interrupt requests address: $0014 bit 7654321bit 0 read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 figure 16-12. sci control register 2 (scc2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 222 serial communications interface (sci) motorola scrie ? sci receive interrupt enable bit this read/write bit enables the scrf bit to generate sci receiver cpu interrupt requests. setting the scrie bit in scc3 enables the scrf bit to generate cpu interrupt requests. reset clears the scrie bit. 1 = scrf enabled to generate cpu interrupt 0 = scrf not enabled to generate cpu interrupt ilie ? idle line interrupt enable bit this read/write bit enables the idle bit to generate sci receiver cpu interrupt requests. reset clears the ilie bit. 1 = idle enabled to generate cpu interrupt requests 0 = idle not enabled to generate cpu interrupt requests te ? transmitter enable bit setting this read/write bit begins the transmission by sending a preamble of 10 or 11 logic 1s from the transmit shift register to the txd pin. if software clears the te bit, the transmitter completes any transmission in progress before the txd returns to the idle condition (logic 1). clearing and then setting te during a transmission queues an idle character to be sent after the character currently being transmitted. reset clears the te bit. 1 = transmitter enabled 0 = transmitter disabled note: writing to the te bit is not allowed when the enable sci bit (ensci) is clear. ensci is in sci control register 1. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 223 re ? receiver enable bit setting this read/write bit enables the receiver. clearing the re bit disables the receiver but does not affect receiver interrupt flag bits. reset clears the re bit. 1 = receiver enabled 0 = receiver disabled note: writing to the re bit is not allowed when the enable sci bit (ensci) is clear. ensci is in sci control register 1. rwu ? receiver wakeup bit this read/write bit puts the receiver in a standby state during which receiver interrupts are disabled. the wake bit in scc1 determines whether an idle input or an address mark brings the receiver out of the standby state and clears the rwu bit. reset clears the rwu bit. 1 = standby state 0 = normal operation sbk ? send break bit setting and then clearing this read/write bit transmits a break character followed by a logic 1. the logic 1 after the break character guarantees recognition of a valid start bit. if sbk remains set, the transmitter continuously transmits break characters with no logic 1s between them. reset clears the sbk bit. 1 = transmit break characters 0 = no break characters being transmitted note: do not toggle the sbk bit immediately after setting the scte bit. toggling sbk before the preamble begins causes the sci to send a break character instead of a preamble. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 224 serial communications interface (sci) motorola 16.9.3 sci control register 3 sci control register 3: stores the ninth sci data bit received and the ninth sci data bit to be transmitted. enables the following interrupts: ? receiver overrun interrupts ? noise error interrupts ? framing error interrupts ? parity error interrupts r8 ? received bit 8 when the sci is receiving 9-bit characters, r8 is the read-only ninth bit (bit 8) of the received character. r8 is received at the same time that the scdr receives the other 8 bits. when the sci is receiving 8-bit characters, r8 is a copy of the eighth bit (bit 7). reset has no effect on the r8 bit. t8 ? transmitted bit 8 when the sci is transmitting 9-bit characters, t8 is the read/write ninth bit (bit 8) of the transmitted character. t8 is loaded into the transmit shift register at the same time that the scdr is loaded into the transmit shift register. reset has no effect on the t8 bit. address: $0015 bit 7654321bit 0 read: r8 t8 r r orie neie feie peie write: reset:uu000000 = unimplemented r = reserved u = unaffected figure 16-13. sci control register 3 (scc3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 225 orie ? receiver overrun interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the receiver overrun bit, or. 1 = sci error cpu interrupt requests from or bit enabled 0 = sci error cpu interrupt requests from or bit disabled neie ? receiver noise error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the noise error bit, ne. reset clears neie. 1 = sci error cpu interrupt requests from ne bit enabled 0 = sci error cpu interrupt requests from ne bit disabled feie ? receiver framing error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the framing error bit, fe. reset clears feie. 1 = sci error cpu interrupt requests from fe bit enabled 0 = sci error cpu interrupt requests from fe bit disabled peie ? receiver parity error interrupt enable bit this read/write bit enables sci receiver cpu interrupt requests generated by the parity error bit, pe. reset clears peie. 1 = sci error cpu interrupt requests from pe bit enabled 0 = sci error cpu interrupt requests from pe bit disabled f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 226 serial communications interface (sci) motorola 16.9.4 sci status register 1 sci status register 1 contains flags to signal the following conditions: transfer of scdr data to transmit shift register complete transmission complete transfer of receive shift register data to scdr complete receiver input idle receiver overrun noisy data framing error parity error scte ? sci transmitter empty bit this clearable, read-only bit is set when the scdr transfers a character to the transmit shift register. scte can generate an sci transmitter cpu interrupt request. when the sctie bit in scc2 is set, scte generates an sci transmitter cpu interrupt request. in normal operation, clear the scte bit by reading scs1 with scte set and then writing to scdr. reset sets the scte bit. 1 = scdr data transferred to transmit shift register 0 = scdr data not transferred to transmit shift register address: $0016 bit 7654321bit 0 read: scte tc scrf idle or nf fe pe write: reset:11000000 = unimplemented figure 16-14. sci status register 1 (scs1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 227 tc ? transmission complete bit this read-only bit is set when the scte bit is set, and no data, preamble, or break character is being transmitted. tc generates an sci transmitter cpu interrupt request if the tcie bit in scc2 is also set. tc is cleared automatically when data, preamble, or break is queued and ready to be sent. there may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the transmission actually starting. reset sets the tc bit. 1 = no transmission in progress 0 = transmission in progress scrf ? sci receiver full bit this clearable, read-only bit is set when the data in the receive shift register transfers to the sci data register. scrf can generate an sci receiver cpu interrupt request. when the scrie bit in scc2 is set the scrf generates a cpu interrupt request. in normal operation, clear the scrf bit by reading scs1 with scrf set and then reading the scdr. reset clears scrf. 1 = received data available in scdr 0 = data not available in scdr idle ? receiver idle bit this clearable, read-only bit is set when 10 or 11 consecutive logic 1s appear on the receiver input. idle generates an sci error cpu interrupt request if the ilie bit in scc2 is also set. clear the idle bit by reading scs1 with idle set and then reading the scdr. after the receiver is enabled, it must receive a valid character that sets the scrf bit before an idle condition can set the idle bit. also, after the idle bit has been cleared, a valid character must again set the scrf bit before an idle condition can set the idle bit. reset clears the idle bit. 1 = receiver input idle 0 = receiver input active (or idle since the idle bit was cleared) or ? receiver overrun bit this clearable, read-only bit is set when software fails to read the scdr before the receive shift register receives the next character. the or bit generates an sci error cpu interrupt request if the orie f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 228 serial communications interface (sci) motorola bit in scc3 is also set. the data in the shift register is lost, but the data already in the scdr is not affected. clear the or bit by reading scs1 with or set and then reading the scdr. reset clears the or bit. 1 = receive shift register full and scrf = 1 0 = no receiver overrun software latency may allow an overrun to occur between reads of scs1 and scdr in the flag-clearing sequence. figure 16-15 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. the delayed read of scdr does not clear the or bit because or was not set when scs1 was read. byte 2 caused the overrun and is lost. the next flag-clearing sequence reads byte 3 in the scdr instead of byte 2. in applications that are subject to software latency or in which it is important to know which byte is lost due to an overrun, the flag-clearing routine can check the or bit in a second read of scs1 after reading the data register. figure 16-15. flag clearing sequence byte 1 normal flag clearing sequence read scs1 scrf = 1 read scdr byte 1 scrf = 1 scrf = 1 byte 2 byte 3 byte 4 or = 0 read scs1 scrf = 1 or = 0 read scdr byte 2 scrf = 0 read scs1 scrf = 1 or = 0 scrf = 1 scrf = 0 read scdr byte 3 scrf = 0 byte 1 read scs1 scrf = 1 read scdr byte 1 scrf = 1 scrf = 1 byte 2 byte 3 byte 4 or = 0 read scs1 scrf = 1 or = 1 read scdr byte 3 delayed flag clearing sequence or = 1 scrf = 1 or = 1 scrf = 0 or = 1 scrf = 0 or = 0 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 229 nf ? receiver noise flag bit this clearable, read-only bit is set when the sci detects noise on the rxd pin. nf generates an nf cpu interrupt request if the neie bit in scc3 is also set. clear the nf bit by reading scs1 and then reading the scdr. reset clears the nf bit. 1 = noise detected 0 = no noise detected fe ? receiver framing error bit this clearable, read-only bit is set when a logic 0 is accepted as the stop bit. fe generates an sci error cpu interrupt request if the feie bit in scc3 also is set. clear the fe bit by reading scs1 with fe set and then reading the scdr. reset clears the fe bit. 1 = framing error detected 0 = no framing error detected pe ? receiver parity error bit this clearable, read-only bit is set when the sci detects a parity error in incoming data. pe generates a pe cpu interrupt request if the peie bit in scc3 is also set. clear the pe bit by reading scs1 with pe set and then reading the scdr. reset clears the pe bit. 1 = parity error detected 0 = no parity error detected f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 230 serial communications interface (sci) motorola 16.9.5 sci status register 2 sci status register 2 contains flags to signal the following conditions: break character detected incoming data bkf ? break flag bit this clearable, read-only bit is set when the sci detects a break character on the rxd pin. in scs1, the fe and scrf bits are also set. in 9-bit character transmissions, the r8 bit in scc3 is cleared. bkf does not generate a cpu interrupt request. clear bkf by reading scs2 with bkf set and then reading the scdr. once cleared, bkf can become set again only after logic 1s again appear on the rxd pin followed by another break character. reset clears the bkf bit. 1 = break character detected 0 = no break character detected rpf ? reception in progress flag bit this read-only bit is set when the receiver detects a logic 0 during the rt1 time period of the start bit search. rpf does not generate an interrupt request. rpf is reset after the receiver detects false start bits (usually from noise or a baud rate mismatch), or when the receiver detects an idle character. polling rpf before disabling the sci module or entering stop mode can show whether a reception is in progress. 1 = reception in progress 0 = no reception in progress address: $0017 bit 7654321bit 0 read: 000000bkfrpf write: reset:00000000 = unimplemented figure 16-16. sci status register 2 (scs2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial communications interface (sci) 231 16.9.6 sci data register the sci data register is the buffer between the internal data bus and the receive and transmit shift registers. reset has no effect on data in the sci data register. r7/t7:r0/t0 ? receive/transmit data bits reading address $0018 accesses the read-only received data bits, r7:r0. writing to address $0018 writes the data to be transmitted, t7:t0. reset has no effect on the sci data register. note: do not use read-modify-write instructions on the sci data register. 16.9.7 sci baud rate register the baud rate register selects the baud rate for both the receiver and the transmitter. address: $0018 bit 7654321bit 0 read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset figure 16-17. sci data register (scdr) address: $0019 bit 7654321bit 0 read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented r = reserved figure 16-18. sci baud rate register (scbr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 232 serial communications interface (sci) motorola scp1 and scp0 ? sci baud rate prescaler bits these read/write bits select the baud rate prescaler divisor as shown in table 16-9 . reset clears scp1 and scp0. scr2 ? scr0 ? sci baud rate select bits these read/write bits select the sci baud rate divisor as shown in table 16-10 . reset clears scr2 ? scr0. use the following formula to calculate the sci baud rate: where: f crystal = crystal frequency pd = prescaler divisor bd = baud rate divisor table 16-9. sci baud rate prescaling scp[1:0] prescaler divisor (pd) 00 1 01 3 10 4 11 13 table 16-10. sci baud rate selection scr[2:1:0] baud rate divisor (bd) 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 baud rate f crystal 64 pd bd ------------------------------------ = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 233 serial communications interface (sci) motorola table 16-11 shows the sci baud rates that can be generated with a 4.9152-mhz crystal. table 16-11. sci baud rate selection examples scp[1:0] prescaler divisor (pd) scr[2:1:0] baud rate divisor (bd) baud rate (f crystal = 4.9152 mhz) 00 1 000 1 76,800 00 1 001 2 38,400 00 1 010 4 19,200 00 1 011 8 9600 00 1 100 16 4800 00 1 101 32 2400 00 1 110 64 1200 00 1 111 128 600 01 3 000 1 25,600 01 3 001 2 12,800 01 3 010 4 6400 01 3 011 8 3200 01 3 100 16 1600 01 3 101 32 800 01 3 110 64 400 01 3 111 128 200 10 4 000 1 19,200 10 4 001 2 9600 10 4 010 4 4800 10 4 011 8 2400 10 4 100 16 1200 10 4 101 32 600 10 4 110 64 300 10 4 111 128 150 11 13 000 1 5908 11 13 001 2 2954 11 13 010 4 1477 11 13 011 8 739 11 13 100 16 369 11 13 101 32 185 11 13 110 64 92 11 13 111 128 46 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial communications interface (sci) advance information mc68HC908AS32A ? rev 0.0 234 serial communications interface (sci) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 235 technical data ? mc68HC908AS32A section 17. serial peripheral interface (spi) 17.1 contents 17.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 17.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 17.4 pin name and register name conventions . . . . . . . . . . . . 237 17.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 17.5.1 master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 17.5.2 slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 17.6 transmission formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 17.6.1 clock phase and polarity controls . . . . . . . . . . . . . . . . . 242 17.6.2 transmission format when cpha = 0 . . . . . . . . . . . . . . 243 17.6.3 transmission format when cpha = 1 . . . . . . . . . . . . . . 244 17.6.4 transmission initiation latency . . . . . . . . . . . . . . . . . . . 245 17.7 error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 17.7.1 overflow error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 17.7.2 mode fault error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 17.8 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 17.9 queuing transmission data . . . . . . . . . . . . . . . . . . . . . . . . 252 17.10 resetting the spi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 17.11 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 17.11.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 17.11.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 17.12 spi during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 255 17.13 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 17.13.1 miso (master in/slave out) . . . . . . . . . . . . . . . . . . . . . . . 257 17.13.2 mosi (master out/slave in) . . . . . . . . . . . . . . . . . . . . . . . 257 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 236 serial peripheral interface (spi) motorola 17.13.3 spsck (serial clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 17.13.4 ss (slave select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 17.13.5 v ss (clock ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 17.14 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 17.14.1 spi control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 17.14.2 spi status and control register . . . . . . . . . . . . . . . . . . . 262 17.14.3 spi data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 17.2 introduction this section describes the serial peripheral interface (spi) module, which allows full-duplex, synchronous, serial communications with peripheral devices. 17.3 features features of the spi module include: full-duplex operation master and slave modes double-buffered operation with separate transmit and receive registers four master mode frequencies (maximum = bus frequency 2) maximum slave mode frequency = bus frequency serial clock with programmable polarity and phase two separately enabled interrupts with cpu service: ? sprf (spi receiver full) ? spte (spi transmitter empty) mode fault error flag with cpu interrupt capability overflow error flag with cpu interrupt capability programmable wired-or mode i 2 c (inter-integrated circuit) compatibility f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) pin name and register name conventions mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 237 17.4 pin name and register name conventions the generic names of the spi input/output (i/o) pins are: ss (slave select) spsck (spi serial clock) mosi (master out slave in) miso (master in slave out) the spi shares four i/o pins with a parallel i/o port. the full name of an spi pin reflects the name of the shared port pin. table 17-1 shows the full names of the spi i/o pins. the generic pin names appear in the text that follows. the generic names of the spi i/o registers are: spi control register (spcr) spi status and control register (spscr) spi data register (spdr) table 17-2 shows the names and the addresses of the spi i/o registers. table 17-1. pin name conventions spi generic pin name miso mosi ss spsck full spi pin name pte5/miso pte6/mosi pte4/ss pte7/spsck table 17-2. i/o register addresses register name address spi control register (spcr) $0010 spi status and control register (spscr) $0011 spi data register (spdr) $0012 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 238 serial peripheral interface (spi) motorola 17.5 functional description table 17-3 summarizes the spi i/o registers and figure 17-1 shows the structure of the spi module. table 17-3. spi i/o register summary addr register name r/w bit 7 6 5 4 3 2 1 bit 0 $0010 spi control register (spcr) read: sprie r spmstr cpol cpha spwom spe sptie write: reset:0010 1 000 $0011 spi status and control register (spscr) read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:0000 1 000 $0012 spi data register (spdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset r= reserved = unimplemented f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 239 figure 17-1. spi module block diagram the spi module allows full-duplex, synchronous, serial communication between the mcu and peripheral devices, including other mcus. software can poll the spi status flags or spi operation can be interrupt driven. all spi interrupts can be serviced by the cpu. the following paragraphs describe the operation of the spi module. transmitter cpu interrupt request receiver/error cpu interrupt request 76543210 spr1 spmstr transmit data register shift register spr0 clock select 2 clock divider 8 32 128 clock logic cpha cpol spi sprie spe spwom sprf spte ovrf m s pin control logic receive data register sptie spe internal bus bus clock modfen errie control modf spmstr mosi miso spsck ss f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 240 serial peripheral interface (spi) motorola 17.5.1 master mode the spi operates in master mode when the spi master bit, spmstr (spcr $0010), is set. note: configure the spi modules as master and slave before enabling them. enable the master spi before enabling the slave spi. disable the slave spi before disabling the master spi. see spi control register on page 260. only a master spi module can initiate transmissions. software begins the transmission from a master spi module by writing to the spi data register. if the shift register is empty, the byte immediately transfers to the shift register, setting the spi transmitter empty bit, spte (spscr $0011). the byte begins shifting out on the mosi pin under the control of the serial clock. (see table 17-4 ). the spr1 and spr0 bits control the baud rate generator and determine the speed of the shift register. (see spi status and control register on page 262). through the spsck pin, the baud rate generator of the master also controls the shift register of the slave peripheral. figure 17-2. full-duplex master-slave connections shift register shift register baud rate generator master mcu slave mcu v dd mosi mosi miso miso spsck spsck ss ss f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) functional description mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 241 as the byte shifts out on the mosi pin of the master, another byte shifts in from the slave on the master ? s miso pin. the transmission ends when the receiver full bit, sprf (spscr), becomes set. at the same time that sprf becomes set, the byte from the slave transfers to the receive data register. in normal operation, sprf signals the end of a transmission. software clears sprf by reading the spi status and control register and then reading the spi data register. writing to the spi data register clears the sptie bit. 17.5.2 slave mode the spi operates in slave mode when the spmstr bit (spcr, $0010) is clear. in slave mode the spsck pin is the input for the serial clock from the master mcu. before a data transmission occurs, the ss pin of the slave mcu must be at logic 0. ss must remain low until the transmission is complete. (see mode fault error on page 249). in a slave spi module, data enters the shift register under the control of the serial clock from the master spi module. after a byte enters the shift register of a slave spi, it is transferred to the receive data register, and the sprf bit (spscr) is set. to prevent an overflow condition, slave software then must read the spi data register before another byte enters the shift register. the maximum frequency of the spsck for an spi configured as a slave is the bus clock speed, which is twice as fast as the fastest master spsck clock that can be generated. the frequency of the spsck for an spi configured as a slave does not have to correspond to any spi baud rate. the baud rate only controls the speed of the spsck generated by an spi configured as a master. therefore, the frequency of the spsck for an spi configured as a slave can be any frequency less than or equal to the bus speed. when the master spi starts a transmission, the data in the slave shift register begins shifting out on the miso pin. the slave can load its shift register with a new byte for the next transmission by writing to its transmit data register. the slave must write to its transmit data register at least one bus cycle before the master starts the next transmission. otherwise the byte already in the slave shift register shifts out on the miso pin. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 242 serial peripheral interface (spi) motorola data written to the slave shift register during a a transmission remains in a buffer until the end of the transmission. when the clock phase bit (cpha) is set, the first edge of spsck starts a transmission. when cpha is clear, the falling edge of ss starts a transmission. see transmission formats on page 242. if the write to the data register is late, the spi transmits the data already in the shift register from the previous transmission. note: to prevent spsck from appearing as a clock edge, spsck must be in the proper idle state before the slave is enabled. 17.6 transmission formats during an spi transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). a serial clock line synchronizes shifting and sampling on the two serial data lines. a slave select line allows individual selection of a slave spi device; slave devices that are not selected do not interfere with spi bus activities. on a master spi device, the slave select line can be used optionally to indicate a multiple-master bus contention. 17.6.1 clock phase and polarity controls software can select any of four combinations of serial clock (sck) phase and polarity using two bits in the spi control register (spcr). the clock polarity is specified by the cpol control bit, which selects an active high or low clock and has no significant effect on the transmission format. the clock phase (cpha) control bit (spcr) selects one of two fundamentally different transmission formats. the clock phase and polarity should be identical for the master spi device and the communicating slave device. in some cases, the phase and polarity are changed between transmissions to allow a master device to communicate with peripheral slaves having different requirements. note: before writing to the cpol bit or the cpha bit (spcr), disable the spi by clearing the spi enable bit (spe). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) transmission formats mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 243 17.6.2 transmission format when cpha = 0 figure 17-3 shows an spi transmission in which cpha (spcr) is logic 0. the figure should not be used as a replacement for data sheet parametric information. two waveforms are shown for sck: one for cpol = 0 and another for cpol = 1. the diagram may be interpreted as a master or slave timing diagram since the serial clock (sck), master in/slave out (miso), and master out/slave in (mosi) pins are directly connected between the master and the slave. the miso signal is the output from the slave, and the mosi signal is the output from the master. the ss line is the slave select input to the slave. the slave spi drives its miso output only when its slave select input (ss ) is at logic 0, so that only the selected slave drives to the master. the ss pin of the master is not shown but is assumed to be inactive. the ss pin of the master must be high or must be reconfigured as general-purpose i/o not affecting the spi (see mode fault error on page 249). when cpha = 0, the first spsck edge is the msb capture strobe. therefore, the slave must begin driving its data before the first spsck edge, and a falling edge on the ss pin is used to start the transmission. the ss pin must be toggled high and then low again between each byte transmitted. figure 17-3. transmission format (cpha = 0) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb 1234 5678 sck cycle # for reference sck cpol = 0 sck cpol = 1 mosi from master miso from slave ss to slave capture strobe f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 244 serial peripheral interface (spi) motorola 17.6.3 transmission format when cpha = 1 figure 17-4 shows an spi transmission in which cpha (spcr) is logic 1. the figure should not be used as a replacement for data sheet parametric information. two waveforms are shown for sck: one for cpol = 0 and another for cpol = 1. the diagram may be interpreted as a master or slave timing diagram since the serial clock (sck), master in/slave out (miso), and master out/slave in (mosi) pins are directly connected between the master and the slave. the miso signal is the output from the slave, and the mosi signal is the output from the master. the ss line is the slave select input to the slave. the slave spi drives its miso output only when its slave select input (ss ) is at logic 0, so that only the selected slave drives to the master. the ss pin of the master is not shown but is assumed to be inactive. the ss pin of the master must be high or must be reconfigured as general-purpose i/o not affecting the spi. (see mode fault error on page 249). when cpha = 1, the master begins driving its mosi pin on the first spsck edge. therefore, the slave uses the first spsck edge as a start transmission signal. the ss pin can remain low between transmissions. this format may be preferable in systems having only one master and only one slave driving the miso data line. figure 17-4. transmission format (cpha = 1) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb 1234 5678 sck cycle # for reference sck cpol = 0 sck cpol =1 mosi from master miso from slave ss to slave capture strobe f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) transmission formats mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 245 17.6.4 transmission initiation latency when the spi is configured as a master (spmstr = 1), transmissions are started by a software write to the spdr ($0012). cpha has no effect on the delay to the start of the transmission, but it does affect the initial state of the sck signal. when cpha = 0, the sck signal remains inactive for the first half of the first sck cycle. when cpha = 1, the first sck cycle begins with an edge on the sck line from its inactive to its active level. the spi clock rate (selected by spr1 ? spr0) affects the delay from the write to spdr and the start of the spi transmission. (see figure 17-5 ). the internal spi clock in the master is a free-running derivative of the internal mcu clock. it is only enabled when both the spe and spmstr bits (spcr) are set to conserve power. sck edges occur half way through the low time of the internal mcu clock. since the spi clock is free-running, it is uncertain where the write to the spdr will occur relative to the slower sck. this uncertainty causes the variation in the initiation delay shown in figure 17-5 . this delay will be no longer than a single spi bit time. that is, the maximum delay between the write to spdr and the start of the spi transmission is two mcu bus cycles for div2, eight mcu bus cycles for div8, 32 mcu bus cycles for div32, and 128 mcu bus cycles for div128. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 246 serial peripheral interface (spi) motorola figure 17-5. transmission start delay (master) write to spdr initiation delay bus mosi sck cpha = 1 sck cpha = 0 sck cycle number msb bit 6 12 clock write to spdr earliest latest sck = internal clock 2; earliest latest 2 possible start points sck = internal clock 8; 8 possible start points earliest latest sck = internal clock 32; 32 possible start points earliest latest sck = internal clock 128; 128 possible start points write to spdr write to spdr write to spdr bus clock bit 5 3 bus clock bus clock bus clock ? ? ? initiation delay from write spdr to transfer begin f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) error conditions mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 247 17.7 error conditions two flags signal spi error conditions: 1. overflow (ovrf in spscr) ? failing to read the spi data register before the next byte enters the shift register sets the ovrf bit. the new byte does not transfer to the receive data register, and the unread byte still can be read by accessing the spi data register. ovrf is in the spi status and control register. 2. mode fault error (modf in spscr) ? the modf bit indicates that the voltage on the slave select pin (ss ) is inconsistent with the mode of the spi. modf is in the spi status and control register. 17.7.1 overflow error the overflow flag (ovrf in spscr) becomes set if the spi receive data register still has unread data from a previous transmission when the capture strobe of bit 1 of the next transmission occurs. (see figure 17- 3 and figure 17-4 .) if an overflow occurs, the data being received is not transferred to the receive data register so that the unread data can still be read. therefore, an overflow error always indicates the loss of data. ovrf generates a receiver/error cpu interrupt request if the error interrupt enable bit (errie in spscr) is also set. modf and ovrf can generate a receiver/error cpu interrupt request. (see figure 17-8 ). it is not possible to enable only modf or ovrf to generate a receiver/error cpu interrupt request. however, leaving modfen low prevents modf from being set. if an end-of-block transmission interrupt was meant to pull the mcu out of wait, having an overflow condition without overflow interrupts enabled causes the mcu to hang in wait mode. if the ovrf is enabled to generate an interrupt, it can pull the mcu out of wait mode instead. if the cpu sprf interrupt is enabled and the ovrf interrupt is not, watch for an overflow condition. figure 17-6 shows how it is possible to miss an overflow. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 248 serial peripheral interface (spi) motorola figure 17-6. missed read of overflow condition the first part of figure 17-6 shows how to read the spscr and spdr to clear the sprf without problems. however, as illustrated by the second transmission example, the ovrf flag can be set in between the time that spscr and spdr are read. in this case, an overflow can be easily missed. since no more sprf interrupts can be generated until this ovrf is serviced, it will not be obvious that bytes are being lost as more transmissions are completed. to prevent this, either enable the ovrf interrupt or do another read of the spscr after the read of the spdr. this ensures that the ovrf was not set before the sprf was cleared and that future transmissions will complete with an sprf interrupt. figure 17-7 illustrates this process. generally, to avoid this second spscr read, enable the ovrf to the cpu by setting the errie bit (spscr). read spdr read spscr ovrf sprf byte 1 byte 2 byte 3 byte 4 byte 1 sets sprf bit. cpu reads spscr with sprf bit set cpu reads byte 1 in spdr, byte 2 sets sprf bit. cpu reads spscrw with sprf bit set byte 3 sets ovrf bit. byte 3 is lost. cpu reads byte 2 in spdr, clearing sprf bit, byte 4 fails to set sprf bit because 1 1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 clearing sprf bit. but not ovrf bit. ovrf bit is set. byte 4 is lost. and ovrf bit clear. and ovrf bit clear. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) error conditions mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 249 figure 17-7. clearing sprf when ovrf interrupt is not enabled 17.7.2 mode fault error for the modf flag (in spscr) to be set, the mode fault error enable bit (modfen in spscr) must be set. clearing the modfen bit does not clear the modf flag but does prevent modf from being set again after modf is cleared. modf generates a receiver/error cpu interrupt request if the error interrupt enable bit (errie in spscr) is also set. the sprf, modf, and ovrf interrupts share the same cpu interrupt vector. modf and ovrf can generate a receiver/error cpu interrupt request. (see figure 17-8 ). it is not possible to enable only modf or ovrf to generate a receiver/error cpu interrupt request. however, leaving modfen low prevents modf from being set. read spdr read spscr ovrf sprf byte 1 byte 2 byte 3 byte 4 1 byte 1 sets sprf bit. cpu reads spscr with sprf bit set cpu reads byte 1 in spdr, cpu reads spscr again byte 2 sets sprf bit. cpu reads spscr with sprf bit set byte 3 sets ovrf bit. byte 3 is lost. cpu reads byte 2 in spdr, cpu reads spscr again cpu reads byte 2 spdr, byte 4 sets sprf bit. cpu reads spscr. cpu reads byte 4 in spdr, cpu reads spscr again 1 2 3 clearing sprf bit. 4 to check ovrf bit. 5 6 7 8 9 clearing sprf bit. to check ovrf bit. 10 clearing ovrf bit. 11 12 13 14 2 3 4 5 6 7 8 9 10 11 12 13 14 clearing sprf bit. to check ovrf bit. spi receive complete and ovrf bit clear. and ovrf bit clear. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 250 serial peripheral interface (spi) motorola in a master spi with the mode fault enable bit (modfen) set, the mode fault flag (modf) is set if ss goes to logic 0. a mode fault in a master spi causes the following events to occur: if errie = 1, the spi generates an spi receiver/error cpu interrupt request. the spe bit is cleared. the spte bit is set. the spi state counter is cleared. the data direction register of the shared i/o port regains control of port drivers. note: to prevent bus contention with another master spi after a mode fault error, clear all data direction register (ddr) bits associated with the spi shared port pins. note: setting the modf flag (spscr) does not clear the spmstr bit. reading spmstr when modf = 1 will indicate a mode fault error occurred in either master mode or slave mode. when configured as a slave (spmstr = 0), the modf flag is set if ss goes high during a transmission. when cpha = 0, a transmission begins when ss goes low and ends once the incoming spsck returns to its idle level after the shift of the eighth data bit. when cpha = 1, the transmission begins when the spsck leaves its idle level and ss is already low. the transmission continues until the spsck returns to its idle level after the shift of the last data bit. (see transmission formats on page 242). note: when cpha = 0, a modf occurs if a slave is selected (ss is at logic 0) and later deselected (ss is at logic 1) even if no spsck is sent to that slave. this happens because ss at logic 0 indicates the start of the transmission (miso driven out with the value of msb) for cpha = 0. when cpha = 1, a slave can be selected and then later deselected with no transmission occurring. therefore, modf does not occur since a transmission was never begun. in a slave spi (mstr = 0), the modf bit generates an spi receiver/error cpu interrupt request if the errie bit is set. the modf f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) interrupts mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 251 bit does not clear the spe bit or reset the spi in any way. software can abort the spi transmission by toggling the spe bit of the slave. note: a logic 1 voltage on the ss pin of a slave spi puts the miso pin in a high impedance state. also, the slave spi ignores all incoming spsck clocks, even if a transmission has begun. to clear the modf flag, read the spscr and then write to the spcr register. this entire clearing procedure must occur with no modf condition existing or else the flag will not be cleared. 