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motorola.com/semiconductors m68hc12 microcontrollers mc912dt128a/d rev. 4, 10/2003 mc68hc912dt128a mc68hc912dg128a technical data mc68hc912dt128c mc68hc912dg128c mc68hc912dt128p mc68hc912dg128p

mc68hc912dt128a ? rev 4.0 technical data motorola 3 mc68hc912dt128a mc68hc912dg128a mc68hc912dt128c mc68hc912dg128c mc68hc912dt128p mc68hc912dg128p technical data rev 4.0 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 fo r any particular purpose, no r does motorola assume any liability arising out of the app lication or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequ ential 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 applic ations 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 clai ms, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintend ed 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
technical data mc68hc912dt128a ? rev 4.0 4 motorola
mc68hc912dt128a ? rev 4.0 technical data motorola list of paragraphs 5 technical data ? mc68hc912dt128a list of paragraphs technical data ? list of paragrap hs . . . . . . . . . . . . . . . . 5 technical data ? table of contents . . . . . . . . . . . . . . . . . 7 technical data ? list of figures . . . . . . . . . . . . . . . . . . 17 technical data ? list of tables . . . . . . . . . . . . . . . . . . . 21 section 1. general description . . . . . . . . . . . . . . . . . . . . 25 section 2. central processing unit . . . . . . . . . . . . . . . . . 35 section 3. pinout and signal d escriptions . . . . . . . . . . . 41 section 4. registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 section 5. operating modes. . . . . . . . . . . . . . . . . . . . . . . 79 section 6. resource mapping . . . . . . . . . . . . . . . . . . . . . 87 section 7. bus control and input/ output . . . . . . . . . . . 103 section 8. flash memory . . . . . . . . . . . . . . . . . . . . . . . . 115 section 9. eeprom memory . . . . . . . . . . . . . . . . . . . . . 123 section 10. resets and interrupts . . . . . . . . . . . . . . . . . 137 section 11. i/o ports with key wake-up . . . . . . . . . . . . 149 section 12. clock functions . . . . . . . . . . . . . . . . . . . . . 157 section 13. oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 section 14. pulse width modulator . . . . . . . . . . . . . . . . 225 section 15. enhanced capture timer . . . . . . . . . . . . . . 241 section 16. multiple serial interf ace . . . . . . . . . . . . . . . 277
list of paragraphs technical data mc68hc912dt128a ? rev 4.0 6 list of paragraphs motorola section 17. inter ic bus . . . . . . . . . . . . . . . . . . . . . . . . . 301 section 18. mscan controller . . . . . . . . . . . . . . . . . . . . 325 section 19. analog-to-d igital converter . . . . . . . . . . . . 367 section 20. development support. . . . . . . . . . . . . . . . . 395 section 21. electrical sp ecifications. . . . . . . . . . . . . . . 421 section 22. appendix: changes from mc68hc912dg128 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 section 23. appendix: cgm pract ical aspects . . . . . . 447 section 24. appendix : information on mc68hc912dt128a mask set chan ges . . . . . . . . . . . . 457 technical data ? glossary . . . . . . . . . . . . . . . . . . . . . . 461 technical data ? revision history . . . . . . . . . . . . . . . . 473
mc68hc912dt128a ? rev 4.0 technical data motorola table of contents 7 technical data ? mc68hc912dt128a table of contents list of paragraphs table of contents list of figures list of tables section 1. general description 1.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 1.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.3 devices covered in this document. . . . . . . . . . . . . . . . . . . . . .26 1.4 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.5 mc68hc912dt128a block diagram . . . . . . . . . . . . . . . . . . . . 30 1.6 mc68hc912dg128a block diagram. . . . . . . . . . . . . . . . . . . . 31 1.7 ordering information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 section 2. central processing unit 2.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 2.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.3 programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2.4 data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.5 addressing modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 2.6 indexed addressing modes . . . . . . . . . . . . . . . . . . . . . . . . . . .39
table of contents technical data mc68hc912dt128a ? rev 4.0 8 table of contents motorola 2.7 opcodes and operands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 section 3. pinout an d signal descriptions 3.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 3.2 mc68hc912dt128a pin assignments in 112-pi n qfp. . . . . . 41 3.3 power supply pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 3.4 signal descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.5 port signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 section 4. registers 4.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67 4.2 register block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67 section 5. operating modes 5.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 5.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.3 operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.4 background debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84 section 6. resource mapping 6.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87 6.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.3 internal resource mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . .87 6.4 flash eeprom mappi ng through internal memory expansion 92 6.5 miscellaneous system control register . . . . . . . . . . . . . . . . . . 96 6.6 mapping test registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 6.7 memory maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
table of contents mc68hc912dt128a ? rev 4.0 technical data motorola table of contents 9 section 7. bus control and input/output 7.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103 7.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.3 detecting access type from external signals . . . . . . . . . . . .103 7.4 registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104 section 8. flash memory 8.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115 8.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 8.3 overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 8.4 flash eeprom control bl ock . . . . . . . . . . . . . . . . . . . . . . . .116 8.5 flash eeprom arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 8.6 flash eeprom registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.7 operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 8.8 programming the flash eep rom . . . . . . . . . . . . . . . . . . . . . 120 8.9 erasing the flash eeprom . . . . . . . . . . . . . . . . . . . . . . . . . . 121 8.10 stop or wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121 8.11 flash protection bit fpop en . . . . . . . . . . . . . . . . . . . . . . . . .122 section 9. eeprom memory 9.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123 9.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 9.3 eeprom selective write more zeros . . . . . . . . . . . . . . . . . .124 9.4 eeprom programmer? s model . . . . . . . . . . . . . . . . . . . . . . .125 9.5 eeprom control registers . . . . . . . . . . . . . . . . . . . . . . . . . . 126 9.6 program/erase operation. . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.7 shadow word mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
table of contents technical data mc68hc912dt128a ? rev 4.0 10 table of contents motorola 9.8 programming eedivh and eedivl registers. . . . . . . . . . . . 135 section 10. resets and interrupts 10.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137 10.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 10.3 exception priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 10.4 maskable interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138 10.5 latching of interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.6 interrupt control and priority regist ers . . . . . . . . . . . . . . . . .141 10.7 interrupt test registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 10.8 resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 10.9 effects of reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 10.10 register stacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 section 11. i/o port s with key wake-up 11.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149 11.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 11.3 key wake-up and port r egisters . . . . . . . . . . . . . . . . . . . . . . 150 11.4 key wake-up input filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 section 12. clock functions 12.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157 12.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 12.3 clock sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 12.4 phase-locked loop (p ll) . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 12.5 acquisition and tracking modes. . . . . . . . . . . . . . . . . . . . . . .161 12.6 limp-home and fast stop recove ry modes . . . . . . . . . . . . 163
table of contents mc68hc912dt128a ? rev 4.0 technical data motorola table of contents 11 12.7 system clock frequency fo rmulae . . . . . . . . . . . . . . . . . . . . 181 12.8 clock divider chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182 12.9 computer operating prop erly (cop) . . . . . . . . . . . . . . . . . . .185 12.10 real-time interrupt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 12.11 clock monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186 12.12 clock function registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 section 13. oscillator 13.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 13.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 13.3 mc68hc912dt128a oscilla tor specification . . . . . . . . . . . .194 13.4 mc68hc912dx128c colp itts oscillator specif ication . . . . . . 197 13.5 mc68hc912dx128p pierc e oscillator specificat ion . . . . . . . 212 section 14. pulse width modulator 14.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225 14.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 14.3 pwm register descriptions . . . . . . . . . . . . . . . . . . . . . . . . . .229 14.4 pwm boundary cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240 section 15. enhanced capture timer 15.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .241 15.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 15.3 enhanced capture timer modes of operation . . . . . . . . . . . . 247 15.4 timer register description s . . . . . . . . . . . . . . . . . . . . . . . . . . 251 15.5 timer and modulus counter operation in different modes . . 275 section 16. multiple serial interface
table of contents technical data mc68hc912dt128a ? rev 4.0 12 table of contents motorola 16.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277 16.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 16.3 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 16.4 serial communication inte rface (sci) . . . . . . . . . . . . . . . . . .278 16.5 serial peripheral interface (spi) . . . . . . . . . . . . . . . . . . . . . . .289 16.6 port s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 section 17. inter ic bus 17.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301 17.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 17.3 iic features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302 17.4 iic system configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 17.5 iic protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 17.6 iic register descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 17.7 iic programming examples . . . . . . . . . . . . . . . . . . . . . . . . . .318 section 18. mscan controller 18.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .325 18.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 18.3 external pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 18.4 message storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 18.5 identifier acceptance filter . . . . . . . . . . . . . . . . . . . . . . . . . . .332 18.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 18.7 protocol violation protecti on. . . . . . . . . . . . . . . . . . . . . . . . . . 337 18.8 low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338 18.9 timer link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 18.10 clock system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343
table of contents mc68hc912dt128a ? rev 4.0 technical data motorola table of contents 13 18.11 memory map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 18.12 programmer?s model of message storage . . . . . . . . . . . . . . .346 18.13 programmer?s model of control registers . . . . . . . . . . . . . . . 351 section 19. analog-to-digital converter 19.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367 19.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 19.3 modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 19.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370 19.5 atd operational modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372 19.6 atd operation in different mcu modes . . . . . . . . . . . . . . . . 373 19.7 general purpose digital input port operation . . . . . . . . . . . .375 19.8 application considerations . . . . . . . . . . . . . . . . . . . . . . . . . . .376 19.9 atd registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 section 20. development support 20.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395 20.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 20.3 instruction queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395 20.4 background debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .397 20.5 breakpoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 20.6 instruction tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 section 21. electrical specifications 21.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .421 21.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 21.3 tables of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
table of contents technical data mc68hc912dt128a ? rev 4.0 14 table of contents motorola section 22. appendix: ch anges from mc68hc912dg128 22.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441 22.2 significant changes from t he mc68hc912dg128 ( non-suffix de- vice)441 section 23. appendix: cgm practical aspects 23.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .447 23.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 23.3 practical aspects for the pll usage . . . . . . . . . . . . . . . . . .447 23.4 printed circuit board gui delines. . . . . . . . . . . . . . . . . . . . . . .453 section 24. appendix : information on mc68hc912dt128a mask set changes 24.1 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .457 24.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 24.3 oscillator ? major changes . . . . . . . . . . . . . . . . . . . . . . . . . .457 24.4 flash protection feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 24.5 clock circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458 24.6 pseudo stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 24.7 oscillator ? minor changes . . . . . . . . . . . . . . . . . . . . . . . . . .459 24.8 pll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 technical data ? glossary technical data ? revision history 24.9 changes in rev. 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473 24.10 changes from rev 2.0 to rev 3.0 . . . . . . . . . . . . . . . . . . . . . 473 24.11 changes from rev 1.0 to rev 2.0 . . . . . . . . . . . . . . . . . . . . . 475
