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| www.motorola.com/semiconductors m68hc08 microcontrollers MC68HC908GR8A/d rev. 0, 4/2003 MC68HC908GR8A technical data mc68hc908gr4a f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola 3 MC68HC908GR8A mc68hc908gr4a technical data ? 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., 2003 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . technical data MC68HC908GR8A ? 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola list of paragraphs 5 technical data ? MC68HC908GR8A list of paragraphs list of paragraphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 table of contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 list of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 list of figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 section 1. general description . . . . . . . . . . . . . . . . . . . . 25 section 2. memory map . . . . . . . . . . . . . . . . . . . . . . . . . . 35 section 3. low power modes . . . . . . . . . . . . . . . . . . . . . . 49 section 4. resets and interrupts . . . . . . . . . . . . . . . . . . . 61 section 5. analog-to-digital converter (adc) . . . . . . . . 79 section 6. break module (brk) . . . . . . . . . . . . . . . . . . . . 91 section 7. clock generator module (cgmc) . . . . . . . . . 99 section 8. configuration register (config) . . . . . . . . 129 section 9. computer operating properly (cop) . . . . . 133 section 10. central processing unit (cpu) . . . . . . . . . 139 section 11. flash memory . . . . . . . . . . . . . . . . . . . . . . . 157 section 12. external interrupt (irq) . . . . . . . . . . . . . . . 167 section 13. keyboard interrupt (kbi) . . . . . . . . . . . . . . 175 section 14. low-voltage inhibit (lvi) . . . . . . . . . . . . . . 183 section 15. monitor rom (mon) . . . . . . . . . . . . . . . . . . 189 section 16. input/output ports (i/o) . . . . . . . . . . . . . . . 205 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 6 list of paragraphs motorola section 17. ram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 section 18. serial communications interface (sci) . . . 231 section 19. system integration module (sim) . . . . . . . 271 section 20. serial peripheral interface (spi). . . . . . . . . 297 section 21. timebase module (tbm) . . . . . . . . . . . . . . . 329 section 22. timer interface module (tim) . . . . . . . . . . . 335 section 23. electrical specifications. . . . . . . . . . . . . . . 361 section 24. mechanical specifications . . . . . . . . . . . . . 387 section 25. ordering information . . . . . . . . . . . . . . . . . 391 glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola table of contents 7 technical data ? MC68HC908GR8A table of contents list of paragraphs table of contents list of tables list of figures section 1. general description 1.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 1.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 1.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.4 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 1.5 pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 1.6 pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 section 2. memory map 2.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 2.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 2.3 unimplemented memory locations . . . . . . . . . . . . . . . . . . . . . .35 2.4 reserved memory locations . . . . . . . . . . . . . . . . . . . . . . . . . .36 2.5 input/output (i/o) section. . . . . . . . . . . . . . . . . . . . . . . . . . . . .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 . . . table of contents technical data MC68HC908GR8A ? rev 0.0 8 table of contents motorola section 3. low power modes 3.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 3.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 3.3 analog-to-digital converter (adc) . . . . . . . . . . . . . . . . . . . . . .50 3.4 break module (brk). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 3.5 central processor unit (cpu). . . . . . . . . . . . . . . . . . . . . . . . . .51 3.6 clock generator module (cgm) . . . . . . . . . . . . . . . . . . . . . . . .52 3.7 computer operating properly module (cop). . . . . . . . . . . . . .52 3.8 external interrupt module (irq) . . . . . . . . . . . . . . . . . . . . . . . .53 3.9 keyboard interrupt module (kbi) . . . . . . . . . . . . . . . . . . . . . . .53 3.10 low-voltage inhibit module (lvi) . . . . . . . . . . . . . . . . . . . . . . .54 3.11 serial communications interface module (sci) . . . . . . . . . . . .54 3.12 serial peripheral interface module (spi) . . . . . . . . . . . . . . . . .55 3.13 timer interface module (tim1 and tim2) . . . . . . . . . . . . . . . . .55 3.14 timebase module (tbm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 3.15 exiting wait mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 3.16 exiting stop mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58 section 4. resets and interrupts 4.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 4.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 4.3 resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.4 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 section 5. analog-to-digital converter (adc) 5.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 5.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola table of contents 9 5.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80 5.5 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 5.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 5.7 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 5.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85 section 6. break module (brk) 6.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 6.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 6.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92 6.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 6.6 break module registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 section 7. clock generator module (cgmc) 7.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 7.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 7.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.5 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112 7.6 cgmc registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 7.7 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 7.8 special modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 7.9 acquisition/lock time specifications . . . . . . . . . . . . . . . . . . . 125 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 10 table of contents motorola section 8. configuration register (config) 8.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 8.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 8.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 section 9. computer operating properly (cop) 9.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.4 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135 9.5 cop control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 9.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 9.7 monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 9.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 9.9 cop module during break mode . . . . . . . . . . . . . . . . . . . . . .137 section 10. central processing unit (cpu) 10.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.4 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 10.5 arithmetic/logic unit (alu) . . . . . . . . . . . . . . . . . . . . . . . . . . .145 10.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145 10.7 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .146 10.8 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 10.9 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola table of contents 11 section 11. flash memory 11.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 11.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 11.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 11.4 flash control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159 11.5 flash page erase operation . . . . . . . . . . . . . . . . . . . . . . . .160 11.6 flash mass erase operation . . . . . . . . . . . . . . . . . . . . . . . .161 11.7 flash program/read operation . . . . . . . . . . . . . . . . . . . . . .162 11.8 flash block protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 11.9 wait mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 11.10 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 section 12. external interrupt (irq) 12.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167 12.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167 12.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167 12.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168 12.5 irq1 pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170 12.6 irq module during break interrupts . . . . . . . . . . . . . . . . . . .171 12.7 irq status and control register . . . . . . . . . . . . . . . . . . . . . .172 section 13. keyboard interrupt (kbi) 13.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 13.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 13.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 13.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176 13.5 keyboard initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 12 table of contents motorola 13.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180 13.7 keyboard module during break interrupts . . . . . . . . . . . . . . .180 13.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181 section 14. low-voltage inhibit (lvi) 14.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 14.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 14.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 14.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 14.5 lvi status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187 14.6 lvi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 14.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 section 15. monitor rom (mon) 15.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 15.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 15.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 15.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190 15.5 security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202 section 16. input/output ports (i/o) 16.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 16.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 16.3 port a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 16.4 port b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 16.5 port c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 16.6 port d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola table of contents 13 16.7 port e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 section 17. ram 17.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 17.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 17.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 section 18. serial communications interface (sci) 18.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231 18.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231 18.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232 18.4 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233 18.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233 18.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250 18.7 sci during break module interrupts. . . . . . . . . . . . . . . . . . . .251 18.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251 18.9 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252 section 19. system integration module (sim) 19.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271 19.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271 19.3 sim bus clock control and generation . . . . . . . . . . . . . . . . .275 19.4 reset and system initialization. . . . . . . . . . . . . . . . . . . . . . . .276 19.5 sim counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281 19.6 exception control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282 19.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290 19.8 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 14 table of contents motorola section 20. serial peripheral interface (spi) 20.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297 20.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297 20.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298 20.4 pin name conventions and i/o register addresses . . . . . . .298 20.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299 20.6 transmission formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303 20.7 queuing transmission data . . . . . . . . . . . . . . . . . . . . . . . . . .309 20.8 error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310 20.9 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 20.10 resetting the spi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .316 20.11 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317 20.12 spi during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .318 20.13 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .318 20.14 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .322 section 21. timebase module (tbm) 21.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329 21.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329 21.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329 21.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .330 21.5 timebase register description. . . . . . . . . . . . . . . . . . . . . . . .331 21.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .332 21.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333 section 22. timer interface module (tim) 22.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola table of contents 15 22.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 22.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .336 22.4 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .336 22.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337 22.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346 22.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347 22.8 tim during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .348 22.9 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .348 22.10 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .349 section 23. electrical specifications 23.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .361 23.2 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . .362 23.3 functional operating range. . . . . . . . . . . . . . . . . . . . . . . . . .363 23.4 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363 23.5 5.0 v dc electrical characteristics. . . . . . . . . . . . . . . . . . . . .364 23.6 3.0 v dc electrical characteristics. . . . . . . . . . . . . . . . . . . . .366 23.7 5.0 v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368 23.8 3.0 v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 23.9 output high-voltage characteristics . . . . . . . . . . . . . . . . . . .370 23.10 output low-voltage characteristics . . . . . . . . . . . . . . . . . . . .373 23.11 typical supply currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 23.12 adc characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .378 23.13 5.0 v spi characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .379 23.14 3.0 v spi characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .380 23.15 timer interface module characteristics . . . . . . . . . . . . . . . . .383 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 16 table of contents motorola 23.16 clock generation module characteristics . . . . . . . . . . . . . . .383 23.17 memory characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 section 24. mechanical specifications 24.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .387 24.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .387 24.3 32-pin lqfp (case #873a) . . . . . . . . . . . . . . . . . . . . . . . . . .388 24.4 28-pin pdip (case #710) . . . . . . . . . . . . . . . . . . . . . . . . . . . .389 24.5 28-pin soic (case #751f). . . . . . . . . . . . . . . . . . . . . . . . . . .390 section 25. ordering information 25.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 25.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 25.3 mc order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .392 25.4 development tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola list of tables 17 technical data ? MC68HC908GR8A list of tables table title page 2-1 vector addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 4-1 interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70 4-2 interrupt source flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75 5-1 mux channel select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86 5-2 adc clock divide ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88 7-1 numeric example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109 7-2 pre 1 and pre0 programming . . . . . . . . . . . . . . . . . . . . . . .117 7-3 vpr1 and vpr0 programming . . . . . . . . . . . . . . . . . . . . . . .117 7-4 example filter component values . . . . . . . . . . . . . . . . . . . . .127 10-1 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 10-2 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155 11-1 examples of protect start address: . . . . . . . . . . . . . . . . . . . . .166 14-1 lviout bit indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187 15-1 monitor mode signal requirements and options . . . . . . . . . .193 15-2 mode differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 15-3 monitor baud rate selection . . . . . . . . . . . . . . . . . . . . . . . . .197 15-4 read (read memory) command . . . . . . . . . . . . . . . . . . . . .199 15-5 write (write memory) command. . . . . . . . . . . . . . . . . . . . .199 15-6 iread (indexed read) command . . . . . . . . . . . . . . . . . . . . .200 15-7 iwrite (indexed write) command . . . . . . . . . . . . . . . . . . . .200 15-8 readsp (read stack pointer) command . . . . . . . . . . . . . . .201 15-9 run (run user program) command . . . . . . . . . . . . . . . . . . .201 16-1 port control register bits summary. . . . . . . . . . . . . . . . . . . . 208 16-2 port a pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211 16-3 port b pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 16-4 port c pin functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218 16-5 port d pin functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223 16-6 port e pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227 18-1 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 18 list of tables motorola 18-2 start bit verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .244 18-3 data bit recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .244 18-4 stop bit recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245 18-5 character format selection . . . . . . . . . . . . . . . . . . . . . . . . . .255 18-6 sci baud rate prescaling . . . . . . . . . . . . . . . . . . . . . . . . . . .266 18-7 sci baud rate selection . . . . . . . . . . . . . . . . . . . . . . . . . . . .266 18-8 sci baud rate selection examples . . . . . . . . . . . . . . . . . . . .268 19-1 signal name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . .273 19-2 pin bit set timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 19-3 interrupt sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .286 19-4 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 20-1 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299 20-2 spi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 20-3 spi configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .321 20-4 spi master baud rate selection . . . . . . . . . . . . . . . . . . . . . .327 21-1 timebase rate selection for osc1 = 32.768 khz . . . . . . . . .331 22-1 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .336 22-2 prescaler selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351 22-3 mode, edge, and level selection . . . . . . . . . . . . . . . . . . . . . .358 23-1 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . .362 23-2 functional operation range. . . . . . . . . . . . . . . . . . . . . . . . . .363 23-3 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363 23-4 5.0v dc electrical characteristics . . . . . . . . . . . . . . . . . . . . .364 23-5 3.0 v dc electrical characteristics. . . . . . . . . . . . . . . . . . . . .366 23-6 5.0 v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368 23-7 3.0 v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 23-8 timer interface module characteristics . . . . . . . . . . . . . . . . .383 23-9 cgm component specifications. . . . . . . . . . . . . . . . . . . . . . .383 25-1 mc order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .392 25-2 development tool kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393 25-3 development tool components . . . . . . . . . . . . . . . . . . . . . . .393 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola list of figures 19 technical data ? MC68HC908GR8A list of figures figure title page 1-1 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 1-2 qfp pin assignments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 1-3 dip and soic pin assignments. . . . . . . . . . . . . . . . . . . . . . . . 31 1-4 power supply bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 2-1 memory map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 2-2 control, status, and data registers . . . . . . . . . . . . . . . . . . . . .39 4-1 internal reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62 4-2 power-on reset recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 4-3 sim reset status register (srsr) . . . . . . . . . . . . . . . . . . . . .65 4-4 interrupt stacking order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67 4-5 interrupt recognition example . . . . . . . . . . . . . . . . . . . . . . . . .68 4-6 interrupt processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69 4-7 interrupt status register 1 (int1). . . . . . . . . . . . . . . . . . . . . . .76 4-8 interrupt status register 2 (int2). . . . . . . . . . . . . . . . . . . . . . .76 4-9 interrupt status register 3 (int3). . . . . . . . . . . . . . . . . . . . . . .77 5-1 adc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81 5-2 adc status and control register (adscr) . . . . . . . . . . . . . . .85 5-3 adc data register (adr) . . . . . . . . . . . . . . . . . . . . . . . . . . . .87 5-4 adc clock register (adclk) . . . . . . . . . . . . . . . . . . . . . . . . .88 6-1 break module block diagram . . . . . . . . . . . . . . . . . . . . . . . . . .92 6-2 i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93 6-3 break status and control register (brkscr). . . . . . . . . . . . .95 6-4 break address register high (brkh) . . . . . . . . . . . . . . . . . . . 96 6-5 break address register low (brkl) . . . . . . . . . . . . . . . . . . . . 96 6-6 sim break status register (sbsr) . . . . . . . . . . . . . . . . . . . . .96 6-7 sim break flag control register (sbfcr) . . . . . . . . . . . . . . . 98 7-1 cgmc block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101 7-2 cgmc external connections . . . . . . . . . . . . . . . . . . . . . . . . .111 7-3 cgmc i/o register summary . . . . . . . . . . . . . . . . . . . . . . . .114 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 20 list of figures motorola 7-4 pll control register (pctl) . . . . . . . . . . . . . . . . . . . . . . . . .115 7-5 pll bandwidth control register (pbwc) . . . . . . . . . . . . . . .118 7-6 pll multiplier select register high (pmsh) . . . . . . . . . . . . . 119 7-7 pll multiplier select register low (pmsl) . . . . . . . . . . . . . . 120 7-8 pll vco range select register (pmrs) . . . . . . . . . . . . . . .121 7-9 pll reference divider select register (pmds) . . . . . . . . . . 122 7-10 pll filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127 8-1 configuration register 2 (config2) . . . . . . . . . . . . . . . . . . .130 8-2 configuration register 1 (config1) . . . . . . . . . . . . . . . . . . .130 9-1 cop block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 9-2 cop control register (copctl) . . . . . . . . . . . . . . . . . . . . . .136 10-1 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 10-2 accumulator (a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141 10-3 index register (h:x). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141 10-4 stack pointer (sp). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .142 10-5 program counter (pc). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 10-6 condition code register (ccr) . . . . . . . . . . . . . . . . . . . . . . . .143 11-1 flash control register (flcr) . . . . . . . . . . . . . . . . . . . . . .159 11-2 flash programming flowchart . . . . . . . . . . . . . . . . . . . . . . .164 11-3 flash block protect register (flbpr). . . . . . . . . . . . . . . . . 165 11-4 flash block protect start address . . . . . . . . . . . . . . . . . . . . 165 12-1 irq module block diagram . . . . . . . . . . . . . . . . . . . . . . . . . .169 12-2 irq i/o register summary. . . . . . . . . . . . . . . . . . . . . . . . . . .169 12-3 irq status and control register (intscr) . . . . . . . . . . . . . .172 13-1 keyboard module block diagram . . . . . . . . . . . . . . . . . . . . . .177 13-2 i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177 13-3 keyboard status and control register (intkbscr) . . . . . . .181 13-4 keyboard interrupt enable register (intkbier) . . . . . . . . . .182 14-1 lvi module block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .185 14-2 lvi i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . .186 14-3 lvi status register (lvisr) . . . . . . . . . . . . . . . . . . . . . . . . . .187 15-1 monitor mode circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191 15-2 low-voltage monitor mode entry flowchart. . . . . . . . . . . . . .195 15-3 monitor data format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 15-4 break transaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196 15-5 read transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 15-6 write transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 15-7 stack pointer at monitor mode entry . . . . . . . . . . . . . . . . . . .202 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola list of figures 21 15-8 monitor mode entry timing. . . . . . . . . . . . . . . . . . . . . . . . . . .203 16-1 i/o port register summary. . . . . . . . . . . . . . . . . . . . . . . . . . .206 16-2 port a data register (pta) . . . . . . . . . . . . . . . . . . . . . . . . . .209 16-3 data direction register a (ddra) . . . . . . . . . . . . . . . . . . . . .210 16-4 port a i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211 16-5 port a input pullup enable register (ptapue) . . . . . . . . . . .212 16-6 port b data register (ptb) . . . . . . . . . . . . . . . . . . . . . . . . . .213 16-7 data direction register b (ddrb) . . . . . . . . . . . . . . . . . . . . .214 16-8 port b i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 16-9 port c data register (ptc) . . . . . . . . . . . . . . . . . . . . . . . . . .216 16-10 data direction register c (ddrc) . . . . . . . . . . . . . . . . . . . . .217 16-11 port c i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218 16-12 port c input pullup enable register (ptcpue) . . . . . . . . . . .219 16-13 port d data register (ptd) . . . . . . . . . . . . . . . . . . . . . . . . . .220 16-14 data direction register d (ddrd) . . . . . . . . . . . . . . . . . . . . .222 16-15 port d i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223 16-16 port d input pullup enable register (ptdpue) . . . . . . . . . . .224 16-17 port e data register (pte) . . . . . . . . . . . . . . . . . . . . . . . . . .225 16-18 data direction register e (ddre) . . . . . . . . . . . . . . . . . . . . .226 16-19 port e i/o circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227 18-1 sci module block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . .234 18-2 sci i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . .235 18-3 sci data formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236 18-4 sci transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .237 18-5 sci receiver block diagram . . . . . . . . . . . . . . . . . . . . . . . . .242 18-6 receiver data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 18-7 slow data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .246 18-8 fast data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247 18-9 sci control register 1 (scc1). . . . . . . . . . . . . . . . . . . . . . . .253 18-10 sci control register 2 (scc2). . . . . . . . . . . . . . . . . . . . . . . .256 18-11 sci control register 3 (scc3). . . . . . . . . . . . . . . . . . . . . . . .258 18-12 sci status register 1 (scs1) . . . . . . . . . . . . . . . . . . . . . . . .260 18-13 flag clearing sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263 18-14 sci status register 2 (scs2) . . . . . . . . . . . . . . . . . . . . . . . .264 18-15 sci data register (scdr) . . . . . . . . . . . . . . . . . . . . . . . . . . .265 18-16 sci baud rate register (scbr) . . . . . . . . . . . . . . . . . . . . . .265 19-1 sim block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .272 19-2 sim i/o register summary. . . . . . . . . . . . . . . . . . . . . . . . . . .274 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 22 list of figures motorola 19-3 cgm clock signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275 19-4 external reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 19-5 internal reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 19-6 sources of internal reset . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 19-7 por recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279 19-8 interrupt entry timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283 19-9 interrupt recovery timing . . . . . . . . . . . . . . . . . . . . . . . . . . .283 19-10 interrupt processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .284 19-11 interrupt recognition example . . . . . . . . . . . . . . . . . . . . . . . .285 19-12 interrupt status register 1 (int1). . . . . . . . . . . . . . . . . . . . . .288 19-13 interrupt status register 2 (int2). . . . . . . . . . . . . . . . . . . . . .288 19-14 interrupt status register 3 (int3). . . . . . . . . . . . . . . . . . . . . .289 19-15 wait mode entry timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291 19-16 wait recovery from interrupt or break . . . . . . . . . . . . . . . . . . 291 19-17 wait recovery from internal reset. . . . . . . . . . . . . . . . . . . . .292 19-18 stop mode entry timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 19-19 stop mode recovery from interrupt or break . . . . . . . . . . . . .293 19-20 sim break status register (sbsr) . . . . . . . . . . . . . . . . . . . .294 19-21 sim reset status register (srsr) . . . . . . . . . . . . . . . . . . . .295 19-22 sim break flag control register (sbfcr) . . . . . . . . . . . . . .296 20-1 spi i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . .299 20-2 spi module block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . .300 20-3 full-duplex master-slave connections . . . . . . . . . . . . . . . . .301 20-4 transmission format (cpha = 0) . . . . . . . . . . . . . . . . . . . . .305 20-5 cpha/ss timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305 20-6 transmission format (cpha = 1) . . . . . . . . . . . . . . . . . . . . .306 20-7 transmission start delay (master) . . . . . . . . . . . . . . . . . . . . .308 20-8 .sprf/spte cpu interrupt timing . . . . . . . . . . . . . . . . . . . .309 20-9 missed read of overflow condition . . . . . . . . . . . . . . . . . . . .311 20-10 clearing sprf when ovrf interrupt is not enabled . . . . . .312 20-11 spi interrupt request generation . . . . . . . . . . . . . . . . . . . . .315 20-12 cpha/ss timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .320 20-13 spi control register (spcr) . . . . . . . . . . . . . . . . . . . . . . . . .322 20-14 spi status and control register (spscr) . . . . . . . . . . . . . . .325 20-15 spi data register (spdr) . . . . . . . . . . . . . . . . . . . . . . . . . . .328 21-1 timebase block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . .330 21-2 timebase control register (tbcr) . . . . . . . . . . . . . . . . . . . .331 22-1 tim block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola list of figures 23 22-2 tim i/o register summary . . . . . . . . . . . . . . . . . . . . . . . . . . .339 22-3 pwm period and pulse width . . . . . . . . . . . . . . . . . . . . . . . .343 22-4 tim status and control register (tsc) . . . . . . . . . . . . . . . . .349 22-5 tim counter registers high (tcnth) . . . . . . . . . . . . . . . . . .352 22-6 tim counter registers low (tcntl) . . . . . . . . . . . . . . . . . . .352 22-7 tim counter modulo register high (tmodh) . . . . . . . . . . . .353 22-8 tim counter modulo register low (tmodl) . . . . . . . . . . . . .353 22-9 tim counter register high (tcnth) . . . . . . . . . . . . . . . . . . .354 22-10 tim counter register low (tcntl). . . . . . . . . . . . . . . . . . . .354 22-11 tim channel 0 status and control register (tsc0) . . . . . . .355 22-12 tim channel 1 status and control register (tsc1) . . . . . . .355 22-13 chxmax latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359 22-14 tim channel 0 register high (tch0h) . . . . . . . . . . . . . . . . .360 22-15 tim channel 0 register low (tch0l) . . . . . . . . . . . . . . . . . .360 22-16 tim channel 1 register high (tch1h) . . . . . . . . . . . . . . . . .360 22-17 tim channel 1 register low (tch1l) . . . . . . . . . . . . . . . . . .360 23-1 typical high-side driver characteristics ? port pta3?pta0 (v dd = 4.5 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370 23-2 typical high-side driver characteristics ? port pta3?pta0 (v dd = 2.7 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370 23-3 typical high-side driver characteristics ? port ptc1?ptc0 (v dd = 4.5 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .371 23-4 typical high-side driver characteristics ? port ptc1?ptc0 (v dd = 2.7 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .371 23-5 typical high-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 5.5 vdc) . . . . . . . . . . 372 23-6 typical high-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 2.7 vdc) . . . . . . . . . . 372 23-7 typical low-side driver characteristics ? port pta3?pta0 (v dd = 5.5 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 23-8 typical low-side driver characteristics ? port pta3?pta0 (v dd = 2.7 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373 23-9 typical low-side driver characteristics ? port ptc1?ptc0 (v dd = 4.5 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .374 23-10 typical low-side driver characteristics ? port ptc1?ptc0 (v dd = 2.7 vdc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .374 23-11 typical low-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 5.5 vdc) . . . . . . . . . . 375 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 24 list of figures motorola 23-12 typical low-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 2.7 vdc) . . . . . . . . . . 375 23-13 typical operating idd, with all modules turned on (?40 c to 125 c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 23-14 typical wait mode idd, with all modules disabled (?40 c to 125 c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 23-15 typical stop mode idd, with all modules disabled (?40 c to 125 c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .377 23-16 spi master timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .381 23-17 spi slave timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .382 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola general description 25 technical data ? MC68HC908GR8A section 1. general description 1.1 contents 1.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 1.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.4 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 1.5 pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 1.6 pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 1.2 introduction the MC68HC908GR8A is a member of the low-cost, high-performance m68hc08 family of 8-bit microcontroller units (mcus). 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. this document also describes the mc68hc908gr4a. the mc68hc908gr4a is a device identical to the MC68HC908GR8A except that it has less flash memory. only when there are differences from the MC68HC908GR8A is the mc68hc908gr4a specifically mentioned in the text. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 26 general description motorola 1.3 features for convenience, features have been organized to reflect: standard features of the MC68HC908GR8A features of the cpu08 1.3.1 standard features of the MC68HC908GR8A high-performance m68hc08 architecture optimized for c-compilers fully upward-compatible object code with m6805, m146805, and m68hc05 families 8-mhz internal bus frequency flash program memory security 1 on-chip programming firmware for use with host personal computer which does not require high voltage for entry in-system programming system protection features: ? optional computer operating properly (cop) reset ? low-voltage detection with optional reset and selectable trip points for 3.0 v and 5.0 v operation ? illegal opcode detection with reset ? illegal address detection with reset low-power design; fully static with stop and wait modes standard low-power modes of operation: ? wait mode ? stop mode master reset pin and power-on reset (por) 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 . . . general description features MC68HC908GR8A ? rev 0.0 technical data motorola general description 27 7680 bytes of on-chip flash memory on the MC68HC908GR8A and 4096 bytes of on-chip flash memory on the mc68hc908gr4a with in-circuit programming capabilities of flash program memory 384 bytes of on-chip random-access memory (ram) serial peripheral interface module (spi) serial communications interface module (sci) one 16-bit, 2-channel timer (tim1) and one 16-bit, 1-channel timer (tim2) interface modules with selectable input capture, output compare, and pwm capability on each channel 6-channel, 8-bit successive approximation analog-to-digital converter (adc) break module (brk) to allow single breakpoint setting during in-circuit debugging internal pullups on irq and rst to reduce customer system cost clock generator module supporting 1mhz ? 8mhz crystals up to 21 general-purpose input/output (i/o) pins, including: ? 19 shared-function i/o pins ? up to two dedicated i/o pins, depending on package choice selectable pullups on inputs only on ports a, c, and d. selection is on an individual port bit basis. during output mode, pullups are disengaged. high current 10-ma sink/10-ma source capability on all port pins higher current 15-ma sink/source capability on ptc0?ptc1 timebase module with clock prescaler circuitry for eight user selectable periodic real-time interrupts with optional active clock source during stop mode for periodic wakeup from stop using an external crystal oscillator stop mode enable bit (oscstopenb) in the config register to allow user selection of having the oscillator enabled or disabled during stop mode 4-bit keyboard wakeup 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 . . . general description technical data MC68HC908GR8A ? rev 0.0 28 general description motorola 32-pin quad flat pack (qfp) or 28-pin plastic dual-in-line package (dip) or 28-pin small outline integrated circuit (soic) specific features of the MC68HC908GR8A in 28-pin dip and 28-pin soic are: ? port b is only 4 bits: ptb0?ptb3; 4-channel adc module ? no port c bits 1.3.2 features of the cpu08 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 efficient c language support 1.4 mcu block diagram figure 1-1 shows the structure of the MC68HC908GR8A. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola general description 29 figure 1-1. mcu block diagram single brkpt break module clock generator module 24 intr system integration module progr. timebase module monitor module serial peripheral 1-channel timer interface module 2 dual v. low-voltage inhibit module 4-bit keyboard arithmetic/logic unit (alu) cpu registers m68hc08 cpu control and status registers ? 64 bytes MC68HC908GR8A user flash ? 7680 bytes user ram ? 384 bytes monitor rom ? 310 bytes user flash vector space ? 36 bytes single external irq module porta ddra ddrd portd ddre porte internal bus osc1 osc2 cgmxfc * rst * irq interface module interrupt module computer operating properly module pta3/kbd3 ?pta0/kbd0 ? v ddad / v refh 8-bit analog-to-digital converter module ptd6/t2ch0 ? ptd5/t1ch1 ? ptd4/t1ch0 ? ptd3/spsck ? ptd2/mosi ? ptd1/miso ? ptd0/ss ? pte1/rxd pte0/txd v ssad / v refl 2-channel timer interface module 1 4mhz oscillator phase-locked loop serial communications interface module data bus switch module memory map module mask option register1 module security module power v ss v dd v ssa v dda ? ports are software configurable with pullup device if input port. ? higher current drive port pins * pin contains integrated pullup device monitor mode entry module portb ddrb ptb5/ad5?ptb0/ad0 portc ddrc ptc1?ptc0 ? ? power-on reset module flash programming (burn-in) rom ? 544 bytes mask option register2 module mc68hc908gr4a user flash ? 4096bytes f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 30 general description motorola 1.5 pin assignments figure 1-2. qfp pin assignments note: ports ptb4, ptb5, ptc0, and ptc1 are available only with the qfp. ptd3/spsck pta3/kbd3 ptd2/mosi ptd1/miso ptd0/ss irq pte1/rxd pte0/txd rst pta2/kbd2 pta1/kbd1 pta0/kbd0 v ssad /v refl v ddad /v refh ptb5/ad5 ptb4/ad4 ptb3/ad3 osc1 osc2 cgmxfc v ssa v dda ptc1 ptc0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 16 ptb2/ad2 v ss v dd ptd4/t1ch0 ptd5/t1ch1 ptd6/t2ch0 ptb0/ad0 ptb1/ad1 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 functions MC68HC908GR8A ? rev 0.0 technical data motorola general description 31 figure 1-3. dip and soic pin assignments 1.6 pin functions descriptions of the pin functions are provided here. 1.6.1 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 figure 1-4 shows. 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. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 cgmxfc osc2 osc1 rst pte0/txd pte1/rxd irq ptd0/ss ptd1/miso ptd2/mosi ptd3/spsck v ss v dd ptd4/t1ch0 v ssa v dda pta3/kbd3 pta2/kbd2 pta1/kbd1 pta0/kbd0 v ssad /v refl v ddad /v refh ptb3/ad3 ptb2/ad2 ptb1/ad1 ptb0/ad0 ptd6/t2ch0 ptd5/t1ch1 note: ports ptb4, ptb5, ptc0, and ptc1 are available only with the qfp. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 32 general description motorola figure 1-4. power supply bypassing 1.6.2 oscillator pins (osc1 and osc2) the osc1 and osc2 pins are the connections for the on-chip oscillator circuit. see clock generator module (cgmc) . 1.6.3 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. this pin contains an internal pullup resistor that is always activated, even when the reset pin is pulled low. see resets and interrupts . 1.6.4 external interrupt pin (irq ) irq is an asynchronous external interrupt pin. this pin contains an internal pullup resistor that is always activated, even when the reset pin is pulled low. see external interrupt (irq) . 1.6.5 cgm power supply pins (v dda and v ssa ) v dda and v ssa are the power supply pins for the analog portion of the clock generator module (cgm). decoupling of these pins should be as per the digital supply. see clock generator module (cgmc) . 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 functions MC68HC908GR8A ? rev 0.0 technical data motorola general description 33 1.6.6 external filter capacitor pin (cgmxfc) cgmxfc is an external filter capacitor connection for the cgm. see clock generator module (cgmc) . 1.6.7 analog power supply/reference pins (v ddad /v refh and v ssad /v refl ) v ddad and v ssad are the power supply pins for the analog-to-digital converter. decoupling of these pins should be as per the digital supply. note: v refh is the high reference supply for the adc. the v refh signal is internally connected with v ddad and have the same potential as v ddad. v ddad should be tied to the same potential as v dd via separate traces. v refl is the low reference supply for the adc. the v refl pin is internally connected with v ssad and has the same potential as v ssad. v ssad should be tied to the same potential as v ss via separate traces. see analog-to-digital converter (adc) . 