17.8 interrupts four spi status flags can be enabled to generate cpu interrupt requests: the spi transmitter interrupt enable bit (sptie) enables the spte flag to generate transmitter cpu interrupt requests. the spi receiver interrupt enable bit (sprie) enables the sprf bit to generate receiver cpu interrupt, provided that the spi is enabled (spe = 1). the error interrupt enable bit (errie) enables both the modf and ovrf flags to generate a receiver/error cpu interrupt request. the mode fault enable bit (modfen) can prevent the modf flag from being set so that only the ovrf flag is enabled to generate receiver/error cpu interrupt requests. table 17-4. spi interrupts flag request spte (transmitter empty) spi transmitter cpu interrupt request (sptie = 1) sprf (receiver full) spi receiver cpu interrupt request (sprie = 1) ovrf (overflow) spi receiver/error interrupt request (sprie = 1, errie = 1) modf (mode fault) spi receiver/error interrupt request (sprie = 1, errie = 1, modfen = 1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 252 serial peripheral interface (spi) motorola figure 17-8. spi interrupt request generation two sources in the spi status and control register can generate cpu interrupt requests: 1. spi receiver full bit (sprf) ? the sprf bit becomes set every time a byte transfers from the shift register to the receive data register. if the spi receiver interrupt enable bit, sprie, is also set, sprf can generate an spi receiver/error cpu interrupt request. 2. spi transmitter empty (spte) ? the spte bit becomes set every time a byte transfers from the transmit data register to the shift register. if the spi transmit interrupt enable bit, sptie, is also set, spte can generate an spte cpu interrupt request. 17.9 queuing transmission data the double-buffered transmit data register allows a data byte to be queued and transmitted. for an spi configured as a master, a queued data byte is transmitted immediately after the previous transmission has completed. the spi transmitter empty flag (spte in spscr) indicates when the transmit data buffer is ready to accept new data. write to the spi data register only when the spte bit is high. figure 17-9 shows the timing associated with doing back-to-back transmissions with the spi (spsck has cpha:cpol = 1:0). spte sptie sprf sprie errie modf ovrf spe spi transmitter cpu interrupt request spi receiver/error cpu interrupt request f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) queuing transmission data mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 253 figure 17-9. sprf/spte cpu interrupt timing for a slave, the transmit data buffer allows back-to-back transmissions to occur without the slave having to time the write of its data between the transmissions. also, if no new data is written to the data buffer, the last value contained in the shift register will be the next data word transmitted. bit 3 mosi spsck (cpha:cpol = 1:0) spte write to spdr 1 cpu writes byte 2 to spdr, queueing cpu writes byte 1 to spdr, clearing byte 1 transfers from transmit data 3 1 2 2 3 5 spte bit. register to shift register, setting spte bit. sprf read spscr msb bit 6 bit 5 bit 4 bit 2 bit 1 lsb msb bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb bit 6 byte 2 transfers from transmit data cpu writes byte 3 to spdr, queueing byte 3 transfers from transmit data 5 8 10 8 10 4 first incoming byte transfers from shift 6 cpu reads spscr with sprf bit set. 4 6 9 second incoming byte transfers from shift 9 11 byte 2 and clearing spte bit. register to shift register, setting spte bit. register to receive data register, setting sprf bit. byte 3 and clearing spte bit. register to shift register, setting spte bit. register to receive data register, setting sprf bit. 12 cpu reads spdr, clearing sprf bit. bit 5 bit 4 byte 1 byte 2 byte 3 7 12 read spdr 7 cpu reads spdr, clearing sprf bit. 11 cpu reads spscr with sprf bit set. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 254 serial peripheral interface (spi) motorola 17.10 resetting the spi any system reset completely resets the spi. partial reset occurs whenever the spi enable bit (spe) is low. whenever spe is low, the following occurs: the spte flag is set. any transmission currently in progress is aborted. the shift register is cleared. the spi state counter is cleared, making it ready for a new complete transmission. all the spi port logic is defaulted back to being general-purpose i/o. the following additional items are reset only by a system reset: all control bits in the spcr register all control bits in the spscr register (modfen, errie, spr1, and spr0) the status flags sprf, ovrf, and modf by not resetting the control bits when spe is low, the user can clear spe between transmissions without having to reset all control bits when spe is set back to high for the next transmission. by not resetting the sprf, ovrf, and modf flags, the user can still service these interrupts after the spi has been disabled. the user can disable the spi by writing 0 to the spe bit. the spi also can be disabled by a mode fault occurring in an spi that was configured as a master with the modfen bit set. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 255 17.11 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 17.11.1 wait mode the spi module remains active after the execution of a wait instruction. in wait mode, the spi module registers are not accessible by the cpu. any enabled cpu interrupt request from the spi module can bring the mcu out of wait mode. if spi module functions are not required during wait mode, reduce power consumption by disabling the spi module before executing the wait instruction. to exit wait mode when an overflow condition occurs, enable the ovrf bit to generate cpu interrupt requests by setting the error interrupt enable bit (errie). (see interrupts on page 251). 17.11.2 stop mode the spi module is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions. spi operation resumes after the mcu exits stop mode. if stop mode is exited by reset, any transfer in progress is aborted and the spi is reset. 17.12 spi during break interrupts the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr, $fe03) enables software to clear status bits during the break state. (see sim break flag control register on page 122). to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 256 serial peripheral interface (spi) motorola to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a two-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. since the spte bit cannot be cleared during a break with the bcfe bit cleared, a write to the data register in break mode will not initiate a transmission nor will this data be transferred into the shift register. therefore, a write to the spdr in break mode with the bcfe bit cleared has no effect. 17.13 i/o signals the spi module has four i/o pins and shares three of them with a parallel i/o port. miso ? data received mosi ? data transmitted spsck ? serial clock ss ? slave select v ss ? clock ground the spi has limited inter-integrated circuit (i 2 c) capability (requiring software support) as a master in a single-master environment. to communicate with i 2 c peripherals, mosi becomes an open-drain output when the spwom bit in the spi control register is set. in i 2 c communication, the mosi and miso pins are connected to a bidirectional pin from the i 2 c peripheral and through a pullup resistor to v dd . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) i/o signals mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 257 17.13.1 miso (master in/slave out) miso is one of the two spi module pins that transmit serial data. in full duplex operation, the miso pin of the master spi module is connected to the miso pin of the slave spi module. the master spi simultaneously receives data on its miso pin and transmits data from its mosi pin. slave output data on the miso pin is enabled only when the spi is configured as a slave. the spi is configured as a slave when its spmstr bit is logic 0 and its ss pin is at logic 0. to support a multiple- slave system, a logic 1 on the ss pin puts the miso pin in a high- impedance state. when enabled, the spi controls data direction of the miso pin regardless of the state of the data direction register of the shared i/o port. 17.13.2 mosi (master out/slave in) mosi is one of the two spi module pins that transmit serial data. in full duplex operation, the mosi pin of the master spi module is connected to the mosi pin of the slave spi module. the master spi simultaneously transmits data from its mosi pin and receives data on its miso pin. when enabled, the spi controls data direction of the mosi pin regardless of the state of the data direction register of the shared i/o port. 17.13.3 spsck (serial clock) the serial clock synchronizes data transmission between master and slave devices. in a master mcu, the spsck pin is the clock output. in a slave mcu, the spsck pin is the clock input. in full duplex operation, the master and slave mcus exchange a byte of data in eight serial clock cycles. when enabled, the spi controls data direction of the spsck pin regardless of the state of the data direction register of the shared i/o port. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 258 serial peripheral interface (spi) motorola 17.13.4 ss (slave select) the ss pin has various functions depending on the current state of the spi. for an spi configured as a slave, the ss is used to select a slave. for cpha = 0, the ss is used to define the start of a transmission. (see transmission formats .) since it is used to indicate the start of a transmission, the ss must be toggled high and low between each byte transmitted for the cpha = 0 format. however, it can remain low throughout the transmission for the cpha = 1 format. see figure 17-10 . figure 17-10. cpha/ss timing when an spi is configured as a slave, the ss pin is always configured as an input. it cannot be used as a general-purpose i/o regardless of the state of the modfen control bit. however, the modfen bit can still prevent the state of the ss from creating a modf error. (see spi status and control register on page 262). note: a logic 1 voltage on the ss pin of a slave spi puts the miso pin in a high- impedance state. the slave spi ignores all incoming spsck clocks, even if a transmission already has begun. when an spi is configured as a master, the ss input can be used in conjunction with the modf flag to prevent multiple masters from driving mosi and spsck. (see mode fault error on page 249). for the state of the ss pin to set the modf flag, the modfen bit in the spsck register must be set. if the modfen bit is low for an spi master, the ss pin can be used as a general-purpose i/o under the control of the data direction register of the shared i/o port. with modfen high, it is an input-only pin to the spi regardless of the state of the data direction register of the shared i/o port. byte 1 byte 3 miso/mosi byte 2 master ss slave ss cpha = 0 slave ss cpha = 1 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 259 the cpu can always read the state of the ss pin by configuring the appropriate pin as an input and reading the data register. (see table 17- 5 ). 17.13.5 v ss (clock ground) v ss is the ground return for the serial clock pin, spsck, and the ground for the port output buffers. to reduce the ground return path loop and minimize radio frequency (rf) emissions, connect the ground pin of the slave to the v ss pin. 17.14 i/o registers three registers control and monitor spi operation: spi control register (spcr $0010) spi status and control register (spscr $0011) spi data register (spdr $0012) table 17-5. spi configuration spe spmstr modfen spi configuration state of ss logic 0x x not enabled general-purpose i/o; ss ignored by spi 1 0 x slave input-only to spi 1 1 0 master without modf general-purpose i/o; ss ignored by spi 1 1 1 master with modf input-only to spi x = don ? t care f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 260 serial peripheral interface (spi) motorola 17.14.1 spi control register the spi control register: enables spi module interrupt requests selects cpu interrupt requests configures the spi module as master or slave selects serial clock polarity and phase configures the spsck, mosi, and miso pins as open-drain outputs enables the spi module sprie ? spi receiver interrupt enable bit this read/write bit enables cpu interrupt requests generated by the sprf bit. the sprf bit is set when a byte transfers from the shift register to the receive data register. reset clears the sprie bit. 1 = sprf cpu interrupt requests enabled 0 = sprf cpu interrupt requests disabled spmstr ? spi master bit this read/write bit selects master mode operation or slave mode operation. reset sets the spmstr bit. 1 = master mode 0 = slave mode address: $0010 bit 7654321bit 0 read: sprie r spmstr cpol cpha spwom spe sptie write: reset:00101000 r= reserved figure 17-11. spi control register (spcr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 261 cpol ? clock polarity bit this read/write bit determines the logic state of the spsck pin between transmissions. (see figure 17-3 and figure 17-4 .) to transmit data between spi modules, the spi modules must have identical cpol bits. reset clears the cpol bit. cpha ? clock phase bit this read/write bit controls the timing relationship between the serial clock and spi data. (see figure 17-3 and figure 17-4 .) to transmit data between spi modules, the spi modules must have identical cpha bits. when cpha = 0, the ss pin of the slave spi module must be set to logic 1 between bytes. (see figure 17-10 ). reset sets the cpha bit. when cpha = 0 for a slave, the falling edge of ss indicates the beginning of the transmission. this causes the spi to leave its idle state and begin driving the miso pin with the msb of its data. once the transmission begins, no new data is allowed into the shift register from the data register. therefore, the slave data register must be loaded with the desired transmit data before the falling edge of ss . any data written after the falling edge is stored in the data register and transferred to the shift register at the current transmission. when cpha = 1 for a slave, the first edge of the spsck indicates the beginning of the transmission. the same applies when ss is high for a slave. the miso pin is held in a high-impedance state, and the incoming spsck is ignored. in certain cases, it may also cause the modf flag to be set. (see mode fault error on page 249). a logic 1 on the ss pin does not in any way affect the state of the spi state machine. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 262 serial peripheral interface (spi) motorola spwom ? spi wired-or mode bit this read/write bit disables the pullup devices on pins spsck, mosi, and miso so that those pins become open-drain outputs. 1 = wired-or spsck, mosi, and miso pins 0 = normal push-pull spsck, mosi, and miso pins spe ? spi enable bit this read/write bit enables the spi module. clearing spe causes a partial reset of the spi (see resetting the spi on page 254). reset clears the spe bit. 1 = spi module enabled 0 = spi module disabled sptie ? spi transmit interrupt enable bit this read/write bit enables cpu interrupt requests generated by the spte bit. spte is set when a byte transfers from the transmit data register to the shift register. reset clears the sptie bit. 1 = spte cpu interrupt requests enabled 0 = spte cpu interrupt requests disabled 17.14.2 spi status and control register the spi status and control register contains flags to signal the following conditions: receive data register full failure to clear sprf bit before next byte is received (overflow error) inconsistent logic level on ss pin (mode fault error) transmit data register empty the spi status and control register also contains bits that perform these functions: enable error interrupts enable mode fault error detection select master spi baud rate f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 263 sprf ? spi receiver full bit this clearable, read-only flag is set each time a byte transfers from the shift register to the receive data register. sprf generates a cpu interrupt request if the sprie bit in the spi control register is set also. during an sprf cpu interrupt, the cpu clears sprf by reading the spi status and control register with sprf set and then reading the spi data register. any read of the spi data register clears the sprf bit. reset clears the sprf bit. 1 = receive data register full 0 = receive data register not full errie ? error interrupt enable bit this read-only bit enables the modf and ovrf flags to generate cpu interrupt requests. reset clears the errie bit. 1 = modf and ovrf can generate cpu interrupt requests 0 = modf and ovrf cannot generate cpu interrupt requests ovrf ? overflow bit this clearable, read-only flag is set if software does not read the byte in the receive data register before the next byte enters the shift register. in an overflow condition, the byte already in the receive data register is unaffected, and the byte that shifted in last is lost. clear the ovrf bit by reading the spi status and control register with ovrf set and then reading the spi data register. reset clears the ovrf flag. 1 = overflow 0 = no overflow address: $0011 bit 7654321bit 0 read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:00001000 r= reserved = unimplemented figure 17-12. spi status and control register (spscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 264 serial peripheral interface (spi) motorola modf ? mode fault bit this clearable, read-only flag is set in a slave spi if the ss pin goes high during a transmission. in a master spi, the modf flag is set if the ss pin goes low at any time. clear the modf bit by reading the spi status and control register with modf set and then writing to the spi data register. reset clears the modf bit. 1 = ss pin at inappropriate logic level 0 = ss pin at appropriate logic level spte ? spi transmitter empty bit this clearable, read-only flag is set each time the transmit data register transfers a byte into the shift register. spte generates an spte cpu interrupt request if the sptie bit in the spi control register is set also. note: do not write to the spi data register unless the spte bit is high. for an idle master or idle slave that has no data loaded into its transmit buffer, the spte will be set again within two bus cycles since the transmit buffer empties into the shift register. this allows the user to queue up a 16-bit value to send. for an already active slave, the load of the shift register cannot occur until the transmission is completed. this implies that a back-to-back write to the transmit data register is not possible. the spte indicates when the next write can occur. reset sets the spte bit. 1 = transmit data register empty 0 = transmit data register not empty modfen ? mode fault enable bit this read/write bit, when set to 1, allows the modf flag to be set. if the modf flag is set, clearing the modfen does not clear the modf flag. if the spi is enabled as a master and the modfen bit is low, then the ss pin is available as a general-purpose i/o. if the modfen bit is set, then this pin is not available as a general purpose i/o. when the spi is enabled as a slave, the ss pin is not available as a general-purpose i/o regardless of the value of modfen. (see ss (slave select) on page 258). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola serial peripheral interface (spi) 265 if the modfen bit is low, the level of the ss pin does not affect the operation of an enabled spi configured as a master. for an enabled spi configured as a slave, having modfen low only prevents the modf flag from being set. it does not affect any other part of spi operation. (see mode fault error on page 249). spr1 and spr0 ? spi baud rate select bits in master mode, these read/write bits select one of four baud rates as shown in table 17-6 . spr1 and spr0 have no effect in slave mode. reset clears spr1 and spr0. use this formula to calculate the spi baud rate: where: cgmout = base clock output of the clock generator module (cgm), see clock generator module (cgm) on page 123. bd = baud rate divisor table 17-6. spi master baud rate selection spr1:spr0 baud rate divisor (bd) 00 2 01 8 10 32 11 128 baud rate cgmout 2bd -------------------------- = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . serial peripheral interface (spi) advance information mc68HC908AS32A ? rev 0.0 266 serial peripheral interface (spi) motorola 17.14.3 spi data register the spi data register is the read/write buffer for the receive data register and the transmit data register. writing to the spi data register writes data into the transmit data register. reading the spi data register reads data from the receive data register. the transmit data and receive data registers are separate buffers that can contain different values. see figure 17-1 r7 ? r0/t7 ? t0 ? receive/transmit data bits note: do not use read-modify-write instructions on the spi data register since the buffer read is not the same as the buffer written. address: $0012 bit 7654321bit 0 read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: indeterminate after reset figure 17-13. spi data register (spdr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 267 technical data ? mc68HC908AS32A section 18. timer interface module b (timb) 18.1 contents 18.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 18.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 18.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 18.4.1 timb counter prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . 271 18.4.2 input capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 18.4.3 output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 18.4.3.1 unbuffered output compare . . . . . . . . . . . . . . . . . . . . 273 18.4.3.2 buffered output compare . . . . . . . . . . . . . . . . . . . . . . 274 18.4.4 pulse width modulation (pwm) . . . . . . . . . . . . . . . . . . . 274 18.4.4.1 unbuffered pwm signal generation . . . . . . . . . . . . . 275 18.4.4.2 buffered pwm signal generation . . . . . . . . . . . . . . . . 276 18.4.4.3 pwm initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 18.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 18.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 18.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 18.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 18.7 timb during break interrupts . . . . . . . . . . . . . . . . . . . . . . . 279 18.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 18.8.1 timb clock pin (ptd4/atd12/tbclk) . . . . . . . . . . . . . . 280 18.8.2 timb channel i/o pins (ptf5/tbch1 ? ptf4/tbch0) . . 280 18.9 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 18.9.1 timb status and control register . . . . . . . . . . . . . . . . . 281 18.9.2 timb counter registers . . . . . . . . . . . . . . . . . . . . . . . . . 283 18.9.3 timb counter modulo registers . . . . . . . . . . . . . . . . . . . 285 18.9.4 timb channel status and control registers . . . . . . . . . 286 18.9.5 timb channel registers . . . . . . . . . . . . . . . . . . . . . . . . . 290 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 268 timer interface module b (timb) motorola 18.2 introduction this section describes the timer interface module (timb). the timb is a 2-channel timer that provides a timing reference with input capture, output compare and pulse width modulation functions. figure 18-1 is a block diagram of the timb. the timb module is feature of the mc68hc908az60a only. for further information regarding timers on m68hc08 family devices, please consult the hc08 timer reference manual, tim08rm/ad. 18.3 features features of the timb include: two input capture/output compare channels ? rising-edge, falling-edge or any-edge input capture trigger ? set, clear or toggle output compare action buffered and unbuffered pulse width modulation (pwm) signal generation programmable timb clock input ? 7 frequency internal bus clock prescaler selection ? external timb clock input (4 mhz maximum frequency) free-running or modulo up-count operation toggle any channel pin on overflow timb counter stop and reset bits f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) features mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 269 figure 18-1. timb block diagram prescaler prescaler select tclk internal 16-bit comparator ps2 ps1 ps0 16-bit comparator 16-bit latch tch0h:tch0l ms0a els0b els0a ptf4 tof toie inter- channel 0 tmodh:tmodl trst tstop tov0 ch0ie ch0f ch0max ms0b 16-bit counter bus clock ptd4/atd12/tbclk ptf4/tbch0 ptf5/tbch1 logic rupt logic inter- rupt logic 16-bit comparator 16-bit latch tch1h:tch1l ms1a els1b els1a ptf5 channel 1 tov1 ch1ie ch1f ch1max logic inter- rupt logic f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 270 timer interface module b (timb) motorola figure 18-2. timb i/o register summary addr. register name bit 7 6 5 4 3 2 1 bit 0 $0040 timb status/control register (tbsc) tof toie tstop trst 0 ps2 ps1 ps0 $0041 timb counter register high (tbcnth) bit 15 14 13 12 11 10 9 bit 8 $0042 timb counter register low (tbcntl) bit 7 6 5 4321bit 0 $0043 timb counter modulo reg. high (tbmodh) bit 15 14 13 12 11 10 9 bit 8 $0044 timb counter modulo reg. low (tbmodl) bit 7 6 5 4321bit 0 $0045 timb ch. 0 status/control register (tbsc0) ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max $0046 timb ch. 0 register high (tbch0h) bit 15 14 13 12 11 10 9 bit 8 $0047 timb ch. 0 register low (tbch0l) bit 7 6 5 4321bit 0 $0048 timb ch. 1 status/control register (tbsc1) ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max $0049 timb ch. 1 register high (tbch1h) bit 15 14 13 12 11 10 9 bit 8 $004a timb ch. 1 register low (tbch1l) bit 7 6 5 4321bit 0 r= reserved f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 271 18.4 functional description figure 18-1 shows the timb structure. the central component of the timb is the 16-bit timb counter that can operate as a free-running counter or a modulo up-counter. the timb counter provides the timing reference for the input capture and output compare functions. the timb counter modulo registers, tbmodh ? tbmodl, control the modulo value of the timb counter. software can read the timb counter value at any time without affecting the counting sequence. the two timb channels are programmable independently as input capture or output compare channels. 18.4.1 timb counter prescaler the timb clock source can be one of the seven prescaler outputs or the timb clock pin, ptd4/atd12/tbclk. the prescaler generates seven clock rates from the internal bus clock. the prescaler select bits, ps[2:0], in the timb status and control register select the timb clock source. 18.4.2 input capture an input capture function has three basic parts: edge select logic, an input capture latch and a 16-bit counter. two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the free-running counter after the corresponding input capture edge detector senses a defined transition. the polarity of the active edge is programmable. the level transition which triggers the counter transfer is defined by the corresponding input edge bits (elsxb and elsxa in tbsc0 through tbsc1 control registers with x referring to the active channel number). when an active edge occurs on the pin of an input capture channel, the timb latches the contents of the timb counter into the timb channel registers, tbchxh ? tbchxl. input captures can generate timb cpu interrupt requests. software can determine that an input capture event has occurred by enabling input capture interrupts or by polling the status flag bit. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 272 timer interface module b (timb) motorola the free-running counter contents are transferred to the timb channel register (tbchxh ? tbchxl, see timb channel registers on page 290) on each proper signal transition regardless of whether the timb channel flag (ch0f ? ch1f in tbsc0 ? tbsc1 registers) is set or clear. when the status flag is set, a cpu interrupt is generated if enabled. the value of the count latched or ? captured ? is the time of the event. because this value is stored in the input capture register 2 bus cycles after the actual event occurs, user software can respond to this event at a later time and determine the actual time of the event. however, this must be done prior to another input capture on the same pin; otherwise, the previous time value will be lost. by recording the times for successive edges on an incoming signal, software can determine the period and/or pulse width of the signal. to measure a period, two successive edges of the same polarity are captured. to measure a pulse width, two alternate polarity edges are captured. software should track the overflows at the 16-bit module counter to extend its range. another use for the input capture function is to establish a time reference. in this case, an input capture function is used in conjunction with an output compare function. for example, to activate an output signal a specified number of clock cycles after detecting an input event (edge), use the input capture function to record the time at which the edge occurred. a number corresponding to the desired delay is added to this captured value and stored to an output compare register (see timb channel registers on page 290). because both input captures and output compares are referenced to the same 16-bit modulo counter, the delay can be controlled to the resolution of the counter independent of software latencies. reset does not affect the contents of the input capture channel register (tbchxh ? tbchxl). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 273 18.4.3 output compare with the output compare function, the timb can generate a periodic pulse with a programmable polarity, duration and frequency. when the counter reaches the value in the registers of an output compare channel, the timb can set, clear or toggle the channel pin. output compares can generate timb cpu interrupt requests. 18.4.3.1 unbuffered output compare any output compare channel can generate unbuffered output compare pulses as described in output compare on page 273. the pulses are unbuffered because changing the output compare value requires writing the new value over the old value currently in the timb channel registers. an unsynchronized write to the timb channel registers to change an output compare value could cause incorrect operation for up to two counter overflow periods. for example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that counter overflow period. also, using a timb overflow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. the timb may pass the new value before it is written. use the following methods to synchronize unbuffered changes in the output compare value on channel x: when changing to a smaller value, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. the output compare interrupt occurs at the end of the current output compare pulse. the interrupt routine has until the end of the counter overflow period to write the new value. when changing to a larger output compare value, enable timb overflow interrupts and write the new value in the timb overflow interrupt routine. the timb overflow interrupt occurs at the end of the current counter overflow period. writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same counter overflow period. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 274 timer interface module b (timb) motorola 18.4.3.2 buffered output compare channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the ptf4/tbch0 pin. the timb channel registers of the linked pair alternately control the output. setting the ms0b bit in timb channel 0 status and control register (tbsc0) links channel 0 and channel 1. the output compare value in the timb channel 0 registers initially controls the output on the ptf4/tbch0 pin. writing to the timb channel 1 registers enables the timb channel 1 registers to synchronously control the output after the timb overflows. at each subsequent overflow, the timb channel registers (0 or 1) that control the output are the ones written to last. tbsc0 controls and monitors the buffered output compare function and timb channel 1 status and control register (tbsc1) is unused. while the ms0b bit is set, the channel 1 pin, ptf5/tbch1, is available as a general-purpose i/o pin. note: in buffered output compare operation, do not write new output compare values to the currently active channel registers. user software should track the currently active channel to prevent writing a new value to the active channel. writing to the active channel registers is the same as generating unbuffered output compares. 18.4.4 pulse width modulation (pwm) by using the toggle-on-overflow feature with an output compare channel, the timb can generate a pwm signal. the value in the timb counter modulo registers determines the period of the pwm signal. the channel pin toggles when the counter reaches the value in the timb counter modulo registers. the time between overflows is the period of the pwm signal. as figure 18-3 shows, the output compare value in the timb channel registers determines the pulse width of the pwm signal. the time between overflow and output compare is the pulse width. program the timb to clear the channel pin on output compare if the state of the pwm pulse is logic 1. program the timb to set the pin if the state of the pwm pulse is logic 0. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 275 figure 18-3. pwm period and pulse width the value in the timb counter modulo registers and the selected prescaler output determines the frequency of the pwm output. the frequency of an 8-bit pwm signal is variable in 256 increments. writing $00ff (255) to the timb counter modulo registers produces a pwm period of 256 times the internal bus clock period if the prescaler select value is $000 (see timb status and control register ). the value in the timb channel registers determines the pulse width of the pwm output. the pulse width of an 8-bit pwm signal is variable in 256 increments. writing $0080 (128) to the timb channel registers produces a duty cycle of 128/256 or 50%. 18.4.4.1 unbuffered pwm signal generation any output compare channel can generate unbuffered pwm pulses as described in pulse width modulation (pwm) on page 274. the pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the value currently in the timb channel registers. an unsynchronized write to the timb channel registers to change a pulse width value could cause incorrect operation for up to two pwm periods. for example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that pwm period. also, using a timb overflow interrupt routine to write a new, smaller pulse width value may cause the compare ptex/tchx period pulse width overflow overflow overflow output compare output compare output compare f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 276 timer interface module b (timb) motorola to be missed. the timb may pass the new value before it is written to the timb channel registers. use the following methods to synchronize unbuffered changes in the pwm pulse width on channel x: when changing to a shorter pulse width, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. the output compare interrupt occurs at the end of the current pulse. the interrupt routine has until the end of the pwm period to write the new value. when changing to a longer pulse width, enable timb overflow interrupts and write the new value in the timb overflow interrupt routine. the timb overflow interrupt occurs at the end of the current pwm period. writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same pwm period. note: in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self- correct in the event of software error or noise. toggling on output compare also can cause incorrect pwm signal generation when changing the pwm pulse width to a new, much larger value. 18.4.4.2 buffered pwm signal generation channels 0 and 1 can be linked to form a buffered pwm channel whose output appears on the ptf4/tbch0 pin. the timb channel registers of the linked pair alternately control the pulse width of the output. setting the ms0b bit in timb channel 0 status and control register (tbsc0) links channel 0 and channel 1. the timb channel 0 registers initially control the pulse width on the ptf4/tbch0 pin. writing to the timb channel 1 registers enables the timb channel 1 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the timb channel registers (0 or 1) that control the pulse width are the ones written to last. tbsc0 controls and monitors the buffered pwm function, and timb channel 1 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 277 status and control register (tbsc1) is unused. while the ms0b bit is set, the channel 1 pin, ptf5/tbch1, is available as a general-purpose i/o pin. note: in buffered pwm signal generation, do not write new pulse width values to the currently active channel registers. user software should track the currently active channel to prevent writing a new value to the active channel. writing to the active channel registers is the same as generating unbuffered pwm signals. 18.4.4.3 pwm initialization to ensure correct operation when generating unbuffered or buffered pwm signals, use the following initialization procedure: 1. in the timb status and control register (tbsc): a. stop the timb counter by setting the timb stop bit, tstop. b. reset the timb counter and prescaler by setting the timb reset bit, trst. 2. in the timb counter modulo registers (tbmodh ? tbmodl) write the value for the required pwm period. 3. in the timb channel x registers (tbchxh ? tbchxl) write the value for the required pulse width. 