table of contents mc68hc912dt128a ? rev 4.0 technical data motorola table of contents 15 24.12 changes from first versio n (internal release, no revision number) to rev 1.0 . . . . . . . . . . . . . . . . . . . . . . . . . .475
table of contents technical data mc68hc912dt128a ? rev 4.0 16 table of contents motorola
mc68hc912dt128a ? rev 4.0 technical data motorola list of figures 17 technical data ? mc68hc912dt128a list of figures figure title page 1-1 mc68hc912dt128a block diagram . . . . . . . . . . . . . . . . . . . . 30 1-2 mc68hc912dg128a block diagram. . . . . . . . . . . . . . . . . . . . 31 2-1 programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3-1 pin assignments in 112-pin qfp for mc68hc912dt128a . . . 42 3-2 pin assignments in 112-pin qfp for mc68hc912dg128a . . .43 3-3 112-pin qfp mechanical dimensi ons (case no. 987) . . . . . . . 44 3-4 pll loop filter co nnections . . . . . . . . . . . . . . . . . . . . . . . . . .46 3-5 external oscillator connec tions . . . . . . . . . . . . . . . . . . . . . . . .48 6-1 mc68hc912dt128a memory map after reset. . . . . . . . . . . . 100 6-2 mc68hc912dt128a memory paging . . . . . . . . . . . . . . . . . .101 11-1 stop key wake-up filter . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 12-1 internal clock relationships . . . . . . . . . . . . . . . . . . . . . . . . . . 159 12-2 pll functional diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160 12-3 clock loss during normal operation . . . . . . . . . . . . . . . . . . .164 12-4 no clock at power-on reset . . . . . . . . . . . . . . . . . . . . . . . . .166 12-5 stop exit and fast stop recovery . . . . . . . . . . . . . . . . . . . 168 12-6 clock generation chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 12-7 clock chain for sci0, sc i1, rti, cop. . . . . . . . . . . . . . . . . . 183 12-8 clock chain for ect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 12-9 clock chain for ms can, spi, atd0, atd1 and bdm . . . . . . 185 13-1 mc68hc912dt128a colpitts oscilla tor architecture. . . . . . .195 13-2 mc68hc912dx128c colpitts oscilla tor architecture. . . . . . .198 13-3 mc68hc912dx128c cr ystal with dc blo cking capacitor . . . 210 13-4 mc68hc912dx128p pierc e oscillator architectu re. . . . . . . .213 14-1 block diagram of pwm left-ali gned output channel . . . . . . 226 14-2 block diagram of pwm center-a ligned output channel . . . . 227 14-3 pwm clock sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 15-1 timer block diagram in latch mode. . . . . . . . . . . . . . . . . . . .243 15-2 timer block diagram in queue mode. . . . . . . . . . . . . . . . . . . 244
list of figures technical data mc68hc912dt128a ? rev 4.0 18 list of figures motorola 15-3 8-bit pulse accumulators block dia gram . . . . . . . . . . . . . . . .245 15-4 16-bit pulse accumulators block di agram . . . . . . . . . . . . . . .246 15-5 block diagram for port7 wi th output co mpare / pulse accumulator a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 15-6 c3f-c0f interrupt flag setting . . . . . . . . . . . . . . . . . . . . . . .247 16-1 multiple serial interfac e block diagram . . . . . . . . . . . . . . . . .278 16-2 serial communications interface block diagram . . . . . . . . . . 279 16-3 serial peripheral interface block dia gram . . . . . . . . . . . . . . . 291 16-4 spi clock format 0 (cpha = 0) . . . . . . . . . . . . . . . . . . . . . . .292 16-5 spi clock format 1 (cpha = 1) . . . . . . . . . . . . . . . . . . . . . . .293 16-6 normal mode and bidirecti onal mode. . . . . . . . . . . . . . . . . . . 294 17-1 iic block diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303 17-2 iic transmission signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 17-3 iic clock synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . .308 17-4 flow-chart of typical iic interrupt routine . . . . . . . . . . . . . . 323 18-1 the can system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 18-2 user model for message buffer organi zation. . . . . . . . . . . . . 330 18-3 32-bit maskable identifier acceptance filters . . . . . . . . . . . . . 333 18-4 16-bit maskable acceptance filters . . . . . . . . . . . . . . . . . . . . 333 18-5 8-bit maskable acceptance filters . . . . . . . . . . . . . . . . . . . . . 334 18-6 sleep request / acknowle dge cycle . . . . . . . . . . . . . . . . . . 340 18-7 clocking scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 18-8 segments within the bit time . . . . . . . . . . . . . . . . . . . . . . . . . 344 18-9 can standard compliant bit time segment settings . . . . . . 345 18-10 mscan12 memory map . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345 18-11 message buffer organiza tion . . . . . . . . . . . . . . . . . . . . . . . . . 346 18-12 receive/transmit message buffer extended identifie r. . . . . . 347 18-13 standard identifier mappin g . . . . . . . . . . . . . . . . . . . . . . . . . .348 18-14 identifier acceptance re gisters (1st bank) . . . . . . . . . . . . . . .364 18-15 identifier acceptance re gisters (2nd bank) . . . . . . . . . . . . . . 364 18-16 identifier mask registers (1st bank) . . . . . . . . . . . . . . . . . . . .365 18-17 identifier mask register s (2nd bank) . . . . . . . . . . . . . . . . . . .365 19-1 analog-to-digital converter block diagram . . . . . . . . . . . . . . 368 20-1 bdm host to target se rial bit timing. . . . . . . . . . . . . . . . . . . 399 20-2 bdm target to host se rial bit timing (logic 1) . . . . . . . . . . .399 20-3 bdm target to host se rial bit timing (logic 0) . . . . . . . . . . .400 21-1 timer inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .429 21-2 por and external reset timing diagr am . . . . . . . . . . . . . . . 430
list of figures mc68hc912dt128a ? rev 4.0 technical data motorola list of figures 19 21-3 stop recovery timing diagram . . . . . . . . . . . . . . . . . . . . . .431 21-4 wait recovery timing diagram . . . . . . . . . . . . . . . . . . . . . . 432 21-5 interrupt timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 21-6 port read timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .434 21-7 port write timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .434 21-8 multiplexed expansion bus timing dia gram . . . . . . . . . . . . . 436 a) spi master timing (cpha = 0) . . . . . . . . . . . . . . . . . . . . . 438 b) spi master timing (cpha = 1) . . . . . . . . . . . . . . . . . . . . . 438 21-9 spi timing diagram (1 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . 438 21-9 a) spi slave timing (cpha = 0) . . . . . . . . . . . . . . . . . . . . . . 439 21-9 b) spi slave timing (cpha = 1) . . . . . . . . . . . . . . . . . . . . . . 439 21-10 spi timing diagram (2 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . 439
list of figures technical data mc68hc912dt128a ? rev 4.0 20 list of figures motorola
mc68hc912dt128a ? rev 4.0 technical data motorola list of tables 21 technical data ? mc68hc912dt128a list of tables table title page 1-1 device ordering information. . . . . . . . . . . . . . . . . . . . . . . . . . . 32 1-2 development tools ordering information. . . . . . . . . . . . . . . . .33 2-1 m68hc12 addressing mode summary . . . . . . . . . . . . . . . . . .38 2-2 summary of indexed operat ions . . . . . . . . . . . . . . . . . . . . . . . 39 3-1 mc68hc912dt128a po wer and ground connection summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 3-2 mc68hc912dt128a signal descripti on summary . . . . . . . . .54 3-3 mc68hc912dt128a port description summary. . . . . . . . . . . 64 3-4 port pull-up, pull-down and redu ced drive summary . . . . . .65 4-1 register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68 5-1 mode selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80 6-1 mapping precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88 6-2 program space page index . . . . . . . . . . . . . . . . . . . . . . . . . . .93 6-3 flash register space page index. . . . . . . . . . . . . . . . . . . . . . .93 6-4 test mode program space page index. . . . . . . . . . . . . . . . . . . 94 6-5 rfstr stretch bit definiti on . . . . . . . . . . . . . . . . . . . . . . . . . .97 6-6 exstr stretch bit definiti on . . . . . . . . . . . . . . . . . . . . . . . . . .98 7-1 access type vs. bus control pins . . . . . . . . . . . . . . . . . . . . . 104 9-1 eediv selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127 9-2 2k byte eeprom block protection . . . . . . . . . . . . . . . . . . . . 130 9-3 erase selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 9-4 shadow word mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134 10-1 interrupt vector map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 10-2 stacking order on entry to interrupts . . . . . . . . . . . . . . . . . . . 147 12-1 summary of stop mode exit conditions. . . . . . . . . . . . . . . .174 12-2 summary of pseudo stop mode exit conditi ons . . . . . . . . .174 12-3 clock monitor time-outs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 12-4 real time interrupt rates. . . . . . . . . . . . . . . . . . . . . . . . . . . .188 12-5 cop watchdog rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
list of tables technical data mc68hc912dt128a ? rev 4.0 22 list of tables motorola 14-1 clock a and clock b prescaler. . . . . . . . . . . . . . . . . . . . . . . . 230 14-2 pwm left-aligned boundar y conditions . . . . . . . . . . . . . . . . 240 14-3 pwm center-aligned bound ary conditions . . . . . . . . . . . . . . 240 15-1 compare result output action . . . . . . . . . . . . . . . . . . . . . . . . 255 15-2 edge detector circuit configuration . . . . . . . . . . . . . . . . . . . .256 15-3 prescaler selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 16-1 baud rate generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280 16-2 loop mode functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 16-3 ss output selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 16-4 spi clock rate selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 17-1 iic tap and prescale values . . . . . . . . . . . . . . . . . . . . . . . . .310 17-2 iic divider and sda hold values . . . . . . . . . . . . . . . . . . . . . . 311 18-1 mscan12 interrupt vectors . . . . . . . . . . . . . . . . . . . . . . . . . .337 18-2 mscan12 vs. cpu operati ng modes . . . . . . . . . . . . . . . . . . . 338 18-3 data length codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .349 18-4 synchronization jump widt h . . . . . . . . . . . . . . . . . . . . . . . . . .354 18-5 baud rate prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354 18-6 time segment syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355 18-7 time segment values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355 18-8 identifier acceptance m ode settings . . . . . . . . . . . . . . . . . . .362 18-9 identifier acceptance hit indication . . . . . . . . . . . . . . . . . . . . 362 19-1 result data formats available . . . . . . . . . . . . . . . . . . . . . . . . 379 19-2 left justified atd output codes . . . . . . . . . . . . . . . . . . . . . . 380 19-3 atd response to ba ckground debug enable . . . . . . . . . . . . 382 19-4 final sample time selection . . . . . . . . . . . . . . . . . . . . . . . . .383 19-5 clock prescaler values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .384 19-6 conversion sequenc e length coding . . . . . . . . . . . . . . . . . .385 19-7 result register assignm ent for different conversion sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385 19-8 special channel conver sion select coding . . . . . . . . . . . . . .386 19-9 analog input channel select coding . . . . . . . . . . . . . . . . . . .387 19-10 multichannel mode resu lt register assignment (mult=1) . .388 20-1 ipipe decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 20-2 hardware commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 20-3 bdm firmware commands . . . . . . . . . . . . . . . . . . . . . . . . . .403 20-4 bdm registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405 20-5 ttago decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410 20-6 regn decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410
list of tables mc68hc912dt128a ? rev 4.0 technical data motorola list of tables 23 20-7 breakpoint mode control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 20-8 breakpoint address rang e control . . . . . . . . . . . . . . . . . . . . 416 20-9 breakpoint read/write control . . . . . . . . . . . . . . . . . . . . . . . . 418 20-10 tag pin function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420 21-1 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .422 21-2 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423 21-3 dc electrical characterist ics . . . . . . . . . . . . . . . . . . . . . . . . .424 21-4 supply current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 21-5 atd dc electrical characteristics . . . . . . . . . . . . . . . . . . . . . 425 21-6 analog converter characteristics (o perating) . . . . . . . . . . . .426 21-7 atd ac characteristics (operating). . . . . . . . . . . . . . . . . . . .426 21-8 atd maximum ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .427 21-9 eeprom characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .427 21-10 flash eeprom characteristics . . . . . . . . . . . . . . . . . . . . . . .428 21-11 pulse width modulator c haracteristics. . . . . . . . . . . . . . . . . . 428 21-12 control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 21-13 peripheral port timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .434 21-14 multiplexed expansion bu s timing. . . . . . . . . . . . . . . . . . . . .435 21-15 spi timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .437 21-16 cgm characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 21-17 oscillator characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 21-18 stop key wake-up filter . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 23-1 suggested 8mhz synthes is pll filter elements (tracking mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 23-2 suggested 8mhz synthes is pll filter elements (acquisition mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .452
list of tables technical data mc68hc912dt128a ? rev 4.0 24 list of tables motorola
mc68hc912dt128a ? rev 4.0 technical data motorola general description 25 technical data ? mc68hc912dt128a section 1. general description 1.1 contents 1.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.3 devices covered in this document. . . . . . . . . . . . . . . . . . . . . .26 1.4 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.5 mc68hc912dt128a block diagram . . . . . . . . . . . . . . . . . . . . 30 1.6 mc68hc912dg128a block diagram. . . . . . . . . . . . . . . . . . . . 31 1.7 ordering information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 1.2 introduction the mc68hc912dt128a microc ontroller unit (mcu) is a 16-bit device composed of standard on -chip peripherals including a 16-bit central processing unit (cpu12), 128k bytes of flash eeprom, 8k bytes of ram, 2k bytes of ee prom, two asynchronous serial communications interfaces (sci), a serial peripheral in terface (spi), an inter-ic interface (i 2 c), an enhanced capture timer (ect ), two 8-channel, 10-bit analog- to-digital converters (adc), a four-channel pulse-w idth modulator (pwm), and three can 2.0 a, b software compatible modules (mscan12). system resource mappi ng, clock generat ion, interrupt control and bus interfacing are manage d by the lite in tegration module (lim). the mc68 hc912dt128a has full 16-b it data path s throughout, however, the external bus can operat e in an 8-bit narrow mode so single 8-bit wide memory can be interfac ed for lower co st systems. the inclusion of a pll circuit allows pow er consumption an d performance to be adjusted to suit operat ional requirements. in addi tion to the i/o ports available in each module, 16 i/o po rts are available with key-wake-up capability from st op or wait mode.