1.6.8 port a input/output (i/o) pins (pta3/kbd3?pta0/kbd0) pta3?pta0 are special-function, bidirectional i/o port pins. any or all of the port a pins can be programmed to serve as keyboard interrupt pins. see input/output ports (i/o) and external interrupt (irq) . these port pins also have selectable pullups when configured for input mode. the pullups are disengaged when configured for output mode. the pullups are selectable on an individual port bit basis. when the port pins are configured for special-function mode (kbi), pullups will be automatically engaged. as long as the port pins are in special-function mode, the pullups will always be on. 1.6.9 port b i/o pins (ptb5/ad5?ptb0/ad0) ptb5?ptb0 are special-function, bidirectional i/o port pins that can also be used for analog-to-digital converter (adc) inputs. see input/output ports (i/o) and analog-to-digital converter (adc) . there are no pullups associated with this 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 . . . general description technical data MC68HC908GR8A ? rev 0.0 34 general description motorola 1.6.10 port c i/o pins (ptc1?ptc0) ptc1?ptc0 are general-purpose, bidirectional i/o port pins. see input/output ports (i/o) . ptc0 and ptc1 are only available on 32-pin qfp packages. these port pins also have selectable pullups when configured for input mode. the pullups are disengaged when configured for output mode. the pullups are selectable on an individual port bit basis. 1.6.11 port d i/o pins (ptd6/t2ch0?ptd0/ss ) ptd6?ptd0 are special-function, bidirectional i/o port pins. ptd3?ptd0 can be programmed to be serial peripheral interface (spi) pins, while ptd6?ptd4 can be individually programmed to be timer interface module (tim1 and tim2) pins. see timer interface module (tim) , serial peripheral interface (spi) , and input/output ports (i/o) . these port pins also have selectable pullups when configured for input mode. the pullups are disengaged when configured for output mode. the pullups are selectable on an individual port bit basis. when the port pins are configured for special-function mode (spi, tim1, tim2), pullups can be selectable on an individual port pin basis. 1.6.12 port e i/o pins (pte1/rxd?pte0/txd) pte1?pte0 are special-function, bidirectional i/o port pins. these pins can also be programmed to be serial communications interface (sci) pins. see serial communications interface (sci) and input/output ports (i/o) . note: any unused inputs and i/o ports should be tied to an appropriate logic level (either v dd or v ss ). although the i/o ports of the MC68HC908GR8A do not require termination, termination is recommended to reduce the possibility of electro-static discharge damage. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola memory map 35 technical data ? MC68HC908GR8A section 2. memory map 2.1 contents 2.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 2.3 unimplemented memory locations . . . . . . . . . . . . . . . . . . . . . .35 2.4 reserved memory locations . . . . . . . . . . . . . . . . . . . . . . . . . .36 2.5 input/output (i/o) section. . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 2.2 introduction the cpu08 can address 64k bytes of memory space. the memory map, shown in figure 2-1 , includes: 8k bytes of flash memory, 7680 bytes of user space on the MC68HC908GR8A or 4k bytes of flash memory, 4096 bytes of user space on the mc68hc908gr4a 384 bytes of random-access memory (ram) 36 bytes of user-defined vectors 310 bytes of monitor routines in read-only memory (rom) 544 bytes of integrated flash burn-in routines in rom 2.3 unimplemented memory locations accessing an unimplemented location can cause an illegal address reset if illegal address resets are enabled. in the memory map ( figure 2-1 ) and in register figures in this document, unimplemented locations are shaded. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 36 memory map motorola 2.4 reserved memory locations accessing a reserved location can have unpredictable effects on mcu operation. in the figure 2-1 and in register figures in this document, reserved locations are marked with the word reserved or with the letter r. 2.5 input/output (i/o) section most of the control, status, and data registers are in the zero page area of $0000?$003f. additional i/o registers have these addresses: $fe00; sim break status register, sbsr $fe01; sim reset status register, srsr $fe03; sim break flag control register, sbfcr $fe04; interrupt status register 1, int1 $fe05; interrupt status register 2, int2 $fe06; interrupt status register 3, int3 $fe07; reserved flash test control register, fltcr $fe08; flash control register, flcr $fe09; break address register high, brkh $fe0a; break address register low, brkl $fe0b; break status and control register, brkscr $fe0c; lvi status register, lvisr $ff7e; flash block protect register, flbpr data registers are shown in figure 2-2 , and table 2-1 is a list of vector locations. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 input/output (i/o) section MC68HC908GR8A ? rev 0.0 technical data motorola memory map 37 $0000 i/o registers 64 bytes $003f $0040 ram 384 bytes $01bf $01c0 unimplemented 6720 bytes $1bff $1c00 reserved for integrated flash burn-in routines 544 bytes $1e1f $1e20 unimplemented 49,632 bytes $dfff $e000 MC68HC908GR8A flash memory 7680 bytes mc68hc908gr4a unimplemented 3584 bytes $edff $ee00 mc68hc908gr4a flash memory 4096 bytes $fdff $fe00 sim break status register (sbsr) $fe01 sim reset status register (srsr) $fe02 reserved $fe03 sim break flag control register (sbfcr) $fe04 interrupt status register 1 (int1) $fe05 interrupt status register 2 (int2) $fe06 interrupt status register 3 (int3) $fe07 reserved for flash test control register (fltcr) figure 2-1. 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 technical data MC68HC908GR8A ? rev 0.0 38 memory map motorola $fe08 flash control register (flcr) $fe09 break address register high (brkh) $fe0a break address register low (brkl) $fe0b break status and control register (brkscr) $fe0c lvi status register (lvisr) $fe0d reserved 3 bytes $fe0f $fe10 unimplemented 16 bytes reserved for compatibility with monitor code for a-family parts $fe1f $fe20 monitor rom 310 bytes $ff55 $ff56 unimplemented 40 bytes $ff7d $ff7e flash block protect register (flbpr) $ff7f unimplemented 93 bytes $ffdb note: $fff6?$fffd contains 8 security bytes $ffdc flash vectors (36 bytes inluding $ffff) $fffe $ffff low byte of reset vector when read cop control register (copctl) 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 input/output (i/o) section MC68HC908GR8A ? rev 0.0 technical data motorola memory map 39 addr. register name bit 7 6 5 4 3 2 1 bit 0 $0000 port a data register (pta) read: 0 0 0 0 pta3 pta2 pta1 pta0 write: reset: unaffected by reset $0001 port b data register (ptb) read: 0 0 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset $0002 port c data register (ptc) read: 0 0 0 0 0 0 ptc1 ptc0 write: reset: unaffected by reset $0003 port d data register (ptd) read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: reset: unaffected by reset $0004 data direction register a (ddra) read: 0 0 0 0 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 $0005 data direction register b (ddrb) read: 0 0 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 $0006 data direction register c (ddrc) read: 0 0 0 0 0 0 ddrc1 ddrc0 write: reset:00000000 $0007 data direction register d (ddrd) read: 0 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: reset:00000000 $0008 port e data register (pte) read: 0 0 0 0 0 0 pte1 pte0 write: reset: unaffected by reset $0009 unimplemented read: write: reset:00000000 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 1 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 40 memory map motorola $000a unimplemented read: write: reset:00000000 $000b unimplemented read: write: reset:00000000 $000c data direction register e (ddre) read:000000 ddre1 ddre0 write: reset:00000000 $000d port a input pullup enable register (ptapue) read: 0 0 0 0 ptapue3 ptapue2 ptapue1 ptapue0 write: reset:00000000 $000e port c input pullup enable register (ptcpue) read:000000 ptcpue1 ptcpue0 write: reset:00000000 $000f port d input pullup enable register (ptdpue) read: 0 ptdpue6 ptdpue5 ptdpue4 ptdpue3 ptdpue2 ptdpue1 ptdpue0 write: reset:00000000 $0010 spi control register (spcr) read: sprie dmas spmstr cpol cpha spwom spe sptie write: reset:00101000 $0011 spi status and control register (spscr) read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:00001000 $0012 spi data register (spdr) read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0013 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset:00000000 addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 2 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 input/output (i/o) section MC68HC908GR8A ? rev 0.0 technical data motorola memory map 41 $0014 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 $0015 sci control register 3 (scc3) read: r8 t8 dmare dmate orie neie feie peie write: reset:uu000000 $0016 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 $0017 sci status register 2 (scs2) read: bkf rpf write: reset:00000000 $0018 sci data register (scdr) read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0019 sci baud rate register (scbr) read: scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 $001a keyboard status and control register (intkbscr) read: 0 0 0 0 keyf 0 imaskk modek write: ackk reset:00000000 $001b keyboard interrupt enable register (intkbier) read: kbie3 kbie2 kbie1 kbie0 write: reset: 0 0 0 0 $001c time base module control register (tbcr) read: tbif tbr2 tbr1 tbr0 0 tbie tbon r write: tack reset:00000000 $001d irq status and control register (intscr) read: 0 0 0 0 irqf1 0 imask1 mode1 write: ack1 reset:00000000 addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 3 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 42 memory map motorola $001e configuration register 2 (config2)? read:000000 osc- stopenb scibd- src write: reset:00000000 $001f configuration register 1 (config1) ? read: coprs lvistop lvirstd lvipwrd lvi5or3 ? ssrec stop copd write: reset:00000000 $0020 timer 1 status and control register (t1sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 $0021 timer 1 counter register high (t1cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $0022 timer 1 counter register low (t1cntl) read: bit 7 6 5 4 3 2 1 bit 0 write: reset:00000000 $0023 timer 1 counter modulo register high (t1modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 $0024 timer 1 counter modulo register low (t1modl) read: bit 7654321bit 0 write: reset:11111111 $0025 timer 1 channel 0 status and control register (t1sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 $0026 timer 1 channel 0 register high (t1ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0027 timer 1 channel 0 register low (t1ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset ? one-time writeable register after each reset, except lvi5or3 bit. lvi5or3 bit is only reset via por (power-on reset). addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 4 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 input/output (i/o) section MC68HC908GR8A ? rev 0.0 technical data motorola memory map 43 $0028 timer 1 channel 1 status and control register (t1sc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset:00000000 $0029 timer 1 channel 1 register high (t1ch1h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $002a timer 1 channel 1 register low (t1ch1l) read: bit 7654321bit 0 write: reset: indeterminate after reset $002b timer 2 status and control register (t2sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 $002c timer 2 counter register high (t2cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $002d timer 2 counter register low (t2cntl) read: bit 7 6 5 4 3 2 1 bit 0 write: reset:00000000 $002e timer 2 counter modulo register high (t2modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 $002f timer 2 counter modulo register low (t2modl) read: bit 7654321bit 0 write: reset:11111111 $0030 timer 2 channel 0 status and control register (t2sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 $0031 timer 2 channel 0 register high (t2ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 5 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 44 memory map motorola $0032 timer 2 channel 0 register low (t2ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0033 unimplemented read: write: reset:00000000 $0034 unimplemented read: write: reset: indeterminate after reset $0035 unimplemented read: write: reset: indeterminate after reset $0036 pll control register (pctl) read: pllie pllf pllon bcs pre1 pre0 vpr1 vpr0 write: reset:00100000 $0037 pll bandwidth control register (pbwc) read: auto lock acq 0000 r write: reset:00000000 $0038 pll multiplier select high register (pmsh) read: 0 0 0 0 mul11 mul10 mul9 mul8 write: reset:00000000 $0039 pll multiplier select low register (pmsl) read: mul7 mul6 mul5 mul4 mul3 mul2 mul1 mul0 write: reset:01000000 $003a pll vco select range register (pmrs) read: vrs7 vrs6 vrs5 vrs4 vrs3 vrs2 vrs1 vrs0 write: reset:01000000 $003b pll reference divider select register (pmds) read: 0 0 0 0 rds3 rds2 rds1 rds0 write: reset:00000001 addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 6 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 input/output (i/o) section MC68HC908GR8A ? rev 0.0 technical data motorola memory map 45 $003c analog-to-digital status and control register (adscr) read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: r reset:00011111 $003d analog-to-digital data register (adr) read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write:rrrrrrrr reset: indeterminate after reset $003e analog-to-digital input clock register (adclk) read: adiv2 adiv1 adiv0 adiclk 0000 write: rrrr reset:00000000 $003f unimplemented read: write: reset: $fe00 sim break status register (sbsr) read: rrrrrr sbsw r write: note reset:00000000 note: writing a logic 0 clears sbsw. $fe01 sim reset status register (srsr) read: por pin cop ilop ilad modrst lvi 0 write: por:10000000 $fe02 unimplemented read: write: reset: $fe03 sim break flag control register (sbfcr) read: bcferrrrrrr write: reset: 0 $fe04 interrupt status register 1 (int1) read: if6 if5 if4 if3 if2 if1 0 0 write:rrrrrrrr reset:00000000 $fe05 interrupt status register 2 (int2) read: if14 if13 if12 if11 if10 if9 if8 if7 write:rrrrrrrr reset:00000000 addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 7 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 46 memory map motorola $fe06 interrupt status register 3 (int3) read:000000if16if15 write:rrrrrrrr reset:00000000 $fe07 flash test control register (fltcr) read: rrrrrrrr write: reset:00000000 $fe08 flash control register (flcr) read: 0 0 0 0 hven mass erase pgm write: reset:00000000 $fe09 break address register high (brkh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $fe0a break address register low (brkl) read: bit 7654321bit 0 write: reset:00000000 $fe0b break status and control register (brkscr) read: brke brka 000000 write: reset:00000000 $fe0c lvi status register (lvisr) read:lviout0000000 write: reset:00000000 $ff7e flash block protect register (flbpr) ? read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: reset:uuuuuuuu $ffff cop control register (copctl) read: low byte of reset vector write: writing clears cop counter (any value) reset: unaffected by reset ? non-volatile flash register addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented r = reserved u = unaffected figure 2-2. control, status, and data registers (sheet 8 of 8) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 input/output (i/o) section MC68HC908GR8A ? rev 0.0 technical data motorola memory map 47 . table 2-1. vector addresses vector priority vector address vector lowest if16 $ffdc timebase vector (high) $ffdd timebase vector (low) if15 $ffde adc conversion complete vector (high) $ffdf adc conversion complete vector (low) if14 $ffe0 keyboard vector (high) $ffe1 keyboard vector (low) if13 $ffe2 sci transmit vector (high) $ffe3 sci transmit vector (low) if12 $ffe4 sci receive vector (high) $ffe5 sci receive vector (low) if11 $ffe6 sci error vector (high) $ffe7 sci error vector (low) if10 $ffe8 spi transmit vector (high) $ffe9 spi transmit vector (low) if9 $ffea spi receive vector (high) $ffeb spi receive vector (low) if8 $ffec tim2 overflow vector (high) $ffed tim2 overflow vector (low) if7 $ffee reserved $ffef reserved if6 $fff0 tim2 channel 0 vector (high) $fff1 tim2 channel 0 vector (low) if5 $fff2 tim1 overflow vector (high) $fff3 tim1 overflow vector (low) if4 $fff4 tim1 channel 1 vector (high) $fff5 tim1 channel 1 vector (low) if3 $fff6 tim1 channel 0 vector (high) $fff7 tim1 channel 0 vector (low) if2 $fff8 pll vector (high) $fff9 pll vector (low) if1 $fffa irq vector (high) $fffb irq vector (low) ? $fffc swi vector (high) $fffd swi vector (low) ? $fffe reset vector (high) highest $ffff reset vector (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 . . . memory map technical data MC68HC908GR8A ? 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola low power modes 49 technical data ? MC68HC908GR8A section 3. low power modes 3.1 contents 3.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 3.3 analog-to-digital converter (adc) . . . . . . . . . . . . . . . . . . . . . .50 3.4 break module (brk). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 3.5 central processor unit (cpu). . . . . . . . . . . . . . . . . . . . . . . . . .51 3.6 clock generator module (cgm) . . . . . . . . . . . . . . . . . . . . . . . .52 3.7 computer operating properly module (cop). . . . . . . . . . . . . .52 3.8 external interrupt module (irq) . . . . . . . . . . . . . . . . . . . . . . . .53 3.9 keyboard interrupt module (kbi) . . . . . . . . . . . . . . . . . . . . . . .53 3.10 low-voltage inhibit module (lvi) . . . . . . . . . . . . . . . . . . . . . . .54 3.11 serial communications interface module (sci) . . . . . . . . . . . .54 3.12 serial peripheral interface module (spi) . . . . . . . . . . . . . . . . .55 3.13 timer interface module (tim1 and tim2) . . . . . . . . . . . . . . . . .55 3.14 timebase module (tbm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 3.15 exiting wait mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 3.16 exiting stop mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58 3.2 introduction the mcu may enter two low-power modes: wait mode and stop mode. they are common to all hc08 mcus and are entered through instruction execution. this section describes how each module acts in the low-power modes. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes technical data MC68HC908GR8A ? rev 0.0 50 low power modes motorola 3.2.1 wait mode the wait instruction puts the mcu in a low-power standby mode in which the cpu clock is disabled but the bus clock continues to run. power consumption can be further reduced by disabling the lvi module and/or the timebase module through bits in the config register. (see configuration register (config) .) 3.2.2 stop mode stop mode is entered when a stop instruction is executed. the cpu clock is disabled and the bus clock is disabled if the oscstopenb bit in the config register is at a logic 0. (see configuration register (config) .) 3.3 analog-to-digital converter (adc) 3.3.1 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 adch4?adch0 bits in the adc status and control register before executing the wait instruction. 3.3.2 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 after an external interrupt. allow one conversion cycle to stabilize the analog circuitry. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes break module (brk) MC68HC908GR8A ? rev 0.0 technical data motorola low power modes 51 3.4 break module (brk) 3.4.1 wait mode if enabled, the break module is active in wait mode. in the break routine, the user can subtract one from the return address on the stack if the bw bit in the break status register is set. 3.4.2 stop mode the break module is inactive in stop mode. a break interrupt causes exit from stop mode and sets the bw bit in the break status register. the stop instruction does not affect break module register states. 3.5 central processor unit (cpu) 3.5.1 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 3.5.2 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes technical data MC68HC908GR8A ? rev 0.0 52 low power modes motorola 3.6 clock generator module (cgm) 3.6.1 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. 3.6.2 stop mode if the oscstopen bit in the config register is cleared (default), then the stop instruction disables the cgm (oscillator and phase-locked loop) and holds low all cgm outputs (cgmxclk, cgmout, and cgmint). if the stop instruction is executed with the vco clock, cgmvclk, divided by two driving cgmout, the pll automatically clears the bcs bit in the pll control register (pctl), thereby selecting the crystal clock, cgmxclk, divided by two as the source of cgmout. when the mcu recovers from stop, the crystal clock divided by two drives cgmout and bcs remains clear. if the oscstopen bit in the config register is set, then the phase locked loop is shut off, but the oscillator will continue to operate in stop mode. 3.7 computer operating properly module (cop) 3.7.1 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 or a dma service 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 . . . low power modes external interrupt module (irq) MC68HC908GR8A ? rev 0.0 technical data motorola low power modes 53 3.7.2 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. 3.8 external interrupt module (irq) 3.8.1 wait mode the irq module remains active in wait mode. clearing the imask1 bit in the irq status and control register enables irq cpu interrupt requests to bring the mcu out of wait mode. 3.8.2 stop mode the irq module remains active in stop mode. clearing the imask1 bit in the irq status and control register enables irq cpu interrupt requests to bring the mcu out of stop mode. 3.9 keyboard interrupt module (kbi) 3.9.1 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes technical data MC68HC908GR8A ? rev 0.0 54 low power modes motorola 3.9.2 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. 3.10 low-voltage inhibit module (lvi) 3.10.1 wait mode if enabled, the lvi module remains active in wait mode. if enabled to generate resets, the lvi module can generate a reset and bring the mcu out of wait mode. 3.10.2 stop mode if enabled, the lvi module remains active in stop mode. if enabled to generate resets, the lvi module can generate a reset and bring the mcu out of stop mode. 3.11 serial communications interface module (sci) 3.11.1 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes serial peripheral interface module (spi) MC68HC908GR8A ? rev 0.0 technical data motorola low power modes 55 3.11.2 stop mode the sci module is inactive in stop mode. the stop instruction does not affect sci register states. 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. 3.12 serial peripheral interface module (spi) 3.12.1 wait mode the spi module remains active in wait mode. 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. 3.12.2 stop mode the spi module is inactive in stop mode. the stop instruction does not affect spi register states. spi operation resumes after an external interrupt. if stop mode is exited by reset, any transfer in progress is aborted, and the spi is reset. 3.13 timer interface module (tim1 and tim2) 3.13.1 wait mode the tim remains active in wait mode. any enabled cpu interrupt request from the tim can bring the mcu out of wait mode. if tim functions are not required during wait mode, reduce power consumption by stopping the tim 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 . . . low power modes technical data MC68HC908GR8A ? rev 0.0 56 low power modes motorola 3.13.2 stop mode the tim is inactive in stop mode. the stop instruction does not affect register states or the state of the tim counter. tim operation resumes when the mcu exits stop mode after an external interrupt. 3.14 timebase module (tbm) 3.14.1 wait mode the timebase module remains active after execution of the wait instruction. in wait mode, the timebase register is not accessible by the cpu. if the timebase functions are not required during wait mode, reduce the power consumption by stopping the timebase before enabling the wait instruction. 3.14.2 stop mode the timebase module may remain active after execution of the stop instruction if the oscillator has been enabled to operate during stop mode through the oscstopen bit in the config register. the timebase module can be used in this mode to generate a periodic wakeup from stop mode. if the oscillator has not been enabled to operate in stop mode, the timebase module will not be active during stop mode. in stop mode, the timebase register is not accessible by the cpu. if the timebase functions are not required during stop mode, reduce the power consumption by stopping the timebase before enabling the stop 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 . . . low power modes exiting wait mode MC68HC908GR8A ? rev 0.0 technical data motorola low power modes 57 3.15 exiting wait mode these events restart the cpu clock and load the program counter with the reset vector or with an interrupt vector: external reset ? a logic 0 on the rst pin resets the mcu and loads the program counter with the contents of locations $fffe and $ffff. external interrupt ? a high-to-low transition on an external interrupt pin (irq pin) loads the program counter with the contents of locations: $fffa and $fffb; irq pin. break interrupt ? a break interrupt loads the program counter with the contents of $fffc and $fffd. computer operating properly module (cop) reset ? a timeout of the cop counter resets the mcu and loads the program counter with the contents of $fffe and $ffff. low-voltage inhibit module (lvi) reset ? a power supply voltage below the v tripf voltage resets the mcu and loads the program counter with the contents of locations $fffe and $ffff. clock generator module (cgm) interrupt ? a cpu interrupt request from the phase-locked loop (pll) loads the program counter with the contents of $fff8 and $fff9. keyboard module (kbi) interrupt ? a cpu interrupt request from the kbi module loads the program counter with the contents of $ffde and $ffdf. timer 1 interface module (tim1) interrupt ? a cpu interrupt request from the tim1 loads the program counter with the contents of: ? $fff2 and $fff3; tim1 overflow ? $fff4 and $fff5; tim1 channel 1 ? $fff6 and $fff7; tim1 channel 0 timer 2 interface module (tim2) interrupt ? a cpu interrupt request from the tim2 loads the program counter with the contents of: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes technical data MC68HC908GR8A ? rev 0.0 58 low power modes motorola ? $ffec and $ffed; tim2 overflow ? $fff0 and $fff1; tim2 channel 0 serial peripheral interface module (spi) interrupt ? a cpu interrupt request from the spi loads the program counter with the contents of: ? $ffe8 and $ffe9; spi transmitter ? $ffea and $ffeb; spi receiver serial communications interface module (sci) interrupt ? a cpu interrupt request from the sci loads the program counter with the contents of: ? $ffe2 and $ffe3; sci transmitter ? $ffe4 and $ffe5; sci receiver ? $ffe6 and $ffe7; sci receiver error analog-to-digital converter module (adc) interrupt ? a cpu interrupt request from the adc loads the program counter with the contents of: $ffde and $ffdf; adc conversion complete. timebase module (tbm) interrupt ? a cpu interrupt request from the tbm loads the program counter with the contents of: $ffdc and $ffdd; tbm interrupt. 3.16 exiting stop mode these events restart the system clocks and load the program counter with the reset vector or with an interrupt vector: external reset ? a logic 0 on the rst pin resets the mcu and loads the program counter with the contents of locations $fffe and $ffff. external interrupt ? a high-to-low transition on an external interrupt pin loads the program counter with the contents of locations: ? $fffa and $fffb; irq pin ? $ffde and $ffdf; keyboard 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 . . . low power modes technical data MC68HC908GR8A ? rev 0.0 59 low power modes motorola low-voltage inhibit (lvi) reset ? a power supply voltage below the lvi tripf voltage resets the mcu and loads the program counter with the contents of locations $fffe and $ffff. break interrupt ? a break interrupt loads the program counter with the contents of locations $fffc and $fffd. timebase module (tbm) interrupt ? a tbm interrupt loads the program counter with the contents of locations $ffdc and $ffdd when the timebase counter has rolled over. this allows the tbm to generate a periodic wakeup from stop mode. upon exit from stop mode, the system clocks begin running after an oscillator stabilization delay. a 12-bit stop recovery counter inhibits the system clocks for 4096 cgmxclk cycles after the reset or external interrupt. the short stop recovery bit, ssrec, in the configuration register controls the oscillator stabilization delay during stop recovery. setting ssrec reduces stop recovery time from 4096 cgmxclk cycles to 32 cgmxclk cycles. note: use the full stop recovery time (ssrec = 0) in applications that use an external crystal. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 power modes technical data MC68HC908GR8A ? rev 0.0 60 low power modes 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 61 technical data ? MC68HC908GR8A section 4. resets and interrupts 4.1 contents 4.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 4.3 resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.4 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 4.2 introduction resets and interrupts are responses to exceptional events during program execution. a reset re-initializes the mcu to its startup condition. an interrupt vectors the program counter to a service routine. 4.3 resets a reset immediately returns the mcu to a known startup condition and begins program execution from a user-defined memory location. 4.3.1 effects a reset: immediately stops the operation of the instruction being executed initializes certain control and status bits loads the program counter with a user-defined reset vector address from locations $fffe and $ffff selects cgmxclk divided by four as the bus 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 . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 62 resets and interrupts motorola 4.3.2 external reset a logic 0 applied to the rst pin for a time, t irl , generates an external reset. an external reset sets the pin bit in the sim reset status register. 4.3.3 internal reset sources: power-on reset (por) computer operating properly (cop) low-power reset circuits illegal opcode illegal address all internal reset sources pull the rst pin low for 32 cgmxclk cycles to allow resetting of external devices. the mcu is held in reset for an additional 32 cgmxclk cycles after releasing the rst pin. figure 4-1. internal reset timing 4.3.3.1 power-on reset a power-on reset is an internal reset caused by a positive transition on the v dd pin. v dd at the por must go completely to 0 v to reset the mcu. this distinguishes between a reset and a por. the por is not a brown-out detector, low-voltage detector, or glitch detector. rst pin pulled low by mcu internal 32 cycles 32 cycles cgmxclk 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 . . . resets and interrupts resets MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 63 a power-on reset: holds the clocks to the cpu and modules inactive for an oscillator stabilization delay of 4096 cgmxclk cycles drives the rst pin low during the oscillator stabilization delay releases the rst pin 32 cgmxclk cycles after the oscillator stabilization delay releases the cpu to begin the reset vector sequence 64 cgmxclk cycles after the oscillator stabilization delay sets the por bit in the sim reset status register and clears all other bits in the register figure 4-2. power-on reset recovery 4.3.3.2 cop reset a cop reset is an internal reset caused by an overflow of the cop counter. a cop reset sets the cop bit in the system integration module (sim) reset status register. to clear the cop counter and prevent a cop reset, write any value to the cop control register at location $ffff. porrst (1) osc1 cgmxclk cgmout rst pin internal 4096 cycles 32 cycles 32 cycles 1. porrst is an internally generated power-on reset pulse. 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 . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 64 resets and interrupts motorola 4.3.3.3 low-voltage inhibit reset a low-voltage inhibit (lvi) reset is an internal reset caused by a drop in the power supply voltage to the lvi trip voltage, v tripf . an lvi reset: holds the clocks to the cpu and modules inactive for an oscillator stabilization delay of 4096 cgmxclk cycles after the power supply voltage rises to v tripf drives the rst pin low for as long as v dd is below v tripf and during the oscillator stabilization delay releases the rst pin 32 cgmxclk cycles after the oscillator stabilization delay releases the cpu to begin the reset vector sequence 64 cgmxclk cycles after the oscillator stabilization delay sets the lvi bit in the sim reset status register 4.3.3.4 illegal opcode reset an illegal opcode reset is an internal reset caused by an opcode that is not in the instruction set. an illegal opcode reset sets the ilop bit in the sim reset status register. if the stop enable bit, stop, in the mask option register is a logic 0, the stop instruction causes an illegal opcode reset. 4.3.3.5 illegal address reset an illegal address reset is an internal reset caused by opcode fetch from an unmapped address. an illegal address reset sets the ilad bit in the sim reset status register. a data fetch from an unmapped address does not generate a 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 . . . resets and interrupts resets MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 65 4.3.4 sim reset status register this read-only register contains flags to show reset sources. all flag bits are automatically cleared following a read of the register. reset service can read the sim reset status register to clear the register after power-on reset and to determine the source of any subsequent reset. the register is initialized on powerup as shown with the por bit set and all other bits cleared. during a por or any other internal reset, the rst pin is pulled low. after the pin is released, it will be sampled 32 xclk cycles later. if the pin is not above a v ih at that time, then the pin bit in the srsr may be set in addition to whatever other bits are set. note: only a read of the sim reset status register clears all reset flags. after multiple resets from different sources without reading the register, multiple flags remain set. por ? power-on reset flag 1 = power-on reset since last read of srsr 0 = read of srsr since last power-on reset pin ? external reset flag 1 = external reset via rst pin since last read of srsr 0 = por or read of srsr since last external reset cop ? computer operating properly reset bit 1 = last reset caused by timeout of cop counter 0 = por or read of srsr address: $fe01 bit 7 6 5 4 3 2 1 bit 0 read: por pin cop ilop ilad 0 lvi 0 write: por:10000000 = unimplemented figure 4-3. 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 . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 66 resets and interrupts motorola ilop ? illegal opcode reset bit 1 = last reset caused by an illegal opcode 0 = por or read of srsr ilad ? illegal address reset bit 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 caused by low-power supply voltage 0 = por or read of srsr 4.4 interrupts an interrupt temporarily changes the sequence of program execution to respond to a particular event. an interrupt does not stop the operation of the instruction being executed, but begins when the current instruction completes its operation. 4.4.1 effects an interrupt: saves the cpu registers on the stack. at the end of the interrupt, the rti instruction recovers the cpu registers from the stack so that normal processing can resume. sets the interrupt mask (i bit) to prevent additional interrupts. once an interrupt is latched, no other interrupt can take precedence, regardless of its priority. loads the program counter with a user-defined vector address f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . resets and interrupts interrupts MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 67 figure 4-4. interrupt stacking order after every instruction, the cpu checks all pending interrupts if the i bit is not set. if more than one interrupt is pending when an instruction is done, the highest priority interrupt is serviced first. in the example shown in figure 4-5 , if an interrupt is pending upon exit from the interrupt service routine, the pending interrupt is serviced before the lda instruction is executed. condition code register accumulator index register (low byte)* program counter (high byte) program counter (low byte) 1 2 3 4 5 5 4 3 2 1 stacking order *high byte of index register is not stacked. $00ff default address on reset unstacking order f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 68 resets and interrupts motorola figure 4-5 . interrupt recognition example the lda opcode is prefetched by both the int1 and int2 rti instructions. however, in the case of the int1 rti prefetch, this is a redundant operation. note: to maintain compatibility with the m6805 family, the h register is not pushed on the stack during interrupt entry. if the interrupt service routine modifies the h register or uses the indexed addressing mode, save the h register and then restore it prior to exiting the routine. cli lda int1 pulh rti int2 background #$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 . . . resets and interrupts interrupts MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 69 figure 4-6. interrupt processing no no no yes no no yes no yes yes from reset break i bit set? irq interrupt cgm interrupt fetch next instruction unstack cpu registers stack cpu registers set i bit load pc with interrupt vector execute instruction yes yes i bit set? interrupt yes other interrupts no swi instruction rti 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 . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 70 resets and interrupts motorola 4.4.2 sources the sources in table 4-1 can generate cpu interrupt requests. table 4-1. interrupt sources source flag mask (1) int register flag priority (2) vector address reset none none none 0 $fffe ? $ffff swi instruction none none none 0 $fffc ? $fffd irq pin irqf imask1 if1 1 $fffa ? $fffb cgm (pll) pllf pllie if2 2 $fff8?$fff9 tim1 channel 0 ch0f ch0ie if3 3 $fff6?$fff7 tim1 channel 1 ch1f ch1ie if4 4 $fff4?$fff5 tim1 overflow tof toie if5 5 $fff2?$fff3 tim2 channel 0 ch0f ch0ie if6 6 $fff0?$fff1 tim2 overflow tof toie if8 8 $ffec?$ffed spi receiver full sprf sprie if9 9 $ffea?$ffeb spi overflow ovrf errie spi mode fault modf errie spi transmitter empty spte sptie if10 10 $ffe8?$ffe9 sci receiver overrun or orie if11 11 $ffe6?$ffe7 sci noise flag nf neie sci framing error fe feie sci parity error pe peie sci receiver full scrf scrie if12 12 $ffe4?$ffe5 sci input idle idle ilie sci transmitter empty scte sctie if13 13 $ffe2?$ffe3 sci transmission complete tc tcie keyboard pin keyf imaskk if14 14 $ffde?$ffdf adc conversion complete coco aien if15 15 $ffde?$ffdf timebase tbif tbie if16 16 $ffdc?$ffdd note: 1. the i bit in the condition code register is a global mask for all interrupt sources except the swi instruction. 2. 0 = highest priority f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . resets and interrupts interrupts MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 71 4.4.2.1 swi instruction the software interrupt instruction (swi) causes a non-maskable interrupt. note: a software interrupt pushes pc onto the stack. an swi does not push pc ? 1, as a hardware interrupt does. 4.4.2.2 break interrupt the break module causes the cpu to execute an swi instruction at a software-programmable break point. 4.4.2.3 irq pin a logic 0 on the irq1 pin latches an external interrupt request. 4.4.2.4 cgm the cgm can generate a cpu interrupt request every time the phase-locked loop circuit (pll) enters or leaves the locked state. when the lock bit changes state, the pll flag (pllf) is set. the pll interrupt enable bit (pllie) enables pllf cpu interrupt requests. lock is in the pll bandwidth control register. pllf is in the pll control register. 4.4.2.5 tim1 tim1 cpu interrupt sources: tim1 overflow flag (tof) ? the tof bit is set when the tim1 counter value rolls over to $0000 after matching the value in the tim1 counter modulo registers. the tim1 overflow interrupt enable bit, toie, enables tim1 overflow cpu interrupt requests. tof and toie are in the tim1 status and control register. tim1 channel flags (ch1f?ch0f) ? the chxf bit is set when an input capture or output compare occurs on channel x. the channel x interrupt enable bit, chxie, enables channel x tim1 cpu interrupt requests. chxf and chxie are in the tim1 channel x status and control 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 . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 72 resets and interrupts motorola 4.4.2.6 tim2 tim2 cpu interrupt sources: tim2 overflow flag (tof) ? the tof bit is set when the tim2 counter value rolls over to $0000 after matching the value in the tim2 counter modulo registers. the tim2 overflow interrupt enable bit, toie, enables tim2 overflow cpu interrupt requests. tof and toie are in the tim2 status and control register. tim2 channel flag (ch0f) ? the ch0f bit is set when an input capture or output compare occurs on channel 0. the channel 0 interrupt enable bit, ch0ie, enables channel 0 tim2 cpu interrupt requests. ch0f and ch0ie are in the tim2 channel 0 status and control register. 4.4.2.7 spi spi cpu interrupt sources: spi receiver full bit (sprf) ? the sprf bit is set every time a byte transfers from the shift register to the receive data register. the spi receiver interrupt enable bit, sprie, enables sprf cpu interrupt requests. sprf is in the spi status and control register and sprie is in the spi control register. spi transmitter empty (spte) ? the spte bit is set every time a byte transfers from the transmit data register to the shift register. the spi transmit interrupt enable bit, sptie, enables spte cpu interrupt requests. spte is in the spi status and control register and sptie is in the spi control register. mode fault bit (modf) ? the modf bit is set in a slave spi if the ss pin goes high during a transmission with the mode fault enable bit (modfen) set. in a master spi, the modf bit is set if the ss pin goes low at any time with the modfen bit set. the error interrupt enable bit, errie, enables modf cpu interrupt requests. modf, modfen, and errie are in the spi status and control 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 . . . resets and interrupts interrupts MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 73 overflow bit (ovrf) ? the ovrf bit is set if software does not read the byte in the receive data register before the next full byte enters the shift register. the error interrupt enable bit, errie, enables ovrf cpu interrupt requests. ovrf and errie are in the spi status and control register. 4.4.2.8 sci sci cpu interrupt sources: sci transmitter empty bit (scte) ? scte is set when the sci data register transfers a character to the transmit shift register. the sci transmit interrupt enable bit, sctie, enables transmitter cpu interrupt requests. scte is in sci status register 1. sctie is in sci control register 2. transmission complete bit (tc) ? tc is set when the transmit shift register and the sci data register are empty and no break or idle character has been generated. the transmission complete interrupt enable bit, tcie, enables transmitter cpu interrupt requests. tc is in sci status register 1. tcie is in sci control register 2. sci receiver full bit (scrf) ? scrf is set when the receive shift register transfers a character to the sci data register. the sci receive interrupt enable bit, scrie, enables receiver cpu interrupts. scrf is in sci status register 1. scrie is in sci control register 2. idle input bit (idle) ? idle is set when 10 or 11 consecutive logic 1s shift in from the rxd pin. the idle line interrupt enable bit, ilie, enables idle cpu interrupt requests. idle is in sci status register 1. ilie is in sci control register 2. receiver overrun bit (or) ? or is set when the receive shift register shifts in a new character before the previous character was read from the sci data register. the overrun interrupt enable bit, orie, enables or to generate sci error cpu interrupt requests. or is in sci status register 1. orie is in sci control register 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 . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 74 resets and interrupts motorola noise flag (nf) ? nf 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, enables nf to generate sci error cpu interrupt requests. nf is in sci status register 1. neie is in sci control register 3. framing error bit (fe) ? fe is set when a logic 0 occurs where the receiver expects a stop bit. the framing error interrupt enable bit, feie, enables fe to generate sci error cpu interrupt requests. fe is in sci status register 1. feie is in sci control register 3. parity error bit (pe) ? pe is set when the sci detects a parity error in incoming data. the parity error interrupt enable bit, peie, enables pe to generate sci error cpu interrupt requests. pe is in sci status register 1. peie is in sci control register 3. 4.4.2.9 kbd0 ?kbd4 pins a logic 0 on a keyboard interrupt pin latches an external interrupt request. 4.4.2.10 adc (analog-to-digital converter) when the aien bit is set, the adc module is capable of generating a cpu interrupt after each adc conversion. the coco/idmas bit is not used as a conversion complete flag when interrupts are enabled. 4.4.2.11 tbm (timebase module) the timebase module can interrupt the cpu on a regular basis with a rate defined by tbr2?tbr0. when the timebase counter chain rolls over, the tbif flag is set. if the tbie bit is set, enabling the timebase interrupt, the counter chain overflow will generate a cpu interrupt request. interrupts must be acknowledged by writing a logic 1 to the tack 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 . . . resets and interrupts interrupts MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 75 4.4.3 interrupt status registers the flags in the interrupt status registers identify maskable interrupt sources. table 4-2 summarizes the interrupt sources and the interrupt status register flags that they set. the interrupt status registers can be useful for debugging. table 4-2. interrupt source flags interrupt source interrupt status register flag reset ? swi instruction ? irq pin if1 cgm (pll) if2 tim1 channel 0 if3 tim1 channel 1 if4 tim1 overflow if5 tim2 channel 0 if6 reserved if7 tim2 overflow if8 spi receive if9 spi transmit if10 sci error if11 sci receive if12 sci transmit if13 keyboard if14 adc conversion complete if15 timebase if16 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 76 resets and interrupts motorola 4.4.3.1 interrupt status register 1 if6?if1 ? interrupt flags 6?1 these flags indicate the presence of interrupt requests from the sources shown in table 4-2 . 1 = interrupt request present 0 = no interrupt request present bit 1 and bit 0 ? always read 0 4.4.3.2 interrupt status register 2 if14?if7 ? interrupt flags 14?7 these flags indicate the presence of interrupt requests from the sources shown in table 4-2 . 1 = interrupt request present 0 = no interrupt request present address: $fe04 bit 7654321bit 0 read: if6 if5 if4 if3 if2 if1 0 0 write:rrrrrrrr reset:00000000 r = reserved figure 4-7. interrupt status register 1 (int1) address: $fe05 bit 7654321bit 0 read: if14 if13 if12 if11 if10 if9 if8 if7 write:rrrrrrrr reset:00000000 r = reserved figure 4-8. interrupt status register 2 (int2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . resets and interrupts interrupts MC68HC908GR8A ? rev 0.0 technical data motorola resets and interrupts 77 4.4.3.3 interrupt status register 3 if16?if15 ? interrupt flags 16?15 this flag indicates the presence of an interrupt request from the source shown in table 4-2 . 1 = interrupt request present 0 = no interrupt request present bits 7?2 ? always read 0 address: $fe06 bit 7654321bit 0 read:000000if16if15 write:rrrrrrrr reset:00000000 r = reserved figure 4-9. interrupt status register 3 (int3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . resets and interrupts technical data MC68HC908GR8A ? rev 0.0 78 resets and interrupts 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola analog-to-digital converter (adc) 79 technical data ? MC68HC908GR8A section 5. analog-to-digital converter (adc) 5.1 contents 5.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 5.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80 5.5 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 5.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 5.7 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 5.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85 5.2 introduction this section describes the 8-bit analog-to-digital converter (adc). for further information regarding analog-to-digital converters on motorola microcontrollers, please consult the hc08 adc reference manual, adcrm/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 . . . analog-to-digital converter (adc) technical data MC68HC908GR8A ? rev 0.0 80 analog-to-digital converter (adc) motorola 5.3 features features of the adc module include: six channels with multiplexed input linear successive approximation with monotonicity 8-bit resolution single or continuous conversion conversion complete flag or conversion complete interrupt selectable adc clock 5.4 functional description the adc provides six pins for sampling external sources at pins ptb5/atd5?ptb0/atd0. an analog multiplexer allows the single adc converter to select one of six adc channels as adc voltage in (v adin ). v adin is converted by the successive approximation register-based analog-to-digital converter. when the conversion is completed, adc places the result in the adc data register and sets a flag or generates an interrupt. see figure 5-1 . note: references to dma (direct-memory access) and associated functions are only valid if the mcu has a dma module. if the mcu has no dma, any dma-related register bits should be left in their reset state for expected mcu 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 . . . analog-to-digital converter (adc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola analog-to-digital converter (adc) 81 figure 5-1. adc block diagram 5.4.1 adc port i/o pins ptb5/atd5?ptb0/atd0 are general-purpose i/o (input/output) 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 in use by the adc will return a logic 0. internal data bus read ddrbx write ddrbx reset write ptbx read ptbx ptbx ddrbx ptbx interrupt logic channel select adc clock generator conversion complete adc (v adin ) adc clock cgmxclk bus clock adch4?adch0 adc data register aien coco disable disable adc channel x adiv2?adiv0 adiclk voltage in f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 82 analog-to-digital converter (adc) motorola 5.4.2 voltage conversion when the input voltage to the adc equals v refh , the adc converts the signal to $ff (full scale). if the input voltage equals v refl , the adc converts it to $00. input voltages between v refh and v refl are a straight-line linear conversion. all other input voltages will result in $ff, if greater than v refh . note: inside the adc module, the reference voltage, v refh is connected to the adc analog power v ddad ; and v refl is connected to the adc analog ground v ddad . therefore, the adc input voltage should not exceed the analog supply voltages for operation, v ddad should be tied to the same potential as v dd via separate traces 5.4.3 conversion time conversion starts after a write to the adscr. one conversion will take between 16 and 17 adc clock cycles. the adivx and adiclk bits should be set to provide a 1 mhz adc clock frequency. 5.4.4 conversion in 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 is cleared. the coco/idmas bit is set after the first conversion and will stay set until the next write of the adc status and control register or the next read of the adc data register. in single conversion mode, conversion begins with a write to the adscr. only one conversion occurs between writes to the adscr. 16 to17 adc cycles adc frequency conversion time = 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 MC68HC908GR8A ? rev 0.0 technical data motorola analog-to-digital converter (adc) 83 5.4.5 accuracy and precision the conversion process is monotonic and has no missing codes. 5.5 interrupts when the aien bit is set, the adc module is capable of generating cpu interrupts after each adc conversion. a cpu interrupt is generated if the coco/idmas bit is at logic 0. if coco/idmas bit is set, a dma interrupt is generated. the coco/idmas bit is not used as a conversion complete flag when interrupts are enabled. 5.6 low-power modes the wait and stop instruction can put the mcu in low power- consumption standby modes. 5.6.1 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 adch4?adch0 bits in the adc status and control register before executing the wait instruction. 5.6.2 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 after an external interrupt. allow one conversion cycle to stabilize the analog circuitry. 5.7 i/o signals the adc module has six pins shared with port b, ptb5/ad5?ptb0/atd0. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 84 analog-to-digital converter (adc) motorola 5.7.1 adc analog power pin (v ddad )/adc voltage reference high pin (v refh ) the adc analog portion uses v ddad as its power pin. connect the v ddad pin to the same voltage potential as v dd . external filtering may be necessary to ensure clean v ddad for good results. note: for maximum noise immunity, route v ddad carefully and place bypass capacitors as close as possible to the package. 5.7.2 adc analog ground pin (v ssad )/adc voltage reference low pin (v refl ) the adc analog portion uses v ssad as its ground pin. connect the v ssad pin to the same voltage potential as v ss . note: route v ssad cleanly to avoid any offset errors. 5.7.3 adc voltage in (v adin ) v adin is the input voltage signal from one of the six 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 MC68HC908GR8A ? rev 0.0 technical data motorola analog-to-digital converter (adc) 85 5.8 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 (adclk) 5.8.1 adc status and control register function of the adc status and control register (adscr) is described here. coco/idmas ? conversions complete/interrupt dma select bit when the aien bit is a logic 0, the coco/idmas is a read-only bit which is set each time a conversion is completed except in the continuous conversion mode where it is set after the first conversion. this bit is cleared whenever the adscr is written or whenever the adr is read. if the aien bit is a logic 1, the coco/idmas is a read/write bit which selects either cpu or dma to service the adc interrupt request. reset clears this bit. 1 = conversion completed (aien = 0)/dma interrupt (aien = 1) 0 = conversion not completed (aien = 0)/cpu interrupt (aien = 1) caution: because the MC68HC908GR8A does not have a dma module, the idmas bit should never be set when aien is set. doing so will mask adc interrupts and cause unwanted results. address: $0003c bit 7654321bit 0 read: coco/ idmas aien adco adch4 adch3 adch2 adch1 adch0 write: reset:00011111 figure 5-2. 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) technical data MC68HC908GR8A ? rev 0.0 86 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 this bit is set, the adc will convert samples continuously and update the adr register at the end of each conversion. only one conversion is completed between writes to the adscr when this bit is cleared. reset clears the adco bit. 1 = continuous adc conversion 0 = one adc conversion adch4?adch0 ? adc channel select bits adch4?adch0 form a 5-bit field which is used to select one of 16 adc channels. only six channels, ad5?ad0, are available on this mcu. the channels are detailed in table 5-1 . care should be taken when using a port pin as both an analog and digital input simultaneously to prevent switching noise from corrupting the analog signal. see table 5-1 . the adc subsystem is turned off when the channel select bits are all set to 1. this feature allows for reduced power consumption for the mcu when the adc is not being used. note: recovery from the disabled state requires one conversion cycle to stabilize. the voltage levels supplied from internal reference nodes, as specified in table 5-1 , are used to verify the operation of the adc converter both in production test and for user applications. table 5-1. mux channel select adch4 adch3 adch2 adch1 adch0 input select 00000 ptb0/atd0 00001 ptb1/atd1 00010 ptb2/atd2 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola analog-to-digital converter (adc) 87 5.8.2 adc data register one 8-bit result register, adc data register (adr), is provided. this register is updated each time an adc conversion completes. 00011 ptb3/atd3 00100 ptb4/atd4 00101 ptb5/atd5 00110 reserved 00111 reserved reserved 11011 reserved 11100 reserved 11101 v refh 11110 v refl 11111adc power off note: if an unknown channel is selected it should be made clear what value the user will read from the adc data register, unknown or reserved is not specific enough. table 5-1. mux channel select adch4 adch3 adch2 adch1 adch0 input select address: $0003d bit 7654321bit 0 read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write: reset:00000000 = unimplemented figure 5-3. adc data register (adr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 88 analog-to-digital converter (adc) motorola 5.8.3 adc clock register the adc clock register (adclk) selects the clock frequency for the adc. adiv2?adiv0 ? adc clock prescaler bits adiv2?adiv0 form a 3-bit field which selects the divide ratio used by the adc to generate the internal adc clock. table 5-2 shows the available clock configurations. the adc clock should be set to approximately 1 mhz. adiclk ? adc input clock select bit adiclk selects either the bus clock or cgmxclk as the input clock source to generate the internal adc clock. reset selects cgmxclk as the adc clock source. address: $0003e bit 7654321bit 0 read: adiv2 adiv1 adiv0 adiclk 0000 write: reset:00000000 = unimplemented figure 5-4. adc clock register (adclk) table 5-2. 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 r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola analog-to-digital converter (adc) 89 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. 1 = internal bus clock 0 = external clock (cgmxclk) adc input clock frequency adiv2 adiv0 ? ----------------------------------------------------------------------- 1 m h 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 . . . analog-to-digital converter (adc) technical data MC68HC908GR8A ? rev 0.0 90 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola break module (brk) 91 technical data ? MC68HC908GR8A section 6. break module (brk) 6.1 contents 6.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 6.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92 6.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 6.6 break module registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 6.2 introduction this section describes the break module. the break module can generate a break interrupt that stops normal program flow at a defined address to enter a background program. 6.3 features features of the break module include: accessible input/output (i/o) registers during the break interrupt 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) technical data MC68HC908GR8A ? rev 0.0 92 break module (brk) motorola 6.4 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 6-1 shows the structure of the break module. figure 6-1. break module block diagram iab15?iab8 iab7?iab0 8-bit comparator 8-bit comparator control break address register low break address register high iab15?iab0 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 MC68HC908GR8A ? rev 0.0 technical data motorola break module (brk) 93 6.4.1 flag protection during break interrupts the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state. 6.4.2 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 and $fffd ($fefc and $fefd in monitor mode) addr. register name bit 7 6 5 4 3 2 1 bit 0 $fe00 sim break status register (sbsr) read:000100bw0 write:rrrrrrnoter reset:00010000 $fe03 sim break flag control register (sbfcr) read: bcferrrrrrr write: reset: 0 $fe09 break address register high (brkh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $fe0a break address register low (brkl) read: bit 7654321bit 0 write: reset:00000000 $fe0b break status and control register (brkscr) read: brke brka 000000 write: reset:00000000 note: writing a logic 0 clears bw. = unimplemented r = reserved figure 6-2. i/o 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 . . . break module (brk) technical data MC68HC908GR8A ? rev 0.0 94 break module (brk) motorola 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. 6.4.3 timi and tim2 during break interrupts a break interrupt stops the timer counters. 6.4.4 cop during break interrupts the cop is disabled during a break interrupt when v tst is present on the rst pin. 6.5 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 6.5.1 wait mode if enabled, the break module is active in wait mode. in the break routine, the user can subtract one from the return address on the stack if sbsw is set. see low power modes . clear the bw bit by writing logic 0 to it. 6.5.2 stop mode a break interrupt causes exit from stop mode and sets the sbsw bit in the break status register. 6.6 break module registers these registers control and monitor operation of the break module: break status and control register (brkscr) break address register high (brkh) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola break module (brk) 95 break address register low (brkl) sim break status register (sbsr) sim break flag control register (sbfcr) 6.6.1 break status and control register the break status and control register (brkscr) 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 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 address: $fe0e bit 7 6 5 4 3 2 1 bit 0 read: brke brka 000000 write: reset:00000000 = unimplemented figure 6-3. break status and control register (brkscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 96 break module (brk) motorola 6.6.2 break address registers the break address registers (brkh and brkl) contain the high and low bytes of the desired breakpoint address. reset clears the break address registers. 6.6.3 break status register the break status register (sbsr) contains a flag to indicate that a break caused an exit from wait mode. the flag is useful in applications requiring a return to wait mode after exiting from a break interrupt. address: $fe09 bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 figure 6-4. break address register high (brkh) address: $fe0a bit 7654321bit 0 read: bit 7654321bit 0 write: reset:00000000 figure 6-5. break address register low (brkl) address: $fe00 bit 7654321bit 0 read:000100bw0 write:rrrrrrnoter reset:00010000 note: writing a logic 0 clears bw. r = reserved figure 6-6. sim break status register (sbsr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola break module (brk) 97 bw ? break wait bit this read/write bit is set when a break interrupt causes an exit from wait mode. clear bw by writing a logic 0 to it. reset clears bw. 1 = break interrupt during wait mode 0 = no break interrupt during wait mode bw can be read within the break interrupt routine. the user can modify the return address on the stack by subtracting 1 from it. the following code is an example. this code works if the h register was stacked in the break interrupt routine. execute this code at the end of the break interrupt routine. hibyte equ 5 lobyte equ 6 ; if not bw, do rti brclr bw,bsr, return ; ; see if wait mode or stop mode was exited by break. tst lobyte,sp ; if returnlo is not 0, bne dolo ; then just decrement low byte. dec hibyte,sp ; else deal with high byte also. 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 . . . break module (brk) technical data MC68HC908GR8A ? rev 0.0 98 break module (brk) motorola 6.6.4 break flag control register the break flag control register (sbfcr) 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 r= reserved figure 6-7. 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 99 technical data ? MC68HC908GR8A section 7. clock generator module (cgmc) 7.1 contents 7.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 7.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.5 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112 7.6 cgmc registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 7.7 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 7.8 special modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 7.9 acquisition/lock time specifications . . . . . . . . . . . . . . . . . . . 125 7.2 introduction this section describes the clock generator module. the cgmc generates the crystal clock signal, cgmxclk, which operates at the frequency of the crystal. the cgmc also generates the base clock signal, cgmout, which is based on either the crystal clock divided by two or the phase-locked loop (pll) clock, cgmvclk, divided by two. in user mode, cgmout is the clock from which the sim derives the system clocks, including the bus clock, which is at a frequency of cgmout/2. in monitor mode, ptc3 determines the bus clock. the pll is a fully functional frequency generator designed for use with crystals or ceramic resonators. the pll can generate an 8-mhz bus frequency using a 1?8 mhz crystal or external clock source. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 100 clock generator module (cgmc) motorola 7.3 features features of the cgmc include: phase-locked loop with output frequency in integer multiples of an integer dividend of the crystal reference high-frequency crystal operation with low-power operation and high-output frequency resolution 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 configuration register bit to allow oscillator operation during stop mode 7.4 functional description the cgmc 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 sim derives the system clocks from either cgmout or cgmxclk. figure 7-1 shows the structure of the cgmc. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 101 figure 7-1. cgmc block diagram bcs phase detector loop filter frequency divider voltage controlled oscillator automatic mode control lock detector clock cgmxclk cgmout cgmvdv cgmvclk simoscen (from sim) oscillator (osc) interrupt control pllireq cgmrdv pll analog 2 cgmrclk osc2 osc1 select circuit v dda cgmxfc v ssa lock auto acq vpr1?vpr0 pllie pllf mul11?mul0 reference divider vrs7?vrs0 frequency divider pre1?pre0 oscstopenb (from config) (to: sim, timtb15a, adc) phase-locked loop (pll) (to sim) (to sim) rds3?rds0 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 102 clock generator module (cgmc) motorola 7.4.1 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 from the system integration module (sim) or the oscstopenb bit in the config register enable 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. 7.4.2 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. 7.4.3 pll circuits the pll consists of these circuits: voltage-controlled oscillator (vco) modulo vco frequency divider phase detector 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 103 supply and cgm/xfc noise. the vco frequency is bound to a range from roughly one-half to twice the center-of-range frequency, f vrs . modulating the voltage on the cgm/xfc pin changes the frequency within this range. by design, f vrs is equal to the nominal center-of-range frequency, f nom , (38.4 khz) times a linear factor, l, and a power-of-two factor, e, or (l 2 e )f nom . cgmrclk is the pll reference clock, a buffered version of cgmxclk. cgmrclk runs at a frequency, f rclk . the vco?s output clock, cgmvclk, running at a frequency, f vclk , is fed back through a programmable prescale divider and a programmable modulo divider. the prescaler divides the vco clock by a power-of-two factor p and the modulo divider reduces the vco clock by a factor, n. the dividers? output is the vco feedback clock, cgmvdv, running at a frequency, f vdv =f vclk /(n 2 p ). (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 cgm/xfc based on the width and direction of the correction pulse. the filter can make fast or slow corrections depending on its mode, described in acquisition and tracking modes . the value of the external capacitor and the reference frequency determine 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 reference clock, cgmrclk. therefore, the speed of the lock detector is directly proportional to the reference frequency, f rclk . the circuit determines the mode of the pll and the lock condition based on this comparison. 7.4.4 acquisition and tracking modes the pll filter is manually or automatically configurable into one of two operating modes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 104 clock generator module (cgmc) motorola 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 .) 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 .) the pll is automatically in tracking mode when not in acquisition mode or when the acq bit is set. 7.4.5 manual and automatic pll bandwidth modes the pll can change the bandwidth or operational mode of the loop filter manually or automatically. automatic mode is recommended for most users. 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 .) if pll interrupts are enabled, the software can wait for a pll interrupt request and then check the lock bit. if 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 .) 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 for information and precautions on using interrupts.) the following conditions apply when the pll is in automatic bandwidth control 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 (cgmc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 105 the acq bit (see pll bandwidth control register ) is a read-only indicator of the mode of the filter. (see acquisition and tracking modes .) the acq bit is set when the vco frequency is within a certain tolerance and is cleared when the vco frequency is out of a certain tolerance. (see acquisition/lock time specifications for more information.) 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 and is cleared when the vco frequency is out of a certain tolerance. (see acquisition/lock time specifications for more information.) cpu interrupts can occur if enabled (pllie = 1) when the pll?s lock condition changes, toggling the lock bit. (see pll control register .) the pll also may 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 . 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 acquisition/lock time specifications ), 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 cgmc 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 106 clock generator module (cgmc) motorola 7.4.6 programming the pll the following procedure shows how to program the pll. note: the round function in the following equations means that the real number should be rounded to the nearest integer number. 1. choose the desired bus frequency, f busdes . 2. calculate the desired vco frequency (four times the desired bus frequency). 3. choose a practical pll (crystal) reference frequency, f rclk , and the reference clock divider, r. typically, the reference crystal is 1mhz and r = 1. frequency errors to the pll are corrected at a rate of f rclk /r. for stability and lock time reduction, this rate must be as fast as possible. the vco frequency must be an integer multiple of this rate. the relationship between the vco frequency, f vclk , and the reference frequency, f rclk , is p, the power of two multiplier, and n, the range multiplier, are integers. in cases where desired bus frequency has some tolerance, choose f rclk to a value determined either by other module requirements (such as modules which are clocked by cgmxclk), cost requirements, or ideally, as high as the specified range allows. see electrical specifications . choose the reference divider, r = 1. after choosing n and p, the actual bus frequency can be determined using equation in 2 above. when the tolerance on the bus frequency is tight, choose f rclk to an integer divisor of f busdes , and r = 1. if f rclk cannot meet this requirement, use the following equation to solve for r with practical choices of f rclk , and choose the f rclk that gives the f vclkdes 4f busdes = f vclk 2 p n r ----------- f rclk () = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 107 lowest r. 4. select a vco frequency multiplier, n. 5. if n is < n max , use p = 0. if n > n max , choose p using this table: then recalculate n: 6. calculate and verify the adequacy of the vco and bus frequencies f vclk and f bus . 7. select the vco?s power-of-two range multiplier e, according to this table: 8. select a vco linear range multiplier, l, where f nom = 38.4 khz current n value p 0 1 2 3 frequency range e 0 < f vclk < 8mhz 0 8mhz f vclk < 16mhz 1 16mhz f vclk < 32mhz 2 note: do not program e to a value of 3. r round r max f vclkdes f rclk -------------------------- integer f vclkdes f rclk -------------------------- ? = n round rf vclkdes f rclk ------------------------------------ - = 0n clock generator module (cgmc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 109 table 7-1 provides numeric examples (numbers are in hexadecimal notation): 7.4.7 special programming exceptions the programming method described in programming the pll does not account for three possible exceptions. a value of 0 for r, n, or l is meaningless when used in the equations given. to account for these exceptions: a 0 value for r or n is interpreted exactly 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 .) 7.4.8 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 table 7-1. numeric example f bus (mhz) f rclk (mhz) rnpel 1 1 1400104 2 1 1800208 3 1 1120 1156 4 1 1160 1208 5 1 1200 2130 6 1 1240 2156 7 1 1280 2182 8 1 1320 2208 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 110 clock generator module (cgmc) motorola 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. 7.4.9 cgmc external connections in its typical configuration, the cgmc requires up to nine external components. five of these are for the crystal oscillator and two or four are for the pll. the crystal oscillator is normally connected in a pierce oscillator configuration, as shown in figure 7-2 . figure 7-2 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 the series resistor (r s ) is included in the diagram to follow strict pierce oscillator guidelines. refer to the crystal manufacturer?s data for more information regarding values for c1 and c2. figure 7-2 also shows the external components for the pll: bypass capacitor, c byp f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) functional description MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 111 filter network routing should be done with great care to minimize signal cross talk and noise. see cgm component specifications for capacitor and resistor values. figure 7-2. cgmc external connections osc1 c1 c2 simoscen cgmxclk rb x1 rs cbyp osc2 cgmxfc v dda note: filter network in box can be replaced with c f but will degrade stability. v dd oscstopenb (from config) r f1 c f2 c f1 v ssa 0.1 f f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 112 clock generator module (cgmc) motorola 7.5 i/o signals the following paragraphs describe the cgmc i/o signals. 7.5.1 crystal amplifier input pin (osc1) the osc1 pin is an input to the crystal oscillator amplifier. 7.5.2 crystal amplifier output pin (osc2) the osc2 pin is the output of the crystal oscillator inverting amplifier. 7.5.3 external filter capacitor pin (cgmxfc) the cgmxfc pin is required by the loop filter to filter out phase corrections. an external filter network is connected to this pin. (see figure 7-2 .) note: to prevent noise problems, the filter network should be placed as close to the cgmxfc pin as possible, with minimum routing distances and no routing of other signals across the network. 7.5.4 pll 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. 7.5.5 pll analog ground pin (v ssa ) v ssa is a ground pin used by the analog portions of the pll. connect the v ssa pin to the same voltage potential as the v ss pin. note: route v ssa carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) i/o signals MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 113 7.5.6 oscillator enable signal (simoscen) the simoscen signal comes from the system integration module (sim) and enables the oscillator and pll. 7.5.7 oscillator stop mode enable bit (oscstopenb) oscstopenb is a bit in the config register that enables the oscillator to continue operating during stop mode. if this bit is set, the oscillator continues running during stop mode. if this bit is not set (default), the oscillator is controlled by the simoscen signal which will disable the oscillator during stop mode. 7.5.8 crystal output frequency signal (cgmxclk) cgmxclk is the crystal oscillator output signal. it runs at the full speed of the crystal (f xclk ) and comes directly from the crystal oscillator circuit. figure 7-2 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. 7.5.9 cgmc base clock output (cgmout) cgmout is the clock output of the cgmc. this signal goes to the sim, which generates the mcu clocks. cgmout is a 50 percent 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. 7.5.10 cgmc cpu interrupt (cgmint) cgmint is the 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 114 clock generator module (cgmc) motorola 7.6 cgmc registers these registers control and monitor operation of the cgmc: pll control register (pctl) (see pll control register .) pll bandwidth control register (pbwc) (see pll bandwidth control register .) pll multiplier select register high (pmsh) (see pll multiplier select register high .) pll multiplier select register low (pmsl) (see pll multiplier select register low .) pll vco range select register (pmrs) (see pll vco range select register .) pll reference divider select register (pmds) (see pll reference divider select register .) figure 7-3 is a summary of the cgmc registers. addr. register name bit 7 6 5 4 3 2 1 bit 0 $0036 pll control register (pctl) read: pllie pllf pllon bcs pre1 pre0 vpr1 vpr0 write: reset:00100000 $0037 pll bandwidth control register (pbwc) read: auto lock acq 0000 r write: reset:00000000 $0038 pll multiplier select high register (pmsh) read: 0 0 0 0 mul11 mul10 mul9 mul8 write: reset:00000000 $0039 pll multiplier select low register (pmsl) read: mul7 mul6 mul5 mul4 mul3 mul2 mul1 mul0 write: reset:01000000 figure 7-3. cgmc i/o 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 . . . clock generator module (cgmc) cgmc registers MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 115 7.6.1 pll control register the pll control register (pctl) contains the interrupt enable and flag bits, the on/off switch, the base clock selector bit, the prescaler bits, and the vco power-of-two range selector bits. pllie ? pll interrupt enable bit this read/write bit enables the pll to generate an 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. $003a pll vco select range register (pmrs) read: vrs7 vrs6 vrs5 vrs4 vrs3 vrs2 vrs1 vrs0 write: reset:01000000 $003b pll reference divider select register (pmds) read: 0 0 0 0 rds3 rds2 rds1 rds0 write: reset:00000001 = unimplemented r = reserved notes: 1. when auto = 0, pllie is forced clear and is read-only. 2. when auto = 0, pllf and lock read as clear. 3. when auto = 1, acq is read-only. 4. when pllon = 0 or vrs7:vrs0 = $0, bcs is forced clear and is read-only. 5. when pllon = 1, the pll programming register is read-only. 6. when bcs = 1, pllon is forced set and is read-only. figure 7-3. cgmc i/o register summary address: $0036 bit 7654321bit 0 read: pllie pllf pllon bcs pre1 pre0 vpr1 vpr0 write: reset:00100000 = unimplemented figure 7-4. 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 116 clock generator module (cgmc) motorola 1 = pll interrupts enabled 0 = pll interrupts disabled pllf ? pll interrupt flag bit this read-only bit is set whenever the lock bit toggles. pllf generates an 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. 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 .) 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 cgmc 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 .) reset clears 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) cgmc registers MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 117 is set, and bcs cannot be set when pllon is clear. if the pll is off (pllon = 0), selecting cgmvclk requires two writes to the pll control register. (see base clock selector circuit .) pre1 and pre0 ? prescaler program bits these read/write bits control a prescaler that selects the prescaler power-of-two multiplier, p. (see pll circuits and programming the pll .) pre1 and pre0 cannot be written when the pllon bit is set. reset clears these bits. vpr1 and 0 ? vco power-of-two range select bits these read/write bits control the vco?s hardware power-of-two range multiplier e that, in conjunction with l (see pll circuits , programming the pll , and pll vco range select register .) controls the hardware center-of-range frequency, f vrs . vpr1:vpr0 cannot be written when the pllon bit is set. reset clears these bits. table 7-2. pre 1 and pre0 programming pre1 and pre0 p prescaler multiplier 00 0 1 01 1 2 10 2 4 11 3 8 table 7-3. vpr1 and vpr0 programming vpr1 and vpr0 e vco power-of-two range multiplier 00 0 1 01 1 2 10 2 4 11 3 (1) 1. do not program e to a value of 3. 8 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 118 clock generator module (cgmc) motorola 7.6.2 pll bandwidth control register the pll bandwidth control register (pbwc): 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 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. the write one function of this bit is reserved for test, so this bit must always be written a 0. reset clears the lock bit. address: $0037 bit 7654321bit 0 read: auto lock acq 0000 r write: reset:00000000 = unimplemented r= reserved figure 7-5. 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 (cgmc) cgmc registers MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 119 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 7.6.3 pll multiplier select register high the pll multiplier select register high (pmsh) contains the programming information for the high byte of the modulo feedback divider. mul11?mul8 ? multiplier select bits these read/write bits control the high byte of the modulo feedback divider that selects the vco frequency multiplier n. (see pll circuits and programming the pll .) a value of $0000 in the multiplier select registers configures the modulo feedback divider the same as a value of $0001. reset initializes the registers to $0040 for a default multiply value of 64. address: $0038 bit 7654321bit 0 read: 0 0 0 0 mul11 mul10 mul9 mul8 write: reset:00000000 = unimplemented figure 7-6. pll multiplier select register high (pmsh) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 120 clock generator module (cgmc) motorola note: the multiplier select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1). pmsh[7:4] ? unimplemented bits these bits have no function and always read as logic 0s. 7.6.4 pll multiplier select register low the pll multiplier select register low (pmsl) contains the programming information for the low byte of the modulo feedback divider. note: for applications using 1?8 mhz reference frequencies, this register must be reprogrammed before enabling the pll. the reset value of this register will cause applications using 1?8 mhz reference frequencies to become unstable if the pll is enabled without programming an appropriate value. the programmed value must not allow the vco clock to exceed 32 mhz. see 7.4.6 programming the pll for detailed instructions on choosing the proper value for pmsl. mul7?mul0 ? multiplier select bits these read/write bits control the low byte of the modulo feedback divider that selects the vco frequency multiplier, n. (see pll circuits and programming the pll .) mul7?mul0 cannot be written when the pllon bit in the pctl is set. a value of $0000 in the multiplier select registers configures the modulo feedback divider the same as a value of $0001. reset initializes the register to $40 for a default multiply value of 64. note: the multiplier select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1). address: $0038 bit 7654321bit 0 read: mul7 mul6 mul5 mul4 mul3 mul2 mul1 mul0 write: reset:01000000 figure 7-7. pll multiplier select register low (pmsl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) cgmc registers MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 121 7.6.5 pll vco range select register note: pmrs may be called pvrs on other hc08 derivatives. the pll vco range select register (pmrs) contains the programming information required for the hardware configuration of the vco. vrs7?vrs0 ? vco range select bits these read/write bits control the hardware center-of-range linear multiplier l which, in conjunction with e (see pll circuits , programming the pll , and pll control register ), controls the hardware center-of-range frequency, f vrs . vrs7?vrs0 cannot be written when the pllon bit in the pctl is set. (see special programming exceptions .) a value of $00 in the vco range select register disables the pll and clears the bcs bit in the pll control register (pctl). (see base clock selector circuit and special programming exceptions .). reset initializes the register to $40 for a default range multiply value of 64. note: the vco range select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1) and such that the vco clock cannot be selected as the source of the base clock (bcs = 1) if the vco range select bits are all clear. the pll vco range select register must be programmed correctly. incorrect programming can result in failure of the pll to achieve lock. address: $003a bit 7654321bit 0 read: vrs7 vrs6 vrs5 vrs4 vrs3 vrs2 vrs1 vrs0 write: reset:01000000 figure 7-8. pll vco range select register (pmrs) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 122 clock generator module (cgmc) motorola 7.6.6 pll reference divider select register note: pmds may be called prds on other hc08 derivatives. the pll reference divider select register (pmds) contains the programming information for the modulo reference divider. rds3?rds0 ? reference divider select bits these read/write bits control the modulo reference divider that selects the reference division factor, r. (see pll circuits and programming the pll .) rds7?rds0 cannot be written when the pllon bit in the pctl is set. a value of $00 in the reference divider select register configures the reference divider the same as a value of $01. (see special programming exceptions .) reset initializes the register to $01 for a default divide value of 1. note: the reference divider select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1). note: the default divide value of 1 is recommended for all applications. pmds7?pmds4 ? unimplemented bits these bits have no function and always read as logic 0s. address: $003b bit 7654321bit 0 read: 0 0 0 0 rds3 rds2 rds1 rds0 write: reset:00000001 = unimplemented figure 7-9. pll reference divider select register (pmds) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) interrupts MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 123 7.7 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 interrupts from the pll. pllf, the interrupt flag in the pctl, becomes set whether interrupts are enabled or not. when the auto bit is clear, cpu interrupts from the pll are disabled and pllf reads as logic 0. software should read the lock bit after a pll 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, interrupts 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. 7.8 special modes the wait instruction puts the mcu in low power-consumption standby modes. 7.8.1 wait mode the wait instruction does not affect the cgmc. 