4. in timb channel x status and control register (tbscx): a. write 0:1 (for unbuffered output compare or pwm signals) or 1:0 (for buffered output compare or pwm signals) to the mode select bits, msxb ? msxa (see table 18-2 ). b. write 1 to the toggle-on-overflow bit, tovx. c. write 1:0 (to clear output on compare) or 1:1 (to set output on compare) to the edge/level select bits, elsxb ? elsxa. the output action on compare must force the output to the complement of the pulse width level (see table 18-2 ). note: in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self- correct in the event of software error or noise. toggling on output f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 278 timer interface module b (timb) motorola compare can also cause incorrect pwm signal generation when changing the pwm pulse width to a new, much larger value. 5. in the timb status control register (tbsc) clear the timb stop bit, tstop. setting ms0b links channels 0 and 1 and configures them for buffered pwm operation. the timb channel 0 registers (tbch0h ? tbch0l) initially control the buffered pwm output. timb status control register 0 (tbsc0) controls and monitors the pwm signal from the linked channels. ms0b takes priority over ms0a. clearing the toggle-on-overflow bit, tovx, inhibits output toggles on timb overflows. subsequent output compares try to force the output to a state it is already in and have no effect. the result is a 0% duty cycle output. setting the channel x maximum duty cycle bit (chxmax) and setting the tovx bit generates a 100% duty cycle output (see timb channel status and control registers on page 286). 18.5 interrupts the following timb sources can generate interrupt requests: timb overflow flag (tof) ? the tof bit is set when the timb counter value reaches the modulo value programmed in the timb counter modulo registers. the timb overflow interrupt enable bit, toie, enables timb overflow cpu interrupt requests. tof and toie are in the timb status and control register. timb channel flags (ch1f ? ch0f) ? the chxf bit is set when an input capture or output compare occurs on channel x. channel x timb cpu interrupt requests are controlled by the channel x interrupt enable bit, chxie. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 279 18.6 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 18.6.1 wait mode the timb remains active after the execution of a wait instruction. in wait mode, the timb registers are not accessible by the cpu. any enabled cpu interrupt request from the timb can bring the mcu out of wait mode. if timb functions are not required during wait mode, reduce power consumption by stopping the timb before executing the wait instruction. 18.6.2 stop mode the timb is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions or the state of the timb counter. timb operation resumes when the mcu exits stop mode. 18.7 timb during break interrupts a break interrupt stops the timb counter and inhibits input captures. the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state (see sim break flag control register on page 122). to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 280 timer interface module b (timb) motorola i/o registers during the break state without affecting status bits. some status bits have a 2-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 18.8 i/o signals port d shares one of its pins with the timb. port f shares two of its pins with the timb. ptd4/atd12/tbclk is an external clock input to the timb prescaler. the two timb channel i/o pins are ptf4/tbch0 and ptf5/tbch1. 18.8.1 timb clock pin (ptd4/atd12/tbclk) ptd4/atd12/tbclk is an external clock input that can be the clock source for the timb counter instead of the prescaled internal bus clock. select the ptd4/atd12/tbclk input by writing logic 1s to the three prescaler select bits, ps[2:0] (see timb status and control register ). the minimum tclk pulse width, tclk lmin or tclk hmin , is: the maximum tclk frequency is the least: 4 mhz or bus frequency 2. ptd4/atd12/tbclk is available as a general-purpose i/o pin or adc channel when not used as the timb clock input. when the ptd4/atd12/tbclk pin is the timb clock input, it is an input regardless of the state of the ddrd4 bit in data direction register d. 18.8.2 timb channel i/o pins (ptf5/tbch1 ? ptf4/tbch0) each channel i/o pin is programmable independently as an input capture pin or an output compare pin. ptf4/tbch0 and ptf5/tbch1 can be configured as buffered output compare or buffered pwm pins. 1 bus frequency ------------------------------------- t su + f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 281 18.9 i/o registers these i/o registers control and monitor timb operation: timb status and control register (tbsc) timb control registers (tbcnth ? tbcntl) timb counter modulo registers (tbmodh ? tbmodl) timb channel status and control registers (tbsc0 and tbsc1) timb channel registers (tbch0h ? tbch0l, tbch1h ? tbch1l) 18.9.1 timb status and control register the timb status and control register: enables timb overflow interrupts flags timb overflows stops the timb counter resets the timb counter prescales the timb counter clock tof ? timb overflow flag bit this read/write flag is set when the timb counter reaches the modulo value programmed in the timb counter modulo registers. clear tof by reading the timb status and control register when tof is set and then writing a logic 0 to tof. if another timb overflow occurs before address: $0040 bit 7654321bit 0 read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset:00100000 r= reserved figure 18-4. timb status and control register (tbsc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 282 timer interface module b (timb) motorola the clearing sequence is complete, then writing logic 0 to tof has no effect. therefore, a tof interrupt request cannot be lost due to inadvertent clearing of tof. reset clears the tof bit. writing a logic 1 to tof has no effect. 1 = timb counter has reached modulo value 0 = timb counter has not reached modulo value toie ? timb overflow interrupt enable bit this read/write bit enables timb overflow interrupts when the tof bit becomes set. reset clears the toie bit. 1 = timb overflow interrupts enabled 0 = timb overflow interrupts disabled tstop ? timb stop bit this read/write bit stops the timb counter. counting resumes when tstop is cleared. reset sets the tstop bit, stopping the timb counter until software clears the tstop bit. 1 = timb counter stopped 0 = timb counter active note: do not set the tstop bit before entering wait mode if the timb is required to exit wait mode. also, when the tstop bit is set and the timer is configured for input capture operation, input captures are inhibited until tstop is cleared. trst ? timb reset bit setting this write-only bit resets the timb counter and the timb prescaler. setting trst has no effect on any other registers. counting resumes from $0000. trst is cleared automatically after the timb counter is reset and always reads as logic 0. reset clears the trst bit. 1 = prescaler and timb counter cleared 0 = no effect note: setting the tstop and trst bits simultaneously stops the timb counter at a value of $0000. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 283 ps[2:0] ? prescaler select bits these read/write bits select either the ptd4/atd12/tbclk pin or one of the seven prescaler outputs as the input to the timb counter as table 18-1 shows. reset clears the ps[2:0] bits. 18.9.2 timb counter registers the two read-only timb counter registers contain the high and low bytes of the value in the timb counter. reading the high byte (tbcnth) latches the contents of the low byte (tbcntl) into a buffer. subsequent reads of tbcnth do not affect the latched tbcntl value until tbcntl is read. reset clears the timb counter registers. setting the timb reset bit (trst) also clears the timb counter registers. note: if tbcnth is read during a break interrupt, be sure to unlatch tbcntl by reading tbcntl before exiting the break interrupt. otherwise, tbcntl retains the value latched during the break. table 18-1. prescaler selection ps[2:0] timb clock source 000 internal bus clock 1 001 internal bus clock 2 010 internal bus clock 4 011 internal bus clock 8 100 internal bus clock 16 101 internal bus clock 32 110 internal bus clock 64 111 ptd4/atd12/tbclk f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 284 timer interface module b (timb) motorola register name and address tbcnth ? $0041 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write:rrrrrrrr reset:00000000 register name and address tbcntl ? $0042 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write:rrrrrrrr reset:00000000 rr = reserved figure 18-5. timb counter registers (tbcnth and tbcntl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 285 18.9.3 timb counter modulo registers the read/write timb modulo registers contain the modulo value for the timb counter. when the timb counter reaches the modulo value, the overflow flag (tof) becomes set and the timb counter resumes counting from $0000 at the next timer clock. writing to the high byte (tbmodh) inhibits the tof bit and overflow interrupts until the low byte (tbmodl) is written. reset sets the timb counter modulo registers. note: reset the timb counter before writing to the timb counter modulo registers. register name and address tbmodh ? $0043 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset:11111111 register name and address tbmodl ? $0044 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 18-6. timb counter modulo registers (tbmodh and tbmodl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 286 timer interface module b (timb) motorola 18.9.4 timb channel status and control registers each of the timb channel status and control registers: flags input captures and output compares enables input capture and output compare interrupts selects input capture, output compare or pwm operation selects high, low or toggling output on output compare selects rising edge, falling edge or any edge as the active input capture trigger selects output toggling on timb overflow selects 0% and 100% pwm duty cycle selects buffered or unbuffered output compare/pwm operation register name and address tbsc0 ? $0045 bit 7654321bit 0 read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 register name and address tbsc1 ? $0048 bit 7654321bit 0 read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset:00000000 rr = reserved figure 18-7. timb channel status and control registers (tbsc0 ? tbsc1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 287 chxf ? channel x flag bit when channel x is an input capture channel, this read/write bit is set when an active edge occurs on the channel x pin. when channel x is an output compare channel, chxf is set when the value in the timb counter registers matches the value in the timb channel x registers. when chxie = 1, clear chxf by reading timb channel x status and control register with chxf set, and then writing a logic 0 to chxf. if another interrupt request occurs before the clearing sequence is complete, then writing logic 0 to chxf has no effect. therefore, an interrupt request cannot be lost due to inadvertent clearing of chxf. reset clears the chxf bit. writing a logic 1 to chxf has no effect. 1 = input capture or output compare on channel x 0 = no input capture or output compare on channel x chxie ? channel x interrupt enable bit this read/write bit enables timb cpu interrupts on channel x. reset clears the chxie bit. 1 = channel x cpu interrupt requests enabled 0 = channel x cpu interrupt requests disabled msxb ? mode select bit b this read/write bit selects buffered output compare/pwm operation. msxb exists only in the timb channel 0. setting ms0b disables the channel 1 status and control register and reverts tbch1 to general-purpose i/o. reset clears the msxb bit. 1 = buffered output compare/pwm operation enabled 0 = buffered output compare/pwm operation disabled f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 288 timer interface module b (timb) motorola msxa ? mode select bit a when elsxb:a 00, this read/write bit selects either input capture operation or unbuffered output compare/pwm operation (see table 18-2 ). 1 = unbuffered output compare/pwm operation 0 = input capture operation when elsxb:a = 00, this read/write bit selects the initial output level of the tbchx pin once pwm, input capture or output compare operation is enabled (see table 18-2 ). reset clears the msxa bit. 1 = initial output level low 0 = initial output level high note: before changing a channel function by writing to the msxb or msxa bit, set the tstop and trst bits in the timb status and control register (tbsc). elsxb and elsxa ? edge/level select bits when channel x is an input capture channel, these read/write bits control the active edge-sensing logic on channel x. when channel x is an output compare channel, elsxb and elsxa control the channel x output behavior when an output compare occurs. when elsxb and elsxa are both clear, channel x is not connected to port f and pin ptfx/tbchx is available as a general-purpose i/o pin. however, channel x is at a state determined by these bits and becomes transparent to the respective pin when pwm, input capture, or output compare mode is enabled. table 18-2 shows how elsxb and elsxa work. reset clears the elsxb and elsxa bits. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 289 note: before enabling a timb channel register for input capture operation, make sure that the ptfx/tbchx pin is stable for at least two bus clocks. tovx ? toggle-on-overflow bit when channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the timb counter overflows. when channel x is an input capture channel, tovx has no effect. reset clears the tovx bit. 1 = channel x pin toggles on timb counter overflow. 0 = channel x pin does not toggle on timb counter overflow. note: when tovx is set, a timb counter overflow takes precedence over a channel x output compare if both occur at the same time. table 18-2. mode, edge, and level selection msxb:msxa elsxb:elsxa mode configuration x0 00 output preset pin under port control; initialize timer output level high x1 00 pin under port control; initialize timer output level low 00 01 input capture capture on rising edge only 00 10 capture on falling edge only 00 11 capture on rising or falling edge 01 01 output compare or pwm toggle output on compare 01 10 clear output on compare 01 11 set output on compare 1x 01 buffered output compare or buffered pwm toggle output on compare 1x 10 clear output on compare 1x 11 set output on compare f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 290 timer interface module b (timb) motorola chxmax ? channel x maximum duty cycle bit when the tovx bit is at logic 1, setting the chxmax bit forces the duty cycle of buffered and unbuffered pwm signals to 100%. as figure 18-8 shows, the chxmax bit takes effect in the cycle after it is set or cleared. the output stays at the 100% duty cycle level until the cycle after chxmax is cleared. figure 18-8. chxmax latency 18.9.5 timb channel registers these read/write registers contain the captured timb counter value of the input capture function or the output compare value of the output compare function. the state of the timb channel registers after reset is unknown. in input capture mode (msxb ? msxa = 0:0) reading the high byte of the timb channel x registers (tbchxh) inhibits input captures until the low byte (tbchxl) is read. in output compare mode (msxb ? msxa 0:0) writing to the high byte of the timb channel x registers (tbchxh) inhibits output compares and the chxf bit until the low byte (tbchxl) is written. output overflow ptex/tchx period chxmax overflow overflow overflow overflow compare output compare output compare output compare f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module b (timb) 291 register name and address tbch0h ? $0046 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tbch0l ? $0047 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address tbch1h ? $0049 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tbch1l ? $004a bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset figure 18-9. timb channel registers (tbch0h/l ? tbch1h/l) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module b (timb) advance information mc68HC908AS32A ? rev 0.0 292 timer interface module b (timb) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola programmable interrupt timer (pit) 293 technical data ? mc68HC908AS32A section 19. programmable interrupt timer (pit) 19.1 contents 19.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 19.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 19.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 19.5 pit counter prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 19.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 19.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 19.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 19.7 pit during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 297 19.8 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 19.8.1 pit status and control register . . . . . . . . . . . . . . . . . . . 297 19.8.2 pit counter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 19.8.3 pit counter modulo registers . . . . . . . . . . . . . . . . . . . . 301 19.2 introduction this section describes the programmable interrupt timer (pit) which is a periodic interrupt timer whose counter is clocked internally via software programmable options. figure 19-1 is a block diagram of the pit. for further information regarding timers on m68hc08 family devices, please consult the hc08 timer reference manual, tim08rm/ad. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) advance information mc68HC908AS32A ? rev 0.0 294 programmable interrupt timer (pit) motorola 19.3 features features of the pit include: programmable pit clock input free-running or modulo up-count operation pit counter stop and reset bits 19.4 functional description figure 19-1 shows the structure of the pit. the central component of the pit is the 16-bit pit counter that can operate as a free-running counter or a modulo up-counter. the counter provides the timing reference for the interrupt. the pit counter modulo registers, pmodh ? pmodl, control the modulo value of the counter. software can read the counter value at any time without affecting the counting sequence. figure 19-1. pit block diagram prescaler prescaler select internal 16-bit comparator pps2 pps1 pps0 pof poie inter- timpmodh:timpmodl crst cstop 16-bit counter bus clock rupt logic f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) functional description mc68HC908AS32A ? rev 0.0 advance information motorola programmable interrupt timer (pit) 295 register name bit 7654321bit 0 pit status and control register (psc) read: pof poie pstop 00 pps2 pps1 pps0 write: 0 prst reset:00100000 pit counter register high (pcnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 pit counter register low (pcntl) read: bit 7 654321bit 0 write: reset:00000000 pit counter modulo register high (pmodh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 pit counter modulo register low (pmodl) read: bit 7654321bit 0 write: reset:11111111 =unimplemented figure 19-2. pit i/o register summary table 19-1. pit i/o register address summary register psc pcnth pcntl pmodh pmodl address $004b $004c $004d $004e $004f f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) advance information mc68HC908AS32A ? rev 0.0 296 programmable interrupt timer (pit) motorola 19.5 pit counter prescaler the clock source can be one of the seven prescaler outputs. the prescaler generates seven clock rates from the internal bus clock. the prescaler select bits, pps[2:0], in the status and control register select the pit clock source. the value in the pit counter modulo registers and the selected prescaler output determines the frequency of the periodic interrupt. the pit overflow flag (pof) is set when the pit counter value reaches the modulo value programmed in the pit counter modulo registers. the pit interrupt enable bit, poie, enables pit overflow cpu interrupt requests. pof and poie are in the pit status and control register. 19.6 low-power modes the wait and stop instructions put the mcu in low power-consump- tion standby modes. 19.6.1 wait mode the pit remains active after the execution of a wait instruction. in wait mode the pit registers are not accessible by the cpu. any enabled cpu interrupt request from the pit can bring the mcu out of wait mode. if pit functions are not required during wait mode, reduce power consumption by stopping the pit before executing the wait instruction. 19.6.2 stop mode the pit is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions or the state of the pit counter. pit operation resumes when the mcu exits stop mode after an external interrupt. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) pit during break interrupts mc68HC908AS32A ? rev 0.0 advance information motorola programmable interrupt timer (pit) 297 19.7 pit during break interrupts a break interrupt stops the pit counter. the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state (see sim break flag control register on page 122). to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a 2-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 19.8 i/o registers the following i/o registers control and monitor operation of the pit: pit status and control register (psc) pit counter registers (pcnth ? pcntl) pit counter modulo registers (pmodh ? pmodl) 19.8.1 pit status and control register the pit status and control register: enables pit interrupt flags pit overflows stops the pit counter f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) advance information mc68HC908AS32A ? rev 0.0 298 programmable interrupt timer (pit) motorola resets the pit counter prescales the pit counter clock pof ? pit overflow flag bit this read/write flag is set when the pit counter reaches the modulo value programmed in the pit counter modulo registers. clear pof by reading the pit status and control register when pof is set and then writing a logic 0 to pof. if another pit overflow occurs before the clearing sequence is complete, then writing logic 0 to pof has no effect. therefore, a pof interrupt request cannot be lost due to inadvertent clearing of pof. reset clears the pof bit. writing a logic 1 to pof has no effect. 1 = pit counter has reached modulo value 0 = pit counter has not reached modulo value poie ? pit overflow interrupt enable bit this read/write bit enables pit overflow interrupts when the pof bit becomes set. reset clears the poie bit. 1 = pit overflow interrupts enabled 0 = pit overflow interrupts disabled pstop ? pit stop bit this read/write bit stops the pit counter. counting resumes when pstop is cleared. reset sets the pstop bit, stopping the pit counter until software clears the pstop bit. 1 = pit counter stopped 0 = pit counter active address: $004b bit 7654321bit 0 read: pof poie pstop 00 pps2 pps1 pps0 write: 0 prst reset:00100000 = unimplemented figure 19-3. pit status and control register (psc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola programmable interrupt timer (pit) 299 note: do not set the pstop bit before entering wait mode if the pit is required to exit wait mode. prst ? pit reset bit setting this write-only bit resets the pit counter and the pit prescaler. setting prst has no effect on any other registers. counting resumes from $0000. prst is cleared automatically after the pit counter is reset and always reads as logic zero. reset clears the prst bit. 1 = prescaler and pit counter cleared 0 = no effect note: setting the pstop and prst bits simultaneously stops the pit counter at a value of $0000. pps[2:0] ? prescaler select bits these read/write bits select one of the seven prescaler outputs as the input to the pit counter as table 19-2 shows. reset clears the pps[2:0] bits. table 19-2. prescaler selection pps[2:0] pit clock source 000 internal bus clock 1 001 internal bus clock 2 010 internal bus clock 4 011 internal bus clock 8 100 internal bus clock 16 101 internal bus clock 32 110 internal bus clock 64 111 internal bus clock 64 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) advance information mc68HC908AS32A ? rev 0.0 300 programmable interrupt timer (pit) motorola 19.8.2 pit counter registers the two read-only pit counter registers contain the high and low bytes of the value in the pit counter. reading the high byte (pcnth) latches the contents of the low byte (pcntl) into a buffer. subsequent reads of pcnth do not affect the latched pcntl value until pcntl is read. reset clears the pit counter registers. setting the pit reset bit (prst) also clears the pit counter registers. note: if you read pcnth during a break interrupt, be sure to unlatch pcntl by reading pcntl before exiting the break interrupt. otherwise, pcntl retains the value latched during the break. address: $004c bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 address: $004d bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 = unimplemented figure 19-4. pit counter registers (pcnth ? pcntl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola programmable interrupt timer (pit) 301 19.8.3 pit counter modulo registers the read/write pit modulo registers contain the modulo value for the pit counter. when the pit counter reaches the modulo value the overflow flag (pof) becomes set and the pit counter resumes counting from $0000 at the next timer clock. writing to the high byte (pmodh) inhibits the pof bit and overflow interrupts until the low byte (pmodl) is written. reset sets the pit counter modulo registers. note: reset the pit counter before writing to the pit counter modulo registers. address: $004e:$004f bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 address: $004e:$004f bit 7654321bit 0 read: bit 7654321bit 0 write: reset:11111111 figure 19-5. pit counter modulo registers (pmodh ? pmodl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . programmable interrupt timer (pit) advance information mc68HC908AS32A ? rev 0.0 302 programmable interrupt timer (pit) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 303 technical data ? mc68HC908AS32A section 20. input/output ports 20.1 contents 20.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 20.3 port a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 port a data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 data direction register a . . . . . . . . . . . . . . . . . . . . . . . . 305 20.4 port b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 port b data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 data direction register b . . . . . . . . . . . . . . . . . . . . . . . . 308 20.5 port c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 port c data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 data direction register c . . . . . . . . . . . . . . . . . . . . . . . . 311 20.6 port d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 port d data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 data direction register d . . . . . . . . . . . . . . . . . . . . . . . . 314 20.7 port e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 port e data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 data direction register e . . . . . . . . . . . . . . . . . . . . . . . . 318 20.8 port f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 port f data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 data direction register f . . . . . . . . . . . . . . . . . . . . . . . . 321 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 304 input/output ports motorola 20.2 introduction on the52-pin mc68hc908as60a, forty bidirectional input/output (i/o) form six parallel ports. all i/o pins are programmable as inputs or outputs. note: connect any unused i/o pins to an appropriate logic level, either v dd or v ss . although the i/o ports do not require termination for proper operation, termination reduces excess current consumption and the possibility of electrostatic damage. figure 20-1. i/o port register summary addr. register name bit 7654321bit 0 $0000 port a data register (pta) pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 $0001 port b data register (ptb) ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 $0002 port c data register (ptc) 0 0 0 ptc4 ptc3 ptc2 ptc1 ptc0 $0003 port d data register (ptd) 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 $0004 data direction register a (ddra) ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 $0005 data direction register b (ddrb) ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 $0006 data direction register c (ddrc) mclken 0 0 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 $0007 data direction register d (ddrd) 0 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 $0008 port e data register (pte) pte7 pte6 pte5 pte4 pte3 pte2 pte1 pte0 $0009 port f data register (ptf) 0 0 0 0 ptf3 ptf2 ptf1 ptf0 $000c data direction register e (ddre) ddre7 ddre6 ddre5 ddre4 ddre3 ddre2 ddre1 ddre0 $000d data direction register f (ddrf) 0 0 0 0 ddrf3 ddrf2 ddrf1 ddrf0 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port a mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 305 20.3 port a port a is an 8-bit general-purpose bidirectional i/o port. 20.3.1 port a data register the port a data register contains a data latch for each of the eight port a pins. pta[7:0] ? port a data bits these read/write bits are software programmable. data direction of each port a pin is under the control of the corresponding bit in data direction register a. reset has no effect on port a data. 20.3.2 data direction register a data direction register a determines whether each port a pin is an input or an output. writing a logic 1 to a ddra bit enables the output buffer for the corresponding port a pin; a logic 0 disables the output buffer. address: $0000 bit 7654321bit 0 read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset figure 20-2. port a data register (pta) address: $0004 bit 7654321bit 0 read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 figure 20-3. data direction register a (ddra) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 306 input/output ports motorola ddra[7:0] ? data direction register a bits these read/write bits control port a data direction. reset clears ddra[7:0], configuring all port a pins as inputs. 1 = corresponding port a pin configured as output 0 = corresponding port a pin configured as input note: avoid glitches on port a pins by writing to the port a data register before changing data direction register a bits from 0 to 1. figure 20-4 shows the port a i/o logic. figure 20-4. port a i/o circuit when bit ddrax is a logic 1, reading address $0000 reads the ptax data latch. when bit ddrax is a logic 0, reading address $0000 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 20-1 summarizes the operation of the port a pins. table 20-1. port a pin functions ddra bit pta bit i/o pin mode accesses to ddra accesses to pta read/write read write 0 x input, hi-z ddra[7:0] pin pta[7:0] (1) 1 x output ddra[7:0] pta[7:0] pta[7:0] x = don ? t care hi-z = high impedance 1. writing affects data register, but does not affect input. read ddra ($0004) write ddra ($0004) reset write pta ($0000) read pta ($0000) ptax ddrax ptax internal data bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port b mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 307 20.4 port b port b is an 8-bit special function port that shares all of its pins with the analog-to-digital converter. 20.4.1 port b data register the port b data register contains a data latch for each of the eight port b pins. ptb[7:0] ? port b data bits these read/write bits are software programmable. data direction of each port b pin is under the control of the corresponding bit in data direction register b. reset has no effect on port b data. address: $0001 bit 7654321bit 0 read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset alternate functions: atd7 atd6 atd5 atd4 atd3 atd2 atd1 atd0 figure 20-5. port b data register (ptb) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 308 input/output ports motorola atd[7:0] ? adc channels ptb7/atd7 ? ptb0/atd0 are eight of the analog-to-digital converter channels. the adc channel select bits, ch[4:0], determine whether the ptb7/atd7 ? ptb0/atd0 pins are adc channels or general- purpose i/o pins. if an adc channel is selected and a read of this corresponding bit in the port b data register occurs, the data will be 0 if the data direction for this bit is programmed as an input. otherwise, the data will reflect the value in the data latch. (see analog-to-digital converter (adc) on page 361). data direction register b (ddrb) does not affect the data direction of port b pins that are being used by the adc. however, the ddrb bits always determine whether reading port b returns to the states of the latches or logic 0. 20.4.2 data direction register b data direction register b determines whether each port b pin is an input or an output. writing a logic 1 to a ddrb bit enables the output buffer for the corresponding port b pin; a logic 0 disables the output buffer. ddrb[7:0] ? data direction register b bits these read/write bits control port b data direction. reset clears ddrb[7:0], configuring all port b pins as inputs. 1 = corresponding port b pin configured as output 0 = corresponding port b pin configured as input note: avoid glitches on port b pins by writing to the port b data register before changing data direction register b bits from 0 to 1. figure 20-7 shows the port b i/o logic. address: $0005 bit 7654321bit 0 read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 figure 20-6. data direction register b (ddrb) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port b mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 309 figure 20-7. port b i/o circuit when bit ddrbx is a logic 1, reading address $0001 reads the ptbx data latch. when bit ddrbx is a logic 0, reading address $0001 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 20-2 summarizes the operation of the port b pins. table 20-2. port b pin functions ddrb bit ptb bit i/o pin mode accesses to ddrb accesses to ptb read/write read write 0 x input, hi-z ddrb[7:0] pin ptb[7:0] (1) 1 x output ddrb[7:0] ptb[7:0] ptb[7:0] x = don ? t care hi-z = high impedance 1. writing affects data register, but does not affect input. read ddrb ($0005) write ddrb ($0005) reset write ptb ($0001) read ptb ($0001) ptbx ddrbx ptbx internal data bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 310 input/output ports motorola 20.5 port c port c is an 5-bit general-purpose bidirectional i/o port. 20.5.1 port c data register the port c data register contains a data latch for each of the five port c pins. ptc[4:0] ? port c data bits these read/write bits are software-programmable. data direction of each port c pin is under the control of the corresponding bit in data direction register c. reset has no effect on port c data (4:0). mclk ? system clock bit the system clock is driven out of ptc2 when enabled by mclken bit in ptcddr7. address: $0002 bit 7654321bit 0 read: 0 0 0 ptc4 ptc3 ptc2 ptc1 ptc0 write:rrr reset: unaffected by reset r= reserved alternate functions: mclk figure 20-8. port c data register (ptc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port c mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 311 20.5.2 data direction register c data direction register c determines whether each port c pin is an input or an output. writing a logic 1 to a ddrc bit enables the output buffer for the corresponding port c pin; a logic 0 disables the output buffer. mclken ? mclk enable bit this read/write bit enables mclk to be an output signal on ptc2. if mclk is enabled, ddrc2 has no effect. reset clears this bit. 1 = mclk output enabled 0 = mclk output disabled ddrc[4:0] ? data direction register c bits these read/write bits control port c data direction. reset clears ddrc[4:0], configuring all port c pins as inputs. 1 = corresponding port c pin configured as output 0 = corresponding port c pin configured as input note: avoid glitches on port c pins by writing to the port c data register before changing data direction register c bits from 0 to 1. figure 20-10 shows the port c i/o logic. address: $0006 bit 7654321bit 0 read: mclken 00 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: r r reset:00000000 r= reserved figure 20-9. data direction register c (ddrc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 312 input/output ports motorola figure 20-10. port c i/o circuit when bit ddrcx is a logic 1, reading address $0002 reads the ptcx data latch. when bit ddrcx is a logic 0, reading address $0002 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 20-3 summarizes the operation of the port c pins. table 20-3. port c pin functions bit value ptc bit i/o pin mode accesses to ddrc accesses to ptc read/write read write 0 2 input, hi-z ddrc[2] pin ptc2 1 2 output ddrc[2] 0 ? 0 x input, hi-z ddrc[4:0] pin ptc[4:0] (1) 1 x output ddrc[4:0] ptc[4:0] ptc[4:0] x = don ? t care hi-z = high impedance 1. writing affects data register, but does not affect input. read ddrc ($0006) write ddrc ($0006) reset write ptc ($0002) read ptc ($0002) ptcx ddrcx ptcx internal data bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port d mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 313 20.6 port d port d is an 7-bit general-purpose i/o port. 20.6.1 port d data register port d is a 7-bit special function port that shares seven of its pins with the analog to digital converter and two with the timer interface modules. ptd[6:0] ? port d data bits ptd[6:0] are read/write, software programmable bits. data direction of ptd[6:0] pins are under the control of the corresponding bit in data direction register d. atd[14:8] ? adc channel status bits ptd6/atd14/taclk ? ptd0/atd8 are seven of the 15 analog-to- digital converter channels. the adc channel select bits, ch[4:0], determine whether the ptd6/atd14/taclk ? ptd0/atd8 pins are adc channels or general-purpose i/o pins. if an adc channel is selected and a read of this corresponding bit in the port b data register occurs, the data will be 0 if the data direction for this bit is programmed as an input. otherwise, the data will reflect the value in the data latch. (see analog-to-digital converter (adc) on page 361). data direction register d (ddrd) does not affect the data direction of port d pins that are being used by the tima. however, the ddrd bits address: $0003 bit 7654321bit 0 read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: r reset: unaffected by reset alternate functions: r atd14/ taclk atd13 atd12/ tbclk atd11 atd10 atd9 atd8 figure 20-11. port d data register (ptd) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 314 input/output ports motorola always determine whether reading port d returns the states of the latches or logic 0. taclk/tbclk ? timer clock input bit the ptd6/atd14/taclk pin is the external clock input for the tima. the prescaler select bits, ps[2:0], select ptd6/atd14/taclk as the tim clock input. (see tima channel status and control registers on page 352). when not selected as the tim clock, ptd6/atd14/taclk is available for general-purpose i/o. while taclk is selected corresponding ddrd bits have no effect. 