general description technical data mc68hc912dt128a ? rev 4.0 26 general description motorola 1.3 devices covered in this document the mc68hc912dg128a device is si milar to the mc68hc912dt128a, but it has only two mscan12 m odules. the entire databook applies to both devices, except wher e differences are noted. the mc68hc912dt128c and mc68hc912d t128p are devices similar to the mc68hc912dt128a, but with different oscill ator configurations. sections of this book applicable to the mc68hc912d t128a also apply to the mc68hc912dt128c and mc68 hc912dt128p, except for the differences highlighted in section 13. oscillator . the mc68hc912dg128c and mc68hc912dg128p are devices similar to the mc68hc912dg128a, bu t with different oscillator configurations. sections of this book appl icable to the mc68hc912dg128a also apply to the mc68hc912dg128c and mc68hc912dg128p, except for the differences highlighted in section 13. oscillator . note: the generic term mc 68hc912dt128a is us ed throughout the document to mean all de rivatives mentioned above, except in section 13. oscillator , where it refers only to the mc68h c912dt128a and mc68hc912dg128a devices. 1.4 features 16-bit cpu12 ? upward compatible with m68hc11 instruction set ? interrupt stacking and progra mmer?s model identical to m68hc11 ? 20-bit alu ? instruction queue ? enhanced indexed addressing multiplexed bus ? single chip or expanded ? 16 address/16 data wide or 16 address/8 data narrow modes
general description features mc68hc912dt128a ? rev 4.0 technical data motorola general description 27 memory ? 128k byte flash e eprom, made of four 32k byte modules with 8k bytes protected bo ot section in each module ? 2k byte eeprom ? 8k byte ram with vstby, m ade of two 4k byte modules. two analog-to-dig ital converters ? 2 times 8-channels, 10-bit resolution three 1m bit per second, can 2. 0 a, b software compatible modules on the mc68hc 912dt128a (two on the mc68hc912dg128a) ? two receive and three transmit buffers per can ? flexible identifier filter program mable as 2 x 32 bit, 4 x 16 bit or 8x8bit ? four separate interrupt channels for rx, tx, error and wake-up per can ? low-pass filter wake-up function ? loop-back for self test operation ? programmable link to a timer input capture channel, for time- stamping and network synchronization. enhanced capture timer (ect) ? 16-bit main counter with 7-bit prescaler ? 8 programmable input capture or output compare channels; 4 of the 8 input captures with buffer ? input capture filter s and buffers, three successive captures on four channels, or two captur es on four channels with a capture/compare selectab le on the remaining four ? four 8-bit or two 16- bit pulse accumulators ? 16-bit modulus down-counter with 4-bit prescaler ? four user-selectable delay counters for si gnal filtering
general description technical data mc68hc912dt128a ? rev 4.0 28 general description motorola 4 pwm channels with program mable period and duty cycle ? 8-bit 4-channel or 16-bit 2-channel ? separate control for each pulse width and duty cycle ? center- or left-aligned outputs ? programmable clock select logic with a wide range of frequencies serial interfaces ? two asynchronous serial comm unications interfaces (sci) ? inter ic bus interface (i 2 c) ? synchronous serial perip heral interface (spi) lim (lite integration module) ? wcr (windowed cop wa tchdog, real time interrupt, clock monitor) ? roc (reset and clocks) ? mebi (multiplexed external bus interface) ? mmi (memory map and interface) ? int (interrupt control) ? bkp (breakpoints) ? bdm (background debug mode) two 8-bit ports with key wake-up interrupt clock generation ? phase-locked loop cl ock frequency multiplier ? limp home mode in absence of external clock ? slow mode divider ? low power 0.5 to 16 mhz crystal oscillator reference clock ? option of a pierce or colpitts oscillator
general description features mc68hc912dt128a ? rev 4.0 technical data motorola general description 29 112-pin tqfp package ? up to 67 general-pur pose i/o lines on the mc68hc912dt128a (up to 69 on the mc68hc912dg128a), plus up to 18 input-only lines ? 5.0v operation at 8 mhz development support ? single-wire backgr ound debug? mode (bdm) ? on-chip hardware breakpoints
general description technical data mc68hc912dt128a ? rev 4.0 30 general description motorola 1.5 mc68hc912dt128a block diagram figure 1-1. mc68hc 912dt128a block diagram txcan0 ddrh porth kwh4 kwh3 kwh2 kwh1 kwh0 kwh7 kwh6 kwh5 ph4 ph3 ph2 ph1 ph0 ph7 ph6 ph5 ddrj portj pj4 pj3 pj2 pj1 pj0 pj7 pj6 pj5 kwj4 kwj3 kwj2 kwj1 kwj0 kwj7 kwj6 kwj5 ioc0 ioc1 ioc2 ioc3 ioc4 ioc5 ioc6 ioc7 ddrt port t 128k byte flash eeprom 8k byte ram port e enhanced pt0 pt1 pt2 pt3 pt4 pt5 pt6 pt7 spi ddrs port s port ad1 pe1 pe2 pe4 pe5 pe6 pe3 pad13 pad14 pad15 pad16 pad17 vdda vssa vrh1 vrl1 pad10 pad11 pad12 reset extal xtal pw0 pw1 pw2 pw3 pwm ddrp port p pp0 pp1 pp2 pp3 vdd 2 vss 2 sci0 rxd0 txd0 rxd1 txd1 sdi/miso sdo/mosi sck ss ps0 ps1 ps2 ps3 ps4 ps5 ps6 ps7 2k byte eeprom pe0 pe7 an13 an14 an15 an16 an17 vdda vssa vrh1 vrl1 an10 an11 an12 bkgd eclk r/w lstrb moda modb xirq dbe/ cal capture timer lite irq sci1 integration module (lim) cpu12 periodic interrupt cop watchdog clock monitor single-wire background debug module breakpoints pll vsspll xfc vddpll can0 rxcan0 ddra port a ddrb port b pa 4 pa 3 pa 2 pa 1 pa 0 pa 7 pa 6 pa 5 pb4 pb3 pb2 pb1 pb0 pb7 pb6 pb5 data15 multiplexed address/data bus a d d r 1 5 a d d r 1 4 a d d r 1 3 a d d r 1 2 a d d r 1 1 a d d r 1 0 a d d r 9 a d d r 8 data14 data13 data12 data11 data10 data9 data8 a d d r 7 a d d r 6 a d d r 5 a d d r 4 a d d r 3 a d d r 2 a d d r 1 a d d r 0 data7 data6 data5 data4 data3 data2 data1 data0 atd1 port ad0 pad03 pad04 pad05 pad06 pad07 vrh0 vrl0 pad00 pad01 pad02 an03 an04 an05 an06 an07 vdda vssa vrh0 vrl0 an00 an01 an02 atd0 ppage data7 data6 data5 data4 data3 data2 data1 data0 wide bus narrow bus vddx 2 vssx 2 power for internal circuitry power for i/o drivers pk0 pk1 pk2 pk3 vstby iic scl sda pib7 pib6 ddrk port k pix0 pix1 pix2 ecs kwu clock generation module pk7 i/o txcan1 can1 rxcan1 txcan2 can2 rxcan2 ddrib port ib
general description mc68hc912dg128a block diagram mc68hc912dt128a ? rev 4.0 technical data motorola general description 31 1.6 mc68hc912dg128a block diagram figure 1-2. mc68hc912d g128a block diagram txcan1 ddrh porth kwh4 kwh3 kwh2 kwh1 kwh0 kwh7 kwh6 kwh5 ph4 ph3 ph2 ph1 ph0 ph7 ph6 ph5 ddrj portj pj4 pj3 pj2 pj1 pj0 pj7 pj6 pj5 kwj4 kwj3 kwj2 kwj1 kwj0 kwj7 kwj6 kwj5 ioc0 ioc1 ioc2 ioc3 ioc4 ioc5 ioc6 ioc7 ddrt port t 128k byte flash eeprom 8k byte ram port e enhanced pt0 pt1 pt2 pt3 pt4 pt5 pt6 pt7 spi ddrs port s port ad1 pe1 pe2 pe4 pe5 pe6 pe3 pad13 pad14 pad15 pad16 pad17 vdda vssa vrh1 vrl1 pad10 pad11 pad12 reset extal xtal pw0 pw1 pw2 pw3 pwm ddrp port p pp0 pp1 pp2 pp3 vdd 2 vss 2 sci0 rxd0 txd0 rxd1 txd1 sdi/miso sdo/mosi sck ss ps0 ps1 ps2 ps3 ps4 ps5 ps6 ps7 2k byte eeprom pe0 pe7 an13 an14 an15 an16 an17 vdda vssa vrh1 vrl1 an10 an11 an12 bkgd eclk r/w lstrb moda modb xirq dbe/ cal capture timer lite irq pib5 pib4 sci1 integration module (lim) cpu12 periodic interrupt cop watchdog clock monitor single-wire background debug module breakpoints pll vsspll xfc vddpll can1 rxcan1 ddra port a ddrb port b pa 4 pa 3 pa 2 pa 1 pa 0 pa 7 pa 6 pa 5 pb4 pb3 pb2 pb1 pb0 pb7 pb6 pb5 data15 multiplexed address/data bus a d d r 1 5 a d d r 1 4 a d d r 1 3 a d d r 1 2 a d d r 1 1 a d d r 1 0 a d d r 9 a d d r 8 data14 data13 data12 data11 data10 data9 data8 a d d r 7 a d d r 6 a d d r 5 a d d r 4 a d d r 3 a d d r 2 a d d r 1 a d d r 0 data7 data6 data5 data4 data3 data2 data1 data0 atd1 port ad0 pad03 pad04 pad05 pad06 pad07 vrh0 vrl0 pad00 pad01 pad02 an03 an04 an05 an06 an07 vdda vssa vrh0 vrl0 an00 an01 an02 atd0 ppage data7 data6 data5 data4 data3 data2 data1 data0 wide bus narrow bus vddx 2 vssx 2 power for internal circuitry power for i/o drivers pk0 pk1 pk2 pk3 vstby iic scl sda pib7 pib6 ddrk port k pix0 pix1 pix2 ecs ddrib portib kwu clock generation module i/o pk7 i/o txcan0 can0 rxcan0
general description technical data mc68hc912dt128a ? rev 4.0 32 general description motorola 1.7 ordering information table 1-1. device ordering information package ambient temperature order number range designator 112-pin tqfp ?40 to +85 c c mc912dg128acpv ?40 to +105 c v mc912dg128avpv ?40 to +125 c m mc912dg128ampv ?40 to +85 c c mc912dt128acpv ?40 to +105 c v mc912dt128avpv ?40 to +125 c m mc912dt128ampv ?40 to +85 c c mc912dg128ccpv ?40 to +105 c v mc912dg128cvpv ?40 to +125 c m mc912dg128cmpv ?40 to +85 c c mc912dt128ccpv ?40 to +105 c v mc912dt128cvpv ?40 to +125 c m mc912dt128cmpv ?40 to +85 c c mc912dg128pcpv ?40 to +105 c v mc912dg128pvpv ?40 to +125 c m MC912DG128PMPV ?40 to +85 c c mc912dt128pcpv ?40 to +105 c v mc912dt128pvpv ?40 to +125 c m mc912dt128pmpv
general description ordering information mc68hc912dt128a ? rev 4.0 technical data motorola general description 33 table 1-2. development t ools ordering information description details order number evaluation board kit evb and user 's manual only m68evb912dg128 serial debug interface low voltage serial debug interface cable can be ordered separately m68sdil12 complete evaluation board kit evb, mcuez debug software, sdil low voltage serial debug interface cable m68kit912dg128 adapter 112 pin tqfp adapter is also available. m68adp912dg128pv
general description technical data mc68hc912dt128a ? rev 4.0 34 general description motorola
mc68hc912dt128a ? rev 4.0 technical data motorola central processing unit 35 technical data ? mc68hc912dt128a section 2. central processing unit 2.1 contents 2.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.3 programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2.4 data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.5 addressing modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 2.6 indexed addressing modes . . . . . . . . . . . . . . . . . . . . . . . . . . .39 2.7 opcodes and operands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.2 introduction the cpu12 is a high-speed, 16 -bit processing unit. it has full 16-bit data paths and wider internal registers ( up to 20 bits) for high-speed extended math instructions. the instruction set is a proper superset of the m68hc11instruction set. the cpu12 al lows instructions with odd byte counts, including many single-byte in structions. this provides efficient use of rom space. an instruction queue buffers program information so the cpu always has immediate access to at leas t three bytes of machine code at the start of every instruction. the cpu12 also offers an extensive set of indexed addressing capabilities.