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) to save power. less power-sensitive applications can disengage the pll without turning it off, so that the pll clock is immediately available at wait exit. this would be the case also when the pll is to wake the mcu from wait f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 124 clock generator module (cgmc) motorola mode, such as when the pll is first enabled and waiting for lock or lock is lost. 7.8.2 stop mode if the oscstopenb bit in the config register is cleared (default), then the stop instruction disables the cgmc (oscillator and phase locked loop) and holds low all cgmc outputs (cgmxclk, cgmout, and cgmint). if the stop instruction is executed with the vco clock, cgmvclk, divided by two driving cgmout, the pll automatically clears the bcs bit in the pll control register (pctl), thereby selecting the crystal clock, cgmxclk, divided by two as the source of cgmout. when the mcu recovers from stop, the crystal clock divided by two drives cgmout and bcs remains clear. if the oscstopenb bit in the config register is set, then the phase locked loop is shut off but the oscillator will continue to operate in stop mode. 7.8.3 cgmc 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) enables software to clear status bits during the break state. (see sim break flag control register .) 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) acquisition/lock time specifications MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 125 7.9 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. 7.9.1 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 percentage of the step input or when the output settles to the desired value plus or minus a percentage 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 percent 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. 7.9.2 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 126 clock generator module (cgmc) motorola the most critical parameter which affects the reaction times of the pll is the reference frequency, f rdv . 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 under user control via the choice of crystal frequency f xclk and the r value programmed in the reference divider. (see pll circuits , programming the pll , and pll reference divider select register .) another critical parameter is the external filter network. the pll modifies the voltage on the vco by adding or subtracting charge from capacitors in this network. therefore, the rate at which the voltage changes for a given frequency error (thus change in charge) is proportional to the capacitance. 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 .) 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. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) acquisition/lock time specifications MC68HC908GR8A ? rev 0.0 technical data motorola clock generator module (cgmc) 127 7.9.3 choosing a filter as described in parametric influences on reaction time , the external filter network is critical to the stability and reaction time of the pll. the pll is also dependent on reference frequency and supply voltage. figure 7-10 shows two types of filter circuits. in low-cost applications, where stability and reaction time of the pll are not critical, the three component filter network shown in figure 7-10(b) can be replaced by a single capacitor, c f , as shown in figure 7-10(a) . refer to table 7-4 for recommended filter components at various reference frequencies. for reference frequencies between the values listed in the table, extrapolate to the nearest common capacitor value. in general, a slightly larger capacitor provides more stability at the expense of increased lock time. figure 7-10. pll filter table 7-4. example filter component values f rclk c f1 c f2 r f1 c f 1 mhz 8.2 nf 820 pf 2 k 18 nf cgmxfc r f1 c f2 c f1 v ssa (b) (a) cgmxfc c f v ssa f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (cgmc) technical data MC68HC908GR8A ? rev 0.0 128 clock generator module (cgmc) 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola configuration register (config) 129 technical data ? MC68HC908GR8A section 8. configuration register (config) 8.1 contents 8.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 8.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129 8.2 introduction this section describes the configuration registers, config1 and config2. the configuration registers enable or disable these options: stop mode recovery time (32 cgmxclk cycles or 4096 cgmxclk cycles) cop timeout period (2 18 ? 2 4 or 2 13 ? 2 4 cgmxclk cycles) stop instruction computer operating properly module (cop) low-voltage inhibit (lvi) module control and voltage trip point selection enable/disable the oscillator (osc) during stop mode 8.3 functional description the configuration registers are used in the initialization of various options. the configuration registers can be written once after each reset. all of the configuration register bits are cleared during reset. since the various options affect the operation of the mcu, it is recommended that these registers be written immediately after reset. the configuration registers are located at $001e and $001f. the configuration register may be read at anytime. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 130 configuration register (config) motorola note: to ensure correct operation of the mcu under all operating conditions, the user must write data $1c to address $0033 immediately after reset. this is to ensure proper termination of an unused module within the mcu. note: on a flash device, the options except lvi5or3 are one-time writeable by the user after each reset. the lvi5or3 bit is one-time writeable by the user only after each por (power-on reset). the config registers are not in the flash memory but are special registers containing one-time writeable latches after each reset. upon a reset, the config registers default to predetermined settings as shown in figure 8-1 and figure 8-2 . address: $001e bit 7654321bit 0 read:000000osc- stopen b scibd- src write: reset:00000000 = unimplemented figure 8-1. configuration register 2 (config2) address: $001f bit 7654321bit 0 read: coprs lvistop lvirstd lvip- wrd lvi5or3 ssrec stop copd write: reset:0000see note000 note: lvi5or3 bit is only reset via por (power-on reset) figure 8-2. configuration register 1 (config1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) functional description MC68HC908GR8A ? rev 0.0 technical data motorola configuration register (config) 131 oscstopenb? oscillator stop mode enable bar bit oscstopenb enables the oscillator to continue operating during stop mode. setting the oscstopenb bit allows the oscillator to operate continuously even during stop mode. this is useful for driving the timebase module to allow it to generate periodic wakeup while in stop mode. (see clock generator module (cgm) subsection stop mode .) 1 = oscillator enabled to operate during stop mode 0 = oscillator disabled during stop mode (default) scibdsrc ? sci baud rate clock source bit scibdsrc controls the clock source used for the sci. the setting of this bit affects the frequency at which the sci operates. 1 = internal data bus clock used as clock source for sci 0 = external oscillator used as clock source for sci coprs ? cop rate select bit coprs selects the cop timeout period. reset clears coprs. see computer operating properly (cop) . 1 = cop timeout period = 2 13 ? 2 4 cgmxclk cycles 0 = cop timeout period = 2 18 ? 2 4 cgmxclk cycles lvistop ? lvi enable in stop mode bit when the lvipwrd bit is clear, setting the lvistop bit enables the lvi to operate during stop mode. reset clears lvistop. see stop mode . 1 = lvi enabled during stop mode 0 = lvi disabled during stop mode lvirstd ? lvi reset disable bit lvirstd disables the reset signal from the lvi module. see low-voltage inhibit (lvi) . 1 = lvi module resets disabled 0 = lvi module resets enabled lvipwrd ? lvi power disable bit lvipwrd disables the lvi module. see low-voltage inhibit (lvi) . 1 = lvi module power disabled 0 = lvi module power 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) technical data MC68HC908GR8A ? rev 0.0 132 configuration register (config) motorola lvi5or3 ? lvi 5v or 3v operating mode bit lvi5or3 selects the voltage operating mode of the lvi module. see low-voltage inhibit (lvi) . the voltage mode selected for the lvi should match the operating v dd . see electrical specifications for the lvi?s voltage trip points for each of the modes. 1 = lvi operates in 5v mode. 0 = lvi operates in 3v mode. 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. 1 = stop mode recovery after 32 cgmxclk cycles 0 = stop mode recovery after 4096 cgmxclkc cycles note: exiting stop mode by pulling reset will result in the long stop recovery. if using an external crystal oscillator, do not set the ssrec bit. note: when the lvistop is enabled, the system stabilization time for power on reset and long stop recovery (both 4096 cgmxclk cycles) gives a delay longer than the enable time for the lvi. there is no period where the mcu is not protected from a low power condition. however, when using the short stop recovery configuration option, the 32-cgmxclk delay is less than the lvi?s turn-on time and there exists a period in startup where the lvi is not protecting the mcu. 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) . 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola computer operating properly (cop) 133 technical data ? MC68HC908GR8A section 9. computer operating properly (cop) 9.1 contents 9.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.4 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135 9.5 cop control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 9.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136 9.7 monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 9.8 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 9.9 cop module during break mode . . . . . . . . . . . . . . . . . . . . . .137 9.2 introduction the computer operating properly (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 clearing the cop counter periodically. the cop module can be disabled through the copd bit in the config register. 9.3 functional description figure 9-1 shows the structure of the cop 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 . . . computer operating properly (cop) technical data MC68HC908GR8A ? rev 0.0 134 computer operating properly (cop) motorola figure 9-1. cop block diagram the cop counter is a free-running 6-bit counter preceded by a 12-bit prescaler counter. if not cleared by software, the cop counter overflows and generates an asynchronous reset after 2 18 ?2 4 or 2 13 ?2 4 cgmxclk cycles, depending on the state of the cop rate select bit, coprs, in the configuration register. with a 2 13 ?2 4 cgmxclk cycle overflow option, a 32.768-khz crystal gives a cop timeout period of 250 ms. writing any value to location $ffff before an overflow occurs prevents a cop reset by clearing the cop counter and stages 12 through 5 of the prescaler. 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). copctl write cgmxclk reset vector fetch reset circuit reset status register internal reset sources clear stages 5?12 12-bit cop prescaler clear all stages 6-bit cop counter cop disable reset copctl write clear cop module copen (from sim) cop counter cop clock cop timeout stop instruction (from config) cop rate sel (from config) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola computer operating properly (cop) 135 in monitor mode, the cop is disabled if the rst pin or the irq1 is held at v tst . during the break state, v tst 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. 9.4 i/o signals the following paragraphs describe the signals shown in figure 9-1 . 9.4.1 cgmxclk cgmxclk is the crystal oscillator output signal. cgmxclk frequency is equal to the crystal frequency. 9.4.2 stop instruction the stop instruction clears the cop prescaler. 9.4.3 copctl write writing any value to the cop control register (copctl) (see cop control register ) clears the cop counter and clears bits 12 through 5 of the prescaler. reading the cop control register returns the low byte of the reset vector. 9.4.4 power-on reset the power-on reset (por) circuit clears the cop prescaler 4096 cgmxclk cycles after power-up. 9.4.5 internal reset an internal reset clears the cop prescaler and 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) technical data MC68HC908GR8A ? rev 0.0 136 computer operating properly (cop) motorola 9.4.6 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. 9.4.7 copd (cop disable) the copd signal reflects the state of the cop disable bit (copd) in the configuration register. see configuration register (config) . 9.4.8 coprs (cop rate select) the coprs signal reflects the state of the cop rate select bit (coprs) in the configuration register. see configuration register (config) . 9.5 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. 9.6 interrupts the cop does not generate cpu interrupt requests. address: $ffff bit 7654321bit 0 read: low byte of reset vector write: clear cop counter reset: unaffected by reset figure 9-2. 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) monitor mode MC68HC908GR8A ? rev 0.0 technical data motorola computer operating properly (cop) 137 9.7 monitor mode when monitor mode is entered with v tst on the irq pin, the cop is disabled as long as v tst remains on the irq pin or the rst pin. when monitor mode is entered by having blank reset vectors and not having v tst on the irq pin, the cop is automatically disabled until a por occurs. 9.8 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 9.8.1 wait mode the cop remains active during wait mode. to prevent a cop reset during wait mode, periodically clear the cop counter in a cpu interrupt routine. 9.8.2 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. to prevent inadvertently turning off the cop with a stop instruction, a configuration option is available that disables the stop instruction. when the stop bit in the configuration register has the stop instruction disabled, execution of a stop instruction results in an illegal opcode reset. 9.9 cop module during break mode the cop is disabled during a break interrupt when v tst 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 . . . computer operating properly (cop) technical data MC68HC908GR8A ? rev 0.0 138 computer operating properly (cop) 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 139 technical data ? MC68HC908GR8A section 10. central processing unit (cpu) 10.1 contents 10.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.4 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140 10.5 arithmetic/logic unit (alu) . . . . . . . . . . . . . . . . . . . . . . . . . . .145 10.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145 10.7 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .146 10.8 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 10.9 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154 10.2 introduction the m68hc08 cpu (central processor unit) is an enhanced and fully object-code-compatible version of the m68hc05 cpu. the cpu08 reference manual (motorola document order number cpu08rm/ad) contains a description of the cpu instruction set, addressing modes, and architecture. 10.3 features object code fully upward-compatible with m68hc05 family 16-bit stack pointer with stack manipulation instructions 16-bit index register with x-register manipulation instructions 8-mhz cpu internal 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 . . . central processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 140 central processing unit (cpu) motorola 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 modular architecture with expandable internal bus definition for extension of addressing range beyond 64k bytes low-power stop and wait modes 10.4 cpu registers figure 10-1 shows the five cpu registers. cpu registers are not part of the memory map. figure 10-1. 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 processing unit (cpu) cpu registers MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 141 10.4.1 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. 10.4.2 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 10-2. accumulator (a) bit 151413121110987654321 bit 0 h:x read: write: reset:00000000x xxxxxxx x = indeterminate figure 10-3. 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 142 central processing unit (cpu) motorola 10.4.3 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. 10.4.4 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 10-4. 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 processing unit (cpu) cpu registers MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 143 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. 10.4.5 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 h ? half-carry flag bit 151413121110987654321 bit 0 pc read: write: reset: loaded with vector from $fffe and $ffff figure 10-5. program counter (pc) bit 7654321bit 0 ccr read: v11h i nzc write: reset:x11x1xxx x = indeterminate figure 10-6. 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 144 central processing unit (cpu) motorola 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 processing unit (cpu) arithmetic/logic unit (alu) MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 145 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 10.5 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. 10.6 low-power modes the wait and stop instructions put the mcu in low--power consumption standby modes. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 146 central processing unit (cpu) motorola 10.6.1 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 10.6.2 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. 10.7 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 processing unit (cpu) instruction set summary MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 147 10.8 instruction set summary table 10-1 provides a summary of the m68hc08 instruction set. table 10-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i 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 9ee9 9ed9 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 9eeb 9edb 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 9ee4 9ed4 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 9e68 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 9e67 dd ff ff 4 1 1 4 3 5 bcc rel branch if carry bit clear pc (pc) + 2 + rel ? (c) = 0 ? ? ? ? ? ? rel 24 rr 3 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 148 central processing unit (cpu) motorola 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 9ee5 9ed5 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 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 table 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 processing unit (cpu) instruction set summary MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 149 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 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 9e61 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 9e6f dd ff ff 3 1 1 1 3 2 4 table 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 150 central processing unit (cpu) motorola 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 9ee1 9ed1 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 9e63 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 9ee3 9ed3 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 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 9e6b 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 9e6a 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 9ee8 9ed8 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 table 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 processing unit (cpu) instruction set summary MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 151 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 9e6c 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 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 9ee6 9ed6 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 9eee 9ede 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 9e68 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 9e64 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 table 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 152 central processing unit (cpu) motorola 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 9e60 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 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 9eea 9eda 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 9e69 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 9e66 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 table 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 processing unit (cpu) instruction set summary MC68HC908GR8A ? rev 0.0 technical data motorola central processing unit (cpu) 153 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 9ee2 9ed2 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 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 9ee7 9ed7 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 9eef 9edf 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 9ee0 9ed0 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 table 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 154 central processing unit (cpu) motorola 10.9 opcode map see table 10-2 . 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 9e6d dd ff ff 3 1 1 3 2 4 tsx transfer sp to h:x h:x (sp) + 1 ??????inh 95 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 10-1. instruction set summary (continued) source form operation description effect on ccr address mode opcode operand cycles vh i 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 . . . technical data MC68HC908GR8A ? rev 0.0 155 central processing unit (cpu) motorola central processing unit (cpu) 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 1234569e6789abcd9ede9eef 0 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 3 ext 4 sub 3ix2 5 sub 4 sp2 3 sub 2ix1 4 sub 3 sp1 2 sub 1ix 1 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 3 ext 4 cmp 3ix2 5 cmp 4 sp2 3 cmp 2ix1 4 cmp 3 sp1 2 cmp 1ix 2 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 3 ext 4 sbc 3ix2 5 sbc 4 sp2 3 sbc 2ix1 4 sbc 3 sp1 2 sbc 1ix 3 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 3 ext 4 cpx 3ix2 5 cpx 4 sp2 3 cpx 2ix1 4 cpx 3 sp1 2 cpx 1ix 4 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 3 ext 4 and 3ix2 5 and 4 sp2 3 and 2ix1 4 and 3 sp1 2 and 1ix 5 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 3 ext 4 bit 3ix2 5 bit 4 sp2 3 bit 2ix1 4 bit 3 sp1 2 bit 1ix 6 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 3 ext 4 lda 3ix2 5 lda 4 sp2 3 lda 2ix1 4 lda 3 sp1 2 lda 1ix 7 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 3 ext 4 sta 3ix2 5 sta 4 sp2 3 sta 2ix1 4 sta 3 sp1 2 sta 1ix 8 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 3 ext 4 eor 3ix2 5 eor 4 sp2 3 eor 2ix1 4 eor 3 sp1 2 eor 1ix 9 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 3 ext 4 adc 3ix2 5 adc 4 sp2 3 adc 2ix1 4 adc 3 sp1 2 adc 1ix a 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 3 ext 4 ora 3ix2 5 ora 4 sp2 3 ora 2ix1 4 ora 3 sp1 2 ora 1ix b 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 3 ext 4 add 3ix2 5 add 4 sp2 3 add 2ix1 4 add 3 sp1 2 add 1ix c 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 3 ext 4 jmp 3ix2 3 jmp 2ix1 2 jmp 1ix d 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 3 ext 6 jsr 3ix2 5 jsr 2ix1 4 jsr 1ix e 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 3 ext 4 ldx 3ix2 5 ldx 4 sp2 3 ldx 2ix1 4 ldx 3 sp1 2 ldx 1ix f 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 3 ext 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 table 10-2. opcode map 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 . . . central processing unit (cpu) technical data MC68HC908GR8A ? rev 0.0 156 central processing unit (cpu) 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola flash memory 157 technical data ? MC68HC908GR8A section 11. flash memory 11.1 contents 11.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 11.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 11.4 flash control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159 11.5 flash page erase operation . . . . . . . . . . . . . . . . . . . . . . . .160 11.6 flash mass erase operation . . . . . . . . . . . . . . . . . . . . . . . .161 11.7 flash program/read operation . . . . . . . . . . . . . . . . . . . . . .162 11.8 flash block protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163 11.9 wait mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 11.10 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166 11.2 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, erase, and read operations are enabled through the use of an internal charge pump. 11.3 functional description the flash memory is an array of 7,680 bytes for the MC68HC908GR8A or 4,096 bytes for the mc68hc908gr4a with an additional 36 bytes of user vectors and one byte used for block protection. an erased bit reads as logic 1 and a programmed bit reads as a logic 0 . the program and erase operations are facilitated through f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 158 flash memory motorola control bits in the flash control register (flcr). details for these operations appear later in this section. the flash is organized internally as a 8192-word by 8-bit cmos page erase, byte (8-bit) program embedded flash memory. each page consists of 64 bytes. the page erase operation erases all words within a page. a page is composed of two adjacent rows. the address ranges for the user memory and vectors are as follows: $e000?$fdff; user memory for the MC68HC908GR8A $ee00?$fdff; user memory for the mc68hc908gr4a. $ff7e; flash block protect register. $fe08 ; flash control register. $ffdc?$ffff; these locations are reserved for user-defined interrupt and reset vectors. 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 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 register MC68HC908GR8A ? rev 0.0 technical data motorola flash memory 159 11.4 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 8k byte flash array for mass erase operation. 1 = mass erase operation selected 0 = mass erase operation unselected 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 equal to 1 or set to 1 at the same time. 1 = erase operation selected 0 = erase operation unselected address: $fe08 bit 7654321bit 0 read: 0 0 0 0 hven mass erase pgm write: reset:00000000 figure 11-1. 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 technical data MC68HC908GR8A ? rev 0.0 160 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 11.5 flash page erase operation use this step-by-step procedure to erase a page (64 bytes) of flash memory to read as logic 1: 1. set the erase bit, and clear the mass bit in the flash control register. 2. read the flash block protect register. 3. write any data to any flash address within the page address range desired. 4. wait for a time, t nvs (min. 10 s) 5. set the hven bit. 6. wait for a time, t erase (min. 1ms) 7. clear the erase bit. 8. wait for a time, t nvh (min. 5 s) 9. clear the hven bit. 10. after a time, t rcv (typ. 1 s), the memory can be accessed again in read mode. note: while these operations must be performed in the order shown, other unrelated operations may occur between the steps. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola flash memory 161 11.6 flash mass erase operation use this step-by-step procedure to erase entire flash memory to read as logic 1: 1. set both the erase bit, and the mass bit in the flash control register. 2. read from the flash block protect register. 3. write any data to any flash address* within the flash memory address range. 4. wait for a time, t nvs (min. 10 s) 5. set the hven bit. 6. wait for a time, t merase (min. 4ms) 7. clear the erase bit. 8. wait for a time, t nvhl (min. 100 s) 9. clear the hven bit. 10. after a time, t rcv (min. 1 s), the memory can be accessed again in read mode. * when in monitor mode, with security sequence failed monitor rom (mon) , write to the flash block protect register instead of any flash address. note: programming and erasing of flash locations cannot be performed by code being executed from the flash memory. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 162 flash memory motorola 11.7 flash program/read operation programming of the flash memory is done on a row basis. a row consists of 32 consecutive bytes starting from addresses $xx00, $xx20, $xx40, $xx60, $xx80, $xxa0, $xxc0, and $xxe0. use this step-by-step procedure to program a row of flash memory ( figure 11-2 is a flowchart representation): 1. set the pgm bit. this configures the memory for program operation and enables the latching of address and data for programming. 2. read from the flash block protect register. 3. write any data to any flash address within the row address range desired. 4. wait for a time, t nvs (min. 10 s). 5. set the hven bit. 6. wait for a time, t pgs (min. 5 s). 7. write data to the flash address to be programmed.* 8. wait for a time, t prog (min. 30 s). 9. repeat step 7 and 8 until all the bytes within the row are programmed. 10. clear the pgm bit.* 11. wait for a time, t nvh (min. 5 s). 12. clear the hven bit. 13. after time, t rcv (min. 1 s), the memory can be accessed in read mode again. * the time between each flash address change, or the time between the last flash address programmed to clearing pgm bit, must not exceed the maximum programming time, t prog max. this program sequence is repeated throughout the memory until all data is programmed. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 block protection MC68HC908GR8A ? rev 0.0 technical data motorola flash memory 163 note: programming and erasing of flash locations cannot be performed by code being executed from the flash memory. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. do not exceed t prog maximum. see memory characteristics. 11.8 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 a block of memory from unintentional erase or program operations due to system malfunction. this protection is done by using of a flash block protect register (flbpr). the 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 cannot 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 flbpr is programmed with all 0s, the entire memory is protected from being programmed and erased. when all the bits are erased (all 1s), the entire memory is accessible for program and erase. when bits within the flbpr are programmed, they lock a block of memory with address ranges as shown in flash block protect register . once the flbpr is programmed with a value other than $ff, any erase or program of the flbpr or the protected block of flash memory is prohibited. the flbpr itself can be erased or programmed only with an external voltage, v tst , present on the irq pin. this voltage also allows entry from reset into the monitor 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 . . . flash memory technical data MC68HC908GR8A ? rev 0.0 164 flash memory motorola figure 11-2. flash programming 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 (32 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 flash block protection MC68HC908GR8A ? rev 0.0 technical data motorola flash memory 165 11.8.1 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 programming sequence of the flash memory. the value in this register determines the starting location of the protected range within the flash memory. bpr[7:0] ? flash block protect bits these eight bits represent bits [13:6] of a 16-bit memory address. bits [15:14] are logic 1s and bits [5:0] are logic 0s. the resultant 16-bit address is used for specifying the start address of the flash memory for block protection. the 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, $xx40, $xx80, and $xxc0 (64 bytes page boundaries) within the flash memory. figure 11-4. flash block protect start address address: $ff7e bit 7654321bit 0 read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: reset:uuuuuuuu u = unaffected by reset. initial value from factory is 1. write to this register is by a programming sequence to the flash memory. figure 11-3. flash block protect register (flbpr) 1 flbpr value 16-bit memory address 000000 start address of flash block protect 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 . . . flash memory technical data MC68HC908GR8A ? rev 0.0 166 flash memory motorola examples of protect start address: 11.9 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, but there will not be any memory activity since the cpu is inactive. the wait instruction should not be executed while performing a program or erase operation on the flash, otherwise the operation will discontinue, and the flash will be on standby mode. 11.10 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, but there will not be any memory activity since the cpu is inactive. the stop instruction should not be executed while performing a program or erase operation on the flash, otherwise the operation will discontinue, and the flash will be on 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 at a minimum. table 11-1. examples of protect start address: bpr[7:0] start of address of protect range $80 the entire flash memory is protected. $81 ( 1000 0001 )$e040 (11 10 0000 01 00 0000) $82 ( 1000 0010 )$e080 (11 10 0000 10 00 0000) and so on... $fe ( 1111 1110 )$ff80 (11 11 1111 10 00 0000) $ff the entire flash memory is not protected. note: the end address of the protected range is always $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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola external interrupt (irq) 167 technical data ? MC68HC908GR8A section 12. external interrupt (irq) 12.1 contents 12.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167 12.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167 12.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168 12.5 irq1 pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170 12.6 irq module during break interrupts . . . . . . . . . . . . . . . . . . .171 12.7 irq status and control register . . . . . . . . . . . . . . . . . . . . . .172 12.2 introduction the irq (external interrupt) module provides a maskable interrupt input. 12.3 features features of the irq module include: a dedicated external interrupt pin (irq1 ) irq interrupt control bits hysteresis buffer programmable edge-only or edge and level interrupt sensitivity automatic interrupt acknowledge internal 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 . . . external interrupt (irq) technical data MC68HC908GR8A ? rev 0.0 168 external interrupt (irq) motorola 12.4 functional description a logic 0 applied to the external interrupt pin can latch a cpu interrupt request. figure 12-1 shows the structure of the irq module. interrupt signals on the irq1 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 (intscr). writing a logic 1 to the ack bit clears the irq latch. reset ? a reset automatically clears the interrupt latch. the external interrupt pin is falling-edge-triggered and is software-configurable to be either falling-edge or falling-edge and low-level-triggered. the mode bit in the intscr controls the triggering sensitivity of the irq1 pin. when an interrupt pin is edge-triggered only, the interrupt 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 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 mode control bit, thereby clearing the interrupt even if the pin stays low. when set, the imask bit in the intscr mask all external interrupt requests. a latched interrupt request is not presented to the interrupt priority logic unless the imask bit is 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 . . . external interrupt (irq) functional description MC68HC908GR8A ? rev 0.0 technical data motorola external interrupt (irq) 169 note: the interrupt mask (i) in the condition code register (ccr) masks all interrupt requests, including external interrupt requests. figure 12-1. irq module block diagram irq1 ack imask dq ck clr irq high interrupt to mode select logic irq ff request v dd mode voltage detect synchro- nizer irqf to cpu for bil/bih instructions vector fetch decoder internal address bus reset v dd internal pullup device addr. register name bit 7 6 5 4 3 2 1 bit 0 $001d irq status and control register (intscr) read: 0 0 0 0 irqf 0 imask mode write: ack reset:00000000 = unimplemented figure 12-2. irq i/o 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 . . . external interrupt (irq) technical data MC68HC908GR8A ? rev 0.0 170 external interrupt (irq) motorola 12.5 irq1 pin a logic 0 on the irq1 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 irq1 pin is both falling-edge-sensitive and low-level-sensitive. with mode set, both of the following actions must occur to clear irq: 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 (intscr). the ack bit is useful in applications that poll the irq1 pin and require software to clear the irq latch. writing to the ack bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. setting ack does not affect subsequent transitions on the irq1 pin. a falling edge that occurs after writing to the ack bit 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 irq1 pin to logic 1 ? as long as the irq1 pin is at logic 0, irq remains active. the vector fetch or software clear and the return of the irq1 pin to logic 1 may occur in any order. the interrupt request remains pending as long as the irq1 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 irq1 pin is falling-edge-sensitive only. with mode clear, a vector fetch or software clear immediately clears the irq latch. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (irq) irq module during break interrupts MC68HC908GR8A ? rev 0.0 technical data motorola external interrupt (irq) 171 the irqf bit in the intscr 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 irq1 pin. note: when using the level-sensitive interrupt trigger, avoid false interrupts by masking interrupt requests in the interrupt routine. 12.6 irq module during break interrupts the bcfe bit in the sim break flag control register (sbfcr) enables software to clear the latch during the break state. see break module (brk) . 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 cpu interrupt flags 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 interrupt flags. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (irq) technical data MC68HC908GR8A ? rev 0.0 172 external interrupt (irq) motorola 12.7 irq status and control register the irq status and control register (intscr) controls and monitors operation of the irq module. the intscr: shows the state of the irq flag clears the irq latch masks irq interrupt request controls triggering sensitivity of the irq1 interrupt pin 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 address: $001d bit 7654321bit 0 read: irqf 0 imask mode write: ack reset:00000000 = unimplemented figure 12-3. irq status and control register (intscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (irq) irq status and control register MC68HC908GR8A ? rev 0.0 technical data motorola external interrupt (irq) 173 mode ? irq edge/level select bit this read/write bit controls the triggering sensitivity of the irq1 pin. reset clears mode. 1 = irq1 interrupt requests on falling edges and low levels 0 = irq1 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 (irq) technical data MC68HC908GR8A ? rev 0.0 174 external interrupt (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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola keyboard interrupt (kbi) 175 technical data ? MC68HC908GR8A section 13. keyboard interrupt (kbi) 13.1 contents 13.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 13.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175 13.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .176 13.5 keyboard initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 13.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180 13.7 keyboard module during break interrupts . . . . . . . . . . . . . . .180 13.8 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181 13.2 introduction the keyboard interrupt module (kbi) provides four independently maskable external interrupts. 13.3 features four 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 exit from low-power modes i/o (input/output) port bit(s) software configurable with pullup device(s) if configured as input port bit(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 . . . keyboard interrupt (kbi) technical data MC68HC908GR8A ? rev 0.0 176 keyboard interrupt (kbi) motorola 13.4 functional description writing to the kbie3?kbie0 bits in the keyboard interrupt enable register independently enables or disables each port a 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 interrupt pin is low and the pin is keyboard interrupt 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 . . . keyboard interrupt (kbi) functional description MC68HC908GR8A ? rev 0.0 technical data motorola keyboard interrupt (kbi) 177 figure 13-1. keyboard module block diagram kb0ie kb3ie . . . keyboard interrupt dq ck clr vdd modek imaskk keyboard interrupt ff request vector fetch decoder ackk internal bus reset to pullup kbd3 kbd0 to pullup synchronizer keyf enable enable addr. register name bit 7 6 5 4 3 2 1 bit 0 $001a keyboard status and control register (intkbscr) read: 0 0 0 0 keyf 0 imaskk modek write: ackk reset:00000000 $001b keyboard interrupt enable register (intkbier) read: kbie3 kbie2 kbie1 kbie0 write: reset: 0 0 0 0 = unimplemented figure 13-2. i/o 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 . . . keyboard interrupt (kbi) technical data MC68HC908GR8A ? rev 0.0 178 keyboard interrupt (kbi) 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 (intkbscr). 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 can also 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 interrupt (kbi) keyboard initialization MC68HC908GR8A ? rev 0.0 technical data motorola keyboard interrupt (kbi) 179 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. 13.5 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 is: 1. configure the keyboard pins as outputs by setting the appropriate ddra bits in data direction register a. 2. write logic 1s to the appropriate port a data register bits. 3. 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 interrupt (kbi) technical data MC68HC908GR8A ? rev 0.0 180 keyboard interrupt (kbi) motorola 13.6 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 13.6.1 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. 13.6.2 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. 13.7 keyboard module during break interrupts the system integration module (sim) controls whether the keyboard interrupt latch 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. to allow software to clear the keyboard interrupt 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 keyboard acknowledge bit (ackk) in the keyboard status and control register during the break state has no effect. see keyboard status and control 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 interrupt (kbi) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola keyboard interrupt (kbi) 181 13.8 i/o registers these registers control and monitor operation of the keyboard module: keyboard status and control register (intkbscr) keyboard interrupt enable register (intkbier) 13.8.1 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: 0 0 0 0 keyf 0 imaskk modek write: ackk reset:00000000 = unimplemented figure 13-3. keyboard status and control register (intkbscr) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 interrupt (kbi) technical data MC68HC908GR8A ? rev 0.0 182 keyboard interrupt (kbi) 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 13.8.2 keyboard interrupt enable register the keyboard interrupt enable register enables or disables each port a pin to operate as a keyboard interrupt pin. kbie3?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 = ptax pin enabled as keyboard interrupt pin 0 = ptax pin not enabled as keyboard interrupt pin address: $001b bit 7654321bit 0 read: kbie3 kbie2 kbie1 kbie0 write: reset: 0 0 0 0 figure 13-4. keyboard interrupt enable register (intkbier) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola low-voltage inhibit (lvi) 183 technical data ? MC68HC908GR8A section 14. low-voltage inhibit (lvi) 14.1 contents 14.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 14.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 14.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 14.5 lvi status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187 14.6 lvi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 14.