20.6.2 data direction register d data direction register d determines whether each port d pin is an input or an output. writing a logic 1 to a ddrd bit enables the output buffer for the corresponding port d pin; a logic 0 disables the output buffer. ddrd[6:0] ? data direction register d bits these read/write bits control port d data direction. reset clears ddrd[6:0], configuring all port d pins as inputs. 1 = corresponding port d pin configured as output 0 = corresponding port d pin configured as input note: avoid glitches on port d pins by writing to the port d data register before changing data direction register d bits from 0 to 1. figure 20-13 shows the port d i/o logic. address: $0007 bit 7654321bit 0 read: 0 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: r reset:00000000 figure 20-12. data direction register d (ddrd) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port d mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 315 figure 20-13. port d i/o circuit when bit ddrdx is a logic 1, reading address $0003 reads the ptdx data latch. when bit ddrdx is a logic 0, reading address $0003 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 20-4 summarizes the operation of the port d pins. table 20-4. port d pin functions ddrd bit ptd bit i/o pin mode accesses to ddrd accesses to ptd read/write read write 0 x input, hi-z ddrd[6:0] pin ptd[6:0] (1) 1 x output ddrd[6:0] ptd[6:0] ptd[6:0] x = don ? t care hi-z = high impedance 1. writing affects data register, but does not affect input. read ddrd ($0007) write ddrd ($0007) reset write ptd ($0003) read ptd ($0003) ptdx ddrdx ptdx internal data bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 316 input/output ports motorola 20.7 port e port e is an 8-bit special function port that shares two of its pins with the timer interface module (tima), two of its pins with the serial communications interface module (sci), and four of its pins with the serial peripheral interface module (spi). 20.7.1 port e data register the port e data register contains a data latch for each of the eight port e pins. pte[7:0] ? port e data bits pte[7:0] are read/write, software programmable bits. data direction of each port e pin is under the control of the corresponding bit in data direction register e. spsck ? spi serial clock bit the pte7/spsck pin is the serial clock input of an spi slave module and serial clock output of an spi master module. when the spe bit is clear, the pte7/spsck pin is available for general-purpose i/o. (see spi control register on page 260). mosi ? master out/slave in bit the pte6/mosi pin is the master out/slave in terminal of the spi module. when the spe bit is clear, the pte6/mosi pin is available for general-purpose i/o. address: $0008 bit 7654321bit 0 read: pte7 pte6 pte5 pte4 pte3 pte2 pte1 pte0 write: reset: unaffected by reset alternate function: spsck mosi miso ss tach1 tach0 rxd txd figure 20-14. port e data register (pte) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port e mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 317 miso ? master in/slave out bit the pte5/miso pin is the master in/slave out terminal of the spi module. when the spi enable bit, spe, is clear, the spi module is disabled, and the pte5/miso pin is available for general-purpose i/o. (see spi control register on page 260). ss ? slave select bit the pte4/ss pin is the slave select input of the spi module. when the spe bit is clear, or when the spi master bit, spmstr, is set and modfen bit is low, the pte4/ss pin is available for general-purpose i/o. (see ss (slave select) on page 258). when the spi is enabled as a slave, the ddrf0 bit in data direction register e (ddre) has no effect on the pte4/ss pin. note: data direction register e (ddre) does not affect the data direction of port e pins that are being used by the spi module. however, the ddre bits always determine whether reading port e returns the states of the latches or the states of the pins. (see table 20-5 ). tach[1:0] ? timer channel i/o bits the pte3/tach1 ? pte2/tach0 pins are the tim input capture/output compare pins. the edge/level select bits, elsxb:elsxa, determine whether the pte3/tach1 ? pte2/tach0 pins are timer channel i/o pins or general-purpose i/o pins. (see tima channel status and control registers on page 352). note: data direction register e (ddre) does not affect the data direction of port e pins that are being used by the tim. however, the ddre bits always determine whether reading port e returns the states of the latches or the states of the pins. (see table 20-5 ). rxd ? sci receive data input bit the pte1/rxd pin is the receive data input for the sci module. when the enable sci bit, ensci, is clear, the sci module is disabled, and the pte1/rxd pin is available for general-purpose i/o. (see sci control register 1 on page 217). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 318 input/output ports motorola txd ? sci transmit data output the pte0/txd pin is the transmit data output for the sci module. when the enable sci bit, ensci, is clear, the sci module is disabled, and the pte0/txd pin is available for general-purpose i/o. (see sci control register 1 on page 217). note: data direction register e (ddre) does not affect the data direction of port e pins that are being used by the sci module. however, the ddre bits always determine whether reading port e returns the states of the latches or the states of the pins. (see table 20-5 ). 20.7.2 data direction register e data direction register e determines whether each port e pin is an input or an output. writing a logic 1 to a ddre bit enables the output buffer for the corresponding port e pin; a logic 0 disables the output buffer. ddre[7:0] ? data direction register e bits these read/write bits control port e data direction. reset clears ddre[7:0], configuring all port e pins as inputs. 1 = corresponding port e pin configured as output 0 = corresponding port e pin configured as input note: avoid glitches on port e pins by writing to the port e data register before changing data direction register e bits from 0 to 1. figure 20-16 shows the port e i/o logic. address: $000c bit 7654321bit 0 read: ddre7 ddre6 ddre5 ddre4 ddre3 ddre2 ddre1 ddre0 write: reset:00000000 figure 20-15. data direction register e (ddre) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port e mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 319 figure 20-16. port e i/o circuit when bit ddrex is a logic 1, reading address $0008 reads the ptex data latch. when bit ddrex is a logic 0, reading address $0008 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 20-5 summarizes the operation of the port e pins. table 20-5. port e pin functions ddre bit pte bit i/o pin mode accesses to ddre accesses to pte read/write read write 0 x input, hi-z ddre[7:0] pin pte[7:0] (1) 1 x output ddre[7:0] pte[7:0] pte[7:0] x = don ? t care hi-z = high impedance 1. writing affects data register, but does not affect input. read ddre ($000c) write ddre ($000c) reset write pte ($0008) read pte ($0008) ptex ddrex ptex internal data bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 320 input/output ports motorola 20.8 port f port f is a 4-bit special function port that shares four of its pins with the timer interface module (tima-6). 20.8.1 port f data register the port f data register contains a data latch for each of the four port f pins. ptf[3:0] ? port f data bits these read/write bits are software programmable. data direction of each port f pin is under the control of the corresponding bit in data direction register f. reset has no effect on ptf[3:0]. tach[5:2] ? timer a channel i/o bits the ptf3 ? ptf0/tach2 pins are the tim input capture/output compare pins. the edge/level select bits, elsxb:elsxa, determine whether the ptf3 ? ptf0/tach2 pins are timer channel i/o pins or general-purpose i/o pins. (see tima status and control register on page 347). note: data direction register f (ddrf) does not affect the data direction of port f pins that are being used by the tim. however, the ddrf bits always determine whether reading port f returns the states of the latches or the states of the pins. (see table 20-6 ). address: $0009 bit 7654321bit 0 read: 0000 ptf3 ptf2 ptf1 ptf0 write:rrrr reset: unaffected by reset alternate function: tach5 tach4 tach3 tach2 r= reserved figure 20-17. port f data register (ptf) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports port f mc68HC908AS32A ? rev 0.0 advance information motorola input/output ports 321 20.8.2 data direction register f data direction register f determines whether each port f pin is an input or an output. writing a logic 1 to a ddrf bit enables the output buffer for the corresponding port f pin; a logic 0 disables the output buffer. ddrf[3:0] ? data direction register f bits these read/write bits control port f data direction. reset clears ddrf[3:0], configuring all port f pins as inputs. 1 = corresponding port f pin configured as output 0 = corresponding port f pin configured as input note: avoid glitches on port f pins by writing to the port f data register before changing data direction register f bits from 0 to 1. figure 20-19 shows the port f i/o logic. figure 20-19. port f i/o circuit address: $000d bit 7654321bit 0 read: 0000 ddrf3 ddrf2 ddrf1 ddrf0 write:rrrr reset:00000000 r= reserved figure 20-18. data direction register f (ddrf) read ddrf ($000d) write ddrf ($000d) reset write ptf ($0009) read ptf ($0009) ptfx ddrfx ptfx internal data bus f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . input/output ports advance information mc68HC908AS32A ? rev 0.0 322 input/output ports motorola when bit ddrfx is a logic 1, reading address $0009 reads the ptfx data latch. when bit ddrfx is a logic 0, reading address $0009 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 20-6 summarizes the operation of the port f pins. table 20-6. port f pin functions ddrf bit ptf bit i/o pin mode accesses to ddrf accesses to ptf read/write read write 0 x input, hi-z ddrf[3:0] pin ptf[3:0] (1) 1 x output ddrf[3:0] ptf[3:0] ptf[3:0] x = don ? t care hi-z = high impedance 1. writing affects data register, but does not affect input. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola keyboard module (kbd) 323 technical data ? mc68HC908AS32A section 21. keyboard module (kbd) 21.1 contents 21.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 21.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 21.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 21.5 keyboard initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 21.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 21.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 21.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 21.7 keyboard module during break interrupts . . . . . . . . . . . . 328 21.8 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 21.8.1 keyboard status and control register . . . . . . . . . . . . . 329 21.8.2 keyboard interrupt enable register . . . . . . . . . . . . . . . . 330 21.2 introduction the keyboard interrupt module (kbd) provides five independently maskable external interrupt pins. this module is only available on 64-pin package options. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . keyboard module (kbd) advance information mc68HC908AS32A ? rev 0.0 324 keyboard module (kbd) motorola 21.3 features kbd features include: five keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard interrupt mask hysteresis buffers programmable edge-only or edge- and level- interrupt sensitivity automatic interrupt acknowledge exit from low-power modes 21.4 functional description writing to the kbie4 ? kbie0 bits in the keyboard interrupt enable register independently enables or disables each port g or port h pin as a keyboard interrupt pin. enabling a keyboard interrupt pin also enables its internal pullup device. a logic 0 applied to an enabled keyboard interrupt pin latches a keyboard interrupt request. a keyboard interrupt is latched when one or more keyboard pins goes low after all were high. the modek bit in the keyboard status and control register controls the triggering mode of the keyboard interrupt. if the keyboard interrupt is edge-sensitive only, a falling edge on a keyboard pin does not latch an interrupt request if another keyboard pin is already low. to prevent losing an interrupt request on one pin because another pin is still low, software can disable the latter pin while it is low. if the keyboard interrupt is falling edge- and low level-sensitive, an interrupt request is present as long as any keyboard pin is low. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola keyboard module (kbd) 325 keyboard module (kbd) functional description figure 21-1. keyboard module block diagram register name bit 7654321bit 0 keyboard status and control reg- ister (kbscr) read: 0000keyf0 imaskk modek write: ackk reset:00000000 keyboard interrupt enable regis- ter (kbier) read: 0 0 0 kbie4 kbie3 kbie2 kbie1 kbie0 write: reset:00000000 = unimplemented figure 21-2. i/o register summary table 21-1. i/o register address summary register kbscr kbier address $001a $001b kb0ie kb4ie . . . keyboard interrupt dq ck clr v dd modek imaskk keyboard interrupt ff request vector fetch decoder ackk internal bus reset to pullup enable kbd4 kbd0 to pullup enable synchronizer keyf f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . keyboard module (kbd) advance information mc68HC908AS32A ? rev 0.0 326 keyboard module (kbd) motorola if the modek bit is set, the keyboard interrupt pins are both falling edge- and low level-sensitive, and both of the following actions must occur to clear a keyboard interrupt request: vector fetch or software clear ? a vector fetch generates an interrupt acknowledge signal to clear the interrupt request. software may generate the interrupt acknowledge signal by writing a logic 1 to the ackk bit in the keyboard status and control register (kbscr). the ackk bit is useful in applications that poll the keyboard interrupt pins and require software to clear the keyboard interrupt request. writing to the ackk bit prior to leaving an interrupt service routine also can prevent spurious interrupts due to noise. setting ackk does not affect subsequent transitions on the keyboard interrupt pins. a falling edge that occurs after writing to the ackk bit latches another interrupt request. if the keyboard interrupt mask bit, imaskk, is clear, the cpu loads the program counter with the vector address at locations $ffde and $ffdf. return of all enabled keyboard interrupt pins to logic 1. as long as any enabled keyboard interrupt pin is at logic 0, the keyboard interrupt remains set. the vector fetch or software clear and the return of all enabled keyboard interrupt pins to logic 1 may occur in any order. if the modek bit is clear, the keyboard interrupt pin is falling edge- sensitive only. with modek clear, a vector fetch or software clear immediately clears the keyboard interrupt request. reset clears the keyboard interrupt request and the modek bit, clearing the interrupt request even if a keyboard interrupt pin stays at logic 0. the keyboard flag bit (keyf) in the keyboard status and control register can be used to see if a pending interrupt exists. the keyf bit is not affected by the keyboard interrupt mask bit (imaskk) which makes it useful in applications where polling is preferred. to determine the logic level on a keyboard interrupt pin, use the data direction register to configure the pin as an input and read the data register. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . keyboard module (kbd) keyboard initialization mc68HC908AS32A ? rev 0.0 advance information motorola keyboard module (kbd) 327 note: setting a keyboard interrupt enable bit (kbiex) forces the corresponding keyboard interrupt pin to be an input, overriding the data direction register. however, the data direction register bit must be a logic 0 for software to read the pin. 21.5 keyboard initialization when a keyboard interrupt pin is enabled, it takes time for the internal pullup to reach a logic 1. therefore, a false interrupt can occur as soon as the pin is enabled. to prevent a false interrupt on keyboard initialization: 1. mask keyboard interrupts by setting the imaskk bit in the keyboard status and control register 2. enable the kbi pins by setting the appropriate kbiex bits in the keyboard interrupt enable register 3. write to the ackk bit in the keyboard status and control register to clear any false interrupts 4. clear the imaskk bit. an interrupt signal on an edge-triggered pin can be acknowledged immediately after enabling the pin. an interrupt signal on an edge- and level-triggered interrupt pin must be acknowledged after a delay that depends on the external load. another way to avoid a false interrupt: 1. configure the keyboard pins as outputs by setting the appropriate ddrg bits in data direction register g. 2. configure the keyboard pins as outputs by setting the appropriate ddrh bits in data direction register h. 3. write logic 1s to the appropriate port g and port h data register bits. 4. enable the kbi pins by setting the appropriate kbiex bits in the keyboard interrupt enable register. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . keyboard module (kbd) advance information mc68HC908AS32A ? rev 0.0 328 keyboard module (kbd) motorola 21.6 low-power modes the wait and stop instructions put the mcu in low-power- consumption standby modes. 21.6.1 wait mode the keyboard module remains active in wait mode. clearing the imaskk bit in the keyboard status and control register enables keyboard interrupt requests to bring the mcu out of wait mode. 21.6.2 stop mode the keyboard module remains active in stop mode. clearing the imaskk bit in the keyboard status and control register enables keyboard interrupt requests to bring the mcu out of stop mode. 21.7 keyboard module during break interrupts the bcfe bit in the break flag control register (bfcr) enables software to clear status bits during the break state. see break module (brk) on page 157. to allow software to clear the keyf bit during a break interrupt, write a logic 1 to the bcfe bit. if keyf is cleared during the break state, it remains cleared when the mcu exits the break state. to protect the keyf bit during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0, writing to the keyboard acknowledge bit (ackk) in the keyboard status and control register during the break state has no effect. see keyboard status and control register on page 329. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . keyboard module (kbd) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola keyboard module (kbd) 329 21.8 i/o registers the following registers control and monitor operation of the keyboard module: keyboard status and control register (kbscr) keyboard interrupt enable register (kbier) 21.8.1 keyboard status and control register the keyboard status and control register: flags keyboard interrupt requests acknowledges keyboard interrupt requests masks keyboard interrupt requests controls keyboard interrupt triggering sensitivity bits 7 ? 4 ? not used these read-only bits always read as logic 0s. keyf ? keyboard flag bit this read-only bit is set when a keyboard interrupt is pending. reset clears the keyf bit. 1 = keyboard interrupt pending 0 = no keyboard interrupt pending address: $001a bit 7654321bit 0 read: 0000keyf0 imaskk modek write: ackk reset:00000000 = unimplemented figure 21-3. keyboard status and control register (kbscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . keyboard module (kbd) advance information mc68HC908AS32A ? rev 0.0 330 keyboard module (kbd) motorola ackk ? keyboard acknowledge bit writing a logic 1 to this write-only bit clears the keyboard interrupt request. ackk always reads as logic 0. reset clears ackk. imaskk ? keyboard interrupt mask bit writing a logic 1 to this read/write bit prevents the output of the keyboard interrupt mask from generating interrupt requests. reset clears the imaskk bit. 1 = keyboard interrupt requests masked 0 = keyboard interrupt requests not masked modek ? keyboard triggering sensitivity bit this read/write bit controls the triggering sensitivity of the keyboard interrupt pins. reset clears modek. 1 = keyboard interrupt requests on falling edges and low levels 0 = keyboard interrupt requests on falling edges only 21.8.2 keyboard interrupt enable register the keyboard interrupt enable register enables or disables each port g and each port h pin to operate as a keyboard interrupt pin. kbie4 ? kbie0 ? keyboard interrupt enable bits each of these read/write bits enables the corresponding keyboard interrupt pin to latch interrupt requests. reset clears the keyboard interrupt enable register. 1 = pdx pin enabled as keyboard interrupt pin 0 = pdx pin not enabled as keyboard interrupt pin address: $001b bit 7654321bit 0 read: 0 0 0 kbie4 kbie3 kbie2 kbie1 kbie0 write: reset:00000000 = unimplemented figure 21-4. keyboard interrupt enable register (kbier) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 331 technical data ? mc68HC908AS32A section 22. timer interface module a (tima) 22.1 contents 22.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 22.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 22.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 22.4.1 tima counter prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . 335 22.4.2 input capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 22.4.3 output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 22.4.3.1 unbuffered output compare . . . . . . . . . . . . . . . . . . . . 337 22.4.3.2 buffered output compare . . . . . . . . . . . . . . . . . . . . . . 338 22.4.4 pulse width modulation (pwm) . . . . . . . . . . . . . . . . . . . 339 22.4.4.1 unbuffered pwm signal generation . . . . . . . . . . . . . 340 22.4.4.2 buffered pwm signal generation . . . . . . . . . . . . . . . . 341 22.4.4.3 pwm initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 22.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 22.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 22.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 22.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 22.7 tima during break interrupts . . . . . . . . . . . . . . . . . . . . . . . 345 22.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 22.8.1 tima clock pin (ptd6/atd14/ taclk) . . . . . . . . . . . . . 346 22.8.2 tima channel i/o pins (ptf3 ? ptf0/tach2 and pte3/tach1 ? pte2/tach0)346 22.9 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 22.9.1 tima status and control register . . . . . . . . . . . . . . . . . 347 22.9.2 tima counter registers . . . . . . . . . . . . . . . . . . . . . . . . . 349 22.9.3 tima counter modulo registers . . . . . . . . . . . . . . . . . . . 351 22.9.4 tima channel status and control registers . . . . . . . . . 352 22.9.5 tima channel registers . . . . . . . . . . . . . . . . . . . . . . . . . 357 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 332 timer interface module a (tima) motorola 22.2 introduction this section describes the timer interface module (tima). the tima is a 6-channel timer that provides a timing reference with input capture, output compare and pulse-width-modulation functions. figure 22-1 is a block diagram of the tima. for further information regarding timers on m68hc08 family devices, please consult the hc08 timer reference manual, tim08rm/ad. 22.3 features features of the tima include: six input capture/output compare channels ? rising-edge, falling-edge or any-edge input capture trigger ? set, clear or toggle output compare action buffered and unbuffered pulse width modulation (pwm) signal generation programmable tima clock input ? 7 frequency internal bus clock prescaler selection ? external tima clock input (4 mhz maximum frequency) free-running or modulo up-count operation toggle any channel pin on overflow tima counter stop and reset bits f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) features mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 333 figure 22-1. tima block diagram prescaler prescaler select tclk internal 16-bit comparator ps2 ps1 ps0 16-bit comparator 16-bit latch tch0h:tch0l ms0a els0b els0a pte2 tof toie inter- channel 0 tmodh:tmodl trst tstop tov0 ch0ie ch0f ch0max ms0b 16-bit counter bus clock ptd6/atd14/taclk pte2/tach0 pte3/tach1 ptf0/tach2 ptf1/tach3 logic rupt logic inter- rupt logic 16-bit comparator 16-bit latch tch1h:tch1l ms1a els1b els1a pte3 channel 1 tov1 ch1ie ch1f ch1max logic inter- rupt logic 16-bit comparator 16-bit latch tch2h:tch2l ms2a els2b els2a ptf0 channel 2 tov2 ch2ie ch2f ch2max ms2b logic inter- rupt logic 16-bit comparator 16-bit latch tch3h:tch3l ms3a els3b els3a ptf1 channel 3 tov3 ch3ie ch3f ch3max logic inter- rupt logic 16-bit comparator 16-bit latch tch4h:tch4l ms4a els4b els4a ptf2 channel 4 tov4 ch4ie ch4f ch5max ms4b logic inter- rupt logic 16-bit comparator 16-bit latch tch5h:tch5l ms5a els5b els5a ptf3 channel 5 tov5 ch5ie ch5f ch5max logic inter- rupt logic ptf2/tach4 ptf3/tach5 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 334 timer interface module a (tima) motorola figure 22-2. tima i/o register summary addr. register name bit 7 6 5 4 3 2 1 bit 0 $0020 tima status/control register (tasc) tof toie tstop trst 0 ps2 ps1 ps0 $0021 reserved rrrrrrrr $0022 tima counter register high (tacnth) bit 15 14 13 12 11 10 9 bit 8 $0023 tima counter register low (tacntl) bit 7 6 5 4321bit 0 $0024 tima counter modulo reg. high (tamodh) bit 15 14 13 12 11 10 9 bit 8 $0025 tima counter modulo reg. low (tamodl) bit 7 6 5 4321bit 0 $0026 tima ch. 0 status/control register (tasc0) ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max $0027 tima ch. 0 register high (tach0h) bit 15 14 13 12 11 10 9 bit 8 $0028 tima ch. 0 register low (tach0l) bit 7 6 5 4321bit 0 $0029 tima ch. 1 status/control register (tasc1) ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max $002a tima ch. 1 register high (tach1h) bit 15 14 13 12 11 10 9 bit 8 $002b tima ch. 1 register low (tach1l) bit 7 6 5 4321bit 0 $002c tima ch. 2 status/control register (tasc2) ch2f ch2ie ms2b ms2a els2b els2a tov2 ch2max $002d tima ch. 2 register high (tach2h) bit 15 14 13 12 11 10 9 bit 8 $002e tima ch. 2 register low (tach2l) bit 7 6 5 4321bit 0 $002f tima ch. 3 status/control register (tasc3) ch3f ch3ie 0 ms3a els3b els3a tov3 ch3max $0030 tima ch. 3 register high (tach3h) bit 15 14 13 12 11 10 9 bit 8 $0031 tima ch. 3 register low (tach3l) bit 7 6 5 4321bit 0 $0032 tima ch. 4 status/control register (tasc4) ch4f ch4ie ms4b ms4a els4b els4a tov4 ch4max $0033 tima ch. 4 register high (tach4h) bit 15 14 13 12 11 10 9 bit 8 $0034 tima ch. 4 register low (tach4l) bit 7 6 5 4321bit 0 $0035 tima ch. 5 status/control register (tasc5) ch5f ch5ie 0 ms5a els5b els5a tov5 ch5max $0036 tima ch. 5 register high (tach5h) bit 15 14 13 12 11 10 9 bit 8 $0037 tima ch. 5 register low (tach5l) bit 7 6 5 4321bit 0 r= reserved f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 335 22.4 functional description figure 22-1 shows the tima structure. the central component of the tima is the 16-bit tima counter that can operate as a free-running counter or a modulo up-counter. the tima counter provides the timing reference for the input capture and output compare functions. the tima counter modulo registers, tamodh ? tamodl, control the modulo value of the tima counter. software can read the tima counter value at any time without affecting the counting sequence. the six tima channels are programmable independently as input capture or output compare channels. 22.4.1 tima counter prescaler the tima clock source can be one of the seven prescaler outputs or the tima clock pin, ptd6/atd14/taclk. the prescaler generates seven clock rates from the internal bus clock. the prescaler select bits, ps[2:0], in the tima status and control register select the tima clock source. 22.4.2 input capture an input capture function has three basic parts: edge select logic, an input capture latch and a 16-bit counter. two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the free-running counter after the corresponding input capture edge detector senses a defined transition. the polarity of the active edge is programmable. the level transition which triggers the counter transfer is defined by the corresponding input edge bits (elsxb and elsxa in tasc0 through tasc5 control registers with x referring to the active channel number). when an active edge occurs on the pin of an input capture channel, the tima latches the contents of the tima counter into the tima channel registers, tachxh ? tachxl. input captures can generate tima cpu interrupt requests. software can determine that an input capture event has occurred by enabling input capture interrupts or by polling the status flag bit. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 336 timer interface module a (tima) motorola the free-running counter contents are transferred to the tima channel register (tachxh ? tachxl see tima channel registers on page 357) on each proper signal transition regardless of whether the tima channel flag (ch0f ? ch5f in tasc0 ? tasc5 registers) is set or clear. when the status flag is set, a cpu interrupt is generated if enabled. the value of the count latched or ? captured ? is the time of the event. because this value is stored in the input capture register 2 bus cycles after the actual event occurs, user software can respond to this event at a later time and determine the actual time of the event. however, this must be done prior to another input capture on the same pin; otherwise, the previous time value will be lost. by recording the times for successive edges on an incoming signal, software can determine the period and/or pulse width of the signal. to measure a period, two successive edges of the same polarity are captured. to measure a pulse width, two alternate polarity edges are captured. software should track the overflows at the 16-bit module counter to extend its range. another use for the input capture function is to establish a time reference. in this case, an input capture function is used in conjunction with an output compare function. for example, to activate an output signal a specified number of clock cycles after detecting an input event (edge), use the input capture function to record the time at which the edge occurred. a number corresponding to the desired delay is added to this captured value and stored to an output compare register (see tima channel registers on page 357). because both input captures and output compares are referenced to the same 16-bit modulo counter, the delay can be controlled to the resolution of the counter independent of software latencies. reset does not affect the contents of the tima channel register (tachxh ? tachxl). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 337 22.4.3 output compare with the output compare function, the tima can generate a periodic pulse with a programmable polarity, duration and frequency. when the counter reaches the value in the registers of an output compare channel, the tima can set, clear or toggle the channel pin. output compares can generate tima cpu interrupt requests. 22.4.3.1 unbuffered output compare any output compare channel can generate unbuffered output compare pulses as described in output compare on page 337. the pulses are unbuffered because changing the output compare value requires writing the new value over the old value currently in the tima channel registers. an unsynchronized write to the tima channel registers to change an output compare value could cause incorrect operation for up to two counter overflow periods. for example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that counter overflow period. also, using a tima overflow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. the tima may pass the new value before it is written. use the following methods to synchronize unbuffered changes in the output compare value on channel x: when changing to a smaller value, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. the output compare interrupt occurs at the end of the current output compare pulse. the interrupt routine has until the end of the counter overflow period to write the new value. when changing to a larger output compare value, enable tima overflow interrupts and write the new value in the tima overflow interrupt routine. the tima overflow interrupt occurs at the end of the current counter overflow period. writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same counter overflow period. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 338 timer interface module a (tima) motorola 22.4.3.2 buffered output compare channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the pte2/tach0 pin. the tima channel registers of the linked pair alternately control the output. setting the ms0b bit in tima channel 0 status and control register (tasc0) links channel 0 and channel 1. the output compare value in the tima channel 0 registers initially controls the output on the pte2/tach0 pin. writing to the tima channel 1 registers enables the tima channel 1 registers to synchronously control the output after the tima overflows. at each subsequent overflow, the tima channel registers (0 or 1) that control the output are the ones written to last. tasc0 controls and monitors the buffered output compare function and tima channel 1 status and control register (tasc1) is unused. while the ms0b bit is set, the channel 1 pin, pte3/tach1, is available as a general-purpose i/o pin. channels 2 and 3 can be linked to form a buffered output compare channel whose output appears on the ptf0/tach2 pin. the tima channel registers of the linked pair alternately control the output. setting the ms2b bit in tima channel 2 status and control register (tasc2) links channel 2 and channel 3. the output compare value in the tima channel 2 registers initially controls the output on the ptf0/tach2 pin. writing to the tima channel 3 registers enables the tima channel 3 registers to synchronously control the output after the tima overflows. at each subsequent overflow, the tima channel registers (2 or 3) that control the output are the ones written to last. tasc2 controls and monitors the buffered output compare function, and tima channel 3 status and control register (tasc3) is unused. while the ms2b bit is set, the channel 3 pin, ptf1/tach3, is available as a general-purpose i/o pin. channels 4 and 5 can be linked to form a buffered output compare channel whose output appears on the ptf2 pin. the tima channel registers of the linked pair alternately control the output. setting the ms4b bit in tima channel 4 status and control register (tasc4) links channel 4 and channel 5. the output compare value in the f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 339 tima channel 4 registers initially controls the output on the ptf2 pin. writing to the tima channel 5 registers enables the tima channel 5 registers to synchronously control the output after the tima overflows. at each subsequent overflow, the tima channel registers (4 or 5) that control the output are the ones written to last. tasc4 controls and monitors the buffered output compare function and tima channel 5 status and control register (tasc5) is unused. while the ms4b bit is set, the channel 5 pin, ptf3, is available as a general-purpose i/o pin. note: in buffered output compare operation, do not write new output compare values to the currently active channel registers. user software should track the currently active channel to prevent writing a new value to the active channel. writing to the active channel registers is the same as generating unbuffered output compares. 22.4.4 pulse width modulation (pwm) by using the toggle-on-overflow feature with an output compare channel, the tima can generate a pwm signal. the value in the tima counter modulo registers determines the period of the pwm signal. the channel pin toggles when the counter reaches the value in the tima counter modulo registers. the time between overflows is the period of the pwm signal. as figure 22-3 shows, the output compare value in the tima channel registers determines the pulse width of the pwm signal. the time between overflow and output compare is the pulse width. program the tima to clear the channel pin on output compare if the state of the pwm pulse is logic 1. program the tima to set the pin if the state of the pwm pulse is logic 0. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 340 timer interface module a (tima) motorola figure 22-3. pwm period and pulse width the value in the tima counter modulo registers and the selected prescaler output determines the frequency of the pwm output. the frequency of an 8-bit pwm signal is variable in 256 increments. writing $00ff (255) to the tima counter modulo registers produces a pwm period of 256 times the internal bus clock period if the prescaler select value is $000 (see tima status and control register on page 347). the value in the tima channel registers determines the pulse width of the pwm output. the pulse width of an 8-bit pwm signal is variable in 256 increments. writing $0080 (128) to the tima channel registers produces a duty cycle of 128/256 or 50%. 