central processing unit technical data mc68hc912dt128a ? rev 4.0 36 central processing unit motorola 2.3 programming model cpu12 registers are an integral pa rt of the cpu and are not addressed as if they were memory locations. figure 2-1. programming model accumulators a and b are general-purpose 8-bit accumulators used to hold operands and resu lts of arithmetic ca lculations or data manipulations. some instructions tr eat the combinati on of these two 8- bit accumulators as a 16-bit doubl e accumulator (accumulator d). index registers x and y are used for index ed addressing m ode. in the indexed addressing mode, the contents of a 16-bit index register are added to 5-bit, 9-bit, or 16-bit constants or the content of an accumulator to form the effective addre ss of the operand to be us ed in the instruction. 7 15 15 15 15 15 d ix iy sp pc ab n sxh i zvc 0 0 0 0 0 0 7 0 condition code register 8-bit accumulators a & b 16-bit double accumulator d index register x index register y stack pointer program counter or
central processing unit data types mc68hc912dt128a ? rev 4.0 technical data motorola central processing unit 37 stack pointer (sp) points to t he last stack locati on used. the cpu12 supports an automatic pr ogram stack that is used to save system context during subr outine calls and interrupts, and can also be used for temporary storage of dat a. the stack pointer c an also be used in all indexed addressing modes. program counter is a 16-bit register that holds the address of the next instruction to be executed. the pr ogram counter can be used in all indexed addressing modes exce pt autoincrement/decrement. condition code register (ccr) contains five status indicators, two interrupt masking bits, and a stop disable bit. th e five flags are half carry (h), negative (n), zero (z), overflow (v), and carry/borrow (c). the half-carry flag is used only for bcd arithmetic operations. the n, z, v, and c status bits allow for branching based on the results of a previous operation. 2.4 data types the cpu12 supports the following data types: bit data 8-bit and 16-bit si gned and unsi gned integers 16-bit unsigned fractions 16-bit addresses a byte is eight bits wide and can be accessed at any byte location. a word is composed of two consecutiv e bytes with the most significant byte at the lower value address. there are no special requirements for alignment of instructions or operands.
central processing unit technical data mc68hc912dt128a ? rev 4.0 38 central processing unit motorola 2.5 addressing modes addressing modes determine how t he cpu accesses me mory locations to be operated upon. the cpu12 includes all of the addressing modes of the m68hc11 cpu as well as several new forms of indexed addressing. table 2-1 is a summary of the available addressing modes. table 2-1. m68hc12 addressing mode summary addressing mode source format abbreviation description inherent inst (no externally supplied operands) inh operands (if any) are in cpu registers immediate inst # opr8i or inst # opr16i imm operand is included in instruction stream 8- or 16-bit size implied by context direct inst opr8a dir operand is the lower 8-bits of an address in the range $0000 ? $00ff extended inst opr16a ext operand is a 16-bit address relative inst rel8 or inst rel16 rel an 8-bit or 16-bit relative offset from the current pc is supplied in the instruction indexed (5-bit offset) inst oprx5 , xysp idx 5-bit signed constant offset from x, y, sp, or pc indexed (auto pre-decrement) inst oprx3 , ? xys idx auto pre-decrement x, y, or sp by 1 ~ 8 indexed (auto pre-increment) inst oprx3 ,+ xys idx auto pre-increment x, y, or sp by 1 ~ 8 indexed (auto post- decrement) inst oprx3 , xys ? idx auto post-decrement x, y, or sp by 1 ~ 8 indexed (auto post-increment) inst oprx3 , xys + idx auto post-increment x, y, or sp by 1 ~ 8 indexed (accumulator offset) inst abd , xysp idx indexed with 8-bit (a or b) or 16-bit (d) accumulator offset from x, y, sp, or pc indexed (9-bit offset) inst oprx9 , xysp idx1 9-bit signed constant offset from x, y, sp, or pc (lower 8-bits of offset in one extension byte) indexed (16-bit offset) inst oprx16 , xysp idx2 16-bit constant offset from x, y, sp, or pc (16-bit offset in two extension bytes) indexed-indirect (16-bit offset) inst [ oprx16 , xysp ] [idx2] pointer to operand is found at... 16-bit constant offset from x, y, sp, or pc (16-bit offset in two extension bytes) indexed-indirect (d accumulator offset) inst [d, xysp ] [d,idx] pointer to operand is found at... x, y, sp, or pc plus the value in d
central processing unit indexed addressing modes mc68hc912dt128a ? rev 4.0 technical data motorola central processing unit 39 2.6 indexed addressing modes the cpu12 indexed modes reduce execution time and eliminate code size penalties for usi ng the y index register . cpu12 indexed addressing uses a postbyte plus zero, one, or two extension bytes after the instruction opcode. the postbyte and extensions do the following tasks: specify which index register is used. determine whether a value in an accumulator is used as an offset. enable automatic pre- or post-increment or decrement specify use of 5-bit, 9-bi t, or 16-bit si gned offsets. table 2-2. summary of indexed operations postbyte code (xb) source code syntax comments rr0nnnnn ,r n,r ?n,r 5-bit constant offset n = ?16 to +15 rr can specify x, y, sp, or pc 111rr0zs n,r ?n,r constant offset (9- or 16-bit signed) z-0 = 9-bit with sign in lsb of postbyte(s) 1 = 16-bit if z = s = 1, 16-bit offset indexed-indirect (see below) rr can specify x, y, sp, or pc 111rr011 [n,r] 16-bit offset indexed-indirect rr can specify x, y, sp, or pc rr1pnnnn n,?r n,+r n,r? n,r+ auto pre-decrement/increment or auto post-decrement/increment ; p = pre-(0) or post-(1), n = ?8 to ?1, +1 to +8 rr can specify x, y, or sp (pc not a valid choice) 111rr1aa a,r b,r d,r accumulator offset (unsigned 8-bit or 16-bit) aa-00 = a 01 = b 10 = d (16-bit) 11 = see accumulator d offset indexed-indirect rr can specify x, y, sp, or pc 111rr111 [d,r] accumulator d offset indexed-indirect rr can specify x, y, sp, or pc
central processing unit technical data mc68hc912dt128a ? rev 4.0 40 central processing unit motorola 2.7 opcodes and operands the cpu12 uses 8-bit opcodes. each opcode id entifies a particular instruction and associ ated addressing mode to the cpu. several opcodes are require d to provide each instru ction with a range of addressing capabilities. only 256 opcodes would be available if the range of values were restricted to the number that ca n be represented by 8-bit binary numbers. to expand the number of opcodes, a se cond page is added to the opcode map. opc odes on the second p age are preceded by an additional byte with the value $18. to provide additional addressing fl exibility, opcodes can also be followed by a postbyte or extension bytes. post bytes implement certain forms of indexed addre ssing, transfers, exchan ges, and loop primitives. extension bytes contain additional program information such as addresses, offsets, and immediate data.
mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 41 technical data ? mc68hc912dt128a section 3. pinout and signal descriptions 3.1 contents 3.2 mc68hc912dt128a pin assignments in 112-pi n qfp. . . . . . 41 3.3 power supply pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 3.4 signal descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.5 port signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 3.2 mc68hc912dt128a pin as signments in 112-pin qfp the mc68hc912dt128a is available in a 112-pin thin quad flat pack (tqfp). most pins perform two or mo re functions, as described in the signal descriptions . figure 3-1 shows pin assignm ents. in expanded narrow modes the lower byte data is multiplexed with higher byte data through pins 57-64.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 42 pinout and signal descriptions motorola figure 3-1. pin a ssignments in 112-pin qf p for mc68hc912dt128a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 112 111 110 109 108 107 106 105 104 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 mc68hc912dt128a 112tqfp pad17/an17 pad07/an07 pad16/an16 pad06/an06 pad15/an15 pad05/an05 pad14/an14 pad04/an04 pad13/an13 pad03/an03 pad12/an12 pad02/an02 pad11/an11 pad01/an01 pad10/an10 pad00/an00 v rl0 v rh0 v ss v dd pa7/addr15/data15/data7 pa6/addr14/data14/data6 pa5/addr13/data13/data5 pa4/addr12/data12/data4 pa3/addr11/data11/data3 pa2/addr10/data10/data2 pa1/addr9/data9/data1 pa0/addr8/data8/data0 pp3/pw3 pk0/pix0 pk1/pix1 pk2/pix2 pk7/ecs v ddx v ssx rxcan0 txcan0 rxcan1 txcan1 rxcan2 txcan2 pib6/sda pib7/scl test ps7/ss ps6/sck ps5/sdo/mosi ps4/sdi/miso ps3/txd1 ps2/rxd1 ps1/txd0 ps0/rxd0 v ssa v rl1 v rh1 v dda pw2/pp2 pw1/pp1 pw0/pp0 ioc0/pt0 ioc1/pt1 ioc2/pt2 ioc3/pt3 kwj7/pj7 kwj6/pj6 kwj5/pj5 kwj4/pj4 v dd pk3 v ss ioc4/pt4 ioc5/pt5 ioc6/pt6 ioc7/pt7 kwj3/pj3 kwj2/pj2 kwj1/pj1 kwj0/pj0 smodn/taghi/ bkgd addr0/data0/pb0 addr1/data1/pb1 addr2/data2/pb2 addr3/data3/pb3 addr4/data4/pb4 addr5/data5/pb5 addr6/data6/pb6 addr7/data7/pb7 kwh7/ph7 kwh6/ph6 kwh5/ph5 kwh4/ph4 dbe/ cal/pe7 modb/ipipe1/pe6 moda/ipipe0/pe5 eclk/pe4 v ssx vstby v ddx v ddpll xfc v sspll reset extal xtal kwh3/ph3 kwh2/ph2 kwh1/ph1 kwh0/ph0 lstrb /taglo /pe3 r/w /pe2 irq /pe1 xirq /pe0 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 note: test = this pin is used for factory test purposes. it is recommended that this pin is not connected in the application, but it may be bonded to 5.5 v max without issue. never apply voltage higher than 5.5 v to this pin.
pinout and signal descriptions mc68hc912dt128a pin assi gnments in 112-pin qfp mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 43 figure 3-2. pin assign ments in 112-pin qf p for mc68hc912dg128a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 112 111 110 109 108 107 106 105 104 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 mc68hc912dg128a 112tqfp pad17/an17 pad07/an07 pad16/an16 pad06/an06 pad15/an15 pad05/an05 pad14/an14 pad04/an04 pad13/an13 pad03/an03 pad12/an12 pad02/an02 pad11/an11 pad01/an01 pad10/an10 pad00/an00 v rl0 v rh0 v ss v dd pa7/addr15/data15/data7 pa6/addr14/data14/data6 pa5/addr13/data13/data5 pa4/addr12/data12/data4 pa3/addr11/data11/data3 pa2/addr10/data10/data2 pa1/addr9/data9/data1 pa0/addr8/data8/data0 pp3/pw3 pk0/pix0 pk1/pix1 pk2/pix2 pk7/ecs v ddx v ssx rxcan0 txcan0 rxcan1 txcan1 pib4 pib5 pib6/sda pib7/scl test ps7/ss ps6/sck ps5/sdo/mosi ps4/sdi/miso ps3/txd1 ps2/rxd1 ps1/txd0 ps0/rxd0 v ssa v rl1 v rh1 v dda pw2/pp2 pw1/pp1 pw0/pp0 ioc0/pt0 ioc1/pt1 ioc2/pt2 ioc3/pt3 kwj7/pj7 kwj6/pj6 kwj5/pj5 kwj4/pj4 v dd pk3 v ss ioc4/pt4 ioc5/pt5 ioc6/pt6 ioc7/pt7 kwj3/pj3 kwj2/pj2 kwj1/pj1 kwj0/pj0 smodn/taghi/ bkgd addr0/data0/pb0 addr1/data1/pb1 addr2/data2/pb2 addr3/data3/pb3 addr4/data4/pb4 addr5/data5/pb5 addr6/data6/pb6 addr7/data7/pb7 kwh7/ph7 kwh6/ph6 kwh5/ph5 kwh4/ph4 eclk /dbe/ cal/pe7 cgmtst/modb/ipipe1/pe6 moda/ipipe0/pe5 eclk/pe4 v ssx vstby v ddx v ddpll xfc v sspll reset extal xtal kwh3/ph3 kwh2/ph2 kwh1/ph1 kwh0/ph0 lstrb /taglo /pe3 r/w /pe2 irq /pe1 xirq /pe0 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 60 59 58 57 note: test = this pin is used for factory test purposes. it is recommended that this pin is not connected in the application, but it may be bonded to 5.5 v max without issue. never apply voltage higher than 5.5 v to this pin.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 44 pinout and signal descriptions motorola figure 3-3. 112-pin qfp m echanical dimensions (case no. 987) dim a min max 20.000 bsc millimeters a1 10.000 bsc b 20.000 bsc b1 10.000 bsc c --- 1.600 c1 0.050 0.150 c2 1.350 1.450 d 0.270 0.370 e 0.450 0.750 f 0.270 0.330 g 0.650 bsc j 0.090 0.170 k 0.500 ref p 0.325 bsc r1 0.100 0.200 r2 0.100 0.200 s 22.000 bsc s1 11.000 bsc v 22.000 bsc v1 11.000 bsc y 0.250 ref z 1.000 ref aa 0.090 0.160 11 11 13 7 13 view y l-m 0.20 n t 4x 4x 28 tips pin 1 ident 1 112 85 84 28 57 29 56 b v v1 b1 a1 s1 a s view ab 0.10 3 c c2 2 0.050 seating plane gage plane 1 view ab c1 (z) (y) e (k) r2 r1 0.25 j1 view y j1 p g 108x 4x section j1-j1 base rotated 90 counterclockwise metal j aa f d l-m m 0.13 n t 1 2 3 c l l-m 0.20 n t l n m t t 112x x x=l, m or n r r 8 3 0 notes: 1. dimensioning and tolerancing per asme y14.5m, 1994. 2. dimensions in millimeters. 3. datums l, m and n to be determined at seating plane, datum t. 4. dimensions s and v to be determined at seating plane, datum t. 5. dimensions a and b do not include mold protrusion. allowable protrusion is 0.25 per side. dimensions a and b include mold mismatch. 6. dimension d does not include dambar protrusion. allowable dambar protrusion shall not cause the d dimension to exceed 0.46.