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 14.2 introduction this section describes the low-voltage inhibit (lvi) module, which monitors the voltage on the v dd pin and can force a reset when the v dd voltage falls below the lvi trip falling voltage, v tripf . 14.3 features features of the lvi module include: programmable lvi reset selectable lvi trip voltage programmable stop mode 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 . . . low-voltage inhibit (lvi) technical data MC68HC908GR8A ? rev 0.0 184 low-voltage inhibit (lvi) motorola 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. clearing the lvi power disable bit, lvipwrd, enables the lvi to monitor v dd voltage. clearing the lvi reset disable bit, lvirstd, enables the lvi module to generate a reset when v dd falls below the trip point voltage, v tripf . setting the lvi enable in stop mode bit, lvistop, enables the lvi to operate in stop mode. setting the lvi 5v or 3v trip point bit, lvi5or3, enables v tripf to be configured for 5v operation. clearing the lvi5or3 bit enables v tripf to be configured for 3v operation. the actual trip points are shown in electrical specifications . note: after a power-on reset (por) the lvi?s default mode of operation is 3 v. if a 5v system is used, the user must set the lvi5or3 bit to raise the trip point to 5v operation. note that this must be done after every por since the default will revert back to 3v mode after each por. if the v dd supply is below the 5v mode trip voltage but above the 3v mode trip voltage when por is released, the part will operate because v tripf defaults to 3v mode after a por. so, in a 5v system care must be taken to ensure that v dd is above the 5v mode trip voltage after por is released. note: if the user requires 5v mode and sets the lvi5or3 bit after a por while the v dd supply is not above the v tripr for 5v mode, the mcu will immediately go into reset. the lvi in this case will hold the part in reset until either v dd goes above the rising 5v trip point, v tripr , which will release reset or v dd decreases to approximately 0 v which will re-trigger the por and reset the trip point to 3v 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 . . . low-voltage inhibit (lvi) functional description MC68HC908GR8A ? rev 0.0 technical data motorola low-voltage inhibit (lvi) 185 lvistop, lvipwrd, lvi5or3, and lvirstd are in the configuration register (mor1). see configuration register (config) for details of the lvi?s configuration bits. once an lvi reset occurs, the mcu remains in reset until v dd rises above a voltage, v tripr , which causes the mcu to exit reset. see low-voltage inhibit (lvi) reset for details of the interaction between the sim and the lvi. the output of the comparator controls the state of the lviout flag in the lvi status register (lvisr). an lvi reset also drives the rst pin low to provide low-voltage protection to external peripheral devices. figure 14-1. lvi module block diagram low v dd detector lvipwrd stop instruction lvistop lvi reset lviout v dd > lvi trip = 0 v dd lvi trip = 1 from config from config v dd from config lv irs td lvi5or3 from config f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 186 low-voltage inhibit (lvi) motorola 14.4.1 polled lvi operation in applications that can operate at v dd levels below the v tripf level, software can monitor v dd by polling the lviout bit. in the configuration register, the lvipwrd bit must be at logic 0 to enable the lvi module, and the lvirstd bit must be at logic 1 to disable lvi resets. 14.4.2 forced reset operation in applications that require v dd to remain above the v tripf level, enabling lvi resets allows the lvi module to reset the mcu when v dd falls below the v tripf level. in the configuration register, the lvipwrd and lvirstd bits must be at logic 0 to enable the lvi module and to enable lvi resets. 14.4.3 voltage hysteresis protection once the lvi has triggered (by having v dd fall below v tripf ), the lvi will maintain a reset condition until v dd rises above the rising trip point voltage, v tripr . this prevents a condition in which the mcu is continually entering and exiting reset if v dd is approximately equal to v tripf . v tripr is greater than v tripf by the hysteresis voltage, v hys . addr. register name bit 7 6 5 4 3 2 1 bit 0 $fe0c lvi status register (lvisr) read:lviout0000000 write: reset:00000000 = unimplemented figure 14-2. lvi i/o 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 . . . low-voltage inhibit (lvi) lvi status register MC68HC908GR8A ? rev 0.0 technical data motorola low-voltage inhibit (lvi) 187 14.4.4 lvi trip selection the lvi5or3 bit in the configuration register selects whether the lvi is configured for 5v or 3v protection. note: the microcontroller is guaranteed to operate at a minimum supply voltage. the trip point (v tripf [5 v] or v tripf [3 v]) may be lower than this. (see electrical specifications for the actual trip point voltages.) 14.5 lvi status register the lvi status register (lvisr) indicates if the v dd voltage was detected below the v tripf level. lviout ? lvi output bit this read-only flag becomes set when the v dd voltage falls below the v tripf trip voltage. see table 14-1 . reset clears the lviout bit. address: $fe0c bit 7 6 5 4 3 2 1 bit 0 read:lviout0000000 write: reset:00000000 = unimplemented figure 14-3. lvi status register (lvisr) table 14-1. lviout bit indication v dd lviout v dd > v tripr 0 v dd < v tripf 1 v tripf < v dd < v tripr 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) technical data MC68HC908GR8A ? rev 0.0 188 low-voltage inhibit (lvi) motorola 14.6 lvi interrupts the lvi module does not generate interrupt requests. 14.7 low-power modes the stop and wait instructions put the mcu in low power-consumption standby modes. 14.7.1 wait mode if enabled, the lvi module remains active in wait mode. if enabled to generate resets, the lvi module can generate a reset and bring the mcu out of wait mode. 14.7.2 stop mode if enabled in stop mode (lvistop set), the lvi module remains active in stop mode. if enabled to generate resets, the lvi module can generate a reset and bring the mcu out of 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 189 technical data ? MC68HC908GR8A section 15. monitor rom (mon) 15.1 contents 15.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 15.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .189 15.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190 15.5 security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202 15.2 introduction this section describes the monitor rom (mon) and the monitor mode entry methods. the monitor rom allows complete testing of the mcu through a single-wire interface with a host computer. monitor mode entry can be achieved without use of the higher test voltage, v tst , as long as vector addresses $fffe and $ffff are blank, thus reducing the hardware requirements for in-circuit programming. 15.3 features features of the monitor rom include: normal user-mode pin functionality one pin dedicated to serial communication between monitor rom and host computer standard mark/space non-return-to-zero (nrz) communication with host computer execution of code in ram or flash f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . monitor rom (mon) technical data MC68HC908GR8A ? rev 0.0 190 monitor rom (mon) motorola flash memory security feature 1 flash memory programming interface enhanced pll (phase-locked loop) option to allow use of external 32.768-khz crystal to generate internal frequency of 2.4576 mhz 310 byte monitor rom code size ($fe20 to $ff55) monitor mode entry without high voltage, v tst , if reset vector is blank ($fffe and $ffff contain $ff) standard monitor mode entry if high voltage, v tst , is applied to irq 15.4 functional description the monitor rom receives and executes commands from a host computer. figure 15-1 shows an example circuit used to enter monitor mode and communicate with a host computer via a standard rs-232 interface. simple monitor commands can access any memory address. in monitor mode, the mcu can execute code downloaded into ram by a host computer while most mcu pins 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. 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 . . . monitor rom (mon) functional description MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 191 figure 15-1. monitor mode circuit + + + v dda mc145407 mc74hc125 rst irq v dda cgmxfc osc1 osc2 v ss v dd pta0 v dd 10 k ? 0.1 f 10 k ? 6 5 2 4 3 1 db-25 2 3 7 20 18 17 19 16 15 v dd v dd v dd 10 f 10 f 10 f 10 f 1 2 4 7 14 3 0.1 f 5 6 + ptb0 ptb1 68hc08 $ffff $fffe reset vectors v ssad /v refl v ssa v ddad /v refh d c c c d d 6?30 pf 6?30 pf 32.768 khz xtal 10 m ? sw2 sw4 sw3 (see note 2) (see notes 2 (see note 2) (see note 3) notes: 1. sw2, sw3, and sw4: position c ? enter monitor mode using external oscillator. sw2, sw3, and sw4: position d ? enter monitor mode using external xtal and internal pll. 2. see . monitor mode signal requirements and options for irq voltage level requirements. 10 k 0.01 f 0.033 f v tst 330 k ? and 3) pta1 v dd 10 k ? 10 k ? 10 k ? f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 192 monitor rom (mon) motorola the monitor code has been updated from previous versions to allow enabling the pll to generate the internal clock, provided the reset vector is blank, when the device is being clocked by a low-frequency crystal. this addition, which is enabled when irq is held low out of rest, is intended to support serial communication/ programming at 9600 baud in monitor mode by stepping up the external frequency (assumed to be 32.768 khz) by a fixed amount to generate the desired internal frequency (2.4576 mhz). since this feature is enabled only when irq is held low out of reset, it cannot be used when the reset vector is not blank because entry into monitor mode in this case requires v tst on irq . 15.4.1 entering monitor mode table 15-1 shows the pin conditions for entering monitor mode. as specified in the table, monitor mode may be entered after a power-on reset (por) and will allow communication at 9600 baud provided one of the following sets of conditions is met: 1. if $fffe and $ffff contain values not cared: ? the external clock is 9.8304 mhz ?irq = v tst (pll off) 2. if $fffe and $ffff contain $ff, blank state: ? the external clock is 9.8304 mhz ?irq = v dd (this can be implemented through the internal irq pullup; pll off) 3. if $fffe and $ffff contain $ff, blank state: ? the external clock is 32.768 khz (crystal) ?irq = v ss (this setting initiates the pll to boost the external 32.768 khz to an internal bus frequency of 2.4576 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 . . . monitor rom (mon) functional description MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 193 if entering monitor mode with v tst applied on irq (condition set 1), 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. if entering monitor mode without high voltage applied on irq (condition set 2 or 3, where applied voltage is either v dd or v ss ), then all port b pin table 15-1. monitor mode signal requirements and options irq reset $fffe/ $ffff pll ptb0 ptb1 external clock (1) cgmout bus freq cop for serial communication comment pta0 pta1 baud rate (2) (3) x gnd x x x x x 0 0 disabled x x 0 no operation until reset goes high v tst v dd or v tst xoff1 0 9.8304 mhz 4.9152 mhz 2.4576 mhz disabled 1 0 9600 ptb0 and ptb1 voltages only required if irq =v tst x 1 dna v dd v dd $ffff off x x 9.8304 mhz 4.9152 mhz 2.4576 mhz disabled 1 0 9600 external frequency always divided by 4 x 1 dna gnd v dd $ffff on x x 32.768 khz 4.9152 mhz 2.4576 mhz disabled 1 0 9600 pll enabled (bcs set) in monitor code x 1 dna v dd or gnd v tst $ffff off x x x ? ? enabled x x ? enters user mode ? will encounter an illegal address reset v dd or gnd v dd or v tst not $ffff off x x x ? ? enabled x x ? enters user mode notes: 1. external clock is derived by a 32.768 khz crystal or a 9.8304 mhz off-chip oscillator 2. pta0 = 1 if serial communication; pta0 = x if parallel communication 3. pta1 = 0 serial, pta1 = 1 parallel communication for security code entry 4. dna = does not apply, 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 . . . monitor rom (mon) technical data MC68HC908GR8A ? rev 0.0 194 monitor rom (mon) motorola requirements and conditions, are not in effect. this is to reduce circuit requirements when performing in-circuit programming. note: if the reset vector is blank and monitor mode is entered, the chip will see an additional reset cycle after the initial por reset. once the part has been programmed, the traditional method of applying a voltage, v tst , to irq must be used to enter monitor mode. the cop module is disabled in monitor mode based on these conditions: if monitor mode was entered as a result of the reset vector being blank (condition set 2 or 3), the cop is always disabled regardless of the state of irq or rst . if monitor mode was entered with v tst on irq (condition set 1), then the cop is disabled as long as v tst is applied to either irq or rst . the second condition states that as long as v tst is maintained on the irq pin after entering monitor mode, or if v tst is applied to rst after the initial reset to get into monitor mode (when v tst was applied to irq ), then the cop will be disabled. in the latter situation, after v tst is applied to the rst pin, v tst can be removed from the irq pin in the interest of freeing the irq for normal functionality in monitor mode. figure 15-2 shows a simplified diagram of the monitor mode entry when the reset vector is blank and just 1 x v dd voltage is applied to the irq pin. an external oscillator of 9.8304 mhz is required for a baud rate of 9600, as the internal bus frequency is automatically set to the external frequency divided by four. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 195 figure 15-2. low-voltage monitor mode entry flowchart enter monitor mode with pin configuration shown in figure 15-1 by pulling rst low and then high. the rising edge of rst latches monitor mode. once monitor mode is latched, the values on the specified pins can change. once out of reset, the mcu waits for the host to send eight security bytes. (see security .) after the security bytes, the mcu sends a break signal (10 consecutive logic 0s) to the host, indicating that it is ready to receive a command. note: the pta1 pin must remain at logic 0 for 24 bus cycles after the rst pin goes high to enter monitor mode properly. in monitor mode, the mcu uses different vectors for reset, swi (software interrupt), and break interrupt than those for user mode. 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. note: exiting monitor mode after it has been initiated by having a blank reset vector requires a power-on reset. pulling rst low will not exit monitor mode in this situation. is vector blank? por triggered? normal user mode monitor mode execute monitor code no no yes yes por 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 . . . monitor rom (mon) technical data MC68HC908GR8A ? rev 0.0 196 monitor rom (mon) motorola table 15-2 summarizes the differences between user mode and monitor mode. 15.4.2 data format communication with the monitor rom is in standard non-return-to-zero (nrz) mark/space data format. transmit and receive baud rates must be identical. figure 15-3. monitor data format 15.4.3 break signal a start bit (logic 0) followed by nine logic 0 bits is a break signal. when the monitor receives a break signal, it drives the pta0 pin high for the duration of two bits and then echoes back the break signal. figure 15-4. break transaction table 15-2. mode differences modes functions reset vector high reset vector low break vector high break vector low swi vector high swi vector low user $fffe $ffff $fffc $fffd $fffc $fffd monitor $fefe $feff $fefc $fefd $fefc $fefd bit 5 start bit bit 1 next stop bit start bit bit 2 bit 3 bit 4 bit 7 bit 0 bit 6 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 missing stop bit 2-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 MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 197 15.4.4 baud rate the communication baud rate is controlled by the crystal frequency upon entry into monitor mode. the divide by ratio is 1024. if monitor mode was entered with v dd on irq , then the divide by ratio is also set at 1024. if monitor mode was entered with v ss on irq , then the internal pll steps up the external frequency, presumed to be 32.768 khz, to 2.4576 mhz. these latter two conditions for monitor mode entry require that the reset vector is blank. table 15-3 lists external frequencies required to achieve a standard baud rate of 9600 bps. other standard baud rates can be accomplished using proportionally higher or lower frequency generators. if using a crystal as the clock source, be aware of the upper frequency limit that the internal clock module can handle. see 5.0 v control timing and 3.0 v control timing for this limit. 15.4.5 commands the monitor rom firmware uses these commands: read (read memory) write (write memory) iread (indexed read) iwrite (indexed write) readsp (read stack pointer) run (run user program) table 15-3. monitor baud rate selection external frequency irq internal frequency baud rate (bps) 9.8304 mhz v tst 2.4576 mhz 9600 9.8304 mhz v dd 2.4576 mhz 9600 32.768 khz v ss 2.4576 mhz 9600 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 198 monitor rom (mon) motorola the monitor rom firmware echoes each received byte back to the pta0 pin for error checking. an 11-bit delay at the end of each command allows the host to send a break character to cancel the command. a delay of two bit times occurs before each echo and before read, iread, or readsp data is returned. the data returned by a read command appears after the echo of the last byte of the command. note: wait one bit time after each echo before sending the next byte. figure 15-5. read transaction figure 15-6. write transaction read read echo from host address high address high address low address low data return 13, 2 11 4 4 notes: 2 = data return delay, 2 bit times 3 = cancel command delay, 11 bit times 4 = wait 1 bit time before sending next byte. 44 1 = echo delay, 2 bit times write write echo from host address high address high address low address low data data notes: 2 = cancel command delay, 11 bit times 3 = wait 1 bit time before sending next byte. 11 3 11 3 3 32, 3 1 = echo delay, 2 bit times f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 199 a brief description of each monitor mode command is given in table 15-4 through table 15-9 . table 15-4. read (read memory) command description read byte from memory operand 2-byte address in high-byte:low-byte order data returned returns contents of specified address opcode $4a command sequence table 15-5. write (write memory) command description write byte to memory operand 2-byte address in high-byte:low-byte order; low byte followed by data byte data returned none opcode $49 command sequence read read echo sent to monitor address high address high address low data return address low write write echo from host address high address high address low address low data 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 . . . monitor rom (mon) technical data MC68HC908GR8A ? rev 0.0 200 monitor rom (mon) motorola table 15-6. iread (indexed read) command description read next 2 bytes in memory from last address accessed operand 2-byte address in high byte:low byte order data returned returns contents of next two addresses opcode $1a command sequence table 15-7. iwrite (indexed write) command description write to last address accessed + 1 operand single data byte data returned none opcode $19 command sequence iread iread echo from host data return data iwrite iwrite echo from host data 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 . . . monitor rom (mon) functional description MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 201 a sequence of iread or iwrite commands can access a block of memory sequentially over the full 64k byte memory map. table 15-8. readsp (read stack pointer) command description reads stack pointer operand none data returned returns incremented stack pointer value (sp + 1) in high-byte:low-byte order opcode $0c command sequence table 15-9. run (run user program) command description executes pulh and rti instructions operand none data returned none opcode $28 command sequence readsp readsp echo from host sp return sp high low run run echo from host f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 202 monitor rom (mon) motorola the mcu executes the swi and pshh instructions when it enters monitor mode. the run command tells the mcu to execute the pulh and rti instructions. before sending the run command, the host can modify the stacked cpu registers to prepare to run the host program. the readsp command returns the incremented stack pointer value, sp + 1. the high and low bytes of the program counter are at addresses sp + 5 and sp + 6. figure 15-7. stack pointer at monitor mode entry 15.5 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, they should be programmed even if they are not used for vectors. during monitor mode entry, the mcu waits after the power-on reset for the host to send the eight security bytes on pin pta0. 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. if the reset was not a power-on reset, security remains bypassed and security code entry is not required. (see figure 15-8 .) condition code register accumulator low byte of index register high byte of program counter low byte of program counter sp + 1 sp + 2 sp + 3 sp + 4 sp + 5 sp sp + 6 high byte of index register sp + 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) security MC68HC908GR8A ? rev 0.0 technical data motorola monitor rom (mon) 203 figure 15-8. monitor mode entry timing upon power-on reset, if the received bytes of the security code 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 a flash location returns an invalid value and trying to execute code from flash causes an illegal address reset. after receiving the eight security bytes from the host, the mcu transmits a break character, signifying 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. to determine whether the security code entered is correct, check to see if bit 6 of ram address $40 is set. if it is, then the correct security code has been entered and flash can be accessed. byte 1 byte 1 echo byte 2 byte 2 echo byte 8 byte 8 echo command command echo pa0 pa1 rst v dd 4096 + 32 cgmxclk cycles 24 bus cycles 256 bus cycles (minimum) 1 4 1 1 2 1 break notes: 2 = data return delay, 2 bit times 4 = wait 1 bit time before sending next byte. 4 from host from mcu 1 = echo delay, 2 bit times f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 204 monitor rom (mon) motorola if the security sequence fails, the device can be reset and brought up in monitor mode to attempt another entry. after failing the security sequence, the flash mode can also be bulk erased by executing an erase routine that was downloaded into internal ram. the bulk erase operation clears the security code locations so that all eight security bytes become $ff (blank). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 205 technical data ? MC68HC908GR8A section 16. input/output ports (i/o) 16.1 contents 16.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 16.3 port a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 16.4 port b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 16.5 port c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 16.6 port d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 16.7 port e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 16.2 introduction twenty one (21) bidirectional input-output (i/o) pins form five parallel ports. all i/o pins are programmable as inputs or outputs. all individual bits within port a, port c, and port d are software configurable with pullup devices if configured as input port bits. the pullup devices are automatically and dynamically disabled when a port bit is switched to output mode. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (i/o) technical data MC68HC908GR8A ? rev 0.0 206 input/output ports (i/o) motorola addr. register name bit 7 6 5 4 3 2 1 bit 0 $0000 port a data register (pta) read: 0 0 0 0 pta3 pta2 pta1 pta0 write: reset: unaffected by reset $0001 port b data register (ptb) read: 0 0 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset $0002 port c data register (ptc) read:000000 ptc1 ptc0 write: reset: unaffected by reset $0003 port d data register (ptd) read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: reset: unaffected by reset $0004 data direction register a (ddra) read: 0 0 0 0 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 $0005 data direction register b (ddrb) read: 0 0 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 $0006 data direction register c (ddrc) read:000000 ddrc1 ddrc0 write: reset:00000000 $0007 data direction register d (ddrd) read: 0 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: reset:00000000 = unimplemented figure 16-1. i/o port 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 . . . input/output ports (i/o) introduction MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 207 $0008 port e data register (pte) read:000000 pte1 pte0 write: reset: unaffected by reset $000c data direction register e (ddre) read:000000 ddre1 ddre0 write: reset:00000000 $000d port a input pullup enable register (ptapue) read: 0 0 0 0 ptapue3 ptapue2 ptapue1 ptapue0 write: reset:00000000 $000e port c input pullup enable register (ptcpue) read:000000 ptcpue1 ptcpue0 write: reset:00000000 $000f port d input pullup enable register (ptdpue) read: 0 ptdpue6 ptdpue5 ptdpue4 ptdpue3 ptdpue2 ptdpue1 ptdpue0 write: reset:00000000 addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented figure 16-1. i/o port register summary (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 . . . input/output ports (i/o) technical data MC68HC908GR8A ? rev 0.0 208 input/output ports (i/o) motorola table 16-1. port control register bits summary port bit ddr module control pin a 0ddra0 kbd kbie0 pta0/kbd0 1 ddra1 kbie1 pta1/kbd1 2 ddra2 kbie2 pta2/kbd2 3 ddra3 kbie3 pta3/kbd3 --- - -- --- - -- --- - -- --- - -- b 0ddrb0 adc ch0 ptb0/atd0 1 ddrb1 ch1 ptb1/atd1 2 ddrb2 ch2 ptb2/atd2 3 ddrb3 ch3 ptb3/atd3 4 ddrb4 ch4 ptb4/atd4 5 ddrb5 ch5 ptb5/atd5 --- - -- --- - -- c 0 ddrc0 ptc0 1 ddrc1 ptc1 --- -- --- -- --- -- --- -- --- -- d 0 ddrd0 spi ptd0/ss 1 ddrd1 ptd1/miso 2 ddrd2 ptd2/mosi 3 ddrd3 ptd3/spsck 4 ddrd4 tim1 ptd4/t1ch0 5 ddrd5 ptd5/t1ch1 6 ddrd6 tim2 ptd6/t2ch0 --- -- e 0ddre0 sci pte0/txd 1 ddre1 pte1/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 . . . input/output ports (i/o) port a MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 209 16.3 port a port a is an 4-bit special-function port that shares all four of its pins with the keyboard interrupt (kbi) module. port a also has software configurable pullup devices if configured as an input port. 16.3.1 port a data register the port a data register (pta) contains a data latch for each of the four port a pins. pta3?pta0 ? 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. kbd3?kbd0 ? keyboard inputs the keyboard interrupt enable bits, kbie3?kbie0, in the keyboard interrupt control register (kbicr) enable the port a pins as external interrupt pins. see keyboard interrupt (kbi) . address: $0000 bit 7 6 5 4 3 2 1 bit 0 read: 0 0 0 0 pta3 pta2 pta1 pta0 write: reset: unaffected by reset alternate function: kbd3 kbd2 kbd1 kbd0 figure 16-2. port a data register (pta) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (i/o) technical data MC68HC908GR8A ? rev 0.0 210 input/output ports (i/o) motorola 16.3.2 data direction register a data direction register a (ddra) 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. ddra3?ddra0 ? data direction register a bits these read/write bits control port a data direction. reset clears ddra3?ddra0, 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 16-4 shows the port a i/o logic. address: $0004 bit 7654321bit 0 read: 0 0 0 0 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 figure 16-3. 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 (i/o) port a MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 211 figure 16-4. 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 16-2 summarizes the operation of the port a pins. read ddra ($0004) write ddra ($0004) reset write pta ($0000) read pta ($0000) ptax ddrax ptax internal data bus v dd ptapuex internal pullup device table 16-2. port a pin functions ptapue bit ddra bit pta bit i/o pin mode accesses to ddra accesses to pta read/write read write 10 x (1) input, v dd (4) ddra3?ddra0 pin pta3?pta0 (3 ) 00x input, hi-z (2) ddra3?ddra0 pin pta3?pta0 (3 ) x 1 x output ddra3?ddra0 pta3?pta0 pta3?pta0 notes: 1. x = don?t care 2. hi-z = high impedance 3. writing affects data register, but does not affect input. 4. i/o pin pulled up to v dd by internal pullup 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 . . . input/output ports (i/o) technical data MC68HC908GR8A ? rev 0.0 212 input/output ports (i/o) motorola 16.3.3 port a input pullup enable register the port a input pullup enable register (ptapue) contains a software configurable pullup device for each of the four port a pins. each bit is individually configurable and requires that the data direction register, ddra, bit be configured as an input. each pullup is automatically and dynamically disabled when a port bit?s ddra is configured for output mode. ptapue3?ptapue0 ? port a input pullup enable bits these writeable bits are software programmable to enable pullup devices on an input port bit. 1 = corresponding port a pin configured to have internal pullup 0 = corresponding port a pin has internal pullup disconnected address: $000d bit 7654321bit 0 read: 0 0 0 0 ptapue3 ptapue2 ptapue1 ptapue0 write: reset:00000000 figure 16-5. port a input pullup enable register (ptapue) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (i/o) port b MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 213 16.4 port b port b is an 6-bit special-function port that shares all six of its pins with the analog-to-digital converter (adc) module. 16.4.1 port b data register the port b data register (ptb) contains a data latch for each of the six port pins. ptb5?ptb0 ? 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. ad5?ad0 ? analog-to-digital input bits ad5?ad0 are pins used for the input channels to the analog-to-digital converter module. the channel select bits in the adc status and control register define which port b pin will be used as an adc input and overrides any control from the port i/o logic by forcing that pin as the input to the analog circuitry. note: care must be taken when reading port b while applying analog voltages to ad5?ad0 pins. if the appropriate adc channel is not enabled, excessive current drain may occur if analog voltages are applied to the ptbx/adx pin, while ptb is read as a digital input. those ports not selected as analog input channels are considered digital i/o ports. note: ptb4 and 5 are not available in a 28-pin dip and soic package address: $0001 bit 7654321bit 0 read: 0 0 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset alternate function: ad5 ad4 ad3 ad2 ad1 ad0 figure 16-6. 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 (i/o) technical data MC68HC908GR8A ? rev 0.0 214 input/output ports (i/o) motorola 16.4.2 data direction register b data direction register b (ddrb) 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. ddrb5?ddrb0 ? data direction register b bits these read/write bits control port b data direction. reset clears ddrb5?ddrb0], 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. note: for those devices packaged in a 28-pin dip and soic package, ptb5,4 are not connected. set ddrb5,4 to a 1 to configure ptb5,4 as outputs. figure 16-8 shows the port b i/o logic. address: $0005 bit 7654321bit 0 read: 0 0 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 figure 16-7. 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 (i/o) port b MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 215 figure 16-8. 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 16-3 summarizes the operation of the port b pins. read ddrb ($0005) write ddrb ($0005) reset write ptb ($0001) read ptb ($0001) ptbx ddrbx ptbx internal data bus table 16-3. port b pin functions ddrb bit ptb bit i/o pin mode accesses to ddrb accesses to ptb read/write read write 0 x (1) input, hi-z (2) ddrb5?ddrb0 pin ptb5?ptb0 (3) 1 x output ddrb5?ddrb0 ptb5?ptb0 ptb5?ptb0 notes: 1. x = don?t care 2. hi-z = high impedance 3. 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 . . . input/output ports (i/o) technical data MC68HC908GR8A ? rev 0.0 216 input/output ports (i/o) motorola 16.5 port c port c is a 2-bit, general-purpose bidirectional i/o port. port c also has software configurable pullup devices if configured as an input port. 16.5.1 port c data register the port c data register (ptc) contains a data latch for each of the two port c pins. ptc1?ptc0 ? 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. note: ptc is not available in a 28-pin dip and soic package address: $0002 bit 7654321bit 0 read:000000 ptc1 ptc0 write: reset: unaffected by reset = unimplemented figure 16-9. 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 (i/o) port c MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 217 16.5.2 data direction register c data direction register c (ddrc) 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. ddrc1?ddrc0 ? data direction register c bits these read/write bits control port c data direction. reset clears ddrc1?ddrc0, 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 16-11 shows the port c i/o logic. note: for those devices packaged in a 28-pin dip and soic package, ptc1,0 are not connected. set ddrc1,0 to a 1 to configure ptc1,0 as outputs. address: $0006 bit 7654321bit 0 read:000000 ddrc1 ddrc0 write: reset:00000000 = unimplemented figure 16-10. 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 (i/o) technical data MC68HC908GR8A ? rev 0.0 218 input/output ports (i/o) motorola figure 16-11. 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 16-4 summarizes the operation of the port c pins. read ddrc ($0006) write ddrc ($0006) reset write ptc ($0002) read ptc ($0002) ptcx ddrcx ptcx internal data bus v dd internal ptcpuex pullup device table 16-4. port c pin functions ptcpue bit ddrc bit ptc bit i/o pin mode accesses to ddrc accesses to ptc read/write read write 10 x (1) input, v dd (4) ddrc1?ddrc0 pin ptc1?ptc0 (3) 00x input, hi-z (2) ddrc1?ddrc0 pin ptc1?ptc0 (3) x 1 x output ddrc1?ddrc0 ptc1?ptc0 ptc1?ptc0 notes: 1. x = don?t care 2. hi-z = high impedance 3. writing affects data register, but does not affect input. 4. i/o pin pulled up to v dd by internal pullup 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 . . . input/output ports (i/o) port c MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 219 16.5.3 port c input pullup enable register the port c input pullup enable register (ptcpue) contains a software configurable pullup device for each of the two port c pins. each bit is individually configurable and requires that the data direction register, ddrc, bit be configured as an input. each pullup is automatically and dynamically disabled when a port bit?s ddrc is configured for output mode. ptcpue1?ptcpue0 ? port c input pullup enable bits these writeable bits are software programmable to enable pullup devices on an input port bit. 1 = corresponding port c pin configured to have internal pullup 0 = corresponding port c pin internal pullup disconnected address: $000e bit 7654321bit 0 read:000000 ptcpue1 ptcpue0 write: reset:00000000 = unimplemented figure 16-12. port c input pullup enable register (ptcpue) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (i/o) technical data MC68HC908GR8A ? rev 0.0 220 input/output ports (i/o) motorola 16.6 port d port d is an 7-bit special-function port that shares four of its pins with the serial peripheral interface (spi) module and three of its pins with two timer interface (tim1 and tim2) modules. port d also has software configurable pullup devices if configured as an input port. 16.6.1 port d data register the port d data register (ptd) contains a data latch for each of the seven port d pins. . ptd6?ptd0 ? port d data bits these read/write bits are software-programmable. data direction of each port d pin is under the control of the corresponding bit in data direction register d. reset has no effect on port d data. t2ch0 ? timer 2 channel i/o bits the ptd6/t2ch0 pin is the tim2 input capture/output compare pin. the edge/level select bits, elsxb:elsxa, determine whether the ptd6/t2ch0 pin is a timer channel i/o pin or a general-purpose i/o pin. see timer interface module (tim) . address: $0003 bit 7654321bit 0 read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: reset: unaffected by reset alternate function: t2ch0 t1ch1 t1ch0 spsck mosi miso ss figure 16-13. 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 (i/o) port d MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 221 t1ch1 and t1ch0 ? timer 1 channel i/o bits the ptd5/t1ch1?ptd4/t1ch0 pins are the tim1 input capture/output compare pins. the edge/level select bits, elsxb and elsxa, determine whether the ptd5/t1ch1?ptd4/t1ch0 pins are timer channel i/o pins or general-purpose i/o pins. see timer interface module (tim) . spsck ? spi serial clock the ptd3/spsck pin is the serial clock input of the spi module. when the spe bit is clear, the ptd3/spsck pin is available for general-purpose i/o. mosi ? master out/slave in the ptd2/mosi pin is the master out/slave in terminal of the spi module. when the spe bit is clear, the ptd2/mosi pin is available for general-purpose i/o. miso ? master in/slave out the ptd1/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 ptd0/ss pin is available for general-purpose i/o. data direction register d (ddrd) does not affect the data direction of port d pins that are being used by the spi module. however, the ddrd bits always determine whether reading port d returns the states of the latches or the states of the pins. see table 16-5 . ss ? slave select the ptd0/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, the ptd0/ss pin is available for general-purpose i/o. when the spi is enabled, the ddrb0 bit in data direction register b (ddrb) has no effect on the ptd0/ss 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 . . . input/output ports (i/o) technical data MC68HC908GR8A ? rev 0.0 222 input/output ports (i/o) motorola 16.6.2 data direction register d data direction register d (ddrd) 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. ddrd6?ddrd0 ? data direction register d bits these read/write bits control port d data direction. reset clears ddrd6?ddrd0, 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 16-15 shows the port d i/o logic. address: $0007 bit 7654321bit 0 read: 0 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: reset:00000000 figure 16-14. 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 (i/o) port d MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 223 figure 16-15. 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 16-5 summarizes the operation of the port d pins. read ddrd ($0007) write ddrd ($0007) reset write ptd ($0003) read ptd ($0003) ptdx ddrdx ptdx internal data bus vdd internal ptdpuex pullup device table 16-5. port d pin functions ptdpue bit ddrd bit ptd bit i/o pin mode accesses to ddrd accesses to ptd read/write read write 10 x (1) input, v dd (4) ddrd6?ddrd0 pin ptd6?ptd0 (3) 00x input, hi-z (2) ddrd6?ddrd0 pin ptd6?ptd0 (3) x 1 x output ddrd6?ddrd0 ptd6?ptd0 ptd6?ptd0 notes: 1. x = don?t care 2. hi-z = high impedance 3. writing affects data register, but does not affect input. 4. i/o pin pulled up to v dd by internal pullup 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 . . . input/output ports (i/o) technical data MC68HC908GR8A ? rev 0.0 224 input/output ports (i/o) motorola 16.6.3 port d input pullup enable register the port d input pullup enable register (ptdpue) contains a software configurable pullup device for each of the seven port d pins. each bit is individually configurable and requires that the data direction register, ddrd, bit be configured as an input. each pullup is automatically and dynamically disabled when a port bit?s ddrd is configured for output mode. ptdpue6?ptdpue0 ? port d input pullup enable bits these writeable bits are software programmable to enable pullup devices on an input port bit. 1 = corresponding port d pin configured to have internal pullup 0 = corresponding port d pin has internal pullup disconnected address: $000f bit 7654321bit 0 read: 0 ptdpue6 ptdpue5 ptdpue4 ptdpue3 ptdpue2 ptdpue1 ptdpue0 write: reset:00000000 figure 16-16. port d input pullup enable register (ptdpue) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (i/o) port e MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 225 16.7 port e port e is a 2-bit special-function port that shares two of its pins with the serial communications interface (sci) module. 16.7.1 port e data register the port e data register contains a data latch for each of the two port e pins. pte1 and pte0 ? port e data bits pte1 and pte0 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. 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 16-6 . rxd ? sci receive data input 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 serial communications interface (sci) . address: $0008 bit 7654321bit 0 read:000000 pte1 pte0 write: reset: unaffected by reset alternate function: rxd txd = unimplemented figure 16-17. 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 (i/o) technical data MC68HC908GR8A ? rev 0.0 226 input/output ports (i/o) 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 serial communications interface (sci) . 16.7.2 data direction register e data direction register e (ddre) 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. ddre1 and ddre0 ? data direction register e bits these read/write bits control port e data direction. reset clears ddre1 and ddre0, 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 16-19 shows the port e i/o logic. address: $000c bit 7654321bit 0 read:000000 ddre1 ddre0 write: reset:00000000 = unimplemented figure 16-18. 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 (i/o) port e MC68HC908GR8A ? rev 0.0 technical data motorola input/output ports (i/o) 227 figure 16-19. 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 16-6 summarizes the operation of the port e pins. read ddre ($000c) write ddre ($000c) reset write pte ($0008) read pte ($0008) ptex ddrex ptex internal data bus table 16-6. port e pin functions ddre bit pte bit i/o pin mode accesses to ddre accesses to pte read/write read write 0 x (1) input, hi-z (2) ddre1?ddre0 pin pte1?pte0 (3) 1 x output ddre1?ddre0] pte1?pte0 pte1?pte0 notes: 1. x = don?t care 2. hi-z = high impedance 3. 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 . . . input/output ports (i/o) technical data MC68HC908GR8A ? rev 0.0 228 input/output ports (i/o) 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola ram 229 technical data ? MC68HC908GR8A section 17. ram 17.1 contents 17.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 17.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229 17.2 introduction this section describes the 384 bytes of ram (random-access memory). 17.3 functional description addresses $0040 through $01bf are ram locations. the location of the stack ram is programmable. the 16-bit stack pointer allows the stack 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 192 bytes of ram. because the location of the stack ram is programmable, all page zero ram locations can be used for i/o control and user data or code. when the stack pointer is moved from its reset location at $00ff out of page zero, direct addressing mode instructions can efficiently access all page zero ram locations. 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. note: for m6805 compatibility, the h register is not stacked. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 230 ram motorola 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 may 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 231 technical data ? MC68HC908GR8A section 18. serial communications interface (sci) 18.1 contents 18.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231 18.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232 18.4 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233 18.