22.4.4.1 unbuffered pwm signal generation any output compare channel can generate unbuffered pwm pulses as described in pulse width modulation (pwm) on page 339. the pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the value currently in the tima channel registers. an unsynchronized write to the tima channel registers to change a pulse width value could cause incorrect operation for up to two pwm periods. for example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that pwm period. also, using a tima overflow interrupt routine to write a new, smaller pulse width value may cause the compare ptex/tchx period pulse width overflow overflow overflow output compare output compare output compare f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 341 to be missed. the tima may pass the new value before it is written to the tima channel registers. use the following methods to synchronize unbuffered changes in the pwm pulse width on channel x: when changing to a shorter pulse width, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. the output compare interrupt occurs at the end of the current pulse. the interrupt routine has until the end of the pwm period to write the new value. when changing to a longer pulse width, enable tima overflow interrupts and write the new value in the tima overflow interrupt routine. the tima overflow interrupt occurs at the end of the current pwm period. writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same pwm period. note: in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self- correct in the event of software error or noise. toggling on output compare also can cause incorrect pwm signal generation when changing the pwm pulse width to a new, much larger value. 22.4.4.2 buffered pwm signal generation channels 0 and 1 can be linked to form a buffered pwm channel whose output appears on the pte2/tach0 pin. the tima channel registers of the linked pair alternately control the pulse width of the output. setting the ms0b bit in tima channel 0 status and control register (tasc0) links channel 0 and channel 1. the tima channel 0 registers initially control the pulse width on the pte2/tach0 pin. writing to the tima channel 1 registers enables the tima channel 1 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tima channel registers (0 or 1) that control the pulse width are the ones written to last. tasc0 controls and monitors the buffered pwm function and tima channel 1 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 342 timer interface module a (tima) motorola status and control register (tasc1) is unused. while the ms0b bit is set, the channel 1 pin, pte3/tach1, is available as a general-purpose i/o pin. channels 2 and 3 can be linked to form a buffered pwm channel whose output appears on the ptf0/tach2 pin. the tima channel registers of the linked pair alternately control the pulse width of the output. setting the ms2b bit in tima channel 2 status and control register (tasc2) links channel 2 and channel 3. the tima channel 2 registers initially control the pulse width on the ptf0/tach2 pin. writing to the tima channel 3 registers enables the tima channel 3 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tima channel registers (2 or 3) that control the pulse width are the ones written to last. tasc2 controls and monitors the buffered pwm function and tima channel 3 status and control register (tasc3) is unused. while the ms2b bit is set, the channel 3 pin, ptf1/tach3, is available as a general-purpose i/o pin. channels 4 and 5 can be linked to form a buffered pwm channel whose output appears on the ptf2 pin. the tima channel registers of the linked pair alternately control the pulse width of the output. setting the ms4b bit in tima channel 4 status and control register (tasc4) links channel 4 and channel 5. the tima channel 4 registers initially control the pulse width on the ptf2 pin. writing to the tima channel 5 registers enables the tima channel 5 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tima channel registers (4 or 5) that control the pulse width are the ones written to last. tasc4 controls and monitors the buffered pwm function and tima channel 5 status and control register (tasc5) is unused. while the ms4b bit is set, the channel 5 pin, ptf3, is available as a general-purpose i/o pin. note: in buffered pwm signal generation, do not write new pulse width values to the currently active channel registers. user software should track the currently active channel to prevent writing a new value to the active channel. writing to the active channel registers is the same as generating unbuffered pwm signals. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) functional description mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 343 22.4.4.3 pwm initialization to ensure correct operation when generating unbuffered or buffered pwm signals, use the following initialization procedure: 1. in the tima status and control register (tasc): a. stop the tima counter by setting the tima stop bit, tstop. b. reset the tima counter and prescaler by setting the tima reset bit, trst. 2. in the tima counter modulo registers (tamodh ? tamodl) write the value for the required pwm period. 3. in the tima channel x registers (tachxh ? tachxl) write the value for the required pulse width. 4. in tima channel x status and control register (tascx): a. write 0:1 (for unbuffered output compare or pwm signals) or 1:0 (for buffered output compare or pwm signals) to the mode select bits, msxb ? msxa (see table 22-2 ). b. write 1 to the toggle-on-overflow bit, tovx. c. write 1:0 (to clear output on compare) or 1:1 (to set output on compare) to the edge/level select bits, elsxb ? elsxa. the output action on compare must force the output to the complement of the pulse width level (see table 22-2 ). note: in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self- correct in the event of software error or noise. toggling on output compare can also cause incorrect pwm signal generation when changing the pwm pulse width to a new, much larger value. 5. in the tima status control register (tasc) clear the tima stop bit, tstop. setting ms0b links channels 0 and 1 and configures them for buffered pwm operation. the tima channel 0 registers (tach0h ? tach0l) initially control the buffered pwm output. tima status control register 0 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 344 timer interface module a (tima) motorola (tasc0) controls and monitors the pwm signal from the linked channels. ms0b takes priority over ms0a. setting ms2b links channels 2 and 3 and configures them for buffered pwm operation. the tima channel 2 registers (tach2h ? tach2l) initially control the buffered pwm output. tima status control register 2 (tasc2) controls and monitors the pwm signal from the linked channels. ms2b takes priority over ms2a. setting ms4b links channels 4 and 5 and configures them for buffered pwm operation. the tima channel 4 registers (tach4h ? tach4l) initially control the buffered pwm output. tima status control register 4 (tasc4) controls and monitors the pwm signal from the linked channels. ms4b takes priority over ms4a. clearing the toggle-on-overflow bit, tovx, inhibits output toggles on tima overflows. subsequent output compares try to force the output to a state it is already in and have no effect. the result is a 0% duty cycle output. setting the channel x maximum duty cycle bit (chxmax) and setting the tovx bit generates a 100% duty cycle output (see tima channel status and control registers on page 352). 22.5 interrupts the following tima sources can generate interrupt requests: tima overflow flag (tof) ? the tof bit is set when the tima counter reaches the modulo value programmed in the tima counter modulo registers. the tima overflow interrupt enable bit, toie, enables tima overflow cpu interrupt requests. tof and toie are in the tima status and control register. tima channel flags (ch5f ? ch0f) ? the chxf bit is set when an input capture or output compare occurs on channel x. channel x tima cpu interrupt requests are controlled by the channel x interrupt enable bit, chxie. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 345 22.6 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 22.6.1 wait mode the tima remains active after the execution of a wait instruction. in wait mode, the tima registers are not accessible by the cpu. any enabled cpu interrupt request from the tima can bring the mcu out of wait mode. if tima functions are not required during wait mode, reduce power consumption by stopping the tima before executing the wait instruction. 22.6.2 stop mode the tima is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions or the state of the tima counter. tima operation resumes when the mcu exits stop mode. 22.7 tima during break interrupts a break interrupt stops the tima counter and inhibits input captures. the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state (see sim break flag control register on page 122). to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 346 timer interface module a (tima) motorola status bits have a 2-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 22.8 i/o signals port d shares one of its pins with the tima. port e shares two of its pins with the tima and port f shares four of its pins with the tima. ptd6/atd14/taclk is an external clock input to the tima prescaler. the six tima channel i/o pins are pte2/tach0, pte3/tach1, ptf0/tach2, ptf1/tach3, ptf2, and ptf3. 22.8.1 tima clock pin (ptd6/atd14/ taclk) ptd6/atd14/taclk is an external clock input that can be the clock source for the tima counter instead of the prescaled internal bus clock. select the ptd6/atd14/taclk input by writing logic 1s to the three prescaler select bits, ps[2:0] (see tima status and control register ). the minimum tclk pulse width, tclk lmin or tclk hmin , is: the maximum tclk frequency is the least: 4 mhz or bus frequency 2. ptd6/atd14/taclk is available as a general-purpose i/o pin or adc channel when not used as the tima clock input. when the ptd6/atd14/taclk pin is the tima clock input, it is an input regardless of the state of the ddrd6 bit in data direction register d. 22.8.2 tima channel i/o pins (ptf3 ? ptf0/tach2 and pte3/tach1 ? pte2/tach0) each channel i/o pin is programmable independently as an input capture pin or an output compare pin. pte2/tach0, ptf0/tach2 and ptf2 can be configured as buffered output compare or buffered pwm pins. 1 bus frequency ------------------------------------- t su + f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 347 22.9 i/o registers these i/o registers control and monitor tima operation: tima status and control register (tasc) tima control registers (tacnth ? tacntl) tima counter modulo registers (tamodh ? tamodl) tima channel status and control registers (tasc0, tasc1, tasc2, tasc3, tasc4 and tasc5) tima channel registers (tach0h ? tach0l, tach1h ? tach1l, tach2h ? tach2l, tach3h ? tach3l, tach4h ? tach4l and tach5h ? tach5l) 22.9.1 tima status and control register the tima status and control register: enables tima overflow interrupts flags tima overflows stops the tima counter resets the tima counter prescales the tima counter clock address: $0020 bit 7654321bit 0 read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset:00100000 r= reserved figure 22-4. tima status and control register (tasc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 348 timer interface module a (tima) motorola tof ? tima overflow flag bit this read/write flag is set when the tima counter reaches the modulo value programmed in the tima counter modulo registers. clear tof by reading the tima status and control register when tof is set and then writing a logic 0 to tof. if another tima overflow occurs before the clearing sequence is complete, then writing logic 0 to tof has no effect. therefore, a tof interrupt request cannot be lost due to inadvertent clearing of tof. reset clears the tof bit. writing a logic 1 to tof has no effect. 1 = tima counter has reached modulo value. 0 = tima counter has not reached modulo value. toie ? tima overflow interrupt enable bit this read/write bit enables tima overflow interrupts when the tof bit becomes set. reset clears the toie bit. 1 = tima overflow interrupts enabled 0 = tima overflow interrupts disabled tstop ? tima stop bit this read/write bit stops the tima counter. counting resumes when tstop is cleared. reset sets the tstop bit, stopping the tima counter until software clears the tstop bit. 1 = tima counter stopped 0 = tima counter active note: do not set the tstop bit before entering wait mode if the tima is required to exit wait mode. also, when the tstop bit is set and input capture mode is enabled, input captures are inhibited until tstop is cleared. trst ? tima reset bit setting this write-only bit resets the tima counter and the tima prescaler. setting trst has no effect on any other registers. counting resumes from $0000. trst is cleared automatically after the tima counter is reset and always reads as logic 0. reset clears the trst bit. 1 = prescaler and tima counter cleared 0 = no effect f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 349 note: setting the tstop and trst bits simultaneously stops the tima counter at a value of $0000. ps[2:0] ? prescaler select bits these read/write bits select either the ptd6/atd14/taclk pin or one of the seven prescaler outputs as the input to the tima counter as table 22-1 shows. reset clears the ps[2:0] bits. 22.9.2 tima counter registers the two read-only tima counter registers contain the high and low bytes of the value in the tima counter. reading the high byte (tacnth) latches the contents of the low byte (tacntl) into a buffer. subsequent reads of tacnth do not affect the latched tacntl value until tacntl is read. reset clears the tima counter registers. setting the tima reset bit (trst) also clears the tima counter registers. note: if tacnth is read during a break interrupt, be sure to unlatch tacntl by reading tacntl before exiting the break interrupt. otherwise, tacntl retains the value latched during the break. table 22-1. prescaler selection ps[2:0] tima clock source 000 internal bus clock 1 001 internal bus clock 2 010 internal bus clock 4 011 internal bus clock 8 100 internal bus clock 16 101 internal bus clock 32 110 internal bus clock 64 111 ptd6/atd14/taclk f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 350 timer interface module a (tima) motorola register name and address tacnth ? $0022 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write:rrrrrrrr reset:00000000 register name and address tacntl ? $0023 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write:rrrrrrrr reset:00000000 r = reserved figure 22-5. tima counter registers (tacnth and tacntl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 351 22.9.3 tima counter modulo registers the read/write tima modulo registers contain the modulo value for the tima counter. when the tima counter reaches the modulo value, the overflow flag (tof) becomes set and the tima counter resumes counting from $0000 at the next timer clock. writing to the high byte (tamodh) inhibits the tof bit and overflow interrupts until the low byte (tamodl) is written. reset sets the tima counter modulo registers. note: reset the tima counter before writing to the tima counter modulo registers. register name and address tamodh ? $0024 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset:11111111 register name and address tamodl ? $0025 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 22-6. tima counter modulo registers (tamodh and tamodl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 352 timer interface module a (tima) motorola 22.9.4 tima channel status and control registers each of the tima channel status and control registers: flags input captures and output compares enables input capture and output compare interrupts selects input capture, output compare or pwm operation selects high, low or toggling output on output compare selects rising edge, falling edge or any edge as the active input capture trigger selects output toggling on tima overflow selects 0% and 100% pwm duty cycle selects buffered or unbuffered output compare/pwm operation register name and address tasc0 ? $0026 bit 7654321bit 0 read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 register name and address tasc1 ? $0029 bit 7654321bit 0 read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset:00000000 r= reserved figure 22-7. tima channel status and control registers (tasc0 ? tasc5) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 353 register name and address tasc2 ? $002c bit 7654321bit 0 read: ch2f ch2ie ms2b ms2a els2b els2a tov2 ch2max write: 0 reset:00000000 register name and address tasc3 ? $002f bit 7654321bit 0 read: ch3f ch3ie 0 ms3a els3b els3a tov3 ch3max write: 0 r reset:00000000 register name and address tasc4 ? $0032 bit 7654321bit 0 read: ch4f ch4ie ms4b ms4a els4b els4a tov4 ch4max write: 0 reset:00000000 register name and address tasc5 ? $0035 bit 7654321bit 0 read: ch5f ch5ie 0 ms5a els5b els5a tov5 ch5max write: 0 r reset:00000000 r = reserved figure 22-7. tima channel status and control registers (tasc0 ? tasc5) (continued) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 354 timer interface module a (tima) motorola chxf ? channel x flag bit when channel x is an input capture channel, this read/write bit is set when an active edge occurs on the channel x pin. when channel x is an output compare channel, chxf is set when the value in the tima counter registers matches the value in the tima channel x registers. when chxie = 1, clear chxf by reading tima channel x status and control register with chxf set and then writing a logic 0 to chxf. if another interrupt request occurs before the clearing sequence is complete, then writing logic 0 to chxf has no effect. therefore, an interrupt request cannot be lost due to inadvertent clearing of chxf. reset clears the chxf bit. writing a logic 1 to chxf has no effect. 1 = input capture or output compare on channel x 0 = no input capture or output compare on channel x chxie ? channel x interrupt enable bit this read/write bit enables tima cpu interrupts on channel x. reset clears the chxie bit. 1 = channel x cpu interrupt requests enabled 0 = channel x cpu interrupt requests disabled msxb ? mode select bit b this read/write bit selects buffered output compare/pwm operation. msxb exists only in the tima channel 0, tima channel 2 and tima channel 4 status and control registers. setting ms0b disables the channel 1 status and control register and reverts tach1 pin to general-purpose i/o. setting ms2b disables the channel 3 status and control register and reverts tach3 pin to general-purpose i/o. setting ms4b disables the channel 5 status and control register and reverts tach5 pin to general-purpose i/o. reset clears the msxb bit. 1 = buffered output compare/pwm operation enabled 0 = buffered output compare/pwm operation disabled f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 355 msxa ? mode select bit a when elsxb:a 00, this read/write bit selects either input capture operation or unbuffered output compare/pwm operation. see table 22-2 . 1 = unbuffered output compare/pwm operation 0 = input capture operation when elsxb:a = 00, this read/write bit selects the initial output level of the tachx pin once pwm, output compare mode or input capture mode is enabled. see table 22-2 . reset clears the msxa bit. 1 = initial output level low 0 = initial output level high note: before changing a channel function by writing to the msxb or msxa bit, set the tstop and trst bits in the tima status and control register (tasc). elsxb and elsxa ? edge/level select bits when channel x is an input capture channel, these read/write bits control the active edge-sensing logic on channel x. when channel x is an output compare channel, elsxb and elsxa control the channel x output behavior when an output compare occurs. when elsxb and elsxa are both clear, channel x is not connected to port e or port f and pin ptex/tachx or pin ptfx/tachx is available as a general-purpose i/o pin. however, channel x is at a state determined by these bits and becomes transparent to the respective pin when pwm, input capture mode or output compare operation mode is enabled. table 22-2 shows how elsxb and elsxa work. reset clears the elsxb and elsxa bits. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 356 timer interface module a (tima) motorola note: before enabling a tima channel register for input capture operation, make sure that the ptex/tachx pin or ptfx/tachx pin is stable for at least two bus clocks. tovx ? toggle-on-overflow bit when channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the tima counter overflows. when channel x is an input capture channel, tovx has no effect. reset clears the tovx bit. 1 = channel x pin toggles on tima counter overflow. 0 = channel x pin does not toggle on tima counter overflow. note: when tovx is set, a tima counter overflow takes precedence over a channel x output compare if both occur at the same time. table 22-2. mode, edge, and level selection msxb:msxa elsxb:elsxa mode configuration x0 00 output preset pin under port control; initialize timer output level high x1 00 pin under port control; initialize timer output level low 00 01 input capture capture on rising edge only 00 10 capture on falling edge only 00 11 capture on rising or falling edge 01 01 output compare or pwm toggle output on compare 01 10 clear output on compare 01 11 set output on compare 1x 01 buffered output compare or buffered pwm toggle output on compare 1x 10 clear output on compare 1x 11 set output on compare f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 357 chxmax ? channel x maximum duty cycle bit when the tovx bit is at logic 1, setting the chxmax bit forces the duty cycle of buffered and unbuffered pwm signals to 100%. as figure 22-8 shows, the chxmax bit takes effect in the cycle after it is set or cleared. the output stays at the 100% duty cycle level until the cycle after chxmax is cleared. figure 22-8. chxmax latency 22.9.5 tima channel registers these read/write registers contain the captured tima counter value of the input capture function or the output compare value of the output compare function. the state of the tima channel registers after reset is unknown. in input capture mode (msxb ? msxa = 0:0) reading the high byte of the tima channel x registers (tachxh) inhibits input captures until the low byte (tachxl) is read. in output compare mode (msxb ? msxa 0:0) writing to the high byte of the tima channel x registers (tachxh) inhibits output compares and the chxf bit until the low byte (tachxl) is written. output overflow ptex/tchx period chxmax overflow overflow overflow overflow compare output compare output compare output compare f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 358 timer interface module a (tima) motorola register name and address tach0h ? $0027 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tach0l ? $0028 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address tach1h ? $002a bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tach1l ? $002b bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address tach2h ? $002d bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset figure 22-9. tima channel registers (tach0h/l ? tach5h/l) (sheet 1 of 3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola timer interface module a (tima) 359 register name and address tach2l ? $002e bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address tach3h ? $0030 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tach3l ? $0031 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address tach4h ? $0033 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tach4l ? $0034 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset figure 22-9. tima channel registers (tach0h/l ? tach5h/l) (sheet 2 of 3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timer interface module a (tima) advance information mc68HC908AS32A ? rev 0.0 360 timer interface module a (tima) motorola register name and address tach5h ? $0036 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address tach5l ? $0037 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset figure 22-9. tima channel registers (tach0h/l ? tach5h/l) (sheet 3 of 3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola analog-to-digital converter (adc) 361 technical data ? mc68HC908AS32A section 23. analog-to-digital converter (adc) 23.1 contents 23.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 23.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 23.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362 23.4.1 adc port i/o pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 23.4.2 voltage conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 23.4.3 conversion time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 23.4.4 continuous conversion . . . . . . . . . . . . . . . . . . . . . . . . . . 365 23.4.5 accuracy and precision . . . . . . . . . . . . . . . . . . . . . . . . . . 365 23.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 23.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 23.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365 23.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 23.7 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 23.7.1 adc analog power pin (vddaref)/adc voltage reference pin (v refh ) . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 23.7.2 adc analog ground pin (vssa)/adc voltage reference low pin (vrefl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 23.7.3 adc voltage in (adcvin) . . . . . . . . . . . . . . . . . . . . . . . . 366 23.8 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 23.8.1 adc status and control register . . . . . . . . . . . . . . . . . . 367 23.8.2 adc data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 23.8.3 adc input clock register . . . . . . . . . . . . . . . . . . . . . . . . 370 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) advance information mc68HC908AS32A ? rev 0.0 362 analog-to-digital converter (adc) motorola 23.2 introduction this section describes the analog-to-digital converter (adc-15). the adc is an 8-bit analog-to-digital converter. for further information regarding analog-to-digital converters on motorola microcontrollers, please consult the hc08 adc reference manual, adcrm/ad. 23.3 features features of the adc module include: 15 channels with multiplexed input linear successive approximation 8-bit resolution single or continuous conversion conversion complete flag or conversion complete interrupt selectable adc clock 23.4 functional description fifteen adc channels are available for sampling external sources at pins ptd6/atd14/taclk ? ptd0/atd8 and ptb7/atd7 ? ptb0/atd0. an analog multiplexer allows the single adc converter to select one of 15 adc channels as adc voltage in (adcvin). adcvin is converted by the successive approximation register-based counters. when the conversion is completed, adc places the result in the adc data register and sets a flag or generates an interrupt. see figure 23-1 . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) functional description mc68HC908AS32A ? rev 0.0 advance information motorola analog-to-digital converter (adc) 363 figure 23-1. adc block diagram 23.4.1 adc port i/o pins ptd6/atd14/taclk ? ptd0/atd8 and ptb7/atd7 ? ptb0/atd0 are general-purpose i/o pins that share with the adc channels. the channel select bits define which adc channel/port pin will be used as the input signal. the adc overrides the port i/o logic by forcing that pin as input to the adc. the remaining adc channels/port pins are controlled by the port i/o logic and can be used as general-purpose i/o. writes to the port register or ddr will not have any affect on the port pin that is selected by the adc. read of a port pin which is in use by the internal data bus read ddrb/ddrb write ddrb/ddrd reset write ptb/ptd read ptb/ptd ptbx/ptdx ddrbx/ddrdx ptbx/ptdx interrupt logic channel select adc clock generator conversion complete adc voltage in adcvin adc clock cgmxclk bus clock adch[4:0] adc data register adiv[2:0] adiclk aien coco disable disable adc channel x f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) advance information mc68HC908AS32A ? rev 0.0 364 analog-to-digital converter (adc) motorola adc will return a logic 0 if the corresponding ddr bit is at logic 0. if the ddr bit is at logic 1, the value in the port data latch is read. note: do not use adc channels atd14 or atd12 when using the ptd6/atd14/taclk or ptd4/atd12/tbclk pins as the clock inputs for the 16-bit timers. 23.4.2 voltage conversion when the input voltage to the adc equals v refh (see adc characteristics on page 424), the adc converts the signal to $ff (full scale). if the input voltage equals v ssa, the adc converts it to $00. input voltages between v refh and v ssa are a straight-line linear conversion. conversion accuracy of all other input voltages is not guaranteed. avoid current injection on unused adc inputs to prevent potential conversion error. note: input voltage should not exceed the analog supply voltages. 23.4.3 conversion time conversion starts after a write to the adscr (adc status control register, $0038), and requires between 16 and 17 adc clock cycles to complete. conversion time in terms of the number of bus cycles is a function of adiclk select, cgmxclk frequency, bus frequency, and adiv prescaler bits. for example, with a cgmxclk frequency of 4 mhz, bus frequency of 8 mhz, and fixed adc clock frequency of 1 mhz, one conversion will take between 16 and 17 s and there will be between 128 bus cycles between each conversion. sample rate is approximately 60 khz. refer to adc characteristics on page 424. 16 to 17 adc clock cycles conversion time = ???????????? adc clock frequency number of bus cycles = conversion time x bus frequency f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) interrupts mc68HC908AS32A ? rev 0.0 advance information motorola analog-to-digital converter (adc) 365 23.4.4 continuous conversion in the continuous conversion mode, the adc data register will be filled with new data after each conversion. data from the previous conversion will be overwritten whether that data has been read or not. conversions will continue until the adco bit (adc status control register, $0038) is cleared. the coco bit is set after the first conversion and will stay set for the next several conversions until the next write of the adc status and control register or the next read of the adc data register. 23.4.5 accuracy and precision the conversion process is monotonic and has no missing codes. see adc characteristics on page 424 for accuracy information. 23.5 interrupts when the aien bit is set, the adc module is capable of generating a cpu interrupt after each adc conversion. a cpu interrupt is generated if the coco bit (adc status control register, $0038) is at logic 0. if the coco bit is set, an interrupt is generated. the coco bit is not used as a conversion complete flag when interrupts are enabled. 23.6 low-power modes the following subsections describe the low-power modes. 23.6.1 wait mode the adc continues normal operation during wait mode. any enabled cpu interrupt request from the adc can bring the mcu out of wait mode. if the adc is not required to bring the mcu out of wait mode, power down the adc by setting the adch[4:0] bits in the adc status and control register before executing the wait instruction. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) advance information mc68HC908AS32A ? rev 0.0 366 analog-to-digital converter (adc) motorola 23.6.2 stop mode the adc module is inactive after the execution of a stop instruction. any pending conversion is aborted. adc conversions resume when the mcu exits stop mode. allow one conversion cycle to stabilize the analog circuitry before attempting a new adc conversion after exiting stop mode. 23.7 i/o signals the adc module has 15 channels that are shared with i/o ports b and d. refer to adc characteristics on page 424 for voltages referenced below. 23.7.1 adc analog power pin (v ddaref )/adc voltage reference pin (v refh ) the adc analog portion uses v ddaref as its power pin. connect the v dda /v ddaref pin to the same voltage potential as v dd . external filtering may be necessary to ensure clean v ddaref for good results. v refh is the high reference voltage for all analog-to-digital conversions. note: route v ddaref carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. v ddaref must be present for operation of the adc. 23.7.2 adc analog ground pin (v ssa )/adc voltage reference low pin (v refl ) the adc analog portion uses v ssa as its ground pin. connect the v ssa pin to the same voltage potential as v ss . v refl is the lower reference supply for the adc. 23.7.3 adc voltage in (adcvin) adcvin is the input voltage signal from one of the 15 adc channels to the adc module. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola analog-to-digital converter (adc) 367 23.8 i/o registers these i/o registers control and monitor adc operation: adc status and control register (adscr) adc data register (adr) adc clock register (adiclk) 23.8.1 adc status and control register the following paragraphs describe the function of the adc status and control register. coco ? conversions complete bit when the aien bit is a logic 0, the coco is a read-only bit which is set each time a conversion is completed. this bit is cleared whenever the adc status and control register is written or whenever the adc data register is read. if the aien bit is a logic 1, the coco is a read/write bit which selects the cpu to service the adc interrupt request. reset clears this bit. 1 = conversion completed (aien = 0) 0 = conversion not completed (aien = 0) or cpu interrupt enabled (aien = 1) address: $0038 bit 7654321bit 0 read: coco aien adco ch4 ch3 ch2 ch1 ch0 write: r reset:00011111 r= reserved figure 23-2. adc status and control register (adscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) advance information mc68HC908AS32A ? rev 0.0 368 analog-to-digital converter (adc) motorola aien ? adc interrupt enable bit when this bit is set, an interrupt is generated at the end of an adc conversion. the interrupt signal is cleared when the data register is read or the status/control register is written. reset clears the aien bit. 1 = adc interrupt enabled 0 = adc interrupt disabled adco ? adc continuous conversion bit when set, the adc will convert samples continuously and update the adr register at the end of each conversion. only one conversion is allowed when this bit is cleared. reset clears the adco bit. 1 = continuous adc conversion 0 = one adc conversion adch[4:0] ? adc channel select bits adch4, adch3, adch2, adch1, and adch0 form a 5-bit field which is used to select one of 15 adc channels. channel selection is detailed in the following table. care should be taken when using a port pin as both an analog and a digital input simultaneously to prevent switching noise from corrupting the analog signal. see table 23-1 . the adc subsystem is turned off when the channel select bits are all set to one. this feature allows for reduced power consumption for the mcu when the adc is not used. reset sets these bits. note: recovery from the disabled state requires one conversion cycle to stabilize. table 23-1. mux channel select adch4 adch3 adch2 adch1 adch0 input select 00000 ptb0/atd0 00001 ptb1/atd1 00010 ptb2/atd2 00011 ptb3/atd3 00100 ptb4/atd4 00101 ptb5/atd5 00110 ptb6/atd6 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola analog-to-digital converter (adc) 369 00111 ptb7/atd7 01000 ptd0/atd8/atd8 01001 ptd1/atd9/atd9 01010 ptd2/atd10/atd10 01011 ptd3/atd11/atd11 01100 ptd4/atd12/tbclk/ atd12 01101 ptd5/atd13/atd13 01110 ptd6/atd14/taclk/ atd14 range 0 1111 ($0f) to 1 1010 ($1a) unused (see note 1) unused (see note 1) 11011 reserved 1 1 1 0 0 unused (see note 1) 1 1 1 0 1 v refh (see note 2) 1 1 1 1 0 v ssa /v refl (see note 2) 1 1 1 1 1 [adc power off] notes: 1. if any unused channels are selected, the resulting adc conversion will be unknown. 2. the voltage levels supplied from internal reference nodes as specified in the table are used to verify the operation of the adc converter both in production test and for user applications. table 23-1. mux channel select adch4 adch3 adch2 adch1 adch0 input select f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) advance information mc68HC908AS32A ? rev 0.0 370 analog-to-digital converter (adc) motorola 23.8.2 adc data register one 8-bit result register is provided. this register is updated each time an adc conversion completes. 23.8.3 adc input clock register this register selects the clock frequency for the adc. adiv2 ? adiv0 ? adc clock prescaler bits adiv2, adiv1, and adiv0 form a 3-bit field which selects the divide ratio used by the adc to generate the internal adc clock. table 23- 2 shows the available clock configurations. the adc clock should be set to approximately 1 mhz. address: $0039 bit 7654321bit 0 read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write:rrrrrrrr reset: indeterminate after reset r= reserved figure 23-3. adc data register (adr) address: $003a bit 7654321bit 0 read: adiv2 adiv1 adiv0 adiclk 0000 write: rrrr reset: 0 0000000 r= reserved figure 23-4. adc input clock register (adiclk) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) i/o registers mc68HC908AS32A ? rev 0.0 advance information motorola analog-to-digital converter (adc) 371 adiclk ? adc input clock register bit adiclk selects either bus clock or cgmxclk as the input clock source to generate the internal adc clock. reset selects cgmxclk as the adc clock source. if the external clock (cgmxclk) is equal to or greater than 1 mhz, cgmxclk can be used as the clock source for the adc. if cgmxclk is less than 1 mhz, use the pll-generated bus clock as the clock source. as long as the internal adc clock is at approximately 1 mhz, correct operation can be guaranteed. see adc characteristics on page 424. 1 = internal bus clock 0 = external clock (cgmxclk) note: during the conversion process, changing the adc clock will result in an incorrect conversion. table 23-2. adc clock divide ratio adiv2 adiv1 adiv0 adc clock rate 0 0 0 adc input clock /1 0 0 1 adc input clock / 2 0 1 0 adc input clock / 4 0 1 1 adc input clock / 8 1 x x adc input clock / 16 x = don ? t care f xclk or bus frequency 1 mhz = ??????????? adiv[2:0] f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . analog-to-digital converter (adc) advance information mc68HC908AS32A ? rev 0.0 372 analog-to-digital converter (adc) motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 373 technical data ? mc68HC908AS32A section 24. byte data link controller (bdlc) 24.1 contents 24.