pinout and signal descriptions power supply pins mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 45 3.3 power supply pins mc68hc912dt128a power and ground pi ns are described below and summarized in table 3-1 . all power supply pins must be connected to appropriate supplies. on no account must any pins be left floating. 3.3.1 internal power (v dd ) and ground (v ss ) power is supplied to the mcu through v dd and v ss . because fast signal transitions place high, short-dur ation current demands on the power supply, use bypass capacitors with high-frequency characteristics and place them as close to the mcu as possible. 3.3.2 external power (v ddx ) and ground (v ssx ) external power and ground for i/o drivers. because fast signal transitions place high, short-dur ation current demands on the power supply, use bypass capacitors with high-frequency characteristics and place them as close to the mcu as possible. bypass requirements depend on how heavily t he mcu pins are loaded. 3.3.3 v dda , v ssa provides operating voltage and gr ound for the anal og-to-digital converter. this allows the supply voltage to the a/d to be bypassed independently. 3.3.4 analog to digita l reference voltages (v rh , v rl ) v rh0 , v rl0 : reference voltage high and low for atd converter 0. v rh1 , v rl1 : reference voltage high and low for atd converter 1. if the atd modules ar e not used, leaving v rh connected to v dd will not result in an increase of power consumption.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 46 pinout and signal descriptions motorola 3.3.5 v ddpll , v sspll provides operating voltage and gro und for the phase-locked loop. this allows the supply voltage to th e pll to be bypassed independently. note: the vsspll pin should alwa ys be grounded even if the pll is not used. the vddpll pin should not be left floating. it is recommended to connect the vddpll pin to grou nd if the pll is not used. 3.3.6 xfc pll loop filter. please see appendix: cgm practical aspects for information on how to calculate pll loop filter elements. any current leakage on this pi n must be avoided. figure 3-4. pll lo op filter connections mcu xfc r 0 c 0 c a vddpll
pinout and signal descriptions signal descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 47 3.3.7 v stby stand-by voltage supply to static ram. used to maintain the contents of ram with minimal power when the rest of the chip is powered down. 3.4 signal descriptions 3.4.1 crystal driver and exter nal clock input (xtal, extal) these pins provide the interface fo r either a cryst al or a cmos compatible clock to control the inter nal clock generator ci rcuitry. out of reset the frequency applied to extal is twice the desired e?clock rate. all the device clocks are derived fr om the extal i nput frequency. 3.4.1.1 crystal connections refer to section 13. oscillator for details of cr ystal connections. table 3-1. mc68hc912d t128a power and gr ound connection summary mnemonic pin number description 112-pin qfp v dd 12, 65 internal power and ground. v ss 14, 66 v ddx 42, 107 external power and ground, supply to pin drivers. v ssx 40, 106 v dda 85 operating voltage and ground for the analog-to-digital converter, allows the supply voltage to the a/d to be bypassed independently. v ssa 88 v rh1 86 reference voltages for the analog-to-digital converter 1 v rl1 87 v rh0 67 reference voltages for the analog-to-digital converter 0. v rl0 68 v ddpll 43 provides operating voltage and ground for the phase-locked loop. this allows the supply voltage to the pll to be bypassed independently. v sspll 45 v stby 41 stand-by voltage supply to maintain the contents of ram with minimal power when the rest of the chip is powered down.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 48 pinout and signal descriptions motorola note: when selecting a crystal, it is re commended to use one wi th the lowest possible frequency in order to minimise emc emissions. 3.4.1.2 external os cillator connections xtal is the crystal output . the xtal pin must be left unterminated when an external cmos compatible clo ck input is connected to the extal pin. the xtal output is normally in tended to drive only a crystal. the xtal output can be buffered with a high-impedance buf fer to drive the extal input of another device. figure 3-5. external oscillator connections 3.4.2 e-clock output (eclk) eclk is the output connection for the internal bus clock. it is used to demultiplex the address and data in expanded modes and is used as a timing reference. eclk frequency is equal to 1/2 the crystal frequency out of reset. the e-clock output is turn ed off in single chip user mode to reduce the effects of rfi. it can be turned on if necessary. in special single-chip mode, the e-clock is tu rned on at reset and can be turned off. in special periphera l mode the e-clock is an i nput to the m cu. all clocks, including the e clock, are halted when the mcu is in stop mode. it is possible to configure the mcu to inte rface to slow external memory. eclk can be stretched for such accesses. 3.4.3 reset (reset ) an active low bidirect ional contro l signal, reset , acts as an input to initialize the mcu to a known start-up state. it also acts as an open-drain nc mcu extal xtal 2 x e cmos-compatible external oscillator
pinout and signal descriptions signal descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 49 output to indicate that an internal fa ilure has been detecte d in either the clock monitor or cop watchdog ci rcuit. the mcu goes into reset asynchronously and comes out of re set synchronously. this allows the part to reach a pr oper reset state even if the clocks have failed, while allowing synchroniz ed operation when starting out of reset. it is important to use an external low-voltage reset circuit (such as mc34064 or mc34164) to prevent corruption of ram or eeprom due to power transitions. the reset sequence is initiated by any of the following events: power-on-reset (por) cop watchdog enabled and watchdog timer times out clock monitor enabled an d clock monitor detec ts slow or stopped clock user applies a low le vel to the reset pin external circuitry connected to the reset pin should not include a large capacitance that would interf ere with the abili ty of this signal to rise to a valid logic one within nine bus cycles after the low drive is released. upon detection of any rese t, an internal circuit drives the reset pin low and a clocked reset sequence controls when the mcu ca n begin normal processing. in the case of por or a clock monitor error, a 4096 cycle oscillator startup delay is impos ed before the reset recovery sequence starts (reset is driven low throughou t this 4096 cycle delay ). the internal reset recovery sequence then drives reset low for 16 to 17 cycles and releases the drive to allow reset to rise. nine cycles later this circuit samples the reset pin to see if it has risen to a logic one level. if reset is low at this point, the reset is a ssumed to be coming from an external request and the internally latched states of the cop timeout and clock monitor failure are cleared so the normal rese t vector ($fffe:ffff) is taken when reset is finally released. if reset is high after this nine cycle delay, the reset source is tentativel y assumed to be either a cop failure or a clock monitor fail. if the internal ly latched state of the clock monitor fail circuit is true, proc essing begins by fetching th e clock monitor vector ($fffc:fffd). if no clock monitor failure is indi cated, and the latched state of the cop timeout is true, pr ocessing begins by fetching the cop
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 50 pinout and signal descriptions motorola vector ($fffa:fffb). if neither clock monitor fail nor cop timeout are pending, processing begins by fe tching the normal reset vector ($fffe:ffff). 3.4.4 maskable interrupt request (irq ) the irq input provides a means of ap plying asynchronous interrupt requests to the mcu. ei ther falling edge- sensitive triggering or level- sensitive triggering is program selectable (intcr register). irq is always enabled and configured to level- sensitive triggeri ng at reset. it can be disabled by clearing irqen bit (intcr register). when the mcu is reset the irq function is masked in the c ondition code register. this pin is always an input and can always be read. there is an active pull-up on this pin while in reset and immedi ately out of rese t. the pullup can be turned off by clearing pu pe in the pucr register.
pinout and signal descriptions signal descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 51 3.4.5 nonmaskable interrupt (xirq ) the xirq input provides a means of requesting a nonmask able interrupt after reset initialization. during re set, the x bit in the condition code register (ccr) is set and any interrupt is masked until mcu software enables it. because the xirq input is level sensit ive, it can be connected to a multiple-source wired-or network. this pi n is always an input and can always be read. there is an active pull-up on this pin while in reset and immediately out of reset. the pul lup can be turned off by clearing pupe in the pucr register. xirq is often used as a power loss detect interrupt. whenever xirq or irq are used with multiple interrupt sources (irq must be configured for level-sensitive operation if there is more than one source of irq interrupt), each source must drive the interrupt input with an open-drain type of driver to avoi d contention between outputs. there must also be an interlo ck mechanism at each interr upt source so that the source holds the interrupt line low until the mc u recognizes and acknowledges the interrupt request. if the interrupt line is held low, the mcu will recognize another interrupt as soon as t he interrupt mask bit in the mcu is cleared ( normally upon return from an interrupt). 3.4.6 mode select (s modn, moda, and modb) the state of these pins during rese t determine the mcu operating mode. after reset, moda and mo db can be configured as instruction queue tracking signals ipipe0 and ipip e1 in expanded modes. moda and modb have active pulldowns during reset. the smodn pin has an active pullup w hen configured as an input. the pin can be used as bkgd or taghi after reset. 3.4.7 single-wire b ackground mode pin (bkgd) the bkgd pin receives and trans mits serial background debugging commands. a special self-timing protoc ol is used. the bkgd pin has an active pullup when configured as an input; bkgd has no pullup control. refer to development support .
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 52 pinout and signal descriptions motorola 3.4.8 external addres s and data buses (ad dr[15:0] and data[15:0]) external bus pins share functions with general-purpose i/o ports a and b. in single-chip operating modes, the pins can be used for i/o; in expanded modes, the pins are us ed for the external buses. in expanded wide m ode, ports a and b are us ed for multiplexed 16-bit data and address buses. pa[7:0] correspond to addr[15:8]/data[15:8]; pb[7:0] corr espond to addr[7:0]/data[7:0]. in expanded narrow mode, ports a and b are used for the16-bit address bus, and an 8-bit data bus is multiplexed with the most significant half of the address bus on port a. in this mode, 16-bit data is handled as two back-to-back bus cycles, one for the high byte fo llowed by one for the low byte. pa[7:0] correspond to a ddr[15:8] and to data[15:8] or data[7:0], depending on the bus cycl e. the state of the address pins should be latched at t he rising edge of e. to al low for maximum address setup time at external devices, a transparent latch should be used. 3.4.9 read/write (r/w ) in all modes this pi n can be used as a genera l-purpose i/o and is an input with an active pu ll-up out of reset. if th e read/write function is required it should be enabl ed by setting the rd we bit in the pear register. external writes wil l not be possibl e until enabled. 3.4.10 low-byt e strobe (lstrb) in all modes this pi n can be used as a genera l-purpose i/o and is an input with an active pull-up out of reset. if the strobe function is required, it should be enabled by se tting the lstre bit in the pear register. this signal is used in write operations. theref ore external low byte writes will not be possible until this function is enabled. this pin is also used as tag l o in special expanded modes and is multiplexed with the lstrb function.