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233 18.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .250 18.7 sci during break module interrupts. . . . . . . . . . . . . . . . . . . .251 18.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251 18.9 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252 18.2 introduction this section describes the serial communications interface (sci) module, which allows high-speed asynchronous communications with peripheral devices and other mcus. note: references to dma (direct-memory access) and associated functions are only valid if the mcu has a dma module. this mcu does not have the dma function. any dma-related register bits should be left in their reset state for normal mcu 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 . . . serial communications interface (sci) technical data MC68HC908GR8A ? rev 0.0 232 serial communications interface (sci) motorola 18.3 features features of the sci module 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 ? idle receiver input ? receiver overrun ? noise error ? framing error ? parity error receiver framing error detection hardware parity checking 1/16 bit-time noise detection configuration register bit, scibdsrc, to allow selection of baud rate clock source f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 233 18.4 pin name conventions the generic names of the sci i/o pins are: rxd (receive data) txd (transmit data) sci i/o (input/output) 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 18-1 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. 18.5 functional description figure 18-1 shows the structure of the sci module. the sci allows full-duplex, asynchronous, nrz serial communication among 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. the baud rate clock source for the sci can be selected via the configuration bit, scibdsrc, of the config2 register ($001e). source selection values are shown in figure 18-1 . table 18-1. pin name conventions generic pin names: rxd txd full pin names: pe1/rxd pe0/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) technical data MC68HC908GR8A ? rev 0.0 234 serial communications interface (sci) motorola figure 18-1. sci module block diagram scte tc scrf idle or nf fe pe sctie tcie scrie ilie te re rwu sbk r8 t8 dmate 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 dma interrupt control transmitter interrupt control receiver interrupt control error interrupt control control dmare ensci loops ensci pe1/rxd pe2/txd internal bus txinv loops 4 16 pre- scaler baud divider cgmxclk it12 a b sl x scibdsrc from sl = 0 => x = a sl = 1 => x = b config f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 235 addr. register name bit 7 6 5 4 3 2 1 bit 0 $0013 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset:00000000 $0014 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 $0015 sci control register 3 (scc3) read: r8 t8 dmare dmate orie neie feie peie write: reset:uu000000 $0016 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 $0017 sci status register 2 (scs2) read: bkf rpf write: reset:00000000 $0018 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 $0019 sci baud rate register (scbr) read: scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented r = reserved u = unaffected figure 18-2. sci i/o 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 . . . serial communications interface (sci) technical data MC68HC908GR8A ? rev 0.0 236 serial communications interface (sci) motorola 18.5.1 data format the sci uses the standard non-return-to-zero mark/space data format illustrated in figure 18-3 . figure 18-3. sci data formats 18.5.2 transmitter figure 18-4 shows the structure of the sci transmitter. the baud rate clock source for the sci can be selected via the configuration bit, scibdsrc. source selection values are shown in figure 18-4 . 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 bit parity 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 237 figure 18-4. sci transmitter 18.5.2.1 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). dmate scte pen pty h876543210l 11-bit transmit stop start t8 dmate scte sctie tcie sbk tc parity generation msb sci data register load from scdr shift enable preamble all 1s break all 0s transmitter control logic shift register dmate tc sctie tcie scte transmitter cpu interrupt request transmitter dma service request m ensci loops te pe2/txd txinv internal bus 4 pre- scaler scp1 scp0 scr2 scr1 scr0 baud divider 16 sctie cgmxclk it12 a b sl x sl = 0 => x = a sl = 1 => x = b scibdsrc from config2 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 238 serial communications interface (sci) motorola 18.5.2.2 character transmission during an sci transmission, the transmit shift register shifts a character out to the pe2/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 by first reading sci 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 pe2/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. 18.5.2.3 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 239 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 these 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 18.5.2.4 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 pe2/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 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. toggle the te bit for a queued idle character when the scte bit becomes set and just before writing the next byte to the scdr. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 240 serial communications interface (sci) motorola 18.5.2.5 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 . 18.5.2.6 transmitter interrupts these 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. 18.5.3 receiver figure 18-5 shows the structure of the sci receiver. 18.5.3.1 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). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 241 18.5.3.2 character reception during an sci reception, the receive shift register shifts characters in from the pe1/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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 242 serial communications interface (sci) motorola figure 18-5. sci receiver block diagram all 1s all 0s m wake ilty pen pty bkf rpf h876543210l 11-bit receive shift register stop start data recovery dmare scrf or orie nf neie fe feie pe peie dmare scrie scrf ilie idle wakeup logic parity checking msb error cpu interrupt request dma service request cpu interrupt request sci data register r8 dmare orie neie feie peie scrie ilie rwu scrf idle or nf fe pe pe1/rxd internal bus pre- scaler baud divider 4 16 scp1 scp0 scr2 scr1 scr0 scrie dmare cgmxclk it12 a b sl x scibdsrc from sl = 0 => x = a sl = 1 => x = b config2 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 243 18.5.3.3 data sampling the receiver samples the pe1/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 18-6 ): 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. figure 18-6. receiver data sampling to verify the start bit and to detect noise, data recovery logic takes samples at rt3, rt5, and rt7. table 18-2 summarizes the results of the start bit verification samples. 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 pe1/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) technical data MC68HC908GR8A ? rev 0.0 244 serial communications interface (sci) motorola start bit verification is not successful if any two of the three verification samples are logic 1s. if start bit verification is not successful, the rt clock is reset and a new search for a start bit begins. to determine the value of a data bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 18-3 summarizes the results of the data bit samples. table 18-2. 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 table 18-3. 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 245 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 18-4 summarizes the results of the stop bit samples. 18.5.3.4 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. 18.5.3.5 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 table 18-4. 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) technical data MC68HC908GR8A ? rev 0.0 246 serial communications interface (sci) motorola 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. 18.5.3.6 slow data tolerance figure 18-7 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 18-7. slow data 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 18-7 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 9bit 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. msb stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock 154 147 ? 154 ------------------------- - 100 4.54% = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 247 with the misaligned character shown in figure 18-7 , 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 18.5.3.7 fast data tolerance figure 18-8 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 18-8. fast data 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 18-8 , 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 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 154 160 ? 154 ------------------------- - 100 3.90% = f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 248 serial communications interface (sci) motorola 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 18-8 , 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 18.5.3.8 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 pe1/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 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 pe1/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 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) functional description MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 249 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. 18.5.3.9 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 pe1/rxd pin. the idle line interrupt enable bit, ilie, in scc2 enables the idle bit to generate cpu interrupt requests. 18.5.3.10 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 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 250 serial communications interface (sci) motorola 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. 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 sci module remains active after the execution of a wait instruction. in wait mode, the sci module registers are not accessible by the cpu. 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. refer to low power modes for information on exiting wait mode. 18.6.2 stop mode the sci module is inactive after the execution of a stop instruction. the stop instruction does not affect sci register states. sci module operation resumes after an external interrupt. because the internal clock is inactive during stop mode, entering stop mode during an sci transmission or reception results in invalid data. refer to low power modes for information on exiting 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 . . . serial communications interface (sci) sci during break module interrupts MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 251 18.7 sci during break module 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) enables software to clear status bits during the break state. 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. 18.8 i/o signals port e shares two of its pins with the sci module. the two sci i/o pins are: pe2/txd ? transmit data pe1/rxd ? receive data 18.8.1 pe2/txd (transmit data) the pe2/txd pin is the serial data output from the sci transmitter. the sci shares the pe2/txd pin with port e. when the sci is enabled, the pe2/txd pin is an output regardless of the state of the ddre0 bit in 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 . . . serial communications interface (sci) technical data MC68HC908GR8A ? rev 0.0 252 serial communications interface (sci) motorola 18.8.2 pe1/rxd (receive data) the pe1/rxd pin is the serial data input to the sci receiver. the sci shares the pe1/rxd pin with port e. when the sci is enabled, the pe1/rxd pin is an input regardless of the state of the ddre1 bit in data direction register e (ddre). 18.9 i/o registers these 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) 18.9.1 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 controls idle character detection enables parity function controls parity type f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 253 loops ? loop mode select bit this read/write bit enables loop mode operation. in loop mode the pe1/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. m ? mode (character length) bit this read/write bit determines whether sci characters are eight or nine bits long. see table 18-5 . 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. address: $0013 bit 7654321bit 0 read: loops ensci txinv m wake ilty pen pty write: reset:00000000 figure 18-9. 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) technical data MC68HC908GR8A ? rev 0.0 254 serial communications interface (sci) motorola 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 pe1/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 18-5 . when enabled, the parity function inserts a parity bit in the most significant bit position. see figure 18-3 . reset clears the pen bit. 1 = parity function enabled 0 = parity function disabled pty ? parity bit this read/write bit determines whether the sci generates and checks for odd parity or even parity. see table 18-5 . reset clears the pty bit. 1 = odd parity 0 = even parity f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 255 note: changing the pty bit in the middle of a transmission or reception can generate a parity error. 18.9.2 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 enables the transmitter enables the receiver enables sci wakeup transmits sci break characters table 18-5. character format selection control bits character format m pen and pty start bits data bits parity stop bits character length 0 0x 1 8 none 1 10 bits 10x 19none111 bits 010 17even110 bits 0 11 1 7 odd 1 10 bits 110 18even111 bits 1 11 1 8 odd 1 11 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) technical data MC68HC908GR8A ? rev 0.0 256 serial communications interface (sci) motorola sctie ? sci transmit interrupt enable bit this read/write bit enables the scte bit to generate sci transmitter 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 scrie ? sci receive interrupt enable bit this read/write bit enables the scrf bit to generate sci receiver 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 pe2/txd pin. if software clears the te bit, the transmitter completes any transmission in progress before the pe2/txd returns to the idle address: $0014 bit 7654321bit 0 read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 figure 18-10. 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) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 257 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. 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) technical data MC68HC908GR8A ? rev 0.0 258 serial communications interface (sci) motorola 18.9.3 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 these 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 dmare dmate orie neie feie peie write: reset:uu000000 = unimplemented u = unaffected figure 18-11. 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 259 dmare ? dma receive enable bit caution: the dma module is not included on this mcu. writing a logic 1 to dmare or dmate may adversely affect mcu performance. 1 = dma not enabled to service sci receiver dma service requests generated by the scrf bit (sci receiver cpu interrupt requests enabled) 0 = dma not enabled to service sci receiver dma service requests generated by the scrf bit (sci receiver cpu interrupt requests enabled) dmate ? dma transfer enable bit caution: the dma module is not included on this mcu. writing a logic 1 to dmare or dmate may adversely affect mcu performance. 1 = scte dma service requests enabled; scte cpu interrupt requests disabled 0 = scte dma service requests disabled; scte cpu interrupt requests enabled 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 260 serial communications interface (sci) motorola peie ? receiver parity error interrupt enable bit this read/write bit enables sci receiver cpu interrupt requests generated by the parity error bit, pe. see sci status register 1 . reset clears peie. 1 = sci error cpu interrupt requests from pe bit enabled 0 = sci error cpu interrupt requests from pe bit disabled 18.9.4 sci status register 1 sci status register 1 (scs1) contains flags to signal these 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 address: $0016 bit 76 5 43 2 1bit 0 read: scte tc scrf idle or nf fe pe write: reset:11000000 = unimplemented figure 18-12. 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 261 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 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 automatically cleared 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, 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 receiver 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) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 262 serial communications interface (sci) motorola 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 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 18-13 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. nf ? receiver noise flag bit this clearable, read-only bit is set when the sci detects noise on the pe1/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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 263 figure 18-13. flag clearing sequence 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 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) technical data MC68HC908GR8A ? rev 0.0 264 serial communications interface (sci) motorola 18.9.5 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 pe1/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 pe1/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: bkf rpf write: reset:00000000 = unimplemented figure 18-14. 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 265 18.9.6 sci data register the sci data register (scdr) 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. 18.9.7 sci baud rate register the baud rate register (scbr) selects the baud rate for both the receiver and the transmitter. address: $0018 bit 7654321bit 0 read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset figure 18-15. sci data register (scdr) address: $0019 bit 7654321bit 0 read: scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented r = reserved figure 18-16. 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) technical data MC68HC908GR8A ? rev 0.0 266 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 18-6 . 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 18-7 . reset clears scr2?scr0. table 18-6. sci baud rate prescaling scp1 and scp0 prescaler divisor (pd) 00 1 01 3 10 4 11 13 table 18-7. sci baud rate selection scr2, scr1, and scr0 baud rate divisor (bd) 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial communications interface (sci) 267 use this formula to calculate the sci baud rate: where: f bus = bus frequency pd = prescaler divisor bd = baud rate divisor sci_bdsrc is an input to the sci. normally it will be tied off low at the top level to select the bus clock as the clock source. this makes the formula: table 18-8 shows the sci baud rates that can be generated with a 4.9152-mhz bus clock. baud rate f bus 64 pd bd ------------------------------------ = baud rate f bus 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) technical data MC68HC908GR8A ? rev 0.0 268 serial communications interface (sci) motorola table 18-8. sci baud rate selection examples scp1 and scp0 prescaler divisor (pd) scr2, scr1, and scr0 baud rate divisor (bd) baud rate (f bus = 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 269 serial communications interface (sci) motorola 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 table 18-8. sci baud rate selection examples scp1 and scp0 prescaler divisor (pd) scr2, scr1, and scr0 baud rate divisor (bd) baud rate (f bus = 4.9152 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 . . . serial communications interface (sci) technical data MC68HC908GR8A ? rev 0.0 270 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 271 technical data ? MC68HC908GR8A section 19. system integration module (sim) 19.1 contents 19.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .271 19.3 sim bus clock control and generation . . . . . . . . . . . . . . . . .275 19.4 reset and system initialization. . . . . . . . . . . . . . . . . . . . . . . .276 19.5 sim counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281 19.6 exception control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .282 19.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290 19.8 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 19.2 introduction this section describes the system integration module (sim). together with the cpu, the sim controls all mcu activities. a block diagram of the sim is shown in figure 19-1 . table 19-1 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 cop timeout interrupt control: ? acknowledge timing ? arbitration control 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) technical data MC68HC908GR8A ? rev 0.0 272 system integration module (sim) motorola ? vector address generation cpu enable/disable timing modular architecture expandable to 128 interrupt sources table 19-1 shows the internal signal names used in this section. figure 19-1. sim block diagram 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 lv i ( from lv i mod ule) 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 v dd internal pullup 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 . . . system integration module (sim) introduction MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 273 table 19-1. 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) technical data MC68HC908GR8A ? rev 0.0 274 system integration module (sim) motorola addr. register name bit 7 6 5 4 3 2 1 bit 0 $fe00 sim break status register (sbsr) read: rrrrrr sbsw r write: note reset:00000000 note: writing a logic 0 clears sbsw. $fe01 sim reset status register (srsr) read: por pin cop ilop ilad modrst lvi 0 write: por:10000000 $fe02 sim upper byte address register (subar) read: rrrrrrrr write: reset: $fe03 sim break flag control register (sbfcr) read: bcferrrrrrr write: reset: 0 $fe04 interrupt status register 1 (int1) read: if6 if5 if4 if3 if2 if1 0 0 write:rrrrrrrr reset:00000000 $fe05 interrupt status register 2 (int2) read: if14 if13 if12 if11 if10 if9 if8 if7 write:rrrrrrrr reset:00000000 $fe06 interrupt status register 3 (int3) read:000000if16if15 write:rrrrrrrr reset:00000000 = unimplemented figure 19-2. sim i/o 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 . . . system integration module (sim) sim bus clock control and generation MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 275 19.3 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 19-3 . this clock can come from either an external oscillator or from the on-chip pll. see clock generator module (cgmc) . figure 19-3. cgm clock signals 19.3.1 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 external interrupt (irq) . 2 bus clock generators sim sim counter simoscen oscillator (osc) osc2 osc1 phase-locked loop (pll) cgmxclk cgmrclk it12 cgmout to timtb15a, adc oscstopenb from config to rest of chip it23 to rest of 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) technical data MC68HC908GR8A ? rev 0.0 276 system integration module (sim) motorola 19.3.2 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 the 4096 cgmxclk cycle por timeout has completed. the rst pin is driven low by the sim during this entire period. the ibus clocks start upon completion of the timeout. 19.3.3 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 . in wait mode, the cpu clocks are inactive. the sim also produces two sets of clocks for other modules. 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. 19.4 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 277 an internal reset clears the sim counter (see sim counter ), but an external reset does not. each of the resets sets a corresponding bit in the sim reset status register (srsr). see sim registers . 19.4.1 external pin reset the rst pin circuit includes an internal pullup device. 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 19-2 for details. figure 19-4 shows the relative timing. figure 19-4. external reset timing 19.4.2 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 19-5 . an internal reset can be caused by an illegal address, illegal opcode, cop timeout, lvi, or por. see figure 19-6 . note: 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 table 19-2. pin bit set timing reset type number of cycles required to set pin por/lvi 4163 (4096 + 64 + 3) all others 67 (64 + 3) rst iab pc vect h vect l cgmout f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 278 system integration module (sim) motorola then follows the sequence from the falling edge of rst shown in figure 19-5 . figure 19-5. internal reset timing the cop reset is asynchronous to the bus clock. figure 19-6. sources of internal reset the active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the mcu. 19.4.2.1 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. sixty-four cgmxclk cycles later, the cpu and memories are released from reset to allow the reset vector sequence to occur. at power-on, these events occur: a por pulse is generated. irst rst rst pulled low by mcu iab 32 cycles 32 cycles vector high cgmxclk 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 MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 279 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. figure 19-7. por recovery 19.4.2.2 computer operating properly (cop) reset an input to the sim is reserved for the cop reset signal. the overflow of the cop counter causes an internal reset and sets the cop bit in the sim reset status register (srsr). the sim actively pulls down the rst pin for all internal reset sources. to prevent a cop module timeout, write any value to location $ffff. writing to location $ffff clears the cop counter and bits 12 through 4 of the sim counter. the sim counter output, which occurs at least every 2 13 ? 2 4 cgmxclk cycles, drives the cop counter. the cop should be serviced as soon as possible out of reset to guarantee the maximum amount of time before the first timeout. 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) technical data MC68HC908GR8A ? rev 0.0 280 system integration module (sim) motorola the cop module is disabled if the rst pin or the irq pin is held at v tst while the mcu is in monitor mode. the cop module can be disabled only through combinational logic conditioned with the high voltage signal on the rst or the irq pin. this prevents the cop from becoming disabled as a result of external noise. during a break state, v tst on the rst pin disables the cop module. 19.4.2.3 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 mask option register is logic 0, the sim treats the stop instruction as an illegal opcode and causes an illegal opcode reset. the sim actively pulls down the rst pin for all internal reset sources. 19.4.2.4 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 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. 19.4.2.5 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 lvi tripf voltage. the lvi bit in the sim reset status register (srsr) is set, and the external reset pin (rst ) is held low while the sim counter counts out 4096 cgmxclk cycles. sixty-four cgmxclk cycles later, the cpu is released from reset to allow the reset vector sequence to occur. the sim actively pulls down the rst pin for all internal reset sources. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 counter MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 281 19.4.2.6 monitor mode entry module reset (modrst) the monitor mode entry module reset (modrst) asserts its output to the sim when monitor mode is entered in the condition where the reset vectors are blank ($00). (see entering monitor mode .) when modrst gets asserted, an internal reset occurs. the sim actively pulls down the rst pin for all internal reset sources. 19.5 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 13 bits long and is clocked by the falling edge of cgmxclk. 19.5.1 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 is initialized, it enables the clock generation module (cgm) to drive the bus clock state machine. 19.5.2 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, break, or reset, the sim senses the state of the short stop recovery bit, ssrec, in the mask option register. if the ssrec bit is a logic 1, 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 startup times from stop mode. external crystal applications should use the full stop recovery time, that is, with ssrec cleared. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 282 system integration module (sim) motorola 19.5.3 sim counter and reset states external reset has no effect on the sim counter. (see stop mode for details.) the sim counter is free-running after all reset states. (see active resets from internal sources for counter control and internal reset recovery sequences.) 19.6 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 19.6.1 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 19-8 shows interrupt entry timing. figure 19-9 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 19-10 . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) exception control MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 283 figure 19-8 . interrupt entry timing figure 19-9. interrupt recovery timing 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 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) technical data MC68HC908GR8A ? rev 0.0 284 system integration module (sim) motorola figure 19-10. interrupt processing 19.6.1.1 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 no no no yes no no yes no yes yes as many interrupts i bit set? from reset break i bit set? irq0 interrupt? irq 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 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) exception control MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 285 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 19-11 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. figure 19-11 . interrupt recognition example 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 m6805 family, 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. 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) technical data MC68HC908GR8A ? rev 0.0 286 system integration module (sim) motorola 19.6.1.2 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. 19.6.1.3 interrupt status registers the flags in the interrupt status registers identify maskable interrupt sources. table 19-3 summarizes the interrupt sources and the interrupt status register flags that they set. the interrupt status registers can be useful for debugging. table 19-3. interrupt sources priority interrupt source interrupt status register flag highest 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) exception control MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 287 swi instruction ? irq pin i1 pll i2 tim1 channel 0 i3 tim1 channel 1 i4 tim1 overflow i5 tim2 channel 0 i6 reserved i7 tim2 overflow i8 spi receiver full i9 spi transmitter empty i10 sci receive error i11 sci receive i12 sci transmit i13 keyboard i14 adc conversion complete i15 lowest timebase module i16 table 19-3. interrupt sources priority interrupt source interrupt status register flag f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 288 system integration module (sim) motorola 19.6.1.4 interrupt status register 1 i6?i1 ? interrupt flags 1?6 these flags indicate the presence of interrupt requests from the sources shown in table 19-3 . 1 = interrupt request present 0 = no interrupt request present bit 0 and bit 1 ? always read 0 19.6.1.5 interrupt status register 2 i14?i7 ? interrupt flags 14?7 these flags indicate the presence of interrupt requests from the sources shown in table 19-3 . 1 = interrupt request present 0 = no interrupt request present address: $fe04 bit 7654321bit 0 read:i6i5i4i3i2i1 0 0 write:rrrrrrrr reset:00000000 r= reserved figure 19-12. interrupt status register 1 (int1) address: $fe05 bit 7654321bit 0 read: i14 i13 i12 i11 i10 i9 i8 i7 write:rrrrrrrr reset:00000000 r= reserved figure 19-13. interrupt status register 2 (int2) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) exception control MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 289 19.6.1.6 interrupt status register 3 bits 7?2 ? always read 0 i16?i15 ? interrupt flags 16?15 these flags indicate the presence of an interrupt request from the source shown in table 19-3 . 1 = interrupt request present 0 = no interrupt request present 19.6.2 reset all reset sources always have equal and highest priority and cannot be arbitrated. 19.6.3 break interrupts the break module can stop normal program flow at a software-programmable break point by asserting its break interrupt output. see timer interface module (tim) . 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. address: $fe06 bit 7654321bit 0 read:000000i16i15 write:rrrrrrrr reset:00000000 r= reserved figure 19-14. interrupt status register 3 (int3) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 290 system integration module (sim) motorola 19.6.4 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 2-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. 19.7 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 in the following subsections. both stop and wait clear the interrupt mask (i) in the condition code register, allowing interrupts to occur. 19.7.1 wait mode in wait mode, the cpu clocks are inactive while the peripheral clocks continue to run. figure 19-15 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. 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 291 wait mode. some modules can be programmed to be active in wait mode. wait mode also can be exited by a reset or break. a break interrupt during wait mode sets the sim break stop/wait bit, sbsw, in the sim break status register (sbsr). if the cop disable bit, copd, in the mask option register is logic 0, then the computer operating properly module (cop) is enabled and remains active in wait mode. figure 19-15. wait mode entry timing figure 19-16 and figure 19-17 show the timing for wait recovery. figure 19-16. 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, 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) technical data MC68HC908GR8A ? rev 0.0 292 system integration module (sim) motorola figure 19-17. wait recovery from internal reset 19.7.2 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 or break 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 mask option register (mor). 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. a break interrupt during stop mode sets the sim break stop/wait bit (sbsw) in the sim break status register (sbsr). 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 19-18 shows stop mode entry timing. note: to minimize stop current, all pins configured as inputs should be driven to a logic 1 or logic 0. 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 MC68HC908GR8A ? rev 0.0 technical data motorola system integration module (sim) 293 figure 19-18. stop mode entry timing figure 19-19. stop mode recovery from interrupt or break 19.8 sim registers the sim has three memory-mapped registers. table 19-4 shows the mapping of these 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 table 19-4. sim registers address register access mode $fe00 sbsr user $fe01 srsr user $fe03 sbfcr user f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 294 system integration module (sim) motorola 19.8.1 sim break status register the sim break status register (sbsr) contains a flag to indicate that a break caused an exit from stop mode or wait mode. sbsw ? sim break stop/wait this status bit is useful in applications requiring a return to wait or stop mode after exiting from a break interrupt. clear sbsw by writing a logic 0 to it. reset clears sbsw. 1 = stop mode or wait mode was exited by break interrupt. 0 = stop mode or wait mode was not exited by break interrupt. sbsw 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 0 to the sbsw bit clears it. address: $fe00 bit 7654321bit 0 read: rrrrrr sbsw r write: note (1) reset:00000000 r= reserved note: 1. writing a logic 0 clears sbsw. figure 19-20. 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 sbsw, do rti ; brclr sbsw,sbsr, return ; ; see if wait mode or stop mode was exited by break. tst lobyte,sp ;if returnlo is not zero, bne dolo ;then just decrement low 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 . . . system integration module (sim) technical data MC68HC908GR8A ? rev 0.0 295 system integration module (sim) motorola 19.8.2 sim reset status register this register contains six flags that show the source of the last reset provided all previous reset status bits have been cleared. clear the sim reset status register by 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 dec hibyte,sp ;else deal with high byte, too. dolo dec lobyte,sp ;point to wait/stop opcode. return pulh rti ;restore h register. address: $fe01 bit 7654321bit 0 read: por pin cop ilop ilad modrst lvi 0 write: reset:10000000 = unimplemented figure 19-21. 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) technical data MC68HC908GR8A ? rev 0.0 296 system integration module (sim) motorola 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 modrst ? monitor mode entry module reset bit 1 = last reset caused by monitor mode entry when vector locations $fffe and $ffff are $00 after por while irq = v dd 0 = por or read of srsr lvi ? low-voltage inhibit reset bit 1 = last reset caused by the lvi circuit 0 = por or read of srsr 19.8.3 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 r= reserved figure 19-22. 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 297 technical data ? MC68HC908GR8A section 20. serial peripheral interface (spi) 20.1 contents 20.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297 20.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298 20.4 pin name conventions and i/o register addresses . . . . . . .298 20.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299 20.6 transmission formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303 20.7 queuing transmission data . . . . . . . . . . . . . . . . . . . . . . . . . .309 20.8 error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .310 20.9 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 20.10 resetting the spi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .316 20.11 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317 20.12 spi during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .318 20.13 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .318 20.14 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .322 20.2 introduction this section describes the serial peripheral interface (spi) module, which allows full-duplex, synchronous, serial communications with peripheral devices. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 298 serial peripheral interface (spi) motorola 20.3 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: ? 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 i/o (input/output) port bit(s) software configurable with pullup device(s) if configured as input port bit(s) 20.4 pin name conventions and i/o register addresses the text that follows describes the spi. the spi i/o pin names are ss (slave select), spsck (spi serial clock), cgnd (clock ground), mosi (master out slave in), and miso (master in/slave out). the spi shares four i/o pins with four parallel i/o ports. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 299 the full names of the spi i/o pins are shown in table 20-1 . the generic pin names appear in the text that follows. 20.5 functional description figure 20-1 summarizes the spi i/o registers and figure 20-2 shows the structure of the spi module. table 20-1. pin name conventions spi generic pin names: miso mosi ss spsck cgnd full spi pin names: spi ptd1/atd9 ptd2/atd1 0 ptd0/at d8 ptd3/atd11 v ss addr. register name bit 7 6 5 4 3 2 1 bit 0 $0010 spi control register (spcr) read: sprie dmas spmstr cpol cpha spwom spe sptie write: reset:00101000 $0011 spi status and control register (spscr) read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:00001000 $0012 spi data register (spdr) read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset = unimplemented figure 20-1. spi i/o 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 . . . serial peripheral interface (spi) technical data MC68HC908GR8A ? rev 0.0 300 serial peripheral interface (spi) motorola figure 20-2. 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. if a port bit is configured for input, then an internal pullup device may be enabled for that port bit. see port d input pullup enable register . transmitter cpu interrupt request reserved receiver/error cpu interrupt request 76543210 spr1 spmstr transmit data register shift register spr0 cgmout 2 clock select 2 clock divider 8 32 128 clock logic cpha cpol spi sprie dmas spe spwom sprf spte ovrf reserved m s pin control logic receive data register sptie spe internal bus from sim 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) functional description MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 301 the following paragraphs describe the operation of the spi module. 20.5.1 master mode the spi operates in master mode when the spi master bit, spmstr, is set. note: configure the spi modules as master or 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 . only a master spi module can initiate transmissions. software begins the transmission from a master spi module by writing to the transmit data register. if the shift register is empty, the byte immediately transfers to the shift register, setting the spi transmitter empty bit, spte. the byte begins shifting out on the mosi pin under the control of the serial clock. see figure 20-3 . figure 20-3. 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) technical data MC68HC908GR8A ? rev 0.0 302 serial peripheral interface (spi) motorola the spr1 and spr0 bits control the baud rate generator and determine the speed of the shift register. see spi status and control register . through the spsck pin, the baud rate generator of the master also controls the shift register of the slave peripheral. 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, 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 with sprf set and then reading the spi data register. writing to the spi data register clears the spte bit. 20.5.2 slave mode the spi operates in slave mode when the spmstr bit 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 spi must be at logic 0. ss must remain low until the transmission is complete. see mode fault error . 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 transfers to the receive data register, and the sprf bit is set. to prevent an overflow condition, slave software then must read the receive data register before another full 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 303 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. data written to the slave shift register during 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 . note: spsck must be in the proper idle state before the slave is enabled to prevent spsck from appearing as a clock edge. 20.6 transmission formats during an spi transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). a serial clock synchronizes shifting and sampling on the two serial data lines. a slave select line allows selection of an individual 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 optionally be used to indicate multiple-master bus contention. 20.6.1 clock phase and polarity controls software can select any of four combinations of serial clock (spsck) 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 304 serial peripheral interface (spi) motorola the clock phase (cpha) control bit 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, disable the spi by clearing the spi enable bit (spe). 20.6.2 transmission format when cpha = 0 figure 20-4 shows an spi transmission in which cpha is logic 0. the figure should not be used as a replacement for data sheet parametric information. two waveforms are shown for spsck: 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 (spsck), 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 . 