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 24.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 24.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 24.4.1 bdlc operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . 377 24.4.1.1 power off mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 24.4.1.2 reset mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 24.4.1.3 run mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 24.4.1.4 bdlc wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 24.4.1.5 bdlc stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 24.4.1.6 digital loopback mode . . . . . . . . . . . . . . . . . . . . . . . . 379 24.4.1.7 analog loopback mode . . . . . . . . . . . . . . . . . . . . . . . . 379 24.5 bdlc mux interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 24.5.1 rx digital filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 24.5.1.1 operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 24.5.1.2 performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382 24.5.2 j1850 frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 24.5.3 j1850 vpw symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 24.5.4 j1850 vpw valid/invalid bits and symbols . . . . . . . . . . 390 24.5.5 message arbitration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394 24.6 bdlc protocol handler . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 24.6.1 protocol architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 24.6.2 rx and tx shift registers . . . . . . . . . . . . . . . . . . . . . . . . 397 24.6.3 rx and tx shadow registers . . . . . . . . . . . . . . . . . . . . . 398 24.6.4 digital loopback multiplexer . . . . . . . . . . . . . . . . . . . . . 398 24.6.5 state machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 24.6.5.1 4x mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 24.6.5.2 receiving a message in block mode . . . . . . . . . . . . . 399 24.6.5.3 transmitting a message in block mode . . . . . . . . . . . 399 24.6.5.4 j1850 bus errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 374 byte data link controller (bdlc) motorola 24.6.5.5 summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 24.7 bdlc cpu interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 24.7.1 bdlc analog and roundtrip delay register . . . . . . . . . 403 24.7.2 bdlc control register 1 . . . . . . . . . . . . . . . . . . . . . . . . . 404 24.7.3 bdlc control register 2 . . . . . . . . . . . . . . . . . . . . . . . . . 407 24.7.4 bdlc state vector register . . . . . . . . . . . . . . . . . . . . . . 414 24.7.5 bdlc data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 24.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 24.8.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 24.8.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418 24.2 introduction the byte data link controller (bdlc) provides access to an external serial communication multiplex bus, operating according to the society of automotive engineers (sae) j1850 protocol. the bdlc-d is only available on the mc68hc908as60a. 24.3 features features of the bdlc module include: sae j1850 class b data communications network interface compatible and iso compatible for low speed (< 125 kbps) serial data communications in automotive applications 10.4 kbps variable pulse width (vpw) bit format digital noise filter collision detection hardware cyclical redundancy check (crc) generation and checking two power-saving modes with automatic wakeup on network activity polling and cpu interrupts available f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) functional description mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 375 block mode receive and transmit supported supports 4x receive mode, 41.6 kbps digital loopback mode analog loopback mode in-frame response (ifr) types 0, 1, 2, and 3 supported 24.4 functional description figure 24-1 shows the organization of the bdlc module. the cpu interface contains the software addressable registers and provides the link between the cpu and the buffers. the buffers provide storage for data received and data to be transmitted onto the j1850 bus. the protocol handler is responsible for the encoding and decoding of data bits and special message symbols during transmission and reception. the mux interface provides the link between the bdlc digital section and the analog physical interface. the wave shaping, driving, and digitizing of data is performed by the physical interface. use of the bdlc module in message networking fully implements the sae standard j1850 class b data communication network interface specification. note: it is recommended that the reader be familiar with the sae j1850 document and iso serial communication document prior to proceeding with this section of the mc68HC908AS32A specification. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 376 byte data link controller (bdlc) motorola figure 24-1. bdlc block diagram cpu interface to j1850 bus mux interface protocol handler physical interface to cpu bdlc table 24-1. bdlc i/o register summary addr. name bit 7 6 5 4 3 2 1 bit 0 $003b bdlc analog and rou5ndtrip delay register (bard) read: ate rxpol 00 bo3 bo2 bo1 bo0 write: r r $003c bdlc control register 1 (bcr1) read: imsg clks r1 r0 00 ie wcm write: r r $003d bdlc control register 2 (bcr2) read: aloop dloop rx4xe nbfs teod tsifr tmifr1 tmifr0 write: $003e bdlc state vector register (bsvr) read: 0 0 i3 i2 i1 i0 0 0 write: r r r r r r r r $003f bdlc data register (bdr) read: bd7 bd6 bd5 bd4 bd3 bd2 bd1 bd0 write: r= reserved f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) functional description mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 377 24.4.1 bdlc operating modes the bdlc has five main modes of operation which interact with the power supplies, pins, and the remainder of the mcu as shown in figure 24-2 . figure 24-2. bdlc operating modes state diagram 24.4.1.1 power off mode this mode is entered from reset mode whenever the bdlc supply voltage, v dd , drops below its minimum specified value for the bdlc to guarantee operation. the bdlc will be placed in reset mode by low- voltage reset (lvr) before being powered down. in this mode, the pin input and output specifications are not guaranteed. v dd > v dd (minimum) and power off reset bdlc stop run v dd v dd (minimum) stop instruction or (from any mode) bdlc wait network activity or wait instruction and wcm = 1 wait instruction and wcm = 0 any mcu reset source asserted no mcu reset source asserted any mcu reset source asserted network activity or other mcu wakeup other mcu wakeup cop, illaddr, pu, reset, lvr, por f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 378 byte data link controller (bdlc) motorola 24.4.1.2 reset mode this mode is entered from the power off mode whenever the bdlc supply voltage, v dd , rises above its minimum specified value (v dd ? 10%) and some mcu reset source is asserted. the internal mcu reset must be asserted while powering up the bdlc or an unknown state will be entered and correct operation cannot be guaranteed. reset mode is also entered from any other mode as soon as one of the mcu ? s possible reset sources (such as lvr, por, cop watchdog, and reset pin, etc.) is asserted. in reset mode, the internal bdlc voltage references are operative; v dd is supplied to the internal circuits which are held in their reset state; and the internal bdlc system clock is running. registers will assume their reset condition. outputs are held in their programmed reset state. therefore, inputs and network activity are ignored. 24.4.1.3 run mode this mode is entered from the reset mode after all mcu reset sources are no longer asserted. run mode is entered from the bdlc wait mode whenever activity is sensed on the j1850 bus. run mode is entered from the bdlc stop mode whenever network activity is sensed, although messages will not be received properly until the clocks have stabilized and the cpu is in run mode also. in this mode, normal network operation takes place. the user should ensure that all bdlc transmissions have ceased before exiting this mode. 24.4.1.4 bdlc wait mode this power-conserving mode is entered automatically from run mode whenever the cpu executes a wait instruction and if the wcm bit in the bcr1 register is cleared previously. in this mode, the bdlc internal clocks continue to run. the first passive- to-active transition of the bus generates a cpu interrupt request from the bdlc which wakes up the bdlc and the cpu. in addition, if the bdlc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) functional description mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 379 receives a valid eof symbol while operating in wait mode, then the bdlc also will generate a cpu interrupt request which wakes up the bdlc and the cpu. see wait mode . 24.4.1.5 bdlc stop mode this power-conserving mode is entered automatically from run mode whenever the cpu executes a stop instruction or if the cpu executes a wait instruction and the wcm bit in the bcr1 register is set previously. in this mode, the bdlc internal clocks are stopped but the physical interface circuitry is placed in a low-power mode and awaits network activity. if network activity is sensed, then a cpu interrupt request will be generated, restarting the bdlc internal clocks. see stop mode . 24.4.1.6 digital loopback mode when a bus fault has been detected, the digital loopback mode is used to determine if the fault condition is caused by failure in the node ? s internal circuits or elsewhere in the network, including the node ? s analog physical interface. in this mode, the transmit digital output pin (bdtxd) and the receive digital input pin (bdrxd) of the digital interface are disconnected from the analog physical interface and tied together to allow the digital portion of the bdlc to transmit and receive its own messages without driving the j1850 bus. 24.4.1.7 analog loopback mode analog loopback is used to determine if a bus fault has been caused by a failure in the node ? s off-chip analog transceiver or elsewhere in the network. the bcld analog loopback mode does not modify the digital transmit or receive functions of the bdlc. it does, however, ensure that once analog loopback mode is exited, the bdlc will wait for an idle bus condition before participation in network communication resumes. if the off-chip analog transceiver has a loopback mode, it usually causes the input to the output drive stage to be looped back into the receiver, allowing the node to receive messages it has transmitted without driving the j1850 bus. in this mode, the output to the j1850 bus is typically high f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 380 byte data link controller (bdlc) motorola impedance. this allows the communication path through the analog transceiver to be tested without interfering with network activity. using the bdlc analog loopback mode in conjunction with the analog transceiver ? s loopback mode ensures that, once the off-chip analog transceiver has exited loopback mode, the bcld will not begin communicating before a known condition exists on the j1850 bus. 24.5 bdlc mux interface the mux interface is responsible for bit encoding/decoding and digital noise filtering between the protocol handler and the physical interface. figure 24-3. bdlc block diagram 24.5.1 rx digital filter the receiver section of the bdlc includes a digital low pass filter to remove narrow noise pulses from the incoming message. an outline of the digital filter is shown in figure 24-4 . cpu interface to j1850 bus mux interface protocol handler physical interface to cpu bdlc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 381 figure 24-4. bdlc rx digital filter block diagram 24.5.1.1 operation the clock for the digital filter is provided by the mux interface clock (see f bdlc parameter in table 24-4 ). at each positive edge of the clock signal, the current state of the receiver physical interface (bdrxd) signal is sampled. the bdrxd signal state is used to determine whether the counter should increment or decrement at the next negative edge of the clock signal. the counter will increment if the input data sample is high but decrement if the input sample is low. therefore, the counter will thus progress either up toward 15 if, on average, the bdrxd signal remains high or progress down toward 0 if, on average, the bdrxd signal remains low. when the counter eventually reaches the value 15, the digital filter decides that the condition of the bdrxd signal is at a stable logic level 1 and the data latch is set, causing the filtered rx data signal to become a logic level 1. furthermore, the counter is prevented from overflowing and can only be decremented from this state. alternatively, should the counter eventually reach the value 0, the digital filter decides that the condition of the bdrxd signal is at a stable logic level 0 and the data latch is reset, causing the filtered rx data signal to become a logic level 0. furthermore, the counter is prevented from underflowing and can only be incremented from this state. 4-bit up/down couter data latch up/down out d q filtered rx data out mux interface input sync dq rx data from physical interface clock (bdrxd) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 382 byte data link controller (bdlc) motorola the data latch will retain its value until the counter next reaches the opposite end point, signifying a definite transition of the signal. 24.5.1.2 performance the performance of the digital filter is best described in the time domain rather than the frequency domain. if the signal on the bdrxd signal transitions, then there will be a delay before that transition appears at the filtered rx data output signal. this delay will be between 15 and 16 clock periods, depending on where the transition occurs with respect to the sampling points. this filter delay must be taken into account when performing message arbitration. for example, if the frequency of the mux interface clock (f bdlc ) is 1.0486 mhz, then the period (t bdlc ) is 954 ns and the maximum filter delay in the absence of noise will be 15.259 s. the effect of random noise on the bdrxd signal depends on the characteristics of the noise itself. narrow noise pulses on the bdrxd signal will be ignored completely if they are shorter than the filter delay. this provides a degree of low pass filtering. if noise occurs during a symbol transition, the detection of that transition can be delayed by an amount equal to the length of the noise burst. this is just a reflection of the uncertainty of where the transition is truly occurring within the noise. noise pulses that are wider than the filter delay, but narrower than the shortest allowable symbol length, will be detected by the next stage of the bdlc ? s receiver as an invalid symbol. noise pulses that are longer than the shortest allowable symbol length will be detected normally as an invalid symbol or as invalid data when the frame ? s crc is checked. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 383 24.5.2 j1850 frame format all messages transmitted on the j1850 bus are structured using the format shown in figure 24-5 . j1850 states that each message has a maximum length of 101 pwm bit times or 12 vpw bytes, excluding sof, eod, nb, and eof, with each byte transmitted msb first. all vpw symbol lengths in the following descriptions are typical values at a 10.4 kbps bit rate. sof ? start-of-frame symbol all messages transmitted onto the j1850 bus must begin with a long- active 200- s period sof symbol. this indicates the start of a new message transmission. the sof symbol is not used in the crc calculation. data ? in-message data bytes the data bytes contained in the message include the message priority/type, message id byte (typically the physical address of the responder), and any actual data being transmitted to the receiving node. the message format used by the bdlc is similar to the 3-byte consolidated header message format outlined by the sae j1850 document. see sae j1850 ? class b data communications network interface for more information about 1- and 3-byte headers. messages transmitted by the bdlc onto the j1850 bus must contain at least one data byte and, therefore, can be as short as one data byte and one crc byte. each data byte in the message is eight bits in length and is transmitted msb to lsb. data e o d optional i f s idle sof priority (data0) message id (data1) data n crc n b ifr eof idle figure 24-5. j1850 bus message format (vpw) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 384 byte data link controller (bdlc) motorola crc ? cyclical redundancy check byte this byte is used by the receiver(s) of each message to determine if any errors have occurred during the transmission of the message. the bdlc calculates the crc byte and appends it onto any messages transmitted onto the j1850 bus. it also performs crc detection on any messages it receives from the j1850 bus. crc generation uses the divisor polynomial x 8 + x 4 + x 3 + x 2 + 1. the remainder polynomial initially is set to all ones. each byte in the message after the start of frame (sof) symbol is processed serially through the crc generation circuitry. the one ? s complement of the remainder then becomes the 8-bit crc byte, which is appended to the message after the data bytes in msb-to-lsb order. when receiving a message, the bdlc uses the same divisor polynomial. all data bytes, excluding the sof and end of data symbols (eod) but including the crc byte, are used to check the crc. if the message is error free, the remainder polynomial will equal x 7 + x 6 + x 2 = $c4, regardless of the data contained in the message. if the calculated crc does not equal $c4, the bdlc will recognize this as a crc error and set the crc error flag in the bsvr. eod ? end-of-data symbol the eod symbol is a long 200- s passive period on the j1850 bus used to signify to any recipients of a message that the transmission by the originator has completed. no flag is set upon reception of the eod symbol. ifr ? in-frame response bytes the ifr section of the j1850 message format is optional. users desiring further definition of in-frame response should review the sae j1850 ? class b data communications network interface specification. eof ? end-of-frame symbol this symbol is a long 280- s passive period on the j1850 bus and is longer than an end-of-data (eod) symbol, which signifies the end of a message. since an eof symbol is longer than a 200- s eod f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 385 symbol, if no response is transmitted after an eod symbol, it becomes an eof, and the message is assumed to be completed. the eof flag is set upon receiving the eof symbol. ifs ? inter-frame separation symbol the ifs symbol is a 20- s passive period on the j1850 bus which allows proper synchronization between nodes during continuous message transmission. the ifs symbol is transmitted by a node after the completion of the end-of-frame (eof) period and, therefore, is seen as a 300- s passive period. when the last byte of a message has been transmitted onto the j1850 bus and the eof symbol time has expired, all nodes then must wait for the ifs symbol time to expire before transmitting a start-of-frame (sof) symbol, marking the beginning of another message. however, if the bdlc is waiting for the ifs period to expire before beginning a transmission and a rising edge is detected before the ifs time has expired, it will synchronize internally to that edge. if a write to the bdr register (for instance, to initiate transmission) occurred on or before 104 t bdlc from the received rising edge, then the bdlc will transmit and arbitrate for the bus. if a cpu write to the bdr register occurred after 104 t bdlc from the detection of the rising edge, then the bdlc will not transmit, but will wait for the next ifs period to expire before attempting to transmit the byte. a rising edge may occur during the ifs period because of varying clock tolerances and loading of the j1850 bus, causing different nodes to observe the completion of the ifs period at different times. to allow for individual clock tolerances, receivers must synchronize to any sof occurring during an ifs period. note: if two messages are received with a 300 s ( s ) interframe separation (ifs) as measured at the rx pin, the start-of-frame (sof) symbol of the second message will generate an invalid symbol interrupt. this interrupt results in the second message being lost and will therefore be unavailable to the application software. implementations of this bdlc design on silicon have not been exposed to interframe separation rates faster than 320 s in practical application and have therefore previously not exhibited this behavior. ensuring that no nodes on the j1850 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 386 byte data link controller (bdlc) motorola network transmit messages at 300 s ( s ) ifs will avoid this missed message frame. in addition, developing application software to robustly handle lost messages will minimize application impact. break ? break the bdlc cannot transmit a break symbol. if the bdlc is transmitting at the time a break is detected, it treats the break as if a transmission error had occurred and halts transmission. if the bdlc detects a break symbol while receiving a message, it treats the break as a reception error and sets the invalid symbol flag in the bsvr, also ignoring the frame it was receiving. if while receiving a message in 4x mode, the bdlc detects a break symbol, it treats the break as a reception error, sets the invalid symbol flag, and exits 4x mode (for example, the rx4xe bit in bcr2 is cleared automatically). if bus control is required after the break symbol is received and the ifs time has elapsed, the programmer must resend the transmission byte using highest priority. note: the j1850 protocol break symbol is not related to the hc08 break module. see break module (brk) on page 157. idle ? idle bus an idle condition exists on the bus during any passive period after expiration of the ifs period (for instance, 300 s). any node sensing an idle bus condition can begin transmission immediately. 24.5.3 j1850 vpw symbols huntsinger ? s variable pulse width modulation (vpw) is an encoding technique in which each bit is defined by the time between successive transitions and by the level of the bus between transitions (for instance, active or passive). active and passive bits are used alternately. this encoding technique is used to reduce the number of bus transitions for a given bit rate. each logic 1 or logic 0 contains a single transition and can be at either the active or passive level and one of two lengths, either 64 s or 128 s f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 387 (t nom at 10.4 kbps baud rate), depending upon the encoding of the previous bit. the start-of-frame (sof), end-of-data (eod), end-of-frame (eof), and inter-frame separation (ifs) symbols always will be encoded at an assigned level and length. see figure 24-6 . each message will begin with an sof symbol an active symbol and, therefore, each data byte (including the crc byte) will begin with a passive bit, regardless of whether it is a logic 1 or a logic 0. all vpw bit lengths stated in the following descriptions are typical values at a 10.4 kbps bit rate. logic 0 a logic 0 is defined as either: ? an active-to-passive transition followed by a passive period 64 s in length, or ? a passive-to-active transition followed by an active period 128 s in length see figure 24-6 (a) . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 388 byte data link controller (bdlc) motorola figure 24-6. j1850 vpw symbols with nominal symbol times logic 1 a logic 1 is defined as either: ? an active-to-passive transition followed by a passive period 128 s in length, or ? a passive-to-active transition followed by an active period 64 s in length see figure 24-6 (b ) . 128 s active passive 64 s or (a) logic 0 128 s active passive 64 s or ( b) logic 1 200 s active passive ( d) start of frame active passive (f) end of frame 240 s (c) break 200 s ( e) end of data 280 s (g) inter-frame 20 s 300 s idle > 300 s (h) idle separation f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 389 normalization bit (nb) the nb symbol has the same property as a logic 1 or a logic 0. it is only used in ifr message responses. break signal (break) the break signal is defined as a passive-to-active transition followed by an active period of at least 240 s (see figure 24-6 (c) ). start-of-frame symbol (sof) the sof symbol is defined as passive-to-active transition followed by an active period 200 s in length (see figure 24-6 (d ) ). this allows the data bytes which follow the sof symbol to begin with a passive bit, regardless of whether it is a logic 1 or a logic 0. end-of-data symbol (eod) the eod symbol is defined as an active-to-passive transition followed by a passive period 200 s in length (see figure 24-6 (e) ). end-of-frame symbol (eof) the eof symbol is defined as an active-to-passive transition followed by a passive period 280 s in length (see figure 24-6 (f) ). if no ifr byte is transmitted after an eod symbol is transmitted, after another 80 s the eod becomes an eof, indicating completion of the message. inter-frame separation symbol (ifs) the ifs symbol is defined as a passive period 300 s in length. the 20- s ifs symbol contains no transition, since when used it always appends to an eof symbol (see figure 24-6 (g) ). idle an idle is defined as a passive period greater than 300 s in length. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 390 byte data link controller (bdlc) motorola 24.5.4 j1850 vpw valid/invalid bits and symbols the timing tolerances for receiving data bits and symbols from the j1850 bus have been defined to allow for variations in oscillator frequencies. in many cases the maximum time allowed to define a data bit or symbol is equal to the minimum time allowed to define another data bit or symbol. since the minimum resolution of the bdlc for determining what symbol is being received is equal to a single period of the mux interface clock (t bdlc ), an apparent separation in these maximum time/minimum time concurrences equal to one cycle of t bdlc occurs. this one clock resolution allows the bdlc to differentiate properly between the different bits and symbols. this is done without reducing the valid window for receiving bits and symbols from transmitters onto the j1850 bus which have varying oscillator frequencies. in huntsinger ? s ? variable pulse width (vpw) modulation bit encoding, the tolerances for both the passive and active data bits received and the symbols received are defined with no gaps between definitions. for example, the maximum length of a passive logic 0 is equal to the minimum length of a passive logic 1, and the maximum length of an active logic 0 is equal to the minimum length of a valid sof symbol. invalid passive bit see figure 24-7(1) . if the passive-to-active received transition beginning the next data bit or symbol occurs between the active-to- passive transition beginning the current data bit (or symbol) and a , the current bit would be invalid. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 391 figure 24-7. j1850 vpw received passive symbol times valid passive logic 0 see figure 24-7(2) . if the passive-to-active received transition beginning the next data bit (or symbol) occurs between a and b , the current bit would be considered a logic 0. valid passive logic 1 see figure 24-7(3) . if the passive-to-active received transition beginning the next data bit (or symbol) occurs between b and c , the current bit would be considered a logic 1. valid eod symbol see figure 24-7(4) . if the passive-to-active received transition beginning the next data bit (or symbol) occurs between c and d , the current symbol would be considered a valid end-of-data symbol (eod). a bc b a (1) invalid passive bit (2) valid passive logic 0 (3) valid passive logic 1 64 s 128 s cd (4) valid eod symbol 200 s active passive active passive active passive active passive f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 392 byte data link controller (bdlc) motorola figure 24-8. j1850 vpw received passive eof and ifs symbol times valid eof and ifs symbol in figure 24-8(1) , if the passive-to-active received transition beginning the sof symbol of the next message occurs between a and b , the current symbol will be considered a valid end-of-frame (eof) symbol. see figure 24-8(2) . if the passive-to-active received transition beginning the sof symbol of the next message occurs between c and d , the current symbol will be considered a valid eof symbol followed by a valid inter-frame separation symbol (ifs). all nodes must wait until a valid ifs symbol time has expired before beginning transmission. however, due to variations in clock frequencies and bus loading, some nodes may recognize a valid ifs symbol before others and immediately begin transmitting. therefore, any time a node waiting to transmit detects a passive-to-active transition once a valid eof has been detected, it should immediately begin transmission, initiating the arbitration process. idle bus in figure 24-8(2) , if the passive-to-active received transition beginning the start-of-frame (sof) symbol of the next message does not occur before d, the bus is considered to be idle, and any node wishing to transmit a message may do so immediately. cd (2) valid eof+ 280 s 300 s a b ( 1) valid eof symbol active passive active passive ifs symbol f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 393 figure 24-9. j1850 vpw received active symbol times invalid active bit in figure 24-9(1) , if the active-to-passive received transition beginning the next data bit (or symbol) occurs between the passive- to-active transition beginning the current data bit (or symbol) and a , the current bit would be invalid. valid active logic 1 in figure 24-9(2) , if the active-to-passive received transition beginning the next data bit (or symbol) occurs between a and b , the current bit would be considered a logic 1. valid active logic 0 in figure 24-9(3) , if the active-to-passive received transition beginning the next data bit (or symbol) occurs between b and c , the current bit would be considered a logic 0. a bc b a (1) invalid active bit (2) valid active logic 1 (3) valid active logic 0 64 s 128 s cd (4) valid sof symbol 200 s active passive active passive active passive active passive f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 394 byte data link controller (bdlc) motorola valid sof symbol in figure 24-9(4) , if the active-to-passive received transition beginning the next data bit (or symbol) occurs between c and d , the current symbol would be considered a valid sof symbol. valid break symbol in figure 24-10 , if the next active-to-passive received transition does not occur until after e , the current symbol will be considered a valid break symbol. a break symbol should be followed by a start-of- frame (sof) symbol beginning the next message to be transmitted onto the j1850 bus. see j1850 frame format for bdlc response to break symbols. figure 24-10. j1850 vpw received break symbol times 24.5.5 message arbitration message arbitration on the j1850 bus is accomplished in a non- destructive manner, allowing the message with the highest priority to be transmitted, while any transmitters which lose arbitration simply stop transmitting and wait for an idle bus to begin transmitting again. if the bdlc wants to transmit onto the j1850 bus, but detects that another message is in progress, it waits until the bus is idle. however, if multiple nodes begin to transmit in the same synchronization window, message arbitration will occur beginning with the first bit after the sof symbol and will continue with each bit thereafter. (2) valid break symbol 240 s e active passive f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc mux interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 395 the variable pulse width modulation (vpw) symbols and j1850 bus electrical characteristics are chosen carefully so that a logic 0 (active or passive type) will always dominate over a logic 1 (active or passive type) that is simultaneously transmitted. hence, logic 0s are said to be dominant and logic 1s are said to be recessive. whenever a node detects a dominant bit on bdrxd when it transmitted a recessive bit, the node loses arbitration and immediately stops transmitting. this is known as bitwise arbitration. figure 24-11. j1850 vpw bitwise arbitrations since a logic 0 dominates a logic 1, the message with the lowest value will have the highest priority and will always win arbitration. for instance, a message with priority 000 will win arbitration over a message with priority 011. this method of arbitration will work no matter how many bits of priority encoding are contained in the message. during arbitration, or even throughout the transmitting message, when an opposite bit is detected, transmission is stopped immediately unless it occurs on the 8th bit of a byte. in this case, the bdlc automatically will append up to two extra logic 1 bits and then stop transmitting. these two extra bits will be arbitrated normally and thus will not interfere with transmitter a transmitter b j1850 bus sof data bit 1 data bit 4 data bit 5 0 transmitter a detects an active state on the bus and stops transmitting transmitter b wins passive active passive active passive active 0 0 1 1 1 data bit 2 1 1 1 data bit 3 0 0 0 0 1 arbitration and continues transmitting f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 396 byte data link controller (bdlc) motorola another message. the second logic 1 bit will not be sent if the first loses arbitration. if the bdlc has lost arbitration to another valid message, then the two extra logic 1s will not corrupt the current message. however, if the bdlc has lost arbitration due to noise on the bus, then the two extra logic 1s will ensure that the current message will be detected and ignored as a noise-corrupted message. 24.6 bdlc protocol handler the protocol handler is responsible for framing, arbitration, crc generation/checking, and error detection. the protocol handler conforms to sae j1850 ? class b data communications network interface . note: motorola assumes that the reader is familiar with the j1850 specification before this protocol handler description is read. figure 24-12. bdlc block diagram cpu interface to j1850 bus mux interface protocol handler physical interface to cpu bdlc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc protocol handler mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 397 24.6.1 protocol architecture the protocol handler contains the state machine, rx shadow register, tx shadow register, rx shift register, tx shift register, and loopback multiplexer as shown in figure 24-13 . figure 24-13. bdlc protocol handler outline 24.6.2 rx and tx shift registers the rx shift register gathers received serial data bits from the j1850 bus and makes them available in parallel form to the rx shadow register. the tx shift register takes data, in parallel form, from the tx shadow register and presents it serially to the state machine so that it can be transmitted onto the j1850 bus. rx shift register to cpu interface and rx/tx buffers state machine to physical interface rx data tx data control 8 tx shift register bdtxd rxd control 8 rx shadow register tx shadow register loopback bdrxd bdtxd multiplexer dloop from bcr2 aloop loopback control f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 398 byte data link controller (bdlc) motorola 24.6.3 rx and tx shadow registers immediately after the rx shift register has completed shifting in a byte of data, this data is transferred to the rx shadow register and rdrf or rxifr is set (see bdlc state vector register ) and an interrupt is generated if the interrupt enable bit (ie) in bcr1 is set. after the transfer takes place, this new data byte in the rx shadow register is available to the cpu interface, and the rx shift register is ready to shift in the next byte of data. data in the rx shadow register must be retrieved by the cpu before it is overwritten by new data from the rx shift register. once the tx shift register has completed its shifting operation for the current byte, the data byte in the tx shadow register is loaded into the tx shift register. after this transfer takes place, the tx shadow register is ready to accept new data from the cpu when tdre flag in bsvr is set. 24.6.4 digital loopback multiplexer the digital loopback multiplexer connects rxd to either bdtxd or bdrxd, depending on the state of the dloop bit in the bcr2 register (see bdlc control register 2 ). 24.6.5 state machine all of the functions associated with performing the protocol are executed or controlled by the state machine. the state machine is responsible for framing, collision detection, arbitration, crc generation/checking, and error detection. the following sections describe the bdlc ? s actions in a variety of situations. 24.6.5.1 4x mode the bdlc can exist on the same j1850 bus as modules which use a special 4x (41.6 kbps) mode of j1850 variable pulse width modulation (vpw) operation. the bdlc cannot transmit in 4x mode, but can receive messages in 4x mode, if the rx4x bit is set in bcr2 register. if the rx4x bit is not set in the bcr2 register, any 4x message on the j1850 bus is treated as noise by the bdlc and is ignored. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc protocol handler mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 399 24.6.5.2 receiving a message in block mode although not a part of the sae j1850 protocol, the bdlc does allow for a special block mode of operation of the receiver. as far as the bdlc is concerned, a block mode message is simply a long j1850 frame that contains an indefinite number of data bytes. all of the other features of the frame remain the same, including the sof, crc, and eod symbols. another node wishing to send a block mode transmission must first inform all other nodes on the network that this is about to happen. this is usually accomplished by sending a special predefined message. 24.6.5.3 transmitting a message in block mode a block mode message is transmitted inherently by simply loading the bytes one by one into the bdr register until the message is complete. the programmer should wait until the tdre flag (see bdlc state vector register ) is set prior to writing a new byte of data into the bdr register. the bdlc does not contain any predefined maximum j1850 message length requirement. 