pinout and signal descriptions signal descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 53 3.4.11 instruction queue tracki ng signals (ipi pe1 and ipipe0) ipipe1 (pe6) and ipipe0 (pe5) signals are used to track the state of the internal instruction queue. data movement and execution state information is time-multiplex ed on the two signals. refer to development support . 3.4.12 data bus enable (dbe ) the dbe pin (pe7) is an active low signal that will be asserted low during e-clock high time. dbe provides separation between output of a multiplexed address and the input of data. when an external address is stretched, dbe is asserted during what woul d be the last quarter cycle of the last e-clock cycle of stretch. in expanded m odes this pin is used to enable the drive contro l of external buses duri ng external reads. use of the dbe is controlled by th e ndbe bit in the pear register. dbe is enabled out of reset in expanded modes. 3.4.13 inverted e clock (eclk ) the eclk pin (pe7) can be used to latch the address for de- multiplexing. it has the same behavior as the ecl k, except is inverted. in expanded modes this pin is used to enable the drive control of external buses during external re ads. use of the eclk is controlled by the ndbe and dbene bits in th e pear register. 3.4.14 calibrat ion reference (cal) the cal pin (pe7) is the output of the slow mode programmable clock divider, slwclk, and is used as a ca libration referenc e. the slwclk frequency is equal to th e crystal frequency out of reset and always has a 50% duty. if the dbe function is enabled it will override the enabled cal output. the cal pin output is disabled by cl earing cale bit in the pear register.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 54 pinout and signal descriptions motorola 3.4.15 clock generation module test (cgmtst) the cgmtst pin (pe6) is the output of the clocks tested when cgmte bit is set in pear regi ster. the pipoe bit must be cleared for the clocks to be tested. 3.4.16 test this pin is used for fact ory test purposes. it is recommended that this pin is not connected in the applicatio n, but it may be bonded to 5.5 v max without issue. neve r apply voltage hi gher than 5.5 v to this pin table 3-2 . mc68hc912dt128a signal description summary pin name shared port pin number description 112-pin extal - 47 crystal driver and external clock input pins. on reset all the device clocks are derived from the extal input frequency. xtal is the crystal output. xtal - 48 reset - 46 an active low bidirectional control signal, reset acts as an input to initialize the mcu to a known start-up state, and an output when cop or clock monitor causes a reset. addr[7:0] data[7:0] pb[7:0] 31?24 external bus pins share function with general-purpose i/o ports a and b. in single chip modes, the pins can be used for i/o. in expanded modes, the pins are used for the external buses. addr[15:8] data[15:8] pa[7:0] 64?57 dbe pe7 36 data bus control and, in expanded mode, enables the drive control of external buses during external reads. eclk pe7 36 inverted e clock used to latch the address. cal pe7 36 cal is the output of the slow mode programmable clock divider, slwclk, and is used as a calibration reference for functions such as time of day. it is overridden when dbe function is enabled. it always has a 50% duty. cgmtst pe6 37 clock generation module test output. modb/ipip e1, moda/ipip e0 pe6, pe5 37, 38 state of mode select pins during reset determine the initial operating mode of the mcu. after reset, modb and moda can be configured as instruction queue tracking signals ipipe1 and ipipe0 or as general-purpose i/o pins. eclk pe4 39 e clock is the output connection for the external bus clock. eclk is used as a timing reference and for address demultiplexing. lstrb/ta glo pe3 53 low byte strobe (0 = low byte valid), in all modes this pin can be used as i/o. the low strobe function is the exclusive-nor of a0 and the internal sz8 signal. (the sz8 internal signal indicates the size 16/8 access.) pin function ta g l o used in instruction tagging. see development support . r/w pe2 54 indicates direction of data on expansion bus. shares function with general- purpose i/o. read/write in expanded modes.
pinout and signal descriptions signal descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 55 irq pe1 55 maskable interrupt request input provides a means of applying asynchronous interrupt requests to the mcu. either falling edge-sensitive triggering or level- sensitive triggering is progra m selectable (intcr register). xirq pe0 56 provides a means of requesting asynchronous nonmaskable interrupt requests after reset initialization smodn/ bkgd/ tag h i -23 during reset, this pin determines special or normal operating mode. after reset, single-wire background interface pin is dedicated to the background debug function. pin function taghi used in instruct ion tagging. see development support . ix[2:0] pk[2:0] 109-111 page index register emulation outputs. ecs pk7 108 emulation chip select. pw[3:0] pp[3:0] 112, 1?3 pulse width modulator channel outputs. ss ps7 96 slave select output for spi master mode, input for slave mode or master mode. sck ps6 95 serial clock for spi system. sdo/mosi ps5 94 master out/slave in pin for serial peripheral interface sdi/miso ps4 93 master in/slave out pin for serial peripheral interface txd1 ps3 92 sci1 transmit pin rxd1 ps2 91 sci1 receive pin txd0 ps1 90 sci0 transmit pin rxd0 ps0 89 sci0 receive pin ioc[7:0] pt[7:0] 18?15, 7?4 pins used for input capture and output compare in the timer and pulse accumulator subsystem. an1[7:0] pad1[7:0] 84/82/80/ 78/76/74/ 72/70 analog inputs for the analog-to-digital conversion module 1 an0[7:0] pad0[7:0] 83/81/79/ 77/75/73/ 71/69 analog inputs for the analog-to-digital conversion module 0 test - 97 used for factory test purposes. do not connect in the application; may be bonded to 5.5 v max. txcan2 (1) -100 mscan2 transmit pin (mc68hc912dt128a only). leave unconnected if mscan2 is not used. rxcan2 (1) -101 mscan2 receive pin (mc68hc912dt128a only). pin has internal pull-up; where mscan module is not used, do not tie to vss. txcan1 - 102 mscan1 transmit pin. leave unconnected if mscan1 is not used. rxcan1 - 103 mscan1 receive pin. pin has internal pull-up; where mscan module is not used, do not tie to vss. txcan0 - 104 mscan0 transmit pin. leave unconnected if mscan0 is not used. rxcan0 - 105 mscan0 receive pin. pin has internal pull-up; where mscan module is not used, do not tie to vss. scl pib7 98 i 2 c bus serial clock line pin table 3-2 . mc68hc912dt128a signal description summary pin name shared port pin number description 112-pin
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 56 pinout and signal descriptions motorola 3.5 port signals the mc68hc912dt128a inco rporates eleven ports which are used to control and access the various de vice subsystems. when not used for these purposes, port pins may be used for general-purpose i/o. in addition to the pins described below, each port consists of a data register which can be read and writ ten at any time, and, with the exception of port ad0, port ad1, pe[1:0], rx can and txcan, a data direction register which controls the direct ion of each pin. after reset all general purpose i/o pins are conf igured as input. 3.5.1 port a port a pins are used for addr ess and data in expanded modes. when this port is not used fo r external access such as in single-chip mode, these pins can be used as general pur pose i/o. the port data register is not in the address map during expan ded and peripheral mode operation. when it is in the map, port a can be read or written at anytime. register ddra determines whether each port a pin is an input or output. ddra is not in the ad dress map during exp anded and peripheral mode operation. setting a bi t in ddra makes the co rresponding bit in port a an output; clearing a bit in ddra ma kes the corresponding bit in port a an input. the defaul t reset state of dd ra is all zeroes. when the pupa bit in the puc r register is set, all port a input pins are pulled-up internally by an active pull-up device. pucr is not in the address map in peripheral mode. sda pib6 99 i 2 c bus serial data line pin kwj[7:0] pj[7:0] 8?11, 19?22 key wake-up and general purpose i/o; can cause an interrupt when an input transitions from high to low or from low to high (kwpj). kwh[7:0] ph[7:0] 32?35, 49?52 key wake-up and general purpose i/o; can cause an interrupt when an input transitions from high to low or from low to high (kwph). 1. mc68hc912dt128a only table 3-2 . mc68hc912dt128a signal description summary pin name shared port pin number description 112-pin
pinout and signal descriptions port signals mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 57 setting the rdpa bit in r egister rdriv causes al l port a output s to have reduced drive level. rdriv can be wri tten once after rese t. rdriv is not in the address map in pe ripheral mode. refer to bus control and input/output . 3.5.2 port b port b pins are used for addr ess and data in expanded modes. when this port is not used fo r external access such as in single-chip mode, these pins can be used as general pur pose i/o. the port data register is not in the address map during expan ded and peripheral mode operation. when it is in the map, port b can be read or written at anytime. register ddrb determines whether each port b pin is an input or output. ddrb is not in the ad dress map during exp anded and peripheral mode operation. setting a bi t in ddrb makes the co rresponding bit in port b an output; clearing a bit in ddrb ma kes the corresponding bit in port b an input. the defaul t reset state of dd rb is all zeroes. when the pupb bit in the puc r register is set, all port b input pins are pulled-up internally by an active pull-up device. pucr is not in the address map in peripheral mode. setting the rdpb bit in r egister rdriv causes al l port b output s to have reduced drive level. rdriv can be wri tten once after rese t. rdriv is not in the address map in pe ripheral mode. refer to bus control and input/output . 3.5.3 port e port e pins operate differently from port a and b pins. port e pins are used for bus control signals and inte rrupt service request signals. when a pin is not used for one of these specific functi ons, it can be used as general-purpose i/o. however, two of the pins (pe[1:0]) can only be used for input, and the stat es of these pins can be read in the port data register even when t hey are used for irq and xirq . the pear register determines pin function, and register ddre determines whether each pi n is an input or output when it is used for
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 58 pinout and signal descriptions motorola general-purpose i/o. pear settings override ddre settings. because pe[1:0] are input-only pins , only ddre[7:2] have ef fect. setting a bit in the ddre register ma kes the corresponding bi t in port e an output; clearing a bit in the dd re register makes the co rresponding bit in port e an input. the defaul t reset state of dd re is all zeroes. when the pupe bit in the pucr register is set, pe[7,3,2,1,0] are pulled up. pe[7,3,2,0] are active pull-up devices. pupc r is not in the address map in peri pheral mode. neither port e nor ddre is in the map in peripheral mode or in the internal map in exp anded modes with eme set. setting the rdpe bit in r egister rdriv causes al l port e output s to have reduced drive level. rdriv can be wri tten once after rese t. rdriv is not in the address map in pe ripheral mode. refer to bus control and input/output . 3.5.4 port h port h pins are used for key wake- ups that can be used with the pins configured as inputs or outputs. the key wake -ups are triggered with either a rising or falling edge signal (k wph). an interrupt is generated if the corresponding bit is enabl ed (kwieh). if any of the interrupts is not enabled, the correspondi ng pin can be used as a general purpose i/o pin. refer to i/o ports with key wake-up . register ddrh determines whether each port h pin is an input or output. setting a bit in ddrh makes the corresponding bit in port h an output; clearing a bit in ddrh ma kes the corresponding bit in port h an input. the default reset state of ddrh is all zeroes. register kwph not only determines what type of edge the key wake ups are triggered, but it also determines what ty pe of resistive load is used for port h input pins w hen puph bit is set in the pucr register. setting a bit in kwph makes the corresponding key wake up input pin trigger at rising edges and loads a pul l down in the correspon ding port h input pin. clearing a bit in kwph makes the corresponding key wake up input pin trigger at falli ng edges and loads a pul l up in the corresponding port h input pin. the default stat e of kwph is all zeroes.
pinout and signal descriptions port signals mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 59 setting the rdph bit in register rdri v causes all port h outputs to have reduced drive level. rdriv can be wri tten once after rese t. rdriv is not in the address map in pe ripheral mode. refer to bus control and input/output . 3.5.5 port j port j pins are used for key wake-ups that can be used with the pins configured as inputs or outputs. the key wake -ups are triggered with either a rising or falli ng edge signal (kwpj) . an interrupt is generated if the corresponding bit is enab led (kwiej). if any of the interrupts is not enabled, the correspondi ng pin can be used as a general purpose i/o pin. refer to i/o ports with key wake-up . register ddrj determines whether each port j pin is an input or output. setting a bit in ddrj makes the corresponding bi t in port j an output; clearing a bit in ddrj makes the corr esponding bit in port j an input. the default reset state of ddrj is all zeroes. register kwpj not only determines wh at type of edge the key wake ups are triggered, but it also determines what ty pe of resistive load is used for port j input pins when pupj bit is set in t he pucr register. setting a bit in kwpj makes the corresponding key wake up input pin trigger at rising edges and l oads a pull down in the co rresponding port j input pin. clearing a bit in kwpj makes the corresponding key wake up input pin trigger at falli ng edges and loads a pul l up in the corresponding port j input pin. the default state of kwpj is all zeroes. setting the rdpj bit in r egister rdriv causes all port j outputs to have reduced drive level. rdriv can be wri tten once after rese t. rdriv is not in the address map in pe ripheral mode. refer to bus control and input/output . 3.5.6 port k port k pins are used for page index emulation in expanded or peripheral modes. when page index emul ation is not enabled, emk is not set in mode register, or the part is in si ngle chip mode, these pins can be used
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 60 pinout and signal descriptions motorola for general purpose i/o. port k bit 3 is used as a general purpose i/o pin only. the port data register is not in the address map during expanded and peripheral mode operatio n with emk set. when it is in the map, port k can be read or written at anytime. register ddrk determines whether each port k pin is an input or output. ddrk is not in the ad dress map during exp anded and peripheral mode operation with emk set. setting a bi t in ddrk makes the corresponding bit in port k an output; clearing a bit in ddrk makes the corresponding bit in port k an input. the default rese t state of ddrk is all zeroes. when the pupk bit in the puc r register is set, all port k input pins are pulled-up internally by an active pull-up device. pucr is not in the address map in peripheral mode. setting the rdpk bit in r egister rdriv causes al l port k output s to have reduced drive level. rdriv can be wri tten once after rese t. rdriv is not in the address map in pe ripheral mode. refer to bus control and input/output . 3.5.7 port can2 (mc68hc912dt128a only) the mscan2 uses two exte rnal pins, one input (rxcan2) and one output (txcan2). the txcan2 output pin represents the logic level on the can: ?0? is fo r a dominant state, and ?1? is for a recessive state. rxcan2 is on bit 0 of port can2, txcan2 is on bi t 1. if the mscan2 is not used, txcan2 should be left unco nnected and, due to an internal pull-up, the rxcan2 pin should not be tied to vss. 3.5.8 port can1 the mscan1 uses two exte rnal pins, one input (rxcan1) and one output (txcan1). the txcan1 output pin represents the logic level on the can: ?0? is fo r a dominant state, and ?1? is for a recessive state. rxcan1 is on bit 0 of port can1, txcan1 is on bi t 1. if the mscan1 is not used, txcan1 should be left unco nnected and, due to an internal pull-up, the rxcan1 pin should not be tied to vss.
pinout and signal descriptions port signals mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 61 3.5.9 port can0 the mscan0 uses two exte rnal pins, one input (rxcan0) and one output (txcan0). the txcan0 output pin represents the logic level on the can: ?0? is fo r a dominant state, and ?1? is for a recessive state. rxcan0 is on bit 0 of port can0, txcan0 is on bi t 1. if the mscan0 is not used, txcan0 should be left unco nnected and, due to an internal pull-up, the rxcan0 pin should not be tied to vss. 3.5.10 port ib bidirectional pins to iic bus interface subsystem. the iic bus interface uses a serial data line (sda) and serial cl ock line (scl) for data transfer. the pins are connected to a positive voltage supply via a pull up resistor. the pull ups can be enabled internally or connected externally. the output stages hav e open drain outputs in order to perform the wired-and functi on. when the ii c is disabled the pins can be used as general purpose i/o pins. sc l is on bit 7 of port ib and sda is on bit 6. on the mc 68hc912dg128a, the remaini ng two pins of port ib (pib5 and pib4) are co ntrolled by registers in the iic address space. register ddrib determi nes pin direction of port ib when used for general-purpose i/o. when d drib bits are set, t he corresponding pin is configured for output. on reset the ddrib bits are cleared and the corresponding pin is configured for input. when the pupib bit in t he ibpurd register is se t, all input pins are pulled up internally by an active pull- up device. pullups are disabled after reset, except for input ports 0 through 5, whic h are always on regardless of pupib bit. setting the rdpib bit in the ibpurd register c onfigures al l port ib outputs to have reduced drive le vels. levels are at normal drive capability after reset. the ibpurd r egister can be read or written anytime after reset. refer to section inter ic bus .