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 slave data transmission. the slave?s ss pin must be toggled back to high and then low again between each byte transmitted as shown in figure 20-5 . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 305 figure 20-4. transmission format (cpha = 0) figure 20-5. cpha/ss timing 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 transmit data register. therefore, the spi data register of the slave must be loaded with transmit data before the falling edge of ss . any data written after the falling edge is stored in the transmit data register and transferred to the shift register after the current transmission. 20.6.3 transmission format when cpha = 1 figure 20-6 shows an spi transmission in which cpha is logic 1. the figure should not be used as a replacement for data sheet parametric information. two waveforms are shown for spsck: 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 (spsck), master in/slave 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 12345678 spsck cycle # for reference spsck; cpol = 0 spsck; cpol =1 mosi from master miso from slave ss ; to slave capture strobe 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) technical data MC68HC908GR8A ? rev 0.0 306 serial peripheral interface (spi) motorola 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 . 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 20-6. 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 12345678 spsck cycle # for reference spsck; cpol = 0 spsck; 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 307 when cpha = 1 for a slave, the first edge of the spsck 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 transmit data register. therefore, the spi data register of the slave must be loaded with transmit data before the first edge of spsck. any data written after the first edge is stored in the transmit data register and transferred to the shift register after the current transmission. 20.6.4 transmission initiation latency when the spi is configured as a master (spmstr = 1), writing to the spdr starts a transmission. cpha has no effect on the delay to the start of the transmission, but it does affect the initial state of the spsck signal. when cpha = 0, the spsck signal remains inactive for the first half of the first spsck cycle. when cpha = 1, the first spsck cycle begins with an edge on the spsck 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 20-7 . the internal spi clock in the master is a free-running derivative of the internal mcu clock. to conserve power, it is enabled only when both the spe and spmstr bits are set. spsck edges occur halfway 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 occurs relative to the slower spsck. this uncertainty causes the variation in the initiation delay shown in figure 20-7 . this delay is no longer than a single spi bit time. that is, the maximum delay 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) technical data MC68HC908GR8A ? rev 0.0 308 serial peripheral interface (spi) motorola figure 20-7. transmission start delay (master) write to spdr initiation delay bus mosi spsck cpha = 1 spsck cpha = 0 spsck cycle number msb bit 6 12 clock write to spdr earliest latest spsck = internal clock 2; earliest latest 2 possible start points spsck = internal clock 8; 8 possible start points earliest latest spsck = internal clock 32; 32 possible start points earliest latest spsck = 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) queuing transmission data MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 309 20.7 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) indicates when the transmit data buffer is ready to accept new data. write to the transmit data register only when the spte bit is high. figure 20-8 shows the timing associated with doing back-to-back transmissions with the spi (spsck has cpha: cpol = 1:0). figure 20-8. .sprf/spte cpu interrupt timing the transmit data buffer allows back-to-back transmissions without the slave precisely timing its writes between transmissions as in a system with a single data buffer. also, if no new data is written to the data buffer, the last value contained in the shift register is the next data word to be transmitted. bit 3 mosi spsck spte write to spdr 1 cpu writes byte 2 to spdr, queueing byte 2 cpu writes byte 1 to spdr, clearing spte bit. byte 1 transfers from transmit data 3 1 2 2 3 5 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 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 and clearing spte bit. register to shift register, setting spte bit. register to receive data register, setting sprf bit. 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. cpha:cpol = 1:0 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 peripheral interface (spi) technical data MC68HC908GR8A ? rev 0.0 310 serial peripheral interface (spi) motorola for an idle master or idle slave that has no data loaded into its transmit buffer, the spte is set again no more than two bus cycles after 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. 20.8 error conditions the following flags signal spi error conditions: overflow (ovrf) ? failing to read the spi data register before the next full 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. ovrf is in the spi status and control register. mode fault error (modf) ? 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. 20.8.1 overflow error the overflow flag (ovrf) becomes set if the receive data register still has unread data from a previous transmission when the capture strobe of bit 1 of the next transmission occurs. the bit 1 capture strobe occurs in the middle of spsck cycle 7. (see figure 20-4 and figure 20-6 .) if an overflow occurs, all data received after the overflow and before the ovrf bit is cleared does not transfer to the receive data register and does not set the spi receiver full bit (sprf). the unread data that transferred to the receive data register before the overflow occurred can still be read. therefore, an overflow error always indicates the loss of data. clear the overflow flag by reading the spi status and control register and then reading the spi data register. ovrf generates a receiver/error cpu interrupt request if the error interrupt enable bit (errie) is also set. the sprf, modf, and ovrf f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 311 interrupts share the same cpu interrupt vector. see figure 20-11 . it is not possible to enable modf or ovrf individually to generate a receiver/error cpu interrupt request. however, leaving modfen low prevents modf from being set. if the cpu sprf interrupt is enabled and the ovrf interrupt is not, watch for an overflow condition. figure 20-9 shows how it is possible to miss an overflow. the first part of figure 20-9 shows how it is possible to read the spscr and spdr to clear the sprf without problems. however, as illustrated by the second transmission example, the ovrf bit can be set in between the time that spscr and spdr are read. figure 20-9. missed read of overflow condition in this case, an overflow can be missed easily. since no more sprf interrupts can be generated until this ovrf is serviced, it is not 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 following the read of the spdr. this ensures that the ovrf was not set before the sprf was cleared and that future transmissions can set the sprf bit. figure 20-10 illustrates this process. generally, to avoid this second spscr read, enable the ovrf to the cpu by setting the errie bit. read read 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 spscr 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 not cleared. byte 4 is lost. and ovrf bit clear. and ovrf bit clear. spscr 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 . . . serial peripheral interface (spi) technical data MC68HC908GR8A ? rev 0.0 312 serial peripheral interface (spi) motorola figure 20-10. clearing sprf when ovrf interrupt is not enabled 20.8.2 mode fault error setting the spmstr bit selects master mode and configures the spsck and mosi pins as outputs and the miso pin as an input. clearing spmstr selects slave mode and configures the spsck and mosi pins as inputs and the miso pin as an output. the mode fault bit, modf, becomes set any time the state of the slave select pin, ss , is inconsistent with the mode selected by spmstr. to prevent spi pin contention and damage to the mcu, a mode fault error occurs if: the ss pin of a slave spi goes high during a transmission the ss pin of a master spi goes low at any time for the modf flag to be set, the mode fault error enable bit (modfen) 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. read read 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. spscr 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 . . . serial peripheral interface (spi) error conditions MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 313 modf generates a receiver/error cpu interrupt request if the error interrupt enable bit (errie) is also set. the sprf, modf, and ovrf interrupts share the same cpu interrupt vector. see figure 20-11 . it is not possible to enable modf or ovrf individually to generate a receiver/error cpu interrupt request. however, leaving modfen low prevents modf from being set. 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 spi bits of the data direction register of the shared i/o port before enabling the spi. 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 goes back to its idle level following 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 following the shift of the last data bit. see transmission formats . note: setting the modf flag does not clear the spmstr bit. the spmstr bit has no function when spe = 0. reading spmstr when modf = 1 shows the difference between a modf occurring when the spi is a master and when it is a slave. when cpha = 0, a modf occurs if a slave is selected (ss is at logic 0) and later unselected (ss is at logic 1) even if no spsck is sent to that f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 314 serial peripheral interface (spi) motorola 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 unselected 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 bit does not clear the spe bit or reset the spi in any way. software can abort the spi transmission by clearing 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 it was already in the middle of a transmission. to clear the modf flag, read the spscr with the modf bit set and then write to the spcr register. this entire clearing mechanism must occur with no modf condition existing or else the flag is not cleared. 20.9 interrupts four spi status flags can be enabled to generate cpu interrupt requests. table 20-2. spi interrupts flag request spte transmitter empty spi transmitter cpu interrupt request (dmas = 0, sptie = 1, spe = 1) sprf receiver full spi receiver cpu interrupt request (dmas = 0, sprie = 1) ovrf overflow spi receiver/error interrupt request (errie = 1) modf mode fault spi receiver/error interrupt request (errie = 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) interrupts MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 315 reading the spi status and control register with sprf set and then reading the receive data register clears sprf. the clearing mechanism for the spte flag is always just a write to the transmit data register. the spi transmitter interrupt enable bit (sptie) enables the spte flag to generate transmitter cpu interrupt requests, provided that the spi is enabled (spe = 1). the spi receiver interrupt enable bit (sprie) enables the sprf bit to generate receiver cpu interrupt requests, regardless of the state of the spe bit. see figure 20-11 . the error interrupt enable bit (errie) enables both the modf and ovrf bits 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 bit is enabled by the errie bit to generate receiver/error cpu interrupt requests. figure 20-11. spi interrupt request generation spte sptie sprf sprie dmas errie modf ovrf spe cpu interrupt request cpu interrupt request not available spi transmitter not available spi receiver/error f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 316 serial peripheral interface (spi) motorola the following sources in the spi status and control register can generate cpu interrupt requests: 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 generates an spi receiver/error cpu interrupt request. 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 generates an spte cpu interrupt request. 20.10 resetting the spi any system reset completely resets the spi. partial resets occur 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. these 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 set all control bits again when spe is set back high for the next transmission. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 317 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 can also be disabled by a mode fault occurring in an spi that was configured as a master with the modfen bit set. 20.11 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 20.11.1 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 . 20.11.2 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 an external interrupt. if stop mode is exited by reset, any transfer in progress is aborted, and the spi is 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 . . . serial peripheral interface (spi) technical data MC68HC908GR8A ? rev 0.0 318 serial peripheral interface (spi) motorola 20.12 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) enables software to clear status bits during the break state. see system integration module (sim) . 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. since the spte bit cannot be cleared during a break with the bcfe bit cleared, a write to the transmit data register in break mode does not initiate a transmission nor is this data transferred into the shift register. therefore, a write to the spdr in break mode with the bcfe bit cleared has no effect. 20.13 i/o signals the spi module has five i/o pins and shares four of them with a parallel i/o port. they are: miso ? data received mosi ? data transmitted spsck ? serial clock ss ? slave select cgnd ? clock ground (internally connected to v ss ) the spi has limited inter-integrated circuit (i 2 c) capability (requiring software support) as a master in a single-master environment. 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 . . . serial peripheral interface (spi) i/o signals MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 319 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 . 20.13.1 miso (master in/slave out) miso is one of the two spi module pins that transmits 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. 20.13.2 mosi (master out/slave in) mosi is one of the two spi module pins that transmits 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 320 serial peripheral interface (spi) motorola 20.13.3 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. 20.13.4 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 between transmissions for the cpha = 1 format. see figure 20-12 . figure 20-12cpha/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 . 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 it was already in the middle of a transmission. 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 signals MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 321 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 . 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. the cpu can always read the state of the ss pin by configuring the appropriate pin as an input and reading the port data register. see table 20-3 . 20.13.5 cgnd (clock ground) cgnd is the ground return for the serial clock pin, spsck, and the ground for the port output buffers. it is internally connected to v ss as shown in table 20-1 . table 20-3. spi configuration spe spmstr modfen spi configuration state of ss logic 0 x (1) 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 note 1. 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) technical data MC68HC908GR8A ? rev 0.0 322 serial peripheral interface (spi) motorola 20.14 i/o registers three registers control and monitor spi operation: spi control register (spcr) spi status and control register (spscr) spi data register (spdr) 20.14.1 spi control register the spi control register: enables spi module 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 address: $0010 bit 7654321bit 0 read: sprie dmas spmstr cpol cpha spwom spe sptie write: reset:00101000 = unimplemented figure 20-13. 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 323 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 dmas ?dma select bit this read only bit has no effect on this version of the spi. this bit always reads as a 0. 0 = sprf dma and spte dma service requests disabled (sprf cpu and spte cpu interrupt requests enabled) 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 cpol ? clock polarity bit this read/write bit determines the logic state of the spsck pin between transmissions. (see figure 20-4 and figure 20-6 .) to transmit data between spi modules, the spi modules must have identical cpol values. 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 20-4 and figure 20-6 .) to transmit data between spi modules, the spi modules must have identical cpha values. when cpha = 0, the ss pin of the slave spi module must be set to logic 1 between bytes. see figure 20-12 . reset sets the cpha bit. 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 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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) technical data MC68HC908GR8A ? rev 0.0 324 serial peripheral interface (spi) motorola spe ? spi enable this read/write bit enables the spi module. clearing spe causes a partial reset of the spi. see resetting the spi . reset clears the spe bit. 1 = spi module enabled 0 = spi module disabled sptie? spi transmit interrupt enable 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 20.14.2 spi status and control register the spi status and control register contains flags to signal these 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 325 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. reset clears the sprf bit. 1 = receive data register full 0 = receive data register not full errie ? error interrupt enable bit this read/write bit enables the modf and ovrf bits 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 full 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 receive data register. reset clears the ovrf bit. 1 = overflow 0 = no overflow address: $0011 bit 7654321bit 0 read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:00001000 = unimplemented figure 20-14. 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) technical data MC68HC908GR8A ? rev 0.0 326 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 with the modfen bit set. in a master spi, the modf flag is set if the ss pin goes low at any time with the modfen bit set. clear the modf bit by reading the spi status and control register (spscr) with modf set and then writing to the spi control register (spcr). 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 or an spte dma service 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. during an spte cpu interrupt, the cpu clears the spte bit by writing to the transmit data register. 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) . 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 . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola serial peripheral interface (spi) 327 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 20-4 . 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) bd = baud rate divisor table 20-4. spi master baud rate selection spr1 and 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) technical data MC68HC908GR8A ? rev 0.0 328 serial peripheral interface (spi) motorola 20.14.3 spi data register the spi data register consists of the read-only receive data register and the write-only 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 registers that can contain different values. see figure 20-2 . r7?r0/t7?t0 ? receive/transmit data bits note: do not use read-modify-write instructions on the spi data register since the register read is not the same as the register written. address: $0012 bit 7654321bit 0 read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: indeterminate after reset figure 20-15. 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola timebase module (tbm) 329 technical data ? MC68HC908GR8A section 21. timebase module (tbm) 21.1 contents 21.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329 21.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329 21.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .330 21.5 timebase register description. . . . . . . . . . . . . . . . . . . . . . . .331 21.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .332 21.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333 21.2 introduction this section describes the timebase module (tbm). the tbm will generate periodic interrupts at user selectable rates using a counter clocked by the external crystal clock. this tbm version uses 15 divider stages, eight of which are user selectable. for further information regarding timers on m68hc08 family devices, please consult the hc08 timer reference manual, tim08rm/ad. 21.3 features features of the tbm module include: software programmable 1 hz, 4 hz, 16 hz, 256 hz, 512 hz, 1024 hz, 2048 hz, and 4096 hz periodic interrupt using external 32.768 khz crystal user selectable oscillator clock source enable during stop mode to allow periodic wakeup from stop f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timebase module (tbm) technical data MC68HC908GR8A ? rev 0.0 330 timebase module (tbm) motorola 21.4 functional description note: this module is designed for a 32.768 khz oscillator. this module can generate a periodic interrupt by dividing the crystal frequency, cgmxclk. the counter is initialized to all 0s when tbon bit is cleared. the counter, shown in figure 21-1 , starts counting when the tbon bit is set. when the counter overflows at the tap selected by tbr2:tbr0, the tbif bit gets set. if the tbie bit is set, an interrupt request is sent to the cpu. the tbif flag is cleared by writing a 1 to the tack bit. the first time the tbif flag is set after enabling the timebase module, the interrupt is generated at approximately half of the overflow period. subsequent events occur at the exact period. figure 21-1. timebase block diagram 2 2 2 2 2 2 2 2 2 2 2 2 2 2 128 32,768 8192 2048 cgmxclk sel 0 0 0 0 0 1 0 1 0 0 1 1 tbif tbr1 tbr0 tbie tbmint tbon 2 r tack tbr2 1 0 0 1 0 1 1 1 0 1 1 1 64 32 16 8 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timebase module (tbm) timebase register description MC68HC908GR8A ? rev 0.0 technical data motorola timebase module (tbm) 331 21.5 timebase register description the timebase has one register, the tbcr, which is used to enable the timebase interrupts and set the rate. tbif ? timebase interrupt flag this read-only flag bit is set when the timebase counter has rolled over. 1 = timebase interrupt pending 0 = timebase interrupt not pending tbr2:tbr0 ? timebase rate selection these read/write bits are used to select the rate of timebase interrupts as shown in table 21-1 . address: $001c bit 7654321bit 0 read: tbif tbr2 tbr1 tbr0 0 tbie tbon reserved write: tack reset:00000000 = unimplemented figure 21-2. timebase control register (tbcr) table 21-1. timebase rate selection for osc1 = 32.768 khz tbr2 tbr1 tbr0 divider timebase interrupt rate hz ms 0 0 0 32,768 1 1000 0 0 1 8192 4 250 0 1 0 2048 16 62.5 0 1 1 128 256 ~ 3.9 1 0 0 64 512 ~2 1 0 1 32 1024 ~1 1 1 0 16 2048 ~0.5 1 1 1 8 4096 ~0.24 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . timebase module (tbm) technical data MC68HC908GR8A ? rev 0.0 332 timebase module (tbm) motorola note: do not change tbr2?tbr0 bits while the timebase is enabled (tbon = 1). tack? timebase acknowledge the tack bit is a write-only bit and always reads as 0. writing a logic 1 to this bit clears tbif, the timebase interrupt flag bit. writing a logic 0 to this bit has no effect. 1 = clear timebase interrupt flag 0 = no effect tbie ? timebase interrupt enabled this read/write bit enables the timebase interrupt when the tbif bit becomes set. reset clears the tbie bit. 1 = timebase interrupt enabled 0 = timebase interrupt disabled tbon ? timebase enabled this read/write bit enables the timebase. timebase may be turned off to reduce power consumption when its function is not necessary. the counter can be initialized by clearing and then setting this bit. reset clears the tbon bit. 1 = timebase enabled 0 = timebase disabled and the counter initialized to 0s 21.6 interrupts the timebase module can interrupt the cpu on a regular basis with a rate defined by tbr2:tbr0. when the timebase counter chain rolls over, the tbif flag is set. if the tbie bit is set, enabling the timebase interrupt, the counter chain overflow will generate a cpu interrupt request. interrupts must be acknowledged by writing a logic 1 to the tack 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 . . . timebase module (tbm) low-power modes MC68HC908GR8A ? rev 0.0 technical data motorola timebase module (tbm) 333 21.7 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 21.7.1 wait mode the timebase module remains active after execution of the wait instruction. in wait mode, the timebase register is not accessible by the cpu. if the timebase functions are not required during wait mode, reduce the power consumption by stopping the timebase before enabling the wait instruction. 21.7.2 stop mode the timebase module may remain active after execution of the stop instruction if the oscillator has been enabled to operate during stop mode through the oscstopen bit in the config register. the timebase module can be used in this mode to generate a periodic wakeup from stop mode. if the oscillator has not been enabled to operate in stop mode, the timebase module will not be active during stop mode. in stop mode, the timebase register is not accessible by the cpu. if the timebase functions are not required during stop mode, reduce the power consumption by stopping the timebase before enabling the stop 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 . . . timebase module (tbm) technical data MC68HC908GR8A ? rev 0.0 334 timebase module (tbm) 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 335 technical data ? MC68HC908GR8A section 22. timer interface module (tim) 22.1 contents 22.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 22.3 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .336 22.4 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .336 22.5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337 22.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346 22.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347 22.8 tim during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .348 22.9 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .348 22.10 i/o registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .349 22.2 introduction this section describes the timer interface (tim) module. the tim on this part is a 2-channel and a1-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 tim. this particular mcu has two timer interface modules which are denoted as tim1 and tim2. 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 . . . timer interface module (tim) technical data MC68HC908GR8A ? rev 0.0 336 timer interface module (tim) motorola 22.3 features features of the tim include: three 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 tim clock input with 7-frequency internal bus clock prescaler selection free-running or modulo up-count operation toggle any channel pin on overflow tim counter stop and reset bits i/o port bit(s) software configurable with pullup device(s) if configured as input port bit(s) 22.4 pin name conventions the text that follows describes both timers, tim1 and tim2. the tim input/output (i/o) pin names are t[1,2]ch0 (timer 1 channel 0, timer 2 channel 0) and t[1]ch1 (timer channel 1), where ?1? is used to indicate tim1 and ?2? is used to indicate tim2. the two tims share three i/o pins with three port d i/o port pins. the full names of the tim i/o pins are listed in table 22-1 . the generic pin names appear in the text that follows. table 22-1. pin name conventions tim generic pin names: t[1,2]ch0 t[1,2]ch1 full tim pin names: tim1 ptd4/atd12/tblck ptd5/t1ch1 tim2 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 (tim) functional description MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 337 note: references to either timer 1 or timer 2 may be made in the following text by omitting the timer number. for example, tch0 may refer generically to t1ch0 and t2ch0, and tch1 will refer to t1ch1. note: the timer interface module in MC68HC908GR8A is constructed by tim1 which is contained channel 0 and 1, and tim2 which is contained channel 0 only. 22.5 functional description note: references to tclk and external tim clock input are only valid if the mcu has an external tclk pin. if the mcu has no external tclk pin, the tim module must use the internal bus clock prescaler selections. figure 22-1 shows the structure of the tim. the central component of the tim is the 16-bit tim counter that can operate as a free-running counter or a modulo up-counter. the tim counter provides the timing reference for the input capture and output compare functions. the tim counter modulo registers, tmodh:tmodl, control the modulo value of the tim counter. software can read the tim counter value at any time without affecting the counting sequence. the tim channels (per timer) are programmable independently as input capture or output compare channels. if a channel is configured as input capture, then an internal pullup device may be enabled for that channel. see port d input pullup 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 . . . timer interface module (tim) technical data MC68HC908GR8A ? rev 0.0 338 timer interface module (tim) motorola figure 22-1. tim block diagram note: references to either timer 1 or timer 2 may be made in the following text by omitting the timer number. for example, tsc may generically refer to both t1sc and t2sc. note: in figure 22-1 , channel1 will only be available in tim1 while channel 0 will be available in both tim1 and tim2 prescaler prescaler select internal 16-bit comparator ps2 ps1 ps0 16-bit comparator 16-bit latch tch0h:tch0l ms0a els0b els0a port tof toie inter- 16-bit comparator 16-bit latch tch1h:tch1l channel 0 channel 1 tmodh:tmodl trst tstop tov0 ch0ie ch0f els1b els1a tov1 ch1ie ch1max ch1f ch0max ms0b 16-bit counter internal bus bus clock ms1a logic rupt logic inter- rupt logic port logic inter- rupt logic internal tclk t[1,2]ch0 t[1]ch1 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) functional description MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 339 figure 22-2 summarizes the timer registers. addr. register name bit 7 6 5 4 3 2 1 bit 0 $0020 timer 1 status and control register (t1sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 $0021 timer 1 counter register high (t1cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $0022 timer 1 counter register low (t1cntl) read: bit 7 6 5 4 3 2 1 bit 0 write: reset:00000000 $0023 timer 1 counter modulo register high (t1modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 $0024 timer 1 counter modulo register low (t1modl) read: bit 7654321bit 0 write: reset:11111111 $0025 timer 1 channel 0 status and control register (t1sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 $0026 timer 1 channel 0 register high (t1ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0027 timer 1 channel 0 register low (t1ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0028 timer 1 channel 1 status and control register (t1sc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset:00000000 $0029 timer 1 channel 1 register high (t1ch1h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $002a timer 1 channel 1 register low (t1ch1l) read: bit 7654321bit 0 write: reset: indeterminate after reset $002b timer 2 status and control register (t2sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 $002c timer 2 counter register high (t2cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 = unimplemented figure 22-2. tim i/o register summary (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 . . . timer interface module (tim) technical data MC68HC908GR8A ? rev 0.0 340 timer interface module (tim) motorola 22.5.1 tim counter prescaler the tim clock source can be one of the seven prescaler outputs or the tim clock pin, tclk. the prescaler generates seven clock rates from the internal bus clock. the prescaler select bits, ps[2:0], in the tim status and control register select the tim clock source. $002d timer 2 counter register low (t2cntl) read: bit 7 6 5 4 3 2 1 bit 0 write: reset:00000000 $002e timer 2 counter modulo register high (t2modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 $002f timer 2 counter modulo register low (t2modl) read: bit 7654321bit 0 write: reset:11111111 $0030 timer 2 channel 0 status and control register (t2sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 $0031 timer 2 channel 0 register high (t2ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0032 timer 2 channel 0 register low (t2ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0033 unimplemented read: write: reset:00000000 $0034 unimplemented read: write: reset: indeterminate after reset $0035 unimplemented read: write: reset: indeterminate after reset addr. register name bit 7 6 5 4 3 2 1 bit 0 = unimplemented figure 22-2. tim i/o register summary (sheet 2 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 . . . timer interface module (tim) functional description MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 341 22.5.2 input capture with the input capture function, the tim can capture the time at which an external event occurs. when an active edge occurs on the pin of an input capture channel, the tim latches the contents of the tim counter into the tim channel registers, tchxh:tchxl. the polarity of the active edge is programmable. input captures can generate tim cpu interrupt requests. 22.5.3 output compare with the output compare function, the tim 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 tim can set, clear, or toggle the channel pin. output compares can generate tim cpu interrupt requests. 22.5.4 unbuffered output compare any output compare channel can generate unbuffered output compare pulses as described in output compare . the pulses are unbuffered because changing the output compare value requires writing the new value over the old value currently in the tim channel registers. an unsynchronized write to the tim 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 tim overflow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. the tim 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: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) technical data MC68HC908GR8A ? rev 0.0 342 timer interface module (tim) motorola 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 tim overflow interrupts and write the new value in the tim overflow interrupt routine. the tim 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. 22.5.5 buffered output compare channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the tch0 pin. the tim channel registers of the linked pair alternately control the output. setting the ms0b bit in tim channel 0 status and control register (tsc0) links channel 0 and channel 1. the output compare value in the tim channel 0 registers initially controls the output on the tch0 pin. writing to the tim channel 1 registers enables the tim channel 1 registers to synchronously control the output after the tim overflows. at each subsequent overflow, the tim channel registers (0 or 1) that control the output are the ones written to last. tsc0 controls and monitors the buffered output compare function, and tim channel 1 status and control register (tsc1) is unused. while the ms0b bit is set, the channel 1 pin, tch1, 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) functional description MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 343 22.5.6 pulse width modulation (pwm) by using the toggle-on-overflow feature with an output compare channel, the tim can generate a pwm signal. the value in the tim counter modulo registers determines the period of the pwm signal. the channel pin toggles when the counter reaches the value in the tim 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 tim channel registers determines the pulse width of the pwm signal. the time between overflow and output compare is the pulse width. program the tim to clear the channel pin on output compare if the state of the pwm pulse is logic 1. program the tim to set the pin if the state of the pwm pulse is logic 0. the value in the tim 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 tim counter modulo registers produces a pwm period of 256 times the internal bus clock period if the prescaler select value is $000. see tim status and control register . figure 22-3. pwm period and pulse width the value in the tim channel registers determines the pulse width of the pwm output. the pulse width of an 8-bit pwm signal is variable in 256 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 (tim) technical data MC68HC908GR8A ? rev 0.0 344 timer interface module (tim) motorola increments. writing $0080 (128) to the tim channel registers produces a duty cycle of 128/256 or 50%. 22.5.7 unbuffered pwm signal generation any output compare channel can generate unbuffered pwm pulses as described in pulse width modulation (pwm) . the pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the old value currently in the tim channel registers. an unsynchronized write to the tim 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 tim overflow interrupt routine to write a new, smaller pulse width value may cause the compare to be missed. the tim may pass the new value before it is written. 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 tim overflow interrupts and write the new value in the tim overflow interrupt routine. the tim 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) functional description MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 345 22.5.8 buffered pwm signal generation channels 0 and 1 can be linked to form a buffered pwm channel whose output appears on the tch0 pin. the tim channel registers of the linked pair alternately control the pulse width of the output. setting the ms0b bit in tim channel 0 status and control register (tsc0) links channel 0 and channel 1. the tim channel 0 registers initially control the pulse width on the tch0 pin. writing to the tim channel 1 registers enables the tim channel 1 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tim channel registers (0 or 1) that control the pulse width are the ones written to last. tsc0 controls and monitors the buffered pwm function, and tim channel 1 status and control register (tsc1) is unused. while the ms0b bit is set, the channel 1 pin, tch1, 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. 22.5.9 pwm initialization to ensure correct operation when generating unbuffered or buffered pwm signals, use the following initialization procedure: 1. in the tim status and control register (tsc): a. stop the tim counter by setting the tim stop bit, tstop. b. reset the tim counter and prescaler by setting the tim reset bit, trst. 2. in the tim counter modulo registers (tmodh:tmodl), write the value for the required pwm period. 3. in the tim channel x registers (tchxh:tchxl), write the value for the required pulse width. 4. in tim channel x status and control register (tscx): f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) technical data MC68HC908GR8A ? rev 0.0 346 timer interface module (tim) motorola 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 22-3 . 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 22-3 .) 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 tim status control register (tsc), clear the tim stop bit, tstop. setting ms0b links channels 0 and 1 and configures them for buffered pwm operation. the tim channel 0 registers (tch0h:tch0l) initially control the buffered pwm output. tim status control register 0 (tscr0) controls and monitors the pwm signal from the linked channels. clearing the toggle-on-overflow bit, tovx, inhibits output toggles on tim 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 tim channel status and control registers .) 22.6 interrupts the following tim sources can generate 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 . . . timer interface module (tim) low-power modes MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 347 tim overflow flag (tof) ? the tof bit is set when the tim counter value reaches the modulo value programmed in the tim counter modulo registers. the tim overflow interrupt enable bit, toie, enables tim overflow cpu interrupt requests. tof and toie are in the tim status and control register. tim channel flags (ch1f:ch0f) ? the chxf bit is set when an input capture or output compare occurs on channel x. channel x tim cpu interrupt requests and tim dma service requests are controlled by the channel x interrupt enable bit, chxie. channel x tim cpu interrupt requests are enabled when chxie = 1. chxf and chxie are in the tim channel x status and control register. dmaxs is in the tim dma select register. 22.7 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 22.7.1 wait mode the tim remains active after the execution of a wait instruction. in wait mode, the tim registers are not accessible by the cpu. any enabled cpu interrupt request from the tim can bring the mcu out of wait mode. if tim functions are not required during wait mode, reduce power consumption by stopping the tim before executing the wait instruction. 22.7.2 stop mode the tim is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions or the state of the tim counter. tim 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 . . . timer interface module (tim) technical data MC68HC908GR8A ? rev 0.0 348 timer interface module (tim) motorola 22.8 tim during break interrupts a break interrupt stops the tim 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 . 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. 