24.6.5.4 j1850 bus errors the bdlc detects several types of transmit and receive errors which can occur during the transmission of a message onto the j1850 bus. transmission error if the message transmitted by the bdlc contains invalid bits or framing symbols on non-byte boundaries, this constitutes a transmission error. when a transmission error is detected, the bdlc immediately will cease transmitting. the error condition ($1c) is reflected in the bsvr register (see table 24-6 ). if the interrupt enable bit (ie in bcr1) is set, a cpu interrupt request from the bdlc is generated. crc error a cyclical redundancy check (crc) error is detected when the data bytes and crc byte of a received message are processed and the crc calculation result is not equal to $c4. the crc code will detect f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 400 byte data link controller (bdlc) motorola any single and 2-bit errors, as well as all 8-bit burst errors and almost all other types of errors. the crc error flag ($18 in bsvr) is set when a crc error is detected. (see bdlc state vector register .) symbol error a symbol error is detected when an abnormal (invalid) symbol is detected in a message being received from the j1850 bus. however, if the bdlc is transmitting when this happens, it will be treated as a loss of arbitration ($14 in bsvr) rather than a transmitter error. the ($1c) symbol invalid or the out-of-range flag is set when a symbol error is detected. therefore, ($1c) symbol invalid flag is stacked behind the ($14) loa flag during a transmission error process. (see bdlc state vector register .) framing error a framing error is detected if an eod or eof symbol is detected on a non-byte boundary from the j1850 bus. a framing error also is detected if the bdlc is transmitting the eod and instead receives an active symbol. the ($1c) symbol invalid or the out-of-range flag is set when a framing error is detected. (see bdlc state vector register .) bus fault if a bus fault occurs, the response of the bdlc will depend upon the type of bus fault. if the bus is shorted to battery, the bdlc will wait for the bus to fall to a passive state before it will attempt to transmit a message. as long as the short remains, the bdlc will never attempt to transmit a message onto the j1850 bus. if the bus is shorted to ground, the bdlc will see an idle bus, begin to transmit the message, and then detect a transmission error ($1c in bsvr), since the short to ground would not allow the bus to be driven to the active (dominant) sof state. the bdlc will abort that transmission and wait for the next cpu command to transmit. in any case, if the bus fault is temporary, as soon as the fault is cleared, the bdlc will resume normal operation. if the bus fault is permanent, it may result in permanent loss of communication on the j1850 bus. (see bdlc state vector register .) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc protocol handler mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 401 break ? break if a break symbol is received while the bdlc is transmitting or receiving, an invalid symbol ($1c in bsvr) interrupt will be generated. reading the bsvr register (see bdlc state vector register ) will clear this interrupt condition. the bdlc will wait for the bus to idle, then wait for a start-of-frame (sof) symbol. the bdlc cannot transmit a break symbol. it can only receive a break symbol from the j1850 bus. 24.6.5.5 summary table 24-2. bdlc j1850 bus error summary error condition bdlc function transmission error for invalid bits or framing symbols on non-byte boundaries, invalid symbol interrupt will be generated. bdlc stops transmission. cyclical redundancy check (crc) error crc error interrupt will be generated. the bdlc will wait for sof. invalid symbol: bdlc receives invalid bits (noise) the bdlc will abort transmission immediately. invalid symbol interrupt will be generated. framing error invalid symbol interrupt will be generated. the bdlc will wait for start-of-frame (sof). bus short to v dd the bdlc will not transmit until the bus is idle. bus short to gnd thermal overload will shut down physical interface. fault condition is reflected in bsvr as an invalid symbol. bdlc receives break symbol. the bdlc will wait for the next valid sof. invalid symbol interrupt will be generated. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 402 byte data link controller (bdlc) motorola 24.7 bdlc cpu interface the cpu interface provides the interface between the cpu and the bdlc and consists of five user registers. bdlc analog and roundtrip delay register (bard) bdlc control register 1 (bcr1) bdlc control register 2 (bcr2) bdlc state vector register (bsvr) bdlc data register (bdr) figure 24-14. bdlc block diagram cpu interface to j1850 bus mux interface protocol handler physical interface to cpu bdlc f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 403 24.7.1 bdlc analog and roundtrip delay register this register programs the bdlc to compensate for various delays of different external transceivers. the default delay value is16 s. timing adjustments from 9 s to 24 s in steps of 1 s are available. the bard register can be written only once after each reset, after which they become read-only bits. the register may be read at any time. ate ? analog transceiver enable bit the analog transceiver enable (ate) bit is used to select either the on-board or an off-chip analog transceiver. 1 = select on-board analog transceiver 0 = select off-chip analog transceiver note: this device does not contain an on-board transceiver. this bit should be programmed to a logic 0 for proper operation. rxpol ? receive pin polarity bit the receive pin polarity (rxpol) bit is used to select the polarity of an incoming signal on the receive pin. some external analog transceivers invert the receive signal from the j1850 bus before feeding it back to the digital receive pin. 1 = select normal/true polarity; true non-inverted signal from the j1850 bus; for example, the external transceiver does not invert the receive signal 0 = select inverted polarity, where an external transceiver inverts the receive signal from the j1850 bus address: $003b bit 7654321bit 0 read: ate rxpol 00 bo3 bo2 bo1 bo0 write: r r reset:11000111 r= reserved figure 24-15. bdlc analog and roundtrip delay register (bard) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 404 byte data link controller (bdlc) motorola b03 ? b00 ? bard offset bits table 24-3 shows the expected transceiver delay with respect to bard offset values. 24.7.2 bdlc control register 1 this register is used to configure and control the bdlc. table 24-3. bdlc transceiver delay bard offset bits b0[3:0] corresponding expected transceiver ? s delays ( 0000 9 0001 10 0010 11 0011 12 0100 13 0101 14 0110 15 0111 16 1000 17 1001 18 1010 19 1011 20 1100 21 1101 22 1110 23 1111 24 address: $003c bit 7654321bit 0 read: imsg clks r1 r0 00 ie wcm write: r r reset:11100000 r= reserved figure 24-16. bdlc control register 1 (bcr1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 405 imsg ? ignore message bit this bit is used to disable the receiver until a new start-of-frame (sof) is detected. 1 = disable receiver. when set, all bdlc interrupt requests will be masked and the status bits will be held in their reset state. if this bit is set while the bdlc is receiving a message, the rest of the incoming message will be ignored. 0 = enable receiver. this bit is cleared automatically by the reception of an sof symbol or a break symbol. it will then generate interrupt requests and will allow changes of the status register to occur. however, these interrupts may still be masked by the interrupt enable (ie) bit. clks ? clock bit the nominal bdlc operating frequency (f bdlc ) must always be 1.048576 mhz or 1 mhz for j1850 bus communications to take place. the clks register bit allows the user to select the frequency (1.048576 mhz or 1 mhz) used to adjust symbol timing automatically. 1 = binary frequency (1.048576 mhz) selected for f bdlc 0 = integer frequency (1 mhz) selected for f bdlc r1 and r0 ? rate select bits these bits determine the amount by which the frequency of the mcu cgmxclk signal is divided to form the mux interface clock (f bdlc ) which defines the basic timing resolution of the mux interface. they may be written only once after reset, after which they become read- only bits. the nominal frequency of f bdlc must always be 1.048576 mhz or 1.0 mhz for j1850 bus communications to take place. hence, the value programmed into these bits is dependent on the chosen mcu system clock frequency per table 24-4 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 406 byte data link controller (bdlc) motorola . ie ? interrupt enable bit this bit determines whether the bdlc will generate cpu interrupt requests in run mode. it does not affect cpu interrupt requests when exiting the bdlc stop or bdlc wait modes. interrupt requests will be maintained until all of the interrupt request sources are cleared by performing the specified actions upon the bdlc ? s registers. interrupts that were pending at the time that this bit is cleared may be lost. 1 = enable interrupt requests from bdlc 0 = disable interrupt requests from bdlc if the programmer does not wish to use the interrupt capability of the bdlc, the bdlc state vector register (bsvr) can be polled periodically by the programmer to determine bdlc states. see bdlc state vector register for a description of the bsvr. wcm ? wait clock mode bit this bit determines the operation of the bdlc during cpu wait mode. see stop mode and wait mode for more details on its use. 1 = stop bdlc internal clocks during cpu wait mode 0 = run bdlc internal clocks during cpu wait mode table 24-4. bdlc rate selection f xclk frequency r1 r0 division f bdlc 1.049 mhz 0 0 1 1.049 mhz 2.097 mhz 0 1 2 1.049 mhz 4.194 mhz 1 0 4 1.049 mhz 8.389 mhz 1 1 8 1.049 mhz 1.000 mhz 0 0 1 1.00 mhz 2.000 mhz 0 1 2 1.00 mhz 4.000 mhz 1 0 4 1.00 mhz 8.000 mhz 1 1 8 1.00 mhz f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 407 24.7.3 bdlc control register 2 this register controls transmitter operations of the bdlc. it is recommended that bset and bclr instructions be used to manipulate data in this register to ensure that the register ? s content does not change inadvertently. aloop ? analog loopback mode bit this bit determines whether the j1850 bus will be driven by the analog physical interface ? s final drive stage. the programmer can use this bit to reset the bdlc state machine to a known state after the off- chip analog transceiver is placed in loopback mode. when the user clears aloop, to indicate that the off-chip analog transceiver is no longer in loopback mode, the bdlc waits for an eof symbol before attempting to transmit. 1 = input to the analog physical interface ? s final drive stage is looped back to the bdlc receiver. the j1850 bus is not driven. 0 = the j1850 bus will be driven by the bdlc. after the bit is cleared, the bdlc requires the bus to be idle for a minimum of end-of-frame symbol time (t trv4 ) before message reception or a minimum of inter-frame symbol time (t trv6 ) before message transmission. (see bdlc transmitter vpw symbol timings .) address: $003d bit 7654321bit 0 read: aloop dloop rx4xe nbfs teod tsifr tmifr1 tmifr0 write: reset:11000000 figure 24-17. bdlc control register 2 (bcr2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 408 byte data link controller (bdlc) motorola dloop ? digital loopback mode bit this bit determines the source to which the digital receive input (bdrxd) is connected and can be used to isolate bus fault conditions (see figure 24-13 ). if a fault condition has been detected on the bus, this control bit allows the programmer to connect the digital transmit output to the digital receive input. in this configuration, data sent from the transmit buffer will be reflected back into the receive buffer. if no faults exist in the bdlc, the fault is in the physical interface block or elsewhere on the j1850 bus. 1 = when set, bdrxd is connected to bdtxd. the bdlc is now in digital loopback mode. 0 = when cleared, bdtxd is not connected to bdrxd. the bdlc is taken out of digital loopback mode and can now drive the j1850 bus normally. rx4xe ? receive 4x enable bit this bit determines if the bdlc operates at normal transmit and receive speed (10.4 kbps) or receive only at 41.6 kbps. this feature is useful for fast download of data into a j1850 node for diagnostic or factory programming of the node. 1 = when set, the bdlc is put in 4x receive-only operation. 0 = when cleared, the bdlc transmits and receives at 10.4 kbps. nbfs ? normalization bit format select bit this bit controls the format of the normalization bit (nb). (see figure 24-18 .) sae j1850 strongly encourages using an active long (logic 0) for in-frame responses containing cyclical redundancy check (crc) and an active short (logic 1) for in-frame responses without crc. 1 = nb that is received or transmitted is a 0 when the response part of an in-frame response (ifr) ends with a crc byte. nb that is received or transmitted is a 1 when the response part of an in-frame response (ifr) does not end with a crc byte. 0 = nb that is received or transmitted is a 1 when the response part of an in-frame response (ifr) ends with a crc byte. nb that is received or transmitted is a 0 when the response part of an in-frame response (ifr) does not end with a crc byte. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 409 teod ? transmit end of data bit this bit is set by the programmer to indicate the end of a message is being sent by the bdlc. it will append an 8-bit crc after completing transmission of the current byte. this bit also is used to end an in- frame response (ifr). if the transmit shadow register is full when teod is set, the crc byte will be transmitted after the current byte in the tx shift register and the byte in the tx shadow register have been transmitted. (see rx and tx shadow registers for a description of the transmit shadow register.) once teod is set, the transmit data register empty flag (tdre) in the bdlc state vector register (bsvr) is cleared to allow lower priority interrupts to occur. (see bdlc state vector register .) 1 = transmit end-of-data (eod) symbol 0 = the teod bit will be cleared automatically at the rising edge of the first crc bit that is sent or if an error is detected. when teod is used to end an ifr transmission, teod is cleared when the bdlc receives back a valid eod symbol or an error condition occurs. tsifr, tmifr1, and tmifr0 ? transmit in-frame response control bits these three bits control the type of in-frame response being sent. the programmer should not set more than one of these control bits to a 1 at any given time. however, if more than one of these three control bits are set to 1, the priority encoding logic will force these register bits to a known value as shown in table 24-5 . for example, if 011 is written to tsifr, tmifr1, and tmifr0, then internally they will be encoded as 010. however, when these bits are read back, they will read 011. table 24-5. bdlc transmit in-frame response control bit priority encoding write/read tsifr write/read tmifr1 write/read tmifr0 actual tsifr actual tmifr1 actual tmifr0 000000 1xx100 01x010 001001 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 410 byte data link controller (bdlc) motorola the bdlc supports the in-frame response (ifr) feature of j1850 by setting these bits correctly. the four types of j1850 ifr are shown below. the purpose of the in-frame response modes is to allow multiple nodes to acknowledge receipt of the data by responding with their personal id or physical address in a concatenated manner after they have seen the eod symbol. if transmission arbitration is lost by a node while sending its response, it continues to transmit its id/address until observing its unique byte in the response stream. for vpw modulation, because the first bit of the ifr is always passive, a normalization bit (active) must be generated by the responder and sent prior to its id/address byte. when there are multiple responders on the j1850 bus, only one normalization bit is sent which assists all other transmitting nodes to sync up their response. figure 24-18. types of in-frame response (ifr) sof header data field crc eod type 0 ? no ifr header data field crc eod type 3 ? multiple bytes transmitted from a single responder header data field crc eod type 1 ? single byte transmitted from a single responder header data field crc eod type 2 ? single byte transmitted from multiple responders id1 id n ifr data field crc nb nb nb id sof sof sof eof eod eof eod eof eod eof (optional) nb = normalization bit id = identifier (usually the physical address of the responder(s)) header = specifies one of three frame lengths f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 411 tsifr ? transmit single byte ifr with no crc (type 1 or 2) bit the tsifr bit is used to request the bdlc to transmit the byte in the bdlc data register (bdr, $003f) as a single byte ifr with no crc. typically, the byte transmitted is a unique identifier or address of the transmitting (responding) node. see figure 24-18 . 1 = if this bit is set prior to a valid eod being received with no crc error, once the eod symbol has been received the bdlc will attempt to transmit the appropriate normalization bit followed by the byte in the bdr. 0 = the tsifr bit will be cleared automatically, once the bdlc has successfully transmitted the byte in the bdr onto the bus, or teod is set, or an error is detected on the bus. if the programmer attempts to set the tsifr bit immediately after the eod symbol has been received from the bus, the tsifr bit will remain in the reset state and no attempt will be made to transmit the ifr byte. if a loss of arbitration occurs when the bdlc attempts to transmit and after the ifr byte winning arbitration completes transmission, the bdlc will again attempt to transmit the bdr (with no normalization bit). the bdlc will continue transmission attempts until an error is detected on the bus, or teod is set, or the bdlc transmission is successful. if loss or arbitration occurs in the last two bits of the ifr byte, two additional 1 bits will not be sent out because the bdlc will attempt to retransmit the byte in the transmit shift register after the irf byte winning arbitration completes transmission. tmifr1 ? transmit multiple byte ifr with crc (type 3) bit the tmifr1 bit requests the bdlc to transmit the byte in the bdlc data register (bdr) as the first byte of a multiple byte ifr with crc or as a single byte ifr with crc. response ifr bytes are still subject to j1850 message length maximums (see j1850 frame format and figure 24-18 ). if this bit is set prior to a valid eod being received with no crc error, once the eod symbol has been received the bdlc will attempt to transmit the appropriate normalization bit followed by ifr bytes. the f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 412 byte data link controller (bdlc) motorola programmer should set teod after the last ifr byte has been written into the bdr register. after teod has been set and the last ifr byte has been transmitted, the crc byte is transmitted. 0 = the tmifr1 bit will be cleared automatically ? once the bdlc has successfully transmitted the crc byte and eod symbol ? by the detection of an error on the multiplex bus or by a transmitter underrun caused when the programmer does not write another byte to the bdr after the tdre interrupt. if the tmifr1 bit is set, the bdlc will attempt to transmit the normalization symbol followed by the byte in the bdr. after the byte in the bdr has been loaded into the transmit shift register, a tdre interrupt (see bdlc state vector register ) will occur similar to the main message transmit sequence. the programmer should then load the next byte of the ifr into the bdr for transmission. when the last byte of the ifr has been loaded into the bdr, the programmer should set the teod bit in the bdlc control register 2 (bcr2). this will instruct the bdlc to transmit a crc byte once the byte in the bdr is transmitted and then transmit an eod symbol, indicating the end of the ifr portion of the message frame. however, if the programmer wishes to transmit a single byte followed by a crc byte, the programmer should load the byte into the bdr before the eod symbol has been received, and then set the tmifr1 bit. once the tdre interrupt occurs, the programmer should then set the teod bit in the bcr2. this will result in the byte in the bdr being the only byte transmitted before the ifr crc byte, and no tdre interrupt will be generated. if the programmer attempts to set the tmifr1 bit immediately after the eod symbol has been received from the bus, the tmifr1 bit will remain in the reset state, and no attempt will be made to transmit an ifr byte. if a loss of arbitration occurs when the bdlc is transmitting any byte of a multiple byte ifr, the bdlc will go to the loss of arbitration state, set the appropriate flag, and cease transmission. if the bdlc loses arbitration during the ifr, the tmifr1 bit will be cleared and no attempt will be made to retransmit the byte in the bdr. if loss of arbitration occurs in the last two bits of the ifr byte, two additional 1 bits will be sent out. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 413 note: the extra logic 1s are an enhancement to the j1850 protocol which forces a byte boundary condition fault. this is helpful in preventing noise from going onto the j1850 bus from a corrupted message. tmifr0 ? transmit multiple byte ifr without crc (type 3) bit the tmifr0 bit is used to request the bdlc to transmit the byte in the bdlc data register (bdr) as the first byte of a multiple byte ifr without crc. response ifr bytes are still subject to j1850 message length maximums (see j1850 frame format and figure 24-18 ). 1 = if this bit is set prior to a valid eod being received with no crc error, once the eod symbol has been received the bdlc will attempt to transmit the appropriate normalization bit followed by ifr bytes. the programmer should set teod after the last ifr byte has been written into the bdr register. after teod has been set, the last ifr byte to be transmitted will be the last byte which was written into the bdr register. 0 = the tmifr0 bit will be cleared automatically; once the bdlc has successfully transmitted the eod symbol; by the detection of an error on the multiplex bus; or by a transmitter underrun caused when the programmer does not write another byte to the bdr after the tdre interrupt. if the tmifr0 bit is set, the bdlc will attempt to transmit the normalization symbol followed by the byte in the bdr. after the byte in the bdr has been loaded into the transmit shift register, a tdre interrupt (see bdlc state vector register ) will occur similar to the main message transmit sequence. the programmer should then load the next byte of the ifr into the bdr for transmission. when the last byte of the ifr has been loaded into the bdr, the programmer should set the teod bit in the bcr2. this will instruct the bdlc to transmit an eod symbol once the byte in the bdr is transmitted, indicating the end of the ifr portion of the message frame. the bdlc will not append a crc when the tmifr0 is set. if the programmer attempts to set the tmifr0 bit after the eod symbol has been received from the bus, the tmifr0 bit will remain in the reset state, and no attempt will be made to transmit an ifr byte. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 414 byte data link controller (bdlc) motorola if a loss of arbitration occurs when the bdlc is transmitting, the tmifr0 bit will be cleared and no attempt will be made to retransmit the byte in the bdr. if loss of arbitration occurs in the last two bits of the ifr byte, two additional 1 bits (active short bits) will be sent out. note: the extra logic 1s are an enhancement to the j1850 protocol which forces a byte boundary condition fault. this is helpful in preventing noise from going onto the j1850 bus from a corrupted message. 24.7.4 bdlc state vector register this register is provided to substantially decrease the cpu overhead associated with servicing interrupts while under operation of a multiplex protocol. it provides an index offset that is directly related to the bdlc ? s current state, which can be used with a user-supplied jump table to rapidly enter an interrupt service routine. this eliminates the need for the user to maintain a duplicate state machine in software. i0, i1, i2, and i3 ? interrupt source bits these bits indicate the source of the interrupt request that currently is pending. the encoding of these bits are listed in table 24-6 . address: $003e bit 7654321bit 0 read: 0 0 i3 i2 i1 i0 0 0 write:rrrrrrrr reset:00000000 r= reserved figure 24-19. bdlc state vector register (bsvr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) bdlc cpu interface mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 415 bits i0, i1, i2, and i3 are cleared by a read of the bsvr except when the bdlc data register needs servicing (rdrf, rxifr, or tdre conditions). rxifr and rdrf can be cleared only by a read of the bsvr followed by a read of the bdlc data register (bdr). tdre can either be cleared by a read of the bsvr followed by a write to the bdlc bdr or by setting the teod bit in bcr2. upon receiving a bdlc interrupt, the user can read the value within the bsvr, transferring it to the cpu ? s index register. the value can then be used to index into a jump table, with entries four bytes apart, to quickly enter the appropriate service routine. for example: table 24-6. bdlc interrupt sources bsvr i3 i2 i1 i0 interrupt source priority $00 0000 no interrupts pending 0 (lowest) $04 0001 received eof 1 $08 0010 received ifr byte (rxifr) 2 $0c 0011 bdlc rx data register full ( rdrf) 3 $10 0100 bdlc tx data register empty (tdre) 4 $14 0101 loss of arbitration 5 $18 0110cyclical r edundancy check (crc) error 6 $1c 0111 symbol invalid or out of range 7 $20 1000 wakeup 8 (highest) service ldx bsvr fetch state vector number jmp jmptab,x enter service routine, * (must end in rti) * jmptab jmp serve0 service condition #0 nop jmp serve1 service condition #1 nop jmp serve2 service condition #2 nop * jmp serve8 service condition #8 end f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 416 byte data link controller (bdlc) motorola note: the nops are used only to align the jmps onto 4-byte boundaries so that the value in the bsvr can be used intact. each of the service routines must end with an rti instruction to guarantee correct continued operation of the device. note also that the first entry can be omitted since it corresponds to no interrupt occurring. the service routines should clear all of the sources that are causing the pending interrupts. note that the clearing of a high priority interrupt may still leave a lower priority interrupt pending, in which case bits i0, i1, and i2 of the bsvr will then reflect the source of the remaining interrupt request. if fewer states are used or if a different software approach is taken, the jump table can be made smaller or omitted altogether. 24.7.5 bdlc data register this register is used to pass the data to be transmitted to the j1850 bus from the cpu to the bdlc. it is also used to pass data received from the j1850 bus to the cpu. each data byte (after the first one) should be written only after a tx data register empty (tdre) state is indicated in the bsvr. data read from this register will be the last data byte received from the j1850 bus. this received data should only be read after an rx data register full (rdrf) interrupt has occurred. (see bdlc state vector register .) address: $003f bit 7654321bit 0 read: d7 d6 d5 d4 d3 d2 d1 d0 write: reset: unaffected by reset figure 24-20. bdlc data register (bdr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) low-power modes mc68HC908AS32A ? rev 0.0 advance information motorola byte data link controller (bdlc) 417 the bdr is double buffered via a transmit shadow register and a receive shadow register. after the byte in the transmit shift register has been transmitted, the byte currently stored in the transmit shadow register is loaded into the transmit shift register. once the transmit shift register has shifted the first bit out, the tdre flag is set, and the shadow register is ready to accept the next data byte. the receive shadow register works similarly. once a complete byte has been received, the receive shift register stores the newly received byte into the receive shadow register. the rdrf flag is set to indicate that a new byte of data has been received. the programmer has one bdlc byte reception time to read the shadow register and clear the rdrf flag before the shadow register is overwritten by the newly received byte. to abort an in-progress transmission, the programmer should stop loading data into the bdr. this will cause a transmitter underrun error and the bdlc automatically will disable the transmitter on the next non- byte boundary. this means that the earliest a transmission can be halted is after at least one byte plus two extra logic 1s have been transmitted. the receiver will pick this up as an error and relay it in the state vector register as an invalid symbol error. note: the extra logic 1s are an enhancement to the j1850 protocol which forces a byte boundary condition fault. this is helpful in preventing noise from going onto the j1850 bus from a corrupted message. 24.8 low-power modes the following information concerns wait mode and stop mode. 24.8.1 wait mode this power-conserving mode is entered automatically from run mode whenever the cpu executes a wait instruction and the wcm bit in bdlc control register 1 (bcr1) is previously clear. in bdlc wait mode, the bdlc cannot drive any data. a subsequent successfully received message, including one that is in progress at the time that this mode is entered, will cause the bdlc to f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . byte data link controller (bdlc) advance information mc68HC908AS32A ? rev 0.0 418 byte data link controller (bdlc) motorola wake up and generate a cpu interrupt request if the interrupt enable (ie) bit in the bdlc control register 1 (bcr1) is previously set. (see bdlc control register 1 for a better understanding of ie.) this results in less of a power saving, but the bdlc is guaranteed to receive correctly the message which woke it up, since the bdlc internal operating clocks are kept running. note: ensuring that all transmissions are complete or aborted before putting the bdlc into wait mode is important. 24.8.2 stop mode this power-conserving mode is entered automatically from run mode whenever the cpu executes a stop instruction or if the cpu executes a wait instruction and the wcm bit in the bdlc control register 1 (bcr1) is previously set. this is the lowest power mode that the bdlc can enter. a subsequent passive-to-active transition on the j1850 bus will cause the bdlc to wake up and generate a non-maskable cpu interrupt request. when a stop instruction is used to put the bdlc in stop mode, the bdlc is not guaranteed to correctly receive the message which woke it up, since it may take some time for the bdlc internal operating clocks to restart and stabilize. if a wait instruction is used to put the bdlc in stop mode, the bdlc is guaranteed to correctly receive the byte which woke it up, if and only if an end-of-frame (eof) has been detected prior to issuing the wait instruction by the cpu. otherwise, the bdlc will not correctly receive the byte that woke it up. if this mode is entered while the bdlc is receiving a message, the first subsequent received edge will cause the bdlc to wake up immediately, generate a cpu interrupt request, and wait for the bdlc internal operating clocks to restart and stabilize before normal communications can resume. therefore, the bdlc is not guaranteed to receive that message correctly. note: it is important to ensure all transmissions are complete or aborted prior to putting the bdlc into stop mode. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 419 technical data ? mc68HC908AS32A section 25. electrical specification 25.1 contents 25.2 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 25.2.1 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 25.2.2 functional operating range . . . . . . . . . . . . . . . . . . . . . . 421 25.2.3 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 421 25.2.4 5.0 volt dc electrical characteristics . . . . . . . . . . . . . . 422 25.2.5 control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423 25.2.6 adc characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 25.2.7 5.0 vdc . . . . . . . . . . . . . . . . . . . . . . . 428 25.2.9 cgm component information . . . . . . . . . . . . . . . . . . . . . 428 25.2.10 cgm acquisition/lock time information . . . . . . . . . . . . 429 25.2.11 timer module characteristics . . . . . . . . . . . . . . . . . . . . . 430 25.2.12 ram memory characteristics . . . . . . . . . . . . . . . . . . . . . 430 25.2.13 eeprom memory characteristics . . . . . . . . . . . . . . . . . 432 25.2.14 flash memory characteristics . . . . . . . . . . . . . . . . . . . 432 25.2.15 bdlc transmitter vpw symbol timings . . . . . . . . . . . . 432 25.2.16 bdlc receiver vpw symbol timings . . . . . . . . . . . . . . 432 25.2.17 bdlc transmitter dc electrical characteristics . . . . . 433 25.2.18 bdlc receiver dc electrical characteristics . . . . . . . . 433 25.3 mechanical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . 434 25.3.1 52-pin plastic leaded chip carrier (plcc) . . . . . . . . . . 434 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 420 electrical specification motorola 25.2 electrical specifications 25.2.1 maximum ratings maximum ratings are the extreme limits to which the mcu can be exposed without permanently damaging it. note: this device is not guaranteed to operate properly at the maximum ratings. refer to 5.0 volt dc electrical characteristics on page 422 for guaranteed operating conditions. note: this device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum-rated voltages to this high-impedance circuit. for proper operation, it is recommended that v in and v out be constrained to the range v ss supply voltage v dd ? 0.3 to +6.0 v input voltage v in v ss ? 0.3 to v dd +0.3 v maximum current per pin excluding v dd and v ss i 25 ma storage temperature t stg ? 55 to +150 c maximum current out of v ss i mvss 100 ma maximum current into v dd i mvdd 100 ma reset and irq input voltage v hi v dd + 4.5 v note: voltages are referenced to v ss . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 421 25.2.2 functional operating range note: for applications which use the lvi, motorola guarantee the functionality of the device cpu only down to the lvi trip point (v lvi ) within the constraints outlined in low voltage inhibit (lvi) . 25.2.3 thermal characteristics rating symbol value unit operating temperature range (1) 1. t a (max) = 125 c for part suffix mfn t a (max) = 105 c for part suffix vfn t a (max) = 85 c for part suffix cfn t a ? 40 to t a (max) c operating voltage range v dd 5.0 0.5v v characteristic symbol value unit thermal resistance qfp (64 pins) ja 70 c/w thermal resistance plcc (52 pins) ja 50 c/w i/o pin power dissipation p i/o user determined w power dissipation (see note 1) p d p d = (i dd x v dd ) + p i/o = k/(t j + 273 c) w constant (see note 2) k p d x (t a + 273 c) + (p d 2 x ja ) w/ c average junction temperature t j t a + p d x ja c notes: 1.power dissipation is a function of temperature. 2.k is a constant unique to the device. k can be determined from a known t a and measured p d . with this value of k, p d and t j can be determined for any value of t a . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 422 electrical specification motorola 25.2.4 5.0 volt dc electrical characteristics characteristic symbol min typical max unit output high voltage (i load = ? 2.0 ma) all ports v oh v dd ? 0.8 --- ? v (i load = ? 5.0 ma) all ports v dd ? 1.5 --- ? v total source current i oh (tot) ? --- 10 ma output low voltage (i load = 1.6 ma) all ports v ol ? --- 0.4 v (i load = 10.0 ma) all ports ? --- 1.5 v total sink current i ol (tot) ? --- 15 ma input high voltage all ports, irq s , reset, osc1 v ih 0.7 x v dd --- v dd v input low voltage all ports, irq s , reset, osc1 v il v ss --- 0.3 x v dd v v dd supply current run (see note 2) wait (see note 3) stop (see note 4) lvi enabled, t a =25 c lvi disabled, t a =25 c lvi enabled, ? 40 c to +125 c lvi disabled, ? 40 c to +125 c i dd ? ? ? ? ? ? 25 14 100 35 35 20 400 50 500 100 ma ma a a a a i/o ports hi-z leakage current i l ? 11 a input current i in ? 1 1 a capacitance ports (as input or output) c out c in ? ? 12 8 pf low-voltage reset inhibit (trip) (recover) v lvi 3.80 4.49 v por rearm voltage (see note 5) v por 0200mv por reset voltage (see note 6) v porrst 0800mv por rise time ramp rate (see note 7) r por 0.02 ? v/ms high cop disable voltage (see note 8) v hi v dd + 3.0 v dd + 4.5 v monitor mode entry voltage on irq (see note 10) v hi v dd + 3.0 v dd + 4.5 v f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 423 25.2.5 control timing notes: 1. v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = ? 40 c to +t a (max), unless otherwise noted. 2. run (operating) i dd measured using external square wave clock source (f bus = 8.4 mhz). all inputs 0.2 v from rail. no dc loads. less than 100 pf on all outputs. c l = 20 pf on osc2. all ports configured as inputs. osc2 capacitance linearly affects run i dd . measured with all modules enabled. typical values at midpoint of voltage range, 25c only. 3. wait i dd measured using external square wave clock source (f bus = 8.4 mhz). all inputs 0.2 vdc from rail. no dc loads. less than 100 pf on all outputs, c l = 20 pf on osc2. all ports configured as inputs. osc2 capacitance linearly affects wait i dd . measured with all modules enabled. typical values at midpoint of voltage range, 25c only. 4. stop i dd measured with osc1 = v ss . typical values at midpoint of voltage range, 25c only. 5. maximum is highest voltage that por is guaranteed. 6. maximum is highest voltage that por is possible. 7. if minimum v dd is not reached before the internal por reset is released, rst must be driven low externally until minimum v dd is reached. 