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 62 pinout and signal descriptions motorola 3.5.11 port ad1 this port is an analog input interface to the analog-to-digital subsystem and used for general-purpos e input. when analog-to -digital functions are not enabled, the port has eight general -purpose input pins, pad1[7:0]. the adpu bit in the atd1ctl2 regi ster enables the a/d function. port ad1 pins are inputs; no data direction register is associated with this port. the port has no resistive input loads and no reduced drive controls. refer to analog-to-digital converter . 3.5.12 port ad0 this port is an analog input interface to the analog-to-digital subsystem and used for general-purpos e input. when analog-to -digital functions are not enabled, the port has eight general -purpose input pins, pad0[7:0]. the adpu bit in the atd0ctl2 regi ster enables the a/d function. port ad0 pins are inputs; no data direction register is associated with this port. the port has no resistive input loads and no reduced drive controls. refer to analog-to-digital converter . 3.5.13 port p the four pulse-width modulation c hannel outputs share general-purpose port p pins. the pwm function is enabled with the pwen register. enabling pwm pins takes precedenc e over the general -purpose port. when pulse-width m odulation is not in use, t he port pins may be used for general-purpose i/o. register ddrp determines pin dire ction of port p when used for general-purpose i/o. when d drp bits are set, t he corresponding pin is configured for output. on reset the ddrp bits are cleared and the corresponding pin is configured for input. when the pupp bit in the pwctl register is set, all input pins are pulled up internally by an active pull-up device. pullups are disabled after reset.
pinout and signal descriptions port signals mc68hc912dt128a ? rev 4.0 technical data motorola pinout and signal descriptions 63 setting the rdpp bit in the pwctl r egister configures all port p outputs to have reduced drive leve ls. levels are at normal drive capability after reset. the pwctl r egister can be read or wri tten anytime after reset. refer to pulse width modulator . 3.5.14 port s port s is the 8-bit interf ace to the standard serial interface consisting of the two serial communications interf aces (sci1 and sc i0) and the serial peripheral interface (spi) subsystems. port s pins are available for general-purpose i/o when st andard serial functi ons are not enabled. port s pins serve several functi ons depending on the va rious internal control registers. if wo ms bit in the sc0cr1r egister is set, the p- channel drivers of the output buffers are disabled (w ire-or mode) for pins 0 through 3. if swom bit in the sp0cr1 register is set, the p-channel drivers of the output bu ffers are disabled (wir e-or mode) for pins 4 through 7. the open drai n control affects both the serial and the general- purpose outputs. if the rdps bit in the sp0cr2 register is set, port s pin drive capabilities are r educed. if pups bi t in the sp0cr2 register is set, a pull-up device is activated for each port s pin programmed as a general purpose input. if the pin is programmed as a general-purpose output, the pull-up is disconn ected from the pin regar dless of the state of pups bit. see multiple serial interface . 3.5.15 port t this port provides eight general-purpose i/o pins when not enabled for input capture and output compare in the timer and pulse accumulator subsystem. the ten bit in the tscr re gister enables the timer function. the pulse accumulator subsystem is enabled with the p aen bit in the pactl register. register ddrt determines pin direct ion of port t when used for general- purpose i/o. when ddrt bits are set, th e corresponding pin is configured for output. on reset the ddrt bits are cleared and the corresponding pin is configured for input.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 64 pinout and signal descriptions motorola when the pupt bit in the tmsk2 register is set, al l input pins are pulled up internally by an active pull-up device. pullups are disabled after reset. setting the rdpt bit in the tmsk2 r egister configures all port t outputs to have reduced drive leve ls. levels are at normal drive capability after reset. the tmsk2 register can be read or written anytim e after reset. refer to enhanced capture timer . table 3-3 . mc68hc912dt128a port description summary port name pin numbers data direction register (address) description 112-pin port a pa[7:0] 64-57 in/out ddra ($0002) port a and port b pins are used for address and data in expanded modes. the port data registers are not in the address map during expanded and peripheral mode operation. when in the map, port a and port b can be read or written any time. ddra and ddrb are not in the address map in expanded or peripheral modes. port b pb[7:0] 31?24 in/out ddrb ($0003) port ad1 pad1[7:0] 84/82/80/7 8/76/74/72 /70 in analog-to-digital converter 1 and general-purpose i/o. port ad0 pad0[7:0] 83/81/79/7 7/75/73/71 /69 in analog-to-digital converter 0 and general-purpose i/o. port can2 pcan2[1:0] (1) 100?101 pcan2[1] out pcan2[0] in pcan2[1:0] are used with the mscan2 module and cannot be used as general purpose i/o (mc68hc912dt128a only). port can1 pcan1[1:0] 102?103 pcan1[1] out pcan1[0] in pcan1[1:0] are used with the mscan1 module and cannot be used as general purpose i/o. port can0 pcan0[1:0] 104?105 pcan0[1] out pcan0[0] in pcan0[1:0] are used with the mscan0 module and cannot be used as general purpose i/o. port ib pib[7:6] 98?99 in/out ddrib ($00e7) general purpose i/o. pib[7:6] are used with the i-bus module when enabled. port ib pib[5:4] (2) 100?101 in/out ddrib ($00e7) general purpose i/o (mc68hc912dg128a only). port e pe[7:0] 36?39, 53?56 pe[1:0] in pe[7:2] in/out ddre ($0009) mode selection, bus control signals and interrupt service request signals; or general-purpose i/o. port k pk[7,3:0] 13, 108-111 in/out ddrk ($00fd) page index emulation signals in expanded or peripheral mode or general-purpose i/o. port p pp[3:0] 112, 1?3 in/out ddrp ($0057) general-purpose i/o. pp[3:0] are used with the pulse-width modulator when enabled.
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 65 pinout and signal descriptions motorola 3.5.16 port pull-up pull-down and reduced drive mcu ports can be conf igured for internal pull-up. to reduce power consumption and rfi, the pin outpu t drivers can be configured to operate at a reduced driv e level. reduced drive ca uses a slight increase in transition time depending on loadi ng and should be used only for ports which have a light loading. table 3-4 summarizes the po rt pull-up default status and controls. port s ps[7:0] 96?89 in/out ddrs ($00d7) serial communications interfaces 1 and 0 and serial peripheral interface subsystems; or general-purpose i/o. port t pt[7:0] 18?15, 7?4 in/out ddrt ($00af) general-purpose i/o when not enabled for input capture and output compare in the timer and pulse accumulator subsystem. 1. mc68hc912dt128a only 2. mc68hc912dg128a only table 3-3 . mc68hc912dt128a port description summary port name pin numbers data direction register (address) description 112-pin table 3-4. port pull-up, pu ll-down and reduced drive summary enable bit reduced drive control bit port name resistive input loads register (address) bit name reset state register (address) bit name reset state port a pull-up pucr ($000c) pupa disabled rdriv ($000d) rdpa full drive port b pull-up pucr ($000c) pupb disabled rdriv ($000d) rdpb full drive port e: pe7, pe[3:2] pull-up pucr ($000c) pupe enabled rdriv ($000d) rdpe full drive pe[1:0] pull-up pucr ($000c) pupe enabled ? pe[6:4] none ? rdriv ($000d) rdpe full drive port h pull-up or pull-down pucr ($000c) puph disabled rdriv ($000d) rdph full drive port j pull-up or pull-down pucr ($000c) pupj disabled rdriv ($000d) rdpj full drive port k pull-up pucr ($000c) pupk disabled rdriv ($000d) rdpk full drive port p pull-up pwctl ($0054) pupp disabled pwctl ($0054) rdpp full drive port s pull-up sp0cr2 ($00d1) pups enabled sp0cr2 ($00d1) rdps full drive port t pull-up tmsk2 ($008d) tpu disabled tmsk2 ($008d) tdrb full drive port ib[7:6] pull-up ibpurd ($00e5) pupi b disabled ibpurd ($00e5) rdpib full drive
pinout and signal descriptions technical data mc68hc912dt128a ? rev 4.0 66 pinout and signal descriptions motorola port ib[5:4] (1) pull-up ibpurd ($00e5) pupib disabled ibpurd ($00e5) rdpib full drive port ad0 none ? ? port ad1 none ? ? port can2[1] (2) none ? ? port can2[0] (2) pull-up always enabled ? port can1[1] none ? ? port can1[0] pull-up always enabled ? port can0[1] none ? ? port can0[0] pull-up always enabled ? 1. mc68hc912dg128a only 2. mc68hc912dt128a only table 3-4. port pull-up, pu ll-down and reduced drive summary enable bit reduced drive control bit port name resistive input loads register (address) bit name reset state register (address) bit name reset state
mc68hc912dt128a ? rev 4.0 technical data motorola registers 67 technical data ? mc68hc912dt128a section 4. registers 4.1 contents 4.2 register block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67 4.2 register block the register block can be mapped to any 2k byte boundary within the standard 64k byte address space by manipulating bits reg[15:11] in the initrg register. in itrg establishes the upper five bits of the register block?s 16-bit address. the r egister block occupi es the first 1k byte of the 2k byte block. default ad dressing (after reset) is indicated in the table below. for additional inform ation refer to operating modes .