22.9 i/o signals port d shares three of its pins with the tim. (there is an optional tclk which can be used as an external clock input to the tim prescaler, but is not available on this mcu.) the three tim channel i/o pins are t1ch0, t1ch1 and t2ch0 as described in pin name conventions . each channel i/o pin is programmable independently as an input capture pin or an output compare pin. t1ch0 and t2ch0 can be configured as buffered output compare or buffered pwm 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 . . . timer interface module (tim) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 349 22.10 i/o registers note: references to either timer 1 or timer 2 may be made in the following text by omitting the timer number. for example, tsc may generically refer to both t1sc and t2sc. these i/o registers control and monitor operation of the tim: tim status and control register (tsc) tim control registers (tcnth:tcntl) tim counter modulo registers (tmodh:tmodl) tim channel status and control registers (tsc0, tsc1) tim channel registers (tch0h:tch0l, tch1h:tch1l) 22.10.1 tim status and control register the tim status and control register (tsc): enables tim overflow interrupts flags tim overflows stops the tim counter resets the tim counter prescales the tim counter clock address: t1sc, $0020 and t2sc, $002b bit 7654321bit 0 read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 = unimplemented figure 22-4. tim status and control register (tsc) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) technical data MC68HC908GR8A ? rev 0.0 350 timer interface module (tim) motorola tof ? tim overflow flag bit this read/write flag is set when the tim counter reaches the modulo value programmed in the tim counter modulo registers. clear tof by reading the tim status and control register when tof is set and then writing a logic 0 to tof. if another tim 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 = tim counter has reached modulo value 0 = tim counter has not reached modulo value toie ? tim overflow interrupt enable bit this read/write bit enables tim overflow interrupts when the tof bit becomes set. reset clears the toie bit. 1 = tim overflow interrupts enabled 0 = tim overflow interrupts disabled tstop ? tim stop bit this read/write bit stops the tim counter. counting resumes when tstop is cleared. reset sets the tstop bit, stopping the tim counter until software clears the tstop bit. 1 = tim counter stopped 0 = tim counter active note: do not set the tstop bit before entering wait mode if the tim is required to exit wait mode. trst ? tim reset bit setting this write-only bit resets the tim counter and the tim prescaler. setting trst has no effect on any other registers. counting resumes from $0000. trst is cleared automatically after the tim counter is reset and always reads as logic 0. reset clears the trst bit. 1 = prescaler and tim counter cleared 0 = no effect note: setting the tstop and trst bits simultaneously stops the tim 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 (tim) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 351 ps2?ps0 ? prescaler select bits these read/write bits select either the tclk pin or one of the seven prescaler outputs as the input to the tim counter as table 22-2 shows. reset clears the ps[2:0] bits. table 22-2. prescaler selection ps2?ps0 tim 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 not 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 . . . timer interface module (tim) technical data MC68HC908GR8A ? rev 0.0 352 timer interface module (tim) motorola 22.10.2 tim counter registers the two read-only tim counter registers contain the high and low bytes of the value in the tim counter. reading the high byte (tcnth) latches the contents of the low byte (tcntl) into a buffer. subsequent reads of tcnth do not affect the latched tcntl value until tcntl is read. reset clears the tim counter registers. setting the tim reset bit (trst) also clears the tim counter registers. note: if you read tcnth during a break interrupt, be sure to unlatch tcntl by reading tcntl before exiting the break interrupt. otherwise, tcntl retains the value latched during the break. address: t1cnth, $0021 and t2cnth, $002c bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 = unimplemented figure 22-5. tim counter registers high (tcnth) address: t1cntl, $0022 and t2cntl, $002d bit 7654321bit 0 read: bit 7 6 5 4 3 2 1 bit 0 write: reset:00000000 = unimplemented figure 22-6. tim counter registers low (tcntl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 353 22.10.3 tim counter modulo registers the read/write tim modulo registers contain the modulo value for the tim counter. when the tim counter reaches the modulo value, the overflow flag (tof) becomes set, and the tim counter resumes counting from $0000 at the next timer clock. writing to the high byte (tmodh) inhibits the tof bit and overflow interrupts until the low byte (tmodl) is written. reset sets the tim counter modulo registers. note: reset the tim counter before writing to the tim counter modulo registers. address: t1modh, $0023 and t2modh, $002e bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 = unimplemented figure 22-7. tim counter modulo register high (tmodh) address: t1modl, $0024 and t2modl, $002f bit 7654321bit 0 read: bit 7 6 5 4 3 2 1 bit 0 write: reset:11111111 = unimplemented figure 22-8. tim counter modulo register low (tmodl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) technical data MC68HC908GR8A ? rev 0.0 354 timer interface module (tim) motorola 22.10.4 tim counter registers the two read-only tim counter registers contain the high and low bytes of the value in the tim counter. reading the high byte (tcnth) latches the contents of the low byte (tcntl) into a buffer. subsequent reads of tcnth do not affect the latched tcntl value until tcntl is read. reset clears the tim counter registers. setting the tim reset bit (trst) also clears the tim counter registers. note: if you read tcnth during a break interrupt, be sure to unlatch tcntl by reading tcntl before exiting the break interrupt. otherwise, tcntl retains the value latched during the break. address: t1cnth, $0021 and t2cnth, $002c bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 = unimplemented figure 22-9. tim counter register high (tcnth) address: t1cntl, $0022 and t2cntl, $002d bit 7654321bit 0 read: bit 7 6 5 4 3 2 1 bit 0 write: reset:00000000 = unimplemented figure 22-10. tim counter register low (tcntl) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 355 22.10.5 tim channel status and control registers each of the tim 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 tim overflow selects 0% and 100% pwm duty cycle selects buffered or unbuffered output compare/pwm operation address: t1sc0, $0025 and t2sc0, $0030 bit 7654321bit 0 read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 figure 22-11. tim channel 0 status and control register (tsc0) address: t1sc1, $0028 bit 7654321bit 0 read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset:00000000 figure 22-12. tim channel 1 status and control register (tsc1) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 (tim) technical data MC68HC908GR8A ? rev 0.0 356 timer interface module (tim) 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 tim counter registers matches the value in the tim channel x registers. when tim cpu interrupt requests are enabled (chxie = 1), clear chxf by reading tim 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 tim cpu interrupt service requests on channel x. reset clears the chxie bit. 1 = channel x cpu interrupt service requests enabled 0 = channel x cpu interrupt service requests disabled msxb ? mode select bit b this read/write bit selects buffered output compare/pwm operation. msxb exists only in the tim1 channel 0 and tim2 channel 0 status and control registers. setting ms0b disables the channel 1 status and control register and reverts tch1 to general-purpose i/o. reset clears the msxb bit. 1 = buffered output compare/pwm operation enabled 0 = buffered output compare/pwm operation disabled 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 22-3 . 1 = unbuffered output compare/pwm 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 . . . timer interface module (tim) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 357 0 = input capture operation when elsxb:a = 00, this read/write bit selects the initial output level of the tchx pin. see table 22-3 . 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 tim status and control register (tsc). 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 d, and pin ptdx/tchx is available as a general-purpose i/o pin. table 22-3 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 (tim) technical data MC68HC908GR8A ? rev 0.0 358 timer interface module (tim) motorola note: before enabling a tim channel register for input capture operation, make sure that the ptd/tchx 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 tim 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 tim counter overflow. 0 = channel x pin does not toggle on tim counter overflow. note: when tovx is set, a tim counter overflow takes precedence over a channel x output compare if both occur at the same time. table 22-3. mode, edge, and level selection msxb:msxa elsxb:elsxa mode configuration x0 00 output preset pin under port control; initial output level high x1 00 pin under port control; initial 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 (tim) i/o registers MC68HC908GR8A ? rev 0.0 technical data motorola timer interface module (tim) 359 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 . chxmax latency 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 22-13. chxmax latency 22.10.6 tim channel registers these read/write registers contain the captured tim counter value of the input capture function or the output compare value of the output compare function. the state of the tim channel registers after reset is unknown. in input capture mode (msxb:msxa = 0:0), reading the high byte of the tim channel x registers (tchxh) inhibits input captures until the low byte (tchxl) is read. in output compare mode (msxb:msxa 0:0), writing to the high byte of the tim channel x registers (tchxh) inhibits output compares until the low byte (tchxl) 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 (tim) technical data MC68HC908GR8A ? rev 0.0 360 timer interface module (tim) motorola address: t1ch0h, $0026 and t2ch0h, $0031 bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset figure 22-14. tim channel 0 register high (tch0h) address: t1ch0l, $0027 and t2ch0l $0032 bit 7654321bit 0 read: bit 7654321bit 0 write: reset: indeterminate after reset figure 22-15. tim channel 0 register low (tch0l) address: t1ch1h, $0029 bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset figure 22-16. tim channel 1 register high (tch1h) address: t1ch1l, $002a bit 7654321bit 0 read: bit 7654321bit 0 write: reset: indeterminate after reset figure 22-17. tim channel 1 register low (tch1l) f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 361 technical data ? MC68HC908GR8A section 23. electrical specifications 23.1 contents 23.2 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . .362 23.3 functional operating range. . . . . . . . . . . . . . . . . . . . . . . . . .363 23.4 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363 23.5 5.0 v dc electrical characteristics. . . . . . . . . . . . . . . . . . . . .364 23.6 3.0 v dc electrical characteristics. . . . . . . . . . . . . . . . . . . . .366 23.7 5.0 v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368 23.8 3.0 v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 23.9 output high-voltage characteristics . . . . . . . . . . . . . . . . . . .370 23.10 output low-voltage characteristics . . . . . . . . . . . . . . . . . . . .373 23.11 typical supply currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . .376 23.12 adc characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .378 23.13 5.0 v spi characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .379 23.14 3.0 v spi characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .380 23.15 timer interface module characteristics . . . . . . . . . . . . . . . . .383 23.16 clock generation module characteristics . . . . . . . . . . . . . . .383 23.17 memory characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 362 electrical specifications motorola 23.2 absolute 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 beyond the maximum ratings. refer to 5.0 v dc electrical characteristics 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 (v in or v out ) v dd . reliability of operation is enhanced if unused inputs are connected to an appropriate logic voltage level (for example, either v ss or v dd ). table 23-1. absolute maximum ratings characteristic (1) 1. voltages referenced to v ss symbol value unit supply voltage v dd ?0.3 to + 5.5 v input voltage v in v ss ? 0.3 to v dd + 0.3 v maximum current per pin excluding v dd , v ss , and ptc0?ptc1 i 15 ma maximum current for pins ptc0?ptc1 i ptc0?ptc1 25 ma maximum current into v dd i mvdd 150 ma maximum current out of v ss i mvss 150 ma storage temperature t stg ?55 to +150 c note: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications functional operating range MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 363 23.3 functional operating range note: to ensure correct operation of the mcu under all operating conditions, the user must write data $1c to address $0033 immediately after reset. this is to ensure proper termination of an unused module within the mcu. 23.4 thermal characteristics table 23-2. functional operation range characteristic symbol value unit operating temperature range t a ?40 to +125 c operating voltage range v dd 3.0 10% 5.0 10% v table 23-3. thermal characteristics characteristic symbol value unit thermal resistance pdip (28-pin) soic (28-pin) qfp (32-pin) ja 60 60 95 c/w i/o pin power dissipation p i/o user-determined w power dissipation (1) 1. power dissipation is a function of temperature. p d p d = (i dd v dd ) + p i/o = k/(t j + 273 c) w constant (2) 2. k is a constant unique to the device. k can be determined for 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 . k p d x (t a + 273 c ) + p d 2 ja w/ c average junction temperature t j t a + (p d ja ) c maximum junction temperature t jm 140 c notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 364 electrical specifications motorola 23.5 5.0 v dc electrical characteristics table 23-4. 5.0v dc electrical characteristics characteristic (1) symbol min typ (2) max unit output high voltage (i load = ?2.0 ma) all i/o pins (i load = ?10.0 ma) all i/o pins (i load = ?10.0 ma) pins ptc0?ptc1 only maximum combined i oh for port c, port e, port ptd0?ptd3 maximum combined i oh for port ptd4?ptd6, port a, port b maximum total i oh for all port pins v oh v oh v oh i oh1 i oh2 i oht v dd ? 0.8 v dd ? 1.5 v dd ? 0.8 ? ? ? ? ? ? ? ? ? ? ? ? 50 50 100 v v v ma ma ma output low voltage (i load = 1.6 ma) all i/o pins (i load = 10 ma) all i/o pins (i load = 15 ma) pins ptc0?ptc1 only maximum combined i ol for port c, port e, port ptd0?ptd3 maximum combined i ol for port ptd4?ptd6, port a, port b maximum total i ol for all port pins v ol v ol v ol i ol1 i ol2 i olt ? ? ? ? ? ? ? ? ? ? ? ? 0.4 1.5 1.0 50 50 100 v v v ma ma ma input high voltage all ports, irqs, reset osc1 v ih 0.7 x v dd 0.8 x v dd ? v dd v input low voltage all ports, irqs, reset, osc1 v il v ss ? 0.2 x v dd v v dd supply current run (3) wait (4) i dd ? ? 15 4 20 8 ma ma stop (5) (<85 c) stop (>85 c) stop with tbm enabled (6) stop with lvi and tbm enabled (6) i dd ? ? ? ? 3 5 20 300 5 10 35 500 a a a a i/o ports hi-z leakage current (7) i il ?? 10 a input current i in ?? 1 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 specifications 5.0 v dc electrical characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 365 pullup resistors (as input only) ports pta3/kbd3 ?pta0/kbd0 , ptc1?ptc0, ptd6/t2ch0?ptd0/ss r pu 20 45 65 k ? capacitance ports (as input or output) c out c in ? ? ? ? 12 8 pf monitor mode entry voltage v tst v dd +2.5 ?8v low-voltage inhibit, trip falling voltage ? target v tripf 3.85 4.25 4.50 v low-voltage inhibit, trip rising voltage ? target v tripr 3.95 4.35 4.60 v low-voltage inhibit reset/recover hysteresis ? target (v tripf + v hys = v tripr ) v hys ? 100 ? mv por rearm voltage (8) v por 0 ? 100 mv por reset voltage (9) v porrst 0 700 800 mv por rise time ramp rate (10) r por 0.035 ? ? v/ms notes: 1. v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted 2. typical values reflect average measurements at midpoint of voltage range, 25 c only. 3. run (operating) i dd measured using external square wave clock source (f osc = 32.8 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. 4. wait i dd measured using external square wave clock source (f osc = 32.8 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 wait i dd . measured with pll and lvi enabled. 5. stop i dd is measured with osc1 = v ss . 6. stop i dd with tbm enabled is measured using an external square wave clock source (f osc = 32.8 mhz). all inputs 0.2 v from rail. no dc loads. less than 100 pf on all outputs. all inputs configured as inputs. 7. pullups and pulldowns are disabled. port b leakage is specified in adc characteristics . 8. maximum is highest voltage that por is guaranteed. 9. maximum is highest voltage that por is possible. 10. 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. table 23-4. 5.0v dc electrical characteristics characteristic (1) symbol min typ (2) 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 specifications technical data MC68HC908GR8A ? rev 0.0 366 electrical specifications motorola 23.6 3.0 v dc electrical characteristics table 23-5. 3.0 v dc electrical characteristics characteristic (1) symbol min typ (2) max unit output high voltage (i load = ?0.6 ma) all i/o pins (i load = ?4.0 ma) all i/o pins (i load = ?4.0 ma) pins ptc0?ptc1 only maximum combined i oh for port c, port e, port ptd0?ptd3 maximum combined i oh for port ptd4?ptd6, port a, port b maximum total i oh for all port pins v oh v oh v oh i oh1 i oh2 i oht v dd ? 0.3 v dd ? 1.0 v dd ? 0.5 ? ? ? ? ? ? ? ? ? ? ? ? 30 30 60 v v v ma ma ma output low voltage (i load = 0.5 ma) all i/o pins (i load = 6.0 ma) all i/o pins (i load = 10.0 ma) pins ptc0?ptc1 only maximum combined i ol for port c, port e, port ptd0?ptd3 maximum combined i ol for port ptd4?ptd6, port a, port b maximum total i ol for all port pins v ol v ol v ol i ol1 i ol2 i olt ? ? ? ? ? ? ? ? ? ? ? ? 0.3 1.0 0.8 30 30 60 v v v ma ma ma input high voltage all ports, irqs, reset osc1 v ih 0.7 x v dd 0.8 x v dd ? v dd v input low voltage all ports, irqs, reset osc1 v il v ss ? 0.3 x v dd 0.2 x v dd v v dd supply current run (3) wait (4) i dd ? ? 4.5 1.65 8 4 ma ma stop (5) (<85 c) stop (>85 c) stop with tbm enabled (6) stop with lvi and tbm enabled (6) i dd ? ? ? ? 1 3 12 200 3 6 20 300 a a a a i/o ports hi-z leakage current (7) i il ?? 10 a input current i in ?? 1 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 specifications 3.0 v dc electrical characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 367 pullup resistors (as input only) ports pta3/kbd37 ?pta0/kbd0 , ptc1?ptc0, ptd6/t2ch0?ptd0/ss r pu 20 45 65 k ? capacitance ports (as input or output) c out c in ? ? ? ? 12 8 pf monitor mode entry voltage v tst v dd +2.5 ?8v low-voltage inhibit, trip falling voltage ? target v tripf 2.35 2.60 2.70 v low-voltage inhibit, trip rising voltage ? target v tripr 2.45 2.66 2.80 v low-voltage inhibit reset/recover hysteresis ? target (v tripf + v hys = v tripr ) v hys ?60 ?mv por rearm voltage (8) v por 0 ? 100 mv por reset voltage (9) v porrst 0 700 800 mv por rise time ramp rate (10) r por 0.02 ? ? v/ms notes: 1. v dd = 3.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted 2. typical values reflect average measurements at midpoint of voltage range, 25 c only. 3. run (operating) i dd measured using external square wave clock source (f osc = 16.4 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. 4. wait i dd measured using external square wave clock source (f osc = 16.4 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 wait i dd . measured with pll and lvi enabled. 5. stop i dd is measured with osc1 = v ss . 6. stop i dd with tbm enabled is measured using an external square wave clock source (f osc = 16.4 mhz). all inputs 0.2 v from rail. no dc loads. less than 100 pf on all outputs. all inputs configured as inputs. 7. pullups and pulldowns are disabled. 8. maximum is highest voltage that por is guaranteed. 9. maximum is highest voltage that por is possible. 10. 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. table 23-5. 3.0 v dc electrical characteristics characteristic (1) symbol min typ (2) 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 specifications technical data MC68HC908GR8A ? rev 0.0 368 electrical specifications motorola 23.7 5.0 v control timing table 23-6. 5.0 v control timing characteristic (1) 1. v ss = 0 vdc; timing shown with respect to 20% v dd and 70% v ss unless otherwise noted. symbol min max unit frequency of operation (2) crystal option external clock option (3) 2. see clock generation module characteristics for more information. 3. no more than 10% duty cycle deviation from 50% f osc 1 dc (4) 4. some modules may require a minimum frequency greater than dc for proper operation. see appropriate table for this information. 8 32.8 mhz mhz internal operating frequency f op ?8.2mhz internal clock period (1/f op )t cyc 122 ? ns reset input pulse width low (5) 5. minimum pulse width reset is guaranteed to be recognized. it is possible for a smaller pulse width to cause a reset. t irl 50 ? ns irq interrupt pulse width low (6) (edge-triggered) 6. minimum pulse width is for guaranteed interrupt. it is possible for a smaller pulse width to be recognized. t ilih 50 ? ns irq interrupt pulse period t ilil note 8 ? t cyc 16-bit timer (7) input capture pulse width input capture period 7. minimum pulse width is for guaranteed interrupt. it is possible for a smaller pulse width to be recognized. 8. the minimum period, t ilil or t tltl , should not be less than the number of cycles it takes to execute the interrupt service routine plus t cyc . t th, t tl t tltl note 8 ? ? ns t cyc notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications 3.0 v control timing MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 369 23.8 3.0 v control timing table 23-7. 3.0 v control timing characteristic (1) 1. v ss = 0 vdc; timing shown with respect to 20% v dd and 70% v ss unless otherwise noted. symbol min max unit frequency of operation (2) crystal option external clock option (3) 2. see clock generation module characteristics for more information. 3. no more than 10% duty cycle deviation from 50% f osc 1 dc (4) 4. some modules may require a minimum frequency greater than dc for proper operation. see appropriate table for this information. 8 16.4 mhz mhz internal operating frequency f op ?4.1mhz internal clock period (1/f op )t cyc 244 ? ns reset input pulse width low (5) 5. minimum pulse width reset is guaranteed to be recognized. it is possible for a smaller pulse width to cause a reset. t irl 125 ? ns irq interrupt pulse width low (6) (edge-triggered) 6. minimum pulse width is for guaranteed interrupt. it is possible for a smaller pulse width to be recognized. t ilih 125 ? ns irq interrupt pulse period t ilil note 8 ? t cyc 16-bit timer (7) input capture pulse width input capture period 7. minimum pulse width is for guaranteed interrupt. it is possible for a smaller pulse width to be recognized. 8. the minimum period, t ilil or t tltl , should not be less than the number of cycles it takes to execute the interrupt service routine plus t cyc . t th, t tl t tltl note 8 ? ? ns t cyc notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 370 electrical specifications motorola 23.9 output high-voltage characteristics figure 23-1. typical high-side driver characteristics ? port pta3?pta0 (v dd = 4.5 vdc) figure 23-2. typical high-side driver characteristics ? port pta3?pta0 (v dd = 2.7 vdc) ?35 ?30 ?25 ?20 ?15 ?10 ?5 0 ?40 0 25 i oh (ma) ?40 v oh (v) 3 3.4 3.6 3.8 4.0 4.2 3.2 85 v oh > v dd ?0.8 v @ i oh = ?2.0 ma v oh > v dd ?1.5 v @ i oh = ?10.0 ma ?25 ?20 ?15 ?10 ?5 0 ?40 0 25 i oh (ma) 1.3 1.7 1.9 2.1 2.3 2.5 1.5 85 v oh (v) v oh > v dd ?0.3 v @ i oh = ?0.6 ma v oh > v dd ?1.0 v @ i oh = ?4.0 ma f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications output high-voltage characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 371 figure 23-3. typical high-side driver characteristics ? port ptc1?ptc0 (v dd = 4.5 vdc) figure 23-4. typical high-side driver characteristics ? port ptc1?ptc0 (v dd = 2.7 vdc) ?35 ?30 ?25 ?20 ?15 ?10 ?5 0 ?40 0 25 i oh (ma) ?40 v oh (v) 3 3.4 3.6 3.8 4.0 4.2 3.2 85 v oh > v dd ?0.8 v @ i oh = ?10.0 ma ?25 ?20 ?15 ?10 ?5 0 ?40 0 25 i oh (ma) 1.3 1.7 1.9 2.1 2.3 2.5 1.5 85 v oh (v) v oh > v dd ?0.5 v @ i oh = ?4.0 ma f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 372 electrical specifications motorola figure 23-5. typical high-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 5.5 vdc) figure 23-6. typical high-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 2.7 vdc) ?70 ?60 ?50 ?40 ?30 ?20 ?10 0 ?40 0 25 i oh (ma) ?90 v oh (v) 3 3.4 3.6 3.8 4.0 4.2 3.2 85 ?80 4.6 4.4 v oh > v dd ?0.8 v @ i oh = ?2.0 ma v oh > v dd ?1.5 v @ i oh = ?10.0 ma ?25 ?20 ?15 ?10 ?5 0 ?40 0 25 i oh (ma) 1.3 1.7 1.9 2.1 2.3 2.5 1.5 85 v oh (v) v oh > v dd ?0.3 v @ i oh = ?0.6 ma v oh > v dd ?1.0 v @ i oh = ?4.0 ma f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications output low-voltage characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 373 23.10 output low-voltage characteristics figure 23-7. typical low-side driver characteristics ? port pta3?pta0 (v dd = 5.5 vdc) figure 23-8. typical low-side driver characteristics ? port pta3?pta0 (v dd = 2.7 vdc) 5 10 15 20 25 30 35 ?40 0 25 i ol (ma) 0 v ol (v) 0 0.4 0.6 0.8 1.0 1.2 0.2 85 1.4 1.6 v ol < 0.4 v @ i ol = 1.6 ma v ol < 1.5 v @ i ol = 10.0 ma 2 4 6 8 10 12 14 ?40 0 25 i ol (ma) 0 v ol (v) 0.40.60.81.01.2 0.2 85 1.4 1.6 v ol < 0.3 v @ i ol = 0.5 ma v ol < 1.0 v @ i ol = 6.0 ma f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 374 electrical specifications motorola figure 23-9. typical low-side driver characteristics ? port ptc1?ptc0 (v dd = 4.5 vdc) figure 23-10. typical low-side driver characteristics ? port ptc1?ptc0 (v dd = 2.7 vdc) 10 20 30 40 50 60 i ol (ma) 0 v ol (v) 0.4 0.6 0.8 1.0 1.2 1.4 1.6 ?40 0 25 85 v ol < 1.0 v @ i ol = 15 ma 5 10 15 20 25 30 ?40 0 25 i ol (ma) 0 v ol (v) 0.4 0.6 0.8 1.0 1.2 0.2 85 1.4 1.6 v ol < 0.8 v @ i ol = 10 ma f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications output low-voltage characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 375 figure 23-11. typical low-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 5.5 vdc) figure 23-12. typical low-side driver characteristics ? ports ptb5?ptb0, ptd6?ptd0, and pte1?pte0 (v dd = 2.7 vdc) 5 10 15 20 25 30 35 ?40 0 25 i ol (ma) 0 v ol (v) 0 0.4 0.6 0.8 1.0 1.2 0.2 85 1.4 1.6 v ol < 0.4 v @ i ol = 1.6 ma v ol < 1.5 v @ i ol = 10.0 ma 2 4 6 8 10 12 14 ?40 0 25 i ol (ma) 0 v ol (v) 0.20.40.60.81.0 0 85 1.2 1.6 1.4 v ol < 0.3 v @ i ol = 0.5 ma v ol < 1.0 v @ i ol = 6.0 ma f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 376 electrical specifications motorola 23.11 typical supply currents figure 23-13. typical operating i dd , with all modules turned on (?40 c to 125 c) figure 23-14. typical wait mode i dd , with all modules disabled (?40 c to 125 c) 0 2 4 6 8 10 12 0123456789 5.5 v 3.6 v f bus (mhz) i dd (ma) 14 16 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 01 23 456 78 5.5 v 3.6 v i dd (ma) f bus (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 . . . electrical specifications typical supply currents MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 377 figure 23-15. typical stop mode i dd , with all modules disabled (?40 c to 125 c) 1 1.05 1.10 1.15 1.20 1.25 1.30 01 234 567 89 5.5 v 3.6 v f bus (mhz) i dd ( a) 1.35 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 378 electrical specifications motorola 23.12 adc characteristics characteristic (1) symbol min max unit comments supply voltage v ddad 2.7 (v dd min) 5.5 (v dd max) v v ddad should be tied to the same potential as v dd via separate traces. input voltages v adin 0 v ddad v v adin <= v refh resolution b ad 88bits absolute accuracy (v refl = 0 v, v ddad = v refh = 5 v 10%) a ad ?? 1 lsb includes quantization adc internal clock f adic 0.5 1.048 mhz t aic = 1/f adic , tested only at 1 mhz conversion range r ad v refl v refh v v refh = v ddad v refl = v ssad power-up time t adpu 16 t aic cycles conversion time t adc 16 17 t aic cycles sample time (2) t ads 5? t aic cycles zero input reading (3) z adi 00 01 hex v in = v refl full-scale reading (3) f adi fe ff hex v in = v refh input capacitance c adi ? (20) 8 pf not tested input leakage (4) port b ?? 1 a notes: 1. v dd = 5.0 vdc 10%, v ss = 0 vdc, v ddad = 5.0 vdc 10%, v ssad = 0 vdc, v refh = 5.0 vdc 10%, v refl = 0 2. source impedances greater than 10 k ? adversely affect internal rc charging time during input sampling. 3. zero-input/full-scale reading requires sufficient decoupling measures for accurate conversions. 4. 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 specifications 5.0 v spi characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 379 23.13 5.0 v spi characteristics diagram number (1) 1. numbers refer to dimensions in figure 23-16 and figure 23-17 . characteristic (2) 2. all timing is shown with respect to 20% v dd and 70% v dd , unless noted; 100 pf load on all spi pins. symbol min max unit operating frequency master slave f op(m) f op(s) f op /128 dc f op /2 f op mhz mhz 1 cycle time master slave t cyc(m) t cyc(s) 2 1 128 ? t cyc t cyc 2 enable lead time t lead(s) 1? t cyc 3 enable lag time t lag(s) 1? t cyc 4 clock (spsck) high time master slave t sckh(m) t sckh(s) t cyc ?25 1/2 t cyc ?25 64 t cyc ? ns ns 5 clock (spsck) low time master slave t sckl(m) t sckl(s) t cyc ?25 1/2 t cyc ?25 64 t cyc ? ns ns 6 data setup time (inputs) master slave t su(m) t su(s) 30 30 ? ? ns ns 7 data hold time (inputs) master slave t h(m) t h(s) 30 30 ? ? ns ns 8 access time, slave (3) cpha = 0 cpha = 1 3. time to data active from high-impedance state t a(cp0) t a(cp1) 0 0 40 40 ns ns 9 disable time, slave (4) 4. hold time to high-impedance state t dis(s) ?40ns 10 data valid time, after enable edge master slave (5) 5. with 100 pf on all spi pins t v(m) t v(s) ? ? 50 50 ns ns 11 data hold time, outputs, after enable edge master slave t ho(m) t ho(s) 0 0 ? ? ns ns notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 380 electrical specifications motorola 23.14 3.0 v spi characteristics diagram number (1) 1. numbers refer to dimensions in figure 23-16 and figure 23-17 . characteristic (2) 2. all timing is shown with respect to 20% v dd and 70% v dd , unless noted; 100 pf load on all spi pins. symbol min max unit operating frequency master slave f op(m) f op(s) f op /128 dc f op /2 f op mhz mhz 1 cycle time master slave t cyc(m) t cyc(s) 2 1 128 ? t cyc t cyc 2 enable lead time t lead(s) 1? t cyc 3 enable lag time t lag(s) 1? t cyc 4 clock (spsck) high time master slave t sckh(m) t sckh(s) t cyc ?35 1/2 t cyc ?35 64 t cyc ? ns ns 5 clock (spsck) low time master slave t sckl(m) t sckl(s) t cyc ?35 1/2 t cyc ?35 64 t cyc ? ns ns 6 data setup time (inputs) master slave t su(m) t su(s) 40 40 ? ? ns ns 7 data hold time (inputs) master slave t h(m) t h(s) 40 40 ? ? ns ns 8 access time, slave (3) cpha = 0 cpha = 1 3. time to data active from high-impedance state t a(cp0) t a(cp1) 0 0 50 50 ns ns 9 disable time, slave (4) 4. hold time to high-impedance state t dis(s) ?50ns 10 data valid time, after enable edge master slave (5) 5. with 100 pf on all spi pins t v(m) t v(s) ? ? 60 60 ns ns 11 data hold time, outputs, after enable edge master slave t ho(m) t ho(s) 0 0 ? ? ns ns notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications 3.0 v spi characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 381 figure 23-16. spi master timing note note: this first clock edge is generated internally, but is not seen at the spsck pin. ss pin of master held high msb in ss input spsck output spsck 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 11 10 11 7 6 note note: this last clock edge is generated internally, but is not seen at the spsck pin. ss pin of master held high msb in ss input spsck output spsck 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 7 6 a) spi master timing (cpha = 0) b) spi master timing (cpha = 1) cpol = 0 cpol = 1 cpol = 0 cpol = 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 . . . electrical specifications technical data MC68HC908GR8A ? rev 0.0 382 electrical specifications motorola figure 23-17. spi slave timing note: not defined but normally msb of character just received slave ss input spsck input spsck input miso input mosi output 4 5 5 1 4 msb in bits 6?1 8 6 10 5 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 spsck input spsck 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 cpol = 0 cpol = 1 cpol = 0 cpol = 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 . . . electrical specifications timer interface module characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 383 23.15 timer interface module characteristics 23.16 clock generation module characteristics 23.16.1 cgm component specifications table 23-8. timer interface module characteristics characteristic symbol min max unit input capture pulse width t tih , t til 1? t cyc table 23-9. cgm component specifications characteristic symbol min typ max unit crystal reference frequency (1) 1. fundamental mode crystals only f xclk 148mhz crystal load capacitance (2) 2. consult crystal manufacturer?s data. c l ???pf crystal fixed capacitance (2) c 1 ? 2 c l ?pf crystal tuning capacitance (2) c 2 ? 2 c l ?pf feedback bias resistor r b ?22?m ? series resistor r s 0 330k 1m ? notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 384 electrical specifications motorola 23.16.2 cgm electrical specifications description symbol min typ max unit operating voltage v dd 2.7 ? 5.5 v operating temperature t ?40 25 125 o c crystal reference frequency f rclk 148mhz range nominal multiplier f nom ? 38.4 ? khz vco center-of-range frequency (1) 1. 5.0 v 10% v dd f vrs 38.4 k ? 40.0 m hz medium-voltage vco center-of-range frequency (2) 2. 3.0 v 10% v dd f vrs 38.4 k ? 40.0 m hz vco range linear range multiplier l 1 ? 255 vco power-of-two range multiplier 2 e 1?4 vco multiply factor n 1 ? 4095 vco prescale multiplier 2 p 118 reference divider factor r 1 1 15 vco operating frequency f vclk 38.4 k ? 40.0 m hz bus operating frequency (1) f bus ??8.2mhz bus frequency @ medium voltage (2) f bus ??4.1mhz manual acquisition time t lock ??50ms automatic lock time t lock ??50ms pll jitter (3) 3. deviation of average bus frequency over 2 ms. n = vco multiplier. f j 0? f rclk x 0.025% x 2 p n/4 hz external clock input frequency pll disabled f osc dc ? 32.8 m hz external clock input frequency pll enabled f osc 30k ? 8m (4) 4. set the reference divider (r) to reduce the pll input clock (cgmrdv) frequency to below 1.5mhz. hz notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications memory characteristics MC68HC908GR8A ? rev 0.0 technical data motorola electrical specifications 385 23.17 memory characteristics characteristic symbol min typ max unit ram data retention voltage v rdr 1.3 ? ? v 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 (min), there is no erase-disturb, but it reduces the endurance of the flash memory. 1??ms flash mass erase time t merase (3) 3. if the mass erase time is longer than t merase (min), 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 erase) t nvhl 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 64) t hv max. ?? 4ms flash row erase endurance (6) 6. the minimum row endurance value specifies each row of the flash memory is guaranteed to work for at least this many erase / program cycles. ? 10k 100k (7) 7. flash endurance is a function of the temperature at which erasure occurs. typical endurance degrades when the tem- perature while erasing is less than 25 c. ?cycles flash row program endurance (8) 8. the minimum row endurance value specifies each row of the flash memory is guaranteed to work for at least this many erase / program cycles. ? 10k 100k (7) ?cycles flash data retention time (9) 9. the flash is guaranteed to retain data over the entire operating temperature range for at least the minimum time specified. ?10 100 (10) 10. motorola performs reliability testing for data retention. these tests are based on samples tested at elevated temperatures. due to the higher activation energy of the elevated test temperature, calculated life tests correspond to more than 100 years of operation/storage at 55 c ? years notes: f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 specifications technical data MC68HC908GR8A ? rev 0.0 386 electrical specifications 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola mechanical specifications 387 technical data ? MC68HC908GR8A section 24. mechanical specifications 24.1 contents 24.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .387 24.3 32-pin lqfp (case #873a) . . . . . . . . . . . . . . . . . . . . . . . . . .388 24.4 28-pin pdip (case #710) . . . . . . . . . . . . . . . . . . . . . . . . . . . .389 24.5 28-pin soic (case #751f). . . . . . . . . . . . . . . . . . . . . . . . . . .390 24.2 introduction the MC68HC908GR8A is available in these packages: 32-pin low-profile quad flat pack (lqfp) 28-pin dual in-line package (pdip) 28-pin small outline package (soic) the package information contained in this section is the latest available at the time of this publication. to make sure that you have the latest package specifications, contact one of the following: local motorola sales office world wide web at http://www.motorola.com/semiconductors/ follow world wide web on-line instructions to retrieve the current mechanical specifications. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mechanical specifications technical data MC68HC908GR8A ? rev 0.0 388 mechanical specifications motorola 24.3 32-pin lqfp (case #873a) a - u - v - z - s b - t - detail y section ae?ae g -ac- detail ad seating plane 8x m r q k w x 0.20 (0.008) m ac t ? u z a1 s1 1 8 9 17 25 32 9 v1 b1 0.20 (0.008) ac t-u z 4x 0.20 (0.008) ab t-u z 4x -ab- 0.10 (0.004) ac c e h 0.25 (0.010) gauge plane detail ad f n d j base metal ae ae detail y ? t ? , ? u ? , ? z ? p notes: 1. dimensions and tolerancing as per ansi y14.5m, 1982 2. controlling dimension: millimeter 3. datum plane -ab- is located at bottom of lead and is consistent with the lead where the lead exits the plastic body at the bottom of the parting line 4. datums -t-, -u-, and -z- to be determined at datum plane -ab- 5. dimensions s and v to be determined at seating plane -ac- 6. dimensions a and b do not include mold protrusion. allowable protrusion is 0.250 (0.010) per side. dimensions a and b do include mold mismatch and are determined at datum plane -ab- 7. dimension d does not include dambar protrusion. dambar protrusion shall not cause the d dimension to exceed 0.520 (0.020) 8. minimum solder plate thickness shall be 0.0076 (0.0003) 9. exact shape of each corner may vary from depiction dim millimeters inches min max min max a 7.000 bsc 0.276 bsc a1 3.500 bsc 0.138 bsc b 7.000 bsc 0.276 bsc b1 3.500 bsc 0.138 bsc c 1.400 1.600 0.055 0.063 d 0.300 0.450 0.012 0.018 e 1.350 1.450 0.053 0.057 f 0.300 0.400 0.012 0.016 g 0.800 bsc 0.031 bsc h 0.050 0.150 0.002 0.006 j 0.090 0.200 0.004 0.008 k 0.500 0.700 0.020 0.028 m 12 ref 12 ref n 0.090 0.160 0.004 0.006 p 0.400 bsc 0.016 bsc q 1 5 1 5 r 0.150 0.250 0.006 0.010 s 9.000 bsc 0.354 bsc s1 4.500 bsc 0.177 bsc v 9.000 bsc 0.354 bsc v1 4.500 bsc 0.177 bsc w 0.200 ref 0.008 ref x 1.000 ref 0.039 ref f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mechanical specifications 28-pin pdip (case #710) MC68HC908GR8A ? rev 0.0 technical data motorola mechanical specifications 389 24.4 28-pin pdip (case #710) dim. min. max. notes dim. min. max. a 36.45 37.21 1. all dimensions in mm. 2. positional tolerance of leads (?d?) shall be within 0.25 mm at maximum material condition, in relation to seating plane and to each other. 3. dimension ?l? is to centre of leads when formed parallel. 4. dimension ?b? does not include mould protrusion. h 1.65 2.16 b 13.72 14.22 j 0.20 0.38 c 3.94 5.08 k 2.92 3.43 d 0.36 0.56 l 15.24 bsc f 1.02 1.52 m 0 15 g 2.54 bsc n 0.51 1.02 g 1 f d h c n k l m j b a seating plane f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . mechanical specifications technical data MC68HC908GR8A ? rev 0.0 390 mechanical specifications motorola 24.5 28-pin soic (case #751f) g d 28 pl c k ? t ? seating plane m f j 0.25 m b m 0.25 m b s a s t 14 pl r x 45 1 dim. min. max. notes dim. min. max. a 17.80 18.05 1. dimensions ?a? and ?b? are datums and ?t? is a datum surface. 2. dimensioning and tolerancing per ansi y14.5m, 1982. 3. all dimensions in mm. 4. dimensions ?a? and ?b? do not include mould protrusion. 5. maximum mould protrusion is 0.15 mm per side. j 0.229 0.317 b 7.40 7.60 k 0.127 0.292 c 2.35 2.65 m 0 8 d 0.35 0.49 p 10.05 10.55 f 0.41 0.90 r 0.25 0.75 g 1.27 bsc ??? ? a ? ? b ? p f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . MC68HC908GR8A ? rev 0.0 technical data motorola ordering information 391 technical data ? MC68HC908GR8A section 25. ordering information 25.1 contents 25.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .391 25.3 mc order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .392 25.4 development tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393 25.2 introduction this section contains instructions for ordering the MC68HC908GR8A and mc68hc908gr4a. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . ordering information technical data MC68HC908GR8A ? rev 0.0 392 ordering information motorola 25.3 mc order numbers table 25-1. mc order numbers mc order number (1) 1. fa = quad flat pack p = plastic dual in line package dw = small outline integrated circuit (soic) package operating temperature range ( c) production parts MC68HC908GR8Acp MC68HC908GR8Acfa MC68HC908GR8Acdw MC68HC908GR8Avfa MC68HC908GR8Avp MC68HC908GR8Avdw MC68HC908GR8Amfa MC68HC908GR8Amp MC68HC908GR8Amdw ? 40 to + 85 ? 40 to + 85 ? 40 to + 85 ? 40 to + 105 ? 40 to + 105 ? 40 to + 105 ? 40 to + 125 ? 40 to + 125 ? 40 to + 125 mc68hc908gr4acp mc68hc908gr4acfa mc68hc908gr4acdw mc68hc908gr4avfa mc68hc908gr4avp mc68hc908gr4avdw mc68hc908gr4amfa mc68hc908gr4amp mc68hc908gr4amdw ? 40 to + 85 ? 40 to + 85 ? 40 to + 85 ? 40 to + 105 ? 40 to + 105 ? 40 to + 105 ? 40 to + 125 ? 40 to + 125 ? 40 to + 125 tape and reel mc908gr8cfar2 mc908gr8cdwr2 mc908gr8vfar2 mc908gr8vdwr2 mc908gr8mfar2 mc908gr8mdwr2 ? 40 to + 85 ? 40 to + 85 ? 40 to + 105 ? 40 to + 105 ? 40 to + 125 ? 40 to + 125 mc908gr4cfar2 mc908gr4cdwr2 mc908gr4vfar2 mc908gr4vdwr2 mc908gr4mfar2 mc908gr4mdwr2 ? 40 to + 85 ? 40 to + 85 ? 40 to + 105 ? 40 to + 105 ? 40 to + 125 ? 40 to + 125 f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . ordering information development tools MC68HC908GR8A ? rev 0.0 technical data motorola ordering information 393 25.4 development tools table 25-2. development tool kits ordering part number description m68ics08gr hc908gr8 ics kit includes: m68ics08gr programmer board, windows-based ide, 68hc908gr8 sample, ics board & ide documentation, universal power supply, serial cable kitmmevs08gr hc908gr8 evs kit includes: m68mmpfb0508, m68eml08gp32, m68cbl05c, m68tc08gr8p28, m68tc08gr8fa32, m68tqs032sag1, m68tqp032sa1, m68ics08gr kit kitmmds08gr hc908gr8 mmds kit includes: m68mmds0508, m68eml08gp32, m68cbl05c, m68tc08gr8p28, m68tc08gr8fa32, m68tqs032sag1, m68tqp032sa1, m68ics08gr kit table 25-3. development tool components ordering part number description comments m68mmds0508 high performance emulator m68mmpfb0508 mmevs platform board m68eml08gp32 hc908gp32 emulator board used for hc908gr8/gr4 emulation m68cbl05c low noise flex-cable m68tc08gr8p28 28-pin dip target head adapter m68tc08gr8fa32 32-pin qfp target head adapter m68tqs032sag1 32-pin tq socket with guides m68tqp032sa1 32-pin tqpack f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d u c t , g o t o : w w w . f r e e s c a l e . c o m n c . . . ordering information technical data MC68HC908GR8A ? rev 0.0 394 ordering information 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 . . . MC68HC908GR8A ? rev 0.0 technical data motorola glossary 395 technical data ? MC68HC908GR8A 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 technical data MC68HC908GR8A ? rev 0.0 396 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola glossary 397 cgm ? see ?clock generator module (cgm).? 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 398 glossary motorola 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. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola glossary 399 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. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 400 glossary motorola 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. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola glossary 401 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.? 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). f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 402 glossary motorola 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. 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 . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola glossary 403 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. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 404 glossary motorola 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. 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A ? rev 0.0 technical data motorola glossary 405 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." 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. f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 technical data MC68HC908GR8A ? rev 0.0 406 glossary motorola 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 . . . f r e e s c a l e s e m i c o n d u c t o r , i freescale semiconductor, inc. f o r m o r e i n f o r m a t i o n o n t h i s p r o d 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 MC68HC908GR8A/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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