8. see cop module during break interrupts on page 180. v hi applied to rst . 9. although i dd is proportional to bus frequency, a current of several ma is present even at very low frequencies. 10. see monitor mode description within computer operating properly (cop) . v hi applied to irq or rst characteristic symbol min max unit bus operating frequency (4.5 ? 5.5 v ? v dd only) f bus ? 8.4 mhz reset pulse width low t rl 1.5 ? t cyc irq interrupt pulse width low (edge-triggered) t ilhi 1.5 ? t cyc irq interrupt pulse period t ilil note 4 ? t cyc 16-bit timer (see note 2) input capture pulse width (see note 3) input capture period t th, t tl t tltl 2 note 4 ? ? t cyc notes: 1.v dd = 5.0 vdc 0.5v, v ss = 0 vdc, t a = ? 40 c to t a (max), unless otherwise noted. 2.the 2-bit timer prescaler is the limiting factor in determining timer resolution. 3.refer to table 22-2 and supporting note. 4.the minimum period t tltl or t ilil should not be less than the number of cycles it takes to execute the capture interrupt service routine plus tbd t cyc . characteristic symbol min typical max unit f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 424 electrical specification motorola 25.2.6 adc characteristics characteristic min max unit comments resolution 8 8 bits absolute accuracy (v refl = 0 v, v dda /v ddaref = v refh = 5 v 0.5v) ? 1+1lsb includes quantization conversion range (see note 1) v refl v refh v v refl = v ssa power-up time 16 17 s conversion time period input leakage (see note 3) ports b and d ? 11 a conversion time 16 17 adc clock cycles includes sampling time monotonicity inherent within total error zero input reading 00 01 hex v in = v refl full-scale reading fe ff hex v in = v refh sample time (see note 2) 5 ? adc clock cycles input capacitance ? 8pf not tested adc internal clock 500 k 1.048 m hz tested only at 1 mhz analog input voltage v refl v refh v notes: 1.v dd = 5.0 vdc 0.5v, v ss = 0 vdc, v dda /v ddaref = 5.0 vdc 0.5v, v ssa = 0 vdc, v refh = 5.0 vdc 0.5v 2.source impedances greater than 10 k ? adversely affect internal rc charging time during input sampling. 3.the external system error caused by input leakage current is approximately equal to the product of r source and input current. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 425 25.2.7 5.0 vdc num characteristic symbol min max unit operating frequency (see note 3) master slave f bus( m ) f bus( s ) f bus /128 dc f bus /2 f bus mhz 1 cycle time master slave t cyc( m ) t cyc( s ) 2 1 128 ? t cyc 2 enable lead time t lead 15 ? ns 3 enable lag time t lag 15 ? ns 4 clock (sck) high time master slave t w(sckh)m t w(sckh)s 100 50 ? ? ns 5 clock (sck) low time master slave t w(sckl)m t w(sckl)s 100 50 ? ? ns 6 data setup time (inputs) master slave t su(m) t su(s) 45 5 ? ? ns 7 data hold time (inputs) master slave t h(m) t h(s) 0 15 ? ? ns 8 access time, slave (see note 4) cpha = 0 cpha = 1 t a(cp0) t a(cp1) 0 0 40 20 ns 9 slave disable time (hold time to high-impedance state) t dis ? 25 ns 10 enable edge lead time to data valid (see note 6) master slave t ev(m) t ev(s) ? ? 10 40 ns 11 data hold time (outputs, after enable edge) master slave t ho(m) t ho(s) 0 5 ? ? ns 12 data valid master (before capture edge) t v(m) 90 ? ns 13 data hold time (outputs) master (before capture edge) t ho(m) 100 ? ns notes: 1. all timing is shown with respect to 30% v dd and 70% v dd , unless otherwise noted; assumes 100 pf load on all spi pins. 2. item numbers refer to dimensions in figure 25-1 and figure 25-2 . 3. f bus = the currently active bus frequency for the microcontroller. 4. time to data active from high-impedance state. 5. with 100 pf on all spi pins f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 426 electrical specification motorola figure 25-1. spi master timing diagram note note: this first clock edge is generated internally, but is not seen at the sck pin. ss pin of master held high. msb in ss (input) sck (cpol = 0) (output) sck (cpol = 1) (output) miso (input) mosi (output) note 4 5 5 1 4 bits 6 ? 1 lsb in master msb out bits 6 ? 1 master lsb out 10 11 10 11 7 6 note note: this last clock edge is generated internally, but is not seen at the sck pin. ss pin of master held high. msb in ss (input) sck (cpol = 0) (output) sck (cpol = 1) (output) miso (input) mosi (output) note 4 5 5 1 4 bits 6 ? 1 lsb in master msb out bits 6 ? 1 master lsb out 10 11 10 11 7 6 a) spi master timing (cpha = 0) b) spi master timing (cpha = 1) 12 13 12 13 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 427 figure 25-2. spi slave timing diagram note: not defined but normally msb of character just received slave ss (input) sck (cpol = 0) (input) sck (cpol = 1) (input) miso (input) mosi (output) 4 5 5 1 4 msb in bits 6 ? 1 8 6 10 11 11 note slave lsb out 9 3 lsb in 2 7 bits 6 ? 1 msb out note: not defined but normally lsb of character previously transmitted slave ss (input) sck (cpol = 0) (input) sck (cpol = 1) (input) miso (output) mosi (input) 4 5 5 1 4 msb in bits 6 ? 1 8 6 10 note slave lsb out 9 3 lsb in 2 7 bits 6 ? 1 msb out 10 a) spi slave timing (cpha = 0) b) spi slave timing (cpha = 1) 11 11 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 428 electrical specification motorola 25.2.8 cgm operating conditions 1. f cgmvrs is a nominal value described and calulated as an example in the clock generator module (cgm) section for the desired vco operating frequency, f cgmvclk . 25.2.9 cgm component information characteristic symbol min typ max unit comments operating voltage v dd a v dd -0.3 ? v dd +0.3 v v ssa v ss -0.3 ? v ss +0.3 v crystal reference frequency f cgmrclk 1 4.9152 16 mhz module crystal reference frequency f cgmxclk ? 4.9152 ? mhz same frequency as f cgmrclk range nom. multiplier f nom ? 4.9152 ? mhz vco center-of-range frequency f cgmvrs 4.9152 ? note 1 mhz vco operating frequency f cgmvclk 4.9152 ? 32.0 description symbol min typ max unit comments crystal load capacitance c l ???? consult crystal manufacturer ? s data crystal fixed capacitance c1 ? 2 x cl ?? consult crystal manufacturer ? s data crystal tuning capacitance c2 ? 2 x cl ?? consult crystal manufacturer ? s data filter capacitor multiply factor c fact ? 0.0154 ? f/s v filter capacitor c f ? c fact x (v dda / f xclk ) ?? see external filter capacitor pin (cgmxfc) on page 135 bypass capacitor c byp ? 0.1 ? f cbyp must provide low ac impedance from f = f cgmxclk /100 to 100 x f cgmvclk , so series resistance must be considered. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 429 25.2.10 cgm acquisition/lock time information description symbol min typ max unit notes manual mode time to stable t acq ? (8 x v dda ) / (f cgmxclk x k acq) ? s if c f chosen correctly manual stable to lock time t al ? (4 x v dda ) / (f cgmxclk x k trk ) ? s if c f chosen correctly manual acquisition time t lock ? t acq +t al ? s tracking mode entry frequency tolerance d trk 0 ? 3.6 % acquisition mode entry frequency tolerance d unt 6.3 ? 7.2 % lock entry freq. tolerance d lock 0 ? 0.9 % lock exit freq. tolerance d unl 0.9 ? 1.8 % reference cycles per acquisition mode measurement n acq ? 32 ?? reference cycles per tracking mode measurement n trk ? 128 ?? automatic mode time to stable t acq n acq /f xclk (8 x v dda ) / (f xclk x k acq) s if c f chosen correctly automatic stable to lock time t al n trk /f xclk (4 x v dda ) / (f xclk x k trk ) ? s if c f chosen correctly automatic lock time t lock ? 0.65 25 ms pll jitter, deviation of average bus frequency over 2 ms (note 1) 0 ? (f crys ) x (.025%) x (n/4) % n = vco freq. mult. k value for automatic mode time to stable k acq ? 0.2 ?? k value k trk ? 0.004 ?? notes: 1. guaranteed but not tested. 2. v dd = 5.0 vdc 0.5 v, v ss = 0 vdc, t a = -40c to t a (max), unless otherwise noted. 3. conditions for typical and maximum values are for run mode with f cgmxclk = 8mhz, f busdes = 8mhz, n = 4, l = 7, discharged c f = 15 nf, v dd = 5vdc. 4. refer to phase-locked loop (pll) section for guidance on the use of the pll. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 430 electrical specification motorola 25.2.11 timer module characteristics 25.2.12 ram memory characteristics 25.2.13 eeprom memory characteristics characteristic symbol min max unit input capture pulse width t tih, t til 125 ? ns input clock pulse width t tch, t tcl (1/f op ) + 5 ? ns characteristic symbol min max unit ram data retention voltage v rdr 0.7 ? v characteristic symbol min max unit eeprom programming time per byte t eepgm 10 ? ms eeprom erasing time per byte t eebyte 10 ? ms eeprom erasing time per block t eeblock 10 ? ms eeprom erasing time per bulk t eebulk 10 ? ms eeprom programming voltage discharge period t eefpv 100 ? s number of programming operations to the same eeprom byte before erase (1) ?? 8 ? eeprom write/erase cycles @ 10 ms write time ? 10,000 ? cycles eeprom data retention after 10,000 write/erase cycles ? 10 ? years eeprom programming maximum time to ? auto ? bit set --- --- 500 s eeprom erasing maximum time to ? auto ? bit set --- --- 8 ms notes: 1. programming a byte more times than the specified maximum may affect the data integrity of that byte. the byte must be erased before it can be programmed again. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 431 25.2.14 flash memory characteristics characteristic symbol min max unit flash program bus clock frequency ? 1 ? mhz flash read bus clock frequency f read (1) 1. f read is defined as the frequency range for which the flash memory can be read. 32k 8.4m hz flash page erase time t erase (2) 2. if the page erase time is longer than t erase (m in ), there is no erase-disturb, but it reduces the endurance of the flash memory. 1 ? ms flash mass erase time t m erase (3) 3. if the mass erase time is longer than t merase (m in ), there is no erase-disturb, but it reduces the endurance of the flash memory. 4 ? ms flash pgm/erase to hven set up time t nvs 10 ? s flash high voltage hold time t nvh 5 ? s flash high voltage hold time (mass) t nvh l 100 ? s flash program hold time t pgs 5 ? s flash program time t prog 30 40 s flash return to read time t rcv (4) 4. t rcv is defined as the time it needs before the flash can be read after turning off the high voltage charge pump by clearing hven to logic 0. 1 s flash cumulative program hv period t hv (5) 5. t hv is defined as the cumulative high voltage programming time to the same row before next erase. t hv must satisfy this condition: t nvs + t nvh + t pgs + ( t prog x 64) e t hv max. ? 4ms flash row erase endurance (6) 6. the minimum row erase endurance value specifies each row of the flash memory is guaranteed to work for at least this many erase cycles. 10,000 ? cycles flash row program endurance (7) 7. the minimum row program endurance value specifies each row of the flash memory is guaranteed to work for at least this many program cycles. 10,000 ? cycles flash data retention time (8) 8. the flash is guaranteed to retain data over the entire operating temperature range for at least the minimum time spec- ified. 10 ? years f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 432 electrical specification motorola 25.2.15 bdlc transmitter vpw symbol timings 25.2.16 bdlc receiver vpw symbol timings characteristic (1), (2) 1. f bdlc = 1.048576 or 1.0 mhz, v dd = 5.0 v 10%, v ss = 0 v 2. see figure 25-3 . number symbol min typ max unit passive logic 0 10 t tvp1 62 64 66 s passive logic 1 11 t tvp2 126 128 130 s active logic 0 12 t tva1 126 128 130 s active logic 1 13 t tva2 62 64 66 s start-of-frame (sof) 14 t tva3 198 200 202 s end-of-data (eod) 15 t tvp3 198 200 202 s end-of-frame (eof) 16 t tv4 278 280 282 s inter-frame separator (ifs) 17 t tv6 298 300 302 s characteristic (1), (2), (3) 1. f bdlc = 1.048576 or 1.0 mhz, v dd = 5.0 v 10%, v ss = 0 v 2. the receiver symbol timing boundaries are subject to an uncertainty of 1 t bdlc s due to sampling considerations. 3. see figure 25-3 . number symbol min typ max unit passive logic 0 10 t trvp1 34 64 96 s passive logic 1 11 t trvp2 96 128 163 s active logic 0 12 t trva1 96 128 163 s active logic 1 13 t trva2 34 64 96 s start-of-frame (sof) 14 t trva3 163 200 239 s end-of-data (eod) 15 t trvp3 163 200 239 s end-of-frame (eof) 16 t trv4 239 280 320 s break 18 t trv6 280 ?? s f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification electrical specifications mc68HC908AS32A ? rev 0.0 advance information motorola electrical specification 433 figure 25-3. bdlc variable pulse width modulation (vpw) symbol timing 25.2.17 bdlc transmitter dc electrical characteristics 25.2.18 bdlc receiver dc electrical characteristics characteristic (1) 1. v dd = 5.0 vdc + 10%, v ss = 0 vdc, t a = ? 40 o c to +125 o c, unless otherwise noted symbol min max unit bdtxd output low voltage (ibdtxd = 1.6 ma) v oltx ? 0.4 v bdtxd output high voltage (ibdtx = ? 800 a) v ohtx v dd ? 0.8 ? v characteristic (1) 1. v dd = 5.0 vdc + 10%, v ss = 0 vdc, t a = ? 40 o c to +125 o c, unless otherwise noted symbol min max unit bdrxd input low voltage v ilrx v ss 0.3 x v dd v bdrxd input high voltage v ihrx 0.7 x v dd v dd v bdrxd input low current i ilbdrxi ? 1+1 a bdrxd input high current i hbdrx ? 1+1 a 13 11 10 12 16 14 sof 15 18 0 0 1 1 eod brk 0 eof f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . electrical specification advance information mc68HC908AS32A ? rev 0.0 434 electrical specification motorola 25.3 mechanical specifications 25.3.1 52-pin plastic leaded chip carrier (plcc) ? l ? ? m ? ? p ? ? n ? pin 1 pin 52 v w y brk z r a c j e g g1 u b g1 z1 x 0.10 ? t ? seating plane 0.18 t n ? pl ? m m s s s s dim. min. max. notes dim. min. max. a 19.94 20.19 1. datums ? l ? , ? m ? , ? n ? and ? p ? are determined where top of lead shoulder exits plastic body at mould parting line. 2. dimension g1, true position to be measured at datum ? t ? (seating plane). 3. dimensions r and u do not include mould protrusion. allowable mould protrusion is 0.25mm per side. 4. dimensions and tolerancing per ansi y 14.5m, 1982. 5. all dimensions in mm. u 19.05 19.20 b 19.94 20.19 v 1.07 1.21 c 4.20 4.57 w 1.07 1.21 e 2.29 2.79 x 1.07 1.42 f 0.33 0.48 y ? 0.50 g1.27 bsc z2 10 h 0.66 0.81 g1 18.04 18.54 j0.51 ? k1 1.02 ? k0.64 ? z1 2 10 r 19.05 19.20 0.18 t l ? mn ? p m s s s s 0.18 t l ? mn ? p m s s s s 0.18 t n ? pl ? m m s s s s 0.25 t l ? mn ? p s s s s s f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mc68HC908AS32A ? rev 0.0 advance information motorola glossary 435 technical data ? mc68HC908AS32A glossary a ? see ? accumulator (a). ? accumulator (a) ? an 8-bit general-purpose register in the cpu08. the cpu08 uses the accumulator to hold operands and results of arithmetic and logic operations. acquisition mode ? a mode of pll operation during startup before the pll locks on a frequency. also see "tracking mode." address bus ? the set of wires that the cpu or dma uses to read and write memory locations. addressing mode ? the way that the cpu determines the operand address for an instruction. the m68hc08 cpu has 16 addressing modes. alu ? see ? arithmetic logic unit (alu). ? arithmetic logic unit (alu) ? the portion of the cpu that contains the logic circuitry to perform arithmetic, logic, and manipulation operations on operands. asynchronous ? refers to logic circuits and operations that are not synchronized by a common reference signal. baud rate ? the total number of bits transmitted per unit of time. bcd ? see ? binary-coded decimal (bcd). ? binary ? relating to the base 2 number system. binary number system ? the base 2 number system, having two digits, 0 and 1. binary arithmetic is convenient in digital circuit design because digital circuits have two permissible voltage levels, low and high. the binary digits 0 and 1 can be interpreted to correspond to the two digital voltage levels. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary advance information mc68HC908AS32A ? rev 0.0 436 glossary motorola binary-coded decimal (bcd) ? a notation that uses 4-bit binary numbers to represent the 10 decimal digits and that retains the same positional structure of a decimal number. for example, 234 (decimal) = 0010 0011 0100 (bcd) bit ? a binary digit. a bit has a value of either logic 0 or logic 1. branch instruction ? an instruction that causes the cpu to continue processing at a memory location other than the next sequential address. break module ? a module in the m68hc08 family. the break module allows software to halt program execution at a programmable point in order to enter a background routine. breakpoint ? a number written into the break address registers of the break module. when a number appears on the internal address bus that is the same as the number in the break address registers, the cpu executes the software interrupt instruction (swi). break interrupt ? a software interrupt caused by the appearance on the internal address bus of the same value that is written in the break address registers. bus ? a set of wires that transfers logic signals. bus clock ? the bus clock is derived from the cgmout output from the cgm. the bus clock frequency, f op , is equal to the frequency of the oscillator output, cgmxclk, divided by four. byte ? a set of eight bits. c ? the carry/borrow bit in the condition code register. the cpu08 sets the carry/borrow bit when an addition operation produces a carry out of bit 7 of the accumulator or when a subtraction operation requires a borrow. some logical operations and data manipulation instructions also clear or set the carry/borrow bit (as in bit test and branch instructions and shifts and rotates). ccr ? see ? condition code register. ? central processor unit (cpu) ? the primary functioning unit of any computer system. the cpu controls the execution of instructions. cgm ? see ? clock generator module (cgm). ? f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary mc68HC908AS32A ? rev 0.0 advance information motorola glossary 437 clear ? to change a bit from logic 1 to logic 0; the opposite of set. clock ? a square wave signal used to synchronize events in a computer. clock generator module (cgm) ? a module in the m68hc08 family. the cgm generates a base clock signal from which the system clocks are derived. the cgm may include a crystal oscillator circuit and or phase-locked loop (pll) circuit. comparator ? a device that compares the magnitude of two inputs. a digital comparator defines the equality or relative differences between two binary numbers. computer operating properly module (cop) ? a counter module in the m68hc08 family that resets the mcu if allowed to overflow. condition code register (ccr) ? an 8-bit register in the cpu08 that contains the interrupt mask bit and five bits that indicate the results of the instruction just executed. control bit ? one bit of a register manipulated by software to control the operation of the module. control unit ? one of two major units of the cpu. the control unit contains logic functions that synchronize the machine and direct various operations. the control unit decodes instructions and generates the internal control signals that perform the requested operations. the outputs of the control unit drive the execution unit, which contains the arithmetic logic unit (alu), cpu registers, and bus interface. cop ? see "computer operating properly module (cop)." counter clock ? the input clock to the tim counter. this clock is the output of the tim prescaler. cpu ? see ? central processor unit (cpu). ? cpu08 ? the central processor unit of the m68hc08 family. cpu clock ? the cpu clock is derived from the cgmout output from the cgm. the cpu clock frequency is equal to the frequency of the oscillator output, cgmxclk, divided by four. cpu cycles ? a cpu cycle is one period of the internal bus clock, normally derived by dividing a crystal oscillator source by two or more so the high and low times will be equal. the length of time required to execute an instruction is measured in cpu clock cycles. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary advance information mc68HC908AS32A ? rev 0.0 438 glossary motorola cpu registers ? memory locations that are wired directly into the cpu logic instead of being part of the addressable memory map. the cpu always has direct access to the information in these registers. the cpu registers in an m68hc08 are: a (8-bit accumulator) h:x (16-bit index register) sp (16-bit stack pointer) pc (16-bit program counter) ccr (condition code register containing the v, h, i, n, z, and c bits) csic ? customer-specified integrated circuit cycle time ? the period of the operating frequency: t cyc =1/f op . decimal number system ? base 10 numbering system that uses the digits zero through nine. direct memory access module (dma) ? a m68hc08 family module that can perform data transfers between any two cpu-addressable locations without cpu intervention. for transmitting or receiving blocks of data to or from peripherals, dma transfers are faster and more code-efficient than cpu interrupts. dma ? see "direct memory access module (dma)." dma service request ? a signal from a peripheral to the dma module that enables the dma module to transfer data. duty cycle ? a ratio of the amount of time the signal is on versus the time it is off. duty cycle is usually represented by a percentage. eeprom ? electrically erasable, programmable, read-only memory. a nonvolatile type of memory that can be electrically reprogrammed. eprom ? erasable, programmable, read-only memory. a nonvolatile type of memory that can be erased by exposure to an ultraviolet light source and then reprogrammed. exception ? an event such as an interrupt or a reset that stops the sequential execution of the instructions in the main program. external interrupt module (irq) ? a module in the m68hc08 family with both dedicated external interrupt pins and port pins that can be enabled as interrupt pins. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary mc68HC908AS32A ? rev 0.0 advance information motorola glossary 439 fetch ? to copy data from a memory location into the accumulator. firmware ? instructions and data programmed into nonvolatile memory. free-running counter ? a device that counts from zero to a predetermined number, then rolls over to zero and begins counting again. full-duplex transmission ? communication on a channel in which data can be sent and received simultaneously. h ? the upper byte of the 16-bit index register (h:x) in the cpu08. h ? the half-carry bit in the condition code register of the cpu08. this bit indicates a carry from the low-order four bits of the accumulator value to the high-order four bits. the half-carry bit is required for binary-coded decimal arithmetic operations. the decimal adjust accumulator (daa) instruction uses the state of the h and c bits to determine the appropriate correction factor. hexadecimal ? base 16 numbering system that uses the digits 0 through 9 and the letters a through f. high byte ? the most significant eight bits of a word. illegal address ? an address not within the memory map illegal opcode ? a nonexistent opcode. i ? the interrupt mask bit in the condition code register of the cpu08. when i is set, all interrupts are disabled. index register (h:x) ? a 16-bit register in the cpu08. the upper byte of h:x is called h. the lower byte is called x. in the indexed addressing modes, the cpu uses the contents of h:x to determine the effective address of the operand. h:x can also serve as a temporary data storage location. input/output (i/o) ? input/output interfaces between a computer system and the external world. a cpu reads an input to sense the level of an external signal and writes to an output to change the level on an external signal. instructions ? operations that a cpu can perform. instructions are expressed by programmers as assembly language mnemonics. a cpu interprets an opcode and its associated operand(s) and instruction. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary advance information mc68HC908AS32A ? rev 0.0 440 glossary motorola interrupt ? a temporary break in the sequential execution of a program to respond to signals from peripheral devices by executing a subroutine. interrupt request ? a signal from a peripheral to the cpu intended to cause the cpu to execute a subroutine. i/o ? see ? input/output (i/0). ? irq ? see "external interrupt module (irq)." jitter ? short-term signal instability. latch ? a circuit that retains the voltage level (logic 1 or logic 0) written to it for as long as power is applied to the circuit. latency ? the time lag between instruction completion and data movement. least significant bit (lsb) ? the rightmost digit of a binary number. logic 1 ? a voltage level approximately equal to the input power voltage (v dd ). logic 0 ? a voltage level approximately equal to the ground voltage (v ss ). low byte ? the least significant eight bits of a word. low voltage inhibit module (lvi) ? a module in the m68hc08 family that monitors power supply voltage. lvi ? see "low voltage inhibit module (lvi)." m68hc08 ? a motorola family of 8-bit mcus. mark/space ? the logic 1/logic 0 convention used in formatting data in serial communication. mask ? 1. a logic circuit that forces a bit or group of bits to a desired state. 2. a photomask used in integrated circuit fabrication to transfer an image onto silicon. mask option ? a optional microcontroller feature that the customer chooses to enable or disable. mask option register (mor) ? an eprom location containing bits that enable or disable certain mcu features. mcu ? microcontroller unit. see ? microcontroller. ? f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary mc68HC908AS32A ? rev 0.0 advance information motorola glossary 441 memory location ? each m68hc08 memory location holds one byte of data and has a unique address. to store information in a memory location, the cpu places the address of the location on the address bus, the data information on the data bus, and asserts the write signal. to read information from a memory location, the cpu places the address of the location on the address bus and asserts the read signal. in response to the read signal, the selected memory location places its data onto the data bus. memory map ? a pictorial representation of all memory locations in a computer system. microcontroller ? microcontroller unit (mcu). a complete computer system, including a cpu, memory, a clock oscillator, and input/output (i/o) on a single integrated circuit. modulo counter ? a counter that can be programmed to count to any number from zero to its maximum possible modulus. monitor rom ? a section of rom that can execute commands from a host computer for testing purposes. mor ? see "mask option register (mor)." most significant bit (msb) ? the leftmost digit of a binary number. multiplexer ? a device that can select one of a number of inputs and pass the logic level of that input on to the output. n ? the negative bit in the condition code register of the cpu08. the cpu sets the negative bit when an arithmetic operation, logical operation, or data manipulation produces a negative result. nibble ? a set of four bits (half of a byte). object code ? the output from an assembler or compiler that is itself executable machine code, or is suitable for processing to produce executable machine code. opcode ? a binary code that instructs the cpu to perform an operation. open-drain ? an output that has no pullup transistor. an external pullup device can be connected to the power supply to provide the logic 1 output voltage. operand ? data on which an operation is performed. usually a statement consists of an operator and an operand. for example, the operator may be an add instruction, and the operand may be the quantity to be added. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary advance information mc68HC908AS32A ? rev 0.0 442 glossary motorola oscillator ? a circuit that produces a constant frequency square wave that is used by the computer as a timing and sequencing reference. otprom ? one-time programmable read-only memory. a nonvolatile type of memory that cannot be reprogrammed. overflow ? a quantity that is too large to be contained in one byte or one word. page zero ? the first 256 bytes of memory (addresses $0000 ? $00ff). parity ? an error-checking scheme that counts the number of logic 1s in each byte transmitted. in a system that uses odd parity, every byte is expected to have an odd number of logic 1s. in an even parity system, every byte should have an even number of logic 1s. in the transmitter, a parity generator appends an extra bit to each byte to make the number of logic 1s odd for odd parity or even for even parity. a parity checker in the receiver counts the number of logic 1s in each byte. the parity checker generates an error signal if it finds a byte with an incorrect number of logic 1s. pc ? see ? program counter (pc). ? peripheral ? a circuit not under direct cpu control. phase-locked loop (pll) ? a oscillator circuit in which the frequency of the oscillator is synchronized to a reference signal. pll ? see "phase-locked loop (pll)." pointer ? pointer register. an index register is sometimes called a pointer register because its contents are used in the calculation of the address of an operand, and therefore points to the operand. polarity ? the two opposite logic levels, logic 1 and logic 0, which correspond to two different voltage levels, v dd and v ss . polling ? periodically reading a status bit to monitor the condition of a peripheral device. port ? a set of wires for communicating with off-chip devices. prescaler ? a circuit that generates an output signal related to the input signal by a fractional scale factor such as 1/2, 1/8, 1/10 etc. program ? a set of computer instructions that cause a computer to perform a desired operation or operations. program counter (pc) ? a 16-bit register in the cpu08. the pc register holds the address of the next instruction or operand that the cpu will use. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary mc68HC908AS32A ? rev 0.0 advance information motorola glossary 443 pull ? an instruction that copies into the accumulator the contents of a stack ram location. the stack ram address is in the stack pointer. pullup ? a transistor in the output of a logic gate that connects the output to the logic 1 voltage of the power supply. pulse-width ? the amount of time a signal is on as opposed to being in its off state. pulse-width modulation (pwm) ? controlled variation (modulation) of the pulse width of a signal with a constant frequency. push ? an instruction that copies the contents of the accumulator to the stack ram. the stack ram address is in the stack pointer. pwm period ? the time required for one complete cycle of a pwm waveform. ram ? random access memory. all ram locations can be read or written by the cpu. the contents of a ram memory location remain valid until the cpu writes a different value or until power is turned off. rc circuit ? a circuit consisting of capacitors and resistors having a defined time constant. read ? to copy the contents of a memory location to the accumulator. register ? a circuit that stores a group of bits. reserved memory location ? a memory location that is used only in special factory test modes. writing to a reserved location has no effect. reading a reserved location returns an unpredictable value. reset ? to force a device to a known condition. rom ? read-only memory. a type of memory that can be read but cannot be changed (written). the contents of rom must be specified before manufacturing the mcu. sci ? see "serial communication interface module (sci)." serial ? pertaining to sequential transmission over a single line. serial communications interface module (sci) ? a module in the m68hc08 family that supports asynchronous communication. serial peripheral interface module (spi) ? a module in the m68hc08 family that supports synchronous communication. set ? to change a bit from logic 0 to logic 1; opposite of clear. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary advance information mc68HC908AS32A ? rev 0.0 444 glossary motorola shift register ? a chain of circuits that can retain the logic levels (logic 1 or logic 0) written to them and that can shift the logic levels to the right or left through adjacent circuits in the chain. signed ? a binary number notation that accommodates both positive and negative numbers. the most significant bit is used to indicate whether the number is positive or negative, normally logic 0 for positive and logic 1 for negative. the other seven bits indicate the magnitude of the number. software ? instructions and data that control the operation of a microcontroller. software interrupt (swi) ? an instruction that causes an interrupt and its associated vector fetch. spi ? see "serial peripheral interface module (spi)." stack ? a portion of ram reserved for storage of cpu register contents and subroutine return addresses. stack pointer (sp) ? a 16-bit register in the cpu08 containing the address of the next available storage location on the stack. start bit ? a bit that signals the beginning of an asynchronous serial transmission. status bit ? a register bit that indicates the condition of a device. stop bit ? a bit that signals the end of an asynchronous serial transmission. subroutine ? a sequence of instructions to be used more than once in the course of a program. the last instruction in a subroutine is a return from subroutine (rts) instruction. at each place in the main program where the subroutine instructions are needed, a jump or branch to subroutine (jsr or bsr) instruction is used to call the subroutine. the cpu leaves the flow of the main program to execute the instructions in the subroutine. when the rts instruction is executed, the cpu returns to the main program where it left off. synchronous ? refers to logic circuits and operations that are synchronized by a common reference signal. tim ? see "timer interface module (tim)." timer interface module (tim) ? a module used to relate events in a system to a point in time. timer ? a module used to relate events in a system to a point in time. toggle ? to change the state of an output from a logic 0 to a logic 1 or from a logic 1 to a logic 0. tracking mode ? mode of low-jitter pll operation during which the pll is locked on a frequency. also see "acquisition mode." f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary mc68HC908AS32A ? rev 0.0 advance information motorola glossary 445 two ? s complement ? a means of performing binary subtraction using addition techniques. the most significant bit of a two ? s complement number indicates the sign of the number (1 indicates negative). the two ? s complement negative of a number is obtained by inverting each bit in the number and then adding 1 to the result. unbuffered ? utilizes only one register for data; new data overwrites current data. unimplemented memory location ? a memory location that is not used. writing to an unimplemented location has no effect. reading an unimplemented location returns an unpredictable value. executing an opcode at an unimplemented location causes an illegal address reset. v ? the overflow bit in the condition code register of the cpu08. the cpu08 sets the v bit when a two's complement overflow occurs. the signed branch instructions bgt, bge, ble, and blt use the overflow bit. variable ? a value that changes during the course of program execution. vco ? see "voltage-controlled oscillator." vector ? a memory location that contains the address of the beginning of a subroutine written to service an interrupt or reset. voltage-controlled oscillator (vco) ? a circuit that produces an oscillating output signal of a frequency that is controlled by a dc voltage applied to a control input. waveform ? a graphical representation in which the amplitude of a wave is plotted against time. wired-or ? connection of circuit outputs so that if any output is high, the connection point is high. word ? a set of two bytes (16 bits). write ? the transfer of a byte of data from the cpu to a memory location. x ? the lower byte of the index register (h:x) in the cpu08. z ? the zero bit in the condition code register of the cpu08. the cpu08 sets the zero bit when an arithmetic operation, logical operation, or data manipulation produces a result of $00. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . glossary advance information mc68HC908AS32A ? rev 0.0 446 glossary motorola f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . how to reach us: usa/europe/locations not listed: motorola literature distribution; p.o. box 5405, denver, colorado 80217 1-303-675-2140 or 1-800-441-2447 japan: motorola japan ltd.; sps, technical information center, 3-20-1, minami-azabu minato-ku, tokyo 106-8573 japan 81-3-3440-3569 asia/pacific: motorola semiconductors h.k. ltd.; silicon harbour centre, 2 dai king street, tai po industrial estate, tai po, n.t., hong kong 852-26668334 technical information center: 1-800-521-6274 home page: http://www.motorola.com/semiconductors information in this document is provided solely to enable system and software implementers to use motorola products. there are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. motorola reserves the right to make changes without further notice to any products herein. motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. ? typical ? parameters which may be provided in motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including ? typicals ? must be validated for each customer application by customer ? s technical experts. motorola does not convey any license under its patent rights nor the rights of others. motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the motorola product could create a situation where personal injury or death may occur. should buyer purchase or use motorola products for any such unintended or unauthorized application, buyer shall indemnify and hold motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that motorola was negligent regarding the design or manufacture of the part. motorola and the stylized m logo are registered in the u.s. patent and trademark office. digital dna is a trademark of motorola, inc. all other product or service names are the property of their respective owners. motorola, inc. is an equal opportunity/affirmative action employer. ? motorola, inc. 2002 mc68HC908AS32A/d f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . |
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