registers technical data mc68hc912dt128a ? rev 4.0 68 registers motorola address bit 7 6 5 4 3 2 1 bit 0 name $ 0 0 0 0 pa 7 pa 6 pa 5 pa 4 pa 3 pa 2 pa 1 pa 0 porta (1) $0001 pb7 pb6 pb5 pb4 pb3 pb2 pb1 pb0 portb (1) $0002 dda7 dda6 dda5 dda4 dda3 dda2 dda1 dda0 ddra (1) $0003 ddb7 ddb6 ddb5 ddb4 ddb3 ddb2 ddb1 ddb0 ddrb (1) $0004- $0007 00000000 reserved (3) $0008 pe7 pe6 pe5 pe4 pe3 pe2 pe1 pe0 porte (2) $0009 dde7 dde6 dde5 dde4 dde3 dde2 0 0 ddre (2) $000a ndbe cgmte pipoe neclk lstre rdwe cale dbene pear (3) $000b smodn modb moda estr ivis ebswai emk eme mode (3) $000c pupk pupj puph pupe 0 0 pupb pupa pucr (3) $000d rdpk rdpj rdph rdpe 0 0 rdpb rdpa rdriv (3) $000e00000000 reserved (3) $000f00000000 reserved (3) $0010 ram15 ram14 ram13 0 0 0 0 0 initrm $0011 reg15 reg14 reg13 reg12 reg11 0 0 mmswai initrg $0012 ee15 ee14 ee13 ee12 0 0 0 eeon initee $0013 romtst ndrf rfstr1 rfstr0 exstr1 exstr0 romhm romon misc $0014 rtie rswai rsbck reserved rtbyp rtr2 rtr1 rtr0 rtictl $0015rtif0000000rtiflg $0016 cme fcme fcmcop wcop disr cr2 cr1 cr0 copctl $0017 bit 7 6 5 4 3 2 1 bit 0 coprst $0018 ite6 ite8 itea itec it ee itf0 itf2 itf4 itst0 $0019 itd6 itd8 itda itdc itde ite0 ite2 ite4 itst1 $001a itc6 itc8 itca itcc itce itd0 itd2 itd4 itst2 $001b itb6 itb8 itba itbc itbe itc0 itc2 itc4 itst3 $001c ita6 ita8 itaa itac itae itb0 itb2 itb4 itst4 $001d00000000reserved $001e irqe irqen dly 0 0 0 0 0 intcr $001f 1 psel6 psel5 psel4 psel3 psel2 psel1 0 hprio $0020 bken1 bken0 bkpm 0 bk1ale bk0ale 0 0 brkct0 $0021 0 bkdbe bkmbh bkmbl bk1rwe bk1rw bk0rwe bk0rw brkct1 $0022 bit 15 14 13 12 11 10 9 bit 8 brkah $0023 bit 7 6 5 4 3 2 1 bit 0 brkal table 4-1 . register map (sheet 1 of 11)
registers register block mc68hc912dt128a ? rev 4.0 technical data motorola registers 69 $0024 bit 15 14 13 12 11 10 9 bit 8 brkdh $0025 bit 7 6 5 4 3 2 1 bit 0 brkdl $002600000000reserved $002700000000reserved $0028 pj7 pj6 pj5 pj4 pj3 pj2 pj1 pj0 portj $0029 ph7 ph6 ph5 ph4 ph3 ph2 ph1 ph0 porth $002a ddj7 ddj6 ddj5 ddj4 ddj3 ddj2 ddj1 ddj0 ddrj $002b ddh7 ddh6 ddh5 ddh4 ddh3 ddh2 ddh1 ddh0 ddrh $002c kwiej7 kwiej6 kwiej5 kwiej4 k wiej3 kwiej2 kwiej1 kwiej0 kwiej $002d kwieh7 kwieh6 kwieh5 kwieh4 kwieh3 kwieh2 kwieh1 kwieh0 kwieh $002e kwifj7 kwifj6 kwifj5 kwifj4 kwifj3 kwifj2 kwifj1 kwifj0 kwifj $002f kwifh7 kwifh6 kwifh5 kwifh4 k wifh3 kwifh2 kwifh1 kwifh0 kwifh $0030 kwpj7 kwpj6 kwpj5 kwpj4 kwpj3 kwpj2 kwpj1 kwpj0 kwpj $0031 kwph7 kwph6 kwph5 kwph4 kwph3 kwph2 kwph1 kwph0 kwph $003200000000reserved $003300000000reserved $0034? $0037 unimplemented (4) reserved $0038 0 0 syn5 syn4 syn3 syn2 syn1 syn0 synr $0039 0 0 0 0 0 refdv2 refdv1 refdv0 refdv $003a tstout7 tstout6 tstout5 tstout4 tstout3 tstout2 tstout1 tstout0 cgtflg $003b lockif lock 0 0 0 0 lhif lhome pllflg $003c lockie pllon auto acq 0 pstp lhie nolhm pllcr $003d 0 bcsp bcss 0 0 mcs 0 0 clksel $003e 0 0 sldv5 sldv4 sldv3 sldv2 sldv1 sldv0 slow $003f opnle trk tstclke tst4 tst3 tst2 tst1 tst0 cgtctl $0040 con23 con01 pcka2 pcka1 pcka0 pckb2 pckb1 pckb0 pwclk $0041 pclk3 pclk2 pclk1 pclk0 ppol3 ppol2 ppol1 ppol0 pwpol $0042 0 0 0 0 pwen3 pwen2 pwen1 pwen0 pwen $0043 0 bit 6 5 4 3 2 1 bit 0 pwpres $0044 bit 7 6 5 4 3 2 1 bit 0 pwscal0 $0045 bit 7 6 5 4 3 2 1 bit 0 pwscnt0 $0046 bit 7 6 5 4 3 2 1 bit 0 pwscal1 $0047 bit 7 6 5 4 3 2 1 bit 0 pwscnt1 $0048 bit 7 6 5 4 3 2 1 bit 0 pwcnt0 $0049 bit 7 6 5 4 3 2 1 bit 0 pwcnt1 $004a bit 7 6 5 4 3 2 1 bit 0 pwcnt2 $004b bit 7 6 5 4 3 2 1 bit 0 pwcnt3 address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 2 of 11)
registers technical data mc68hc912dt128a ? rev 4.0 70 registers motorola $004c bit 7 6 5 4 3 2 1 bit 0 pwper0 $004d bit 7 6 5 4 3 2 1 bit 0 pwper1 $004e bit 7 6 5 4 3 2 1 bit 0 pwper2 $004fbit 7654321bit 0pwper3 $0050 bit 7 6 5 4 3 2 1 bit 0 pwdty0 $0051 bit 7 6 5 4 3 2 1 bit 0 pwdty1 $0052 bit 7 6 5 4 3 2 1 bit 0 pwdty2 $0053 bit 7 6 5 4 3 2 1 bit 0 pwdty3 $0054 0 0 0 pswai centr rdpp pupp psbck pwctl $0055 discr discp discal 0 0 0 0 0 pwtst $0056 pp7 pp6 pp5 pp4 pp3 pp2 pp1 pp0 portp $0057 ddp7 ddp6 ddp5 ddp4 ddp3 ddp2 ddp1 ddp0 ddrp $0058- $005f 00000000reserved $0060 reserved atd0ctl0 $0061 reserved atd0ctl1 $0062 adpu affc aswai djm dsgn reserved ascie ascif atd0ctl2 $0063 0 0 0 0 s1c fifo frz1 frz0 atd0ctl3 $0064 res10 smp1 smp0 prs4 prs3 prs2 prs1 prs0 atd0ctl4 $0065 0 s8c scan mult cd cc cb ca atd0ctl5 $0066 scf 0 0 0 0 cc2 cc1 cc0 atd0stat0 $0067 ccf7 ccf6 ccf5 ccf4 ccf3 ccf2 ccf1 ccf0 atd0stat1 $0068 sar9 sar8 sar7 sar6 sar5 sar4 sar3 sar2 atd0testh $0069 sar1 sar0 rst tstout tst3 tst2 tst1 tst0 atd0testl $006a?$ 006e 00000000reserved $006f pad07 pad06 pad05 pad04 pad03 pad02 pad01 pad00 portad0 $0070 bit 15 14 13 12 11 10 9 bit 8 adr00h $0071 bit 7 bit 6 0 0 0 0 0 0 adr00l $0072 bit 15 14 13 12 11 10 9 bit 8 adr01h $0073 bit 7 bit 6 0 0 0 0 0 0 adr01l $0074 bit 15 14 13 12 11 10 9 bit 8 adr02h $0075 bit 7 bit 6 0 0 0 0 0 0 adr02l $0076 bit 15 14 13 12 11 10 9 bit 8 adr03h $0077 bit 7 bit 6 0 0 0 0 0 0 adr03l $0078 bit 15 14 13 12 11 10 9 bit 8 adr04h $0079 bit 7 bit 6 0 0 0 0 0 0 adr04l $007a bit 15 14 13 12 11 10 9 bit 8 adr05h $007b bit 7 bit 6 0 0 0 0 0 0 adr05l address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 3 of 11)
registers register block mc68hc912dt128a ? rev 4.0 technical data motorola registers 71 $007c bit 15 14 13 12 11 10 9 bit 8 adr06h $007d bit 7 bit 6 0 0 0 0 0 0 adr06l $007e bit 15 14 13 12 11 10 9 bit 8 adr07h $007f bit 7 bit 6 0 0 0 0 0 0 adr07l $0080 ios7 ios6 ios5 ios4 ios3 ios2 ios1 ios0 tios $0081 foc7 foc6 foc5 foc4 foc3 foc2 foc1 foc0 cforc $0082 oc7m7 oc7m6 oc7m5 oc7m4 oc7m3 oc7m2 oc7m1 oc7m0 oc7m $0083 oc7d7 oc7d6 oc7d5 oc7d4 oc7d3 oc7d2 oc7d1 oc7d0 oc7d $0084 bit 15 14 13 12 11 10 9 bit 8 tcnt $0085 bit 7 6 5 4 3 2 1 bit 0 tcnt $0086 ten tswai tsbck tffca reserved tscr $0087 reserved tqcr $0088 om7 ol7 om6 ol6 om5 ol5 om4 ol4 tctl1 $0089 om3 ol3 om2 ol2 om1 ol1 om0 ol0 tctl2 $008a edg7b edg7a edg6b edg6a edg5b edg5a edg4b edg4a tctl3 $008b edg3b edg3a edg2b edg2a edg1b edg1a edg0b edg0a tctl4 $008c c7i c6i c5i c4i c3i c2i c1i c0i tmsk1 $008d toi 0 pupt rdpt tcre pr2 pr1 pr0 tmsk2 $008e c7f c6f c5f c4f c3f c2f c1f c0f tflg1 $008ftof0000000tflg2 $0090 bit 15 14 13 12 11 10 9 bit 8 tc0 $0091 bit 7 6 5 4 3 2 1 bit 0 tc0 $0092 bit 15 14 13 12 11 10 9 bit 8 tc1 $0093 bit 7 6 5 4 3 2 1 bit 0 tc1 $0094 bit 15 14 13 12 11 10 9 bit 8 tc2 $0095 bit 7 6 5 4 3 2 1 bit 0 tc2 $0096 bit 15 14 13 12 11 10 9 bit 8 tc3 $0097 bit 7 6 5 4 3 2 1 bit 0 tc3 $0098 bit 15 14 13 12 11 10 9 bit 8 tc4 $0099 bit 7 6 5 4 3 2 1 bit 0 tc4 $009a bit 15 14 13 12 11 10 9 bit 8 tc5 $009b bit 7 6 5 4 3 2 1 bit 0 tc5 $009c bit 15 14 13 12 11 10 9 bit 8 tc6 $009d bit 7 6 5 4 3 2 1 bit 0 tc6 $009e bit 15 14 13 12 11 10 9 bit 8 tc7 $009fbit 7654321bit 0tc7 $00a0 0 paen pamod pedge clk1 clk0 paovi pai pactl $00a1 0 0 0 0 0 0 paovf paif paflg address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 4 of 11)
registers technical data mc68hc912dt128a ? rev 4.0 72 registers motorola $00a2 bit 7 6 5 4 3 2 1 bit 0 pacn3 $00a3 bit 7 6 5 4 3 2 1 bit 0 pacn2 $00a4 bit 7 6 5 4 3 2 1 bit 0 pacn1 $00a5 bit 7 6 5 4 3 2 1 bit 0 pacn0 $00a6 mczi modmc rdmcl iclat flmc mcen mcpr1 mcpr0 mcctl $00a7 mczf 0 0 0 polf3 polf2 polf1 polf0 mcflg $00a8 0 0 0 0 pa3en pa2en pa1en pa0en icpar $ 0 0 a 9 0 0 0 0 0 0 d ly 1 d ly 0 d ly c t $00aa novw7 novw6 novw5 novw4 novw3 novw2 novw1 novw0 icovw $00ab sh37 sh26 sh15 sh04 tfmod pacmx bufen latq icsys $00ac 0 0 0 0 0 0 0 0 reserved $00ad000000tcbyp0timtst $00ae pt7 pt6 pt5 pt4 pt3 pt2 pt1 pt0 portt $00af ddt7 ddt6 ddt5 ddt4 ddt3 ddt2 ddt1 ddt0 ddrt $00b0 0 pben 0 0 0 0 pbovi 0 pbctl $00b1 0 0 0 0 0 0 pbovf 0 pbflg $00b2 bit 7 6 5 4 3 2 1 bit 0 pa3h $00b3 bit 7 6 5 4 3 2 1 bit 0 pa2h $00b4 bit 7 6 5 4 3 2 1 bit 0 pa1h $00b5 bit 7 6 5 4 3 2 1 bit 0 pa0h $00b6 bit 15 14 13 12 11 10 9 bit 8 mccnth $00b7 bit 7 6 5 4 3 2 1 bit 0 mccntl $00b8 bit 15 14 13 12 11 10 9 bit 8 tc0h $00b9 bit 7 6 5 4 3 2 1 bit 0 tc0h $00ba bit 15 14 13 12 11 10 9 bit 8 tc1h $00bb bit 7 6 5 4 3 2 1 bit 0 tc1h $00bc bit 15 14 13 12 11 10 9 bit 8 tc2h $00bd bit 7 6 5 4 3 2 1 bit 0 tc2h $00be bit 15 14 13 12 11 10 9 bit 8 tc3h $00bf bit 7 6 5 4 3 2 1 bit 0 tc3h $00c0 btst bspl brld sbr12 sbr11 sbr10 sbr9 sbr8 sc0bdh $00c1 sbr7 sbr6 sbr5 sbr4 sbr3 sbr2 sbr1 sbr0 sc0bdl $00c2 loops woms rsrc m wake ilt pe pt sc0cr1 $00c3 tie tcie rie ilie te re rwu sbk sc0cr2 $00c4 tdre tc rdrf idle or nf fe pf sc0sr1 $00c50000000rafsc0sr2 $00c6 r8 t8 0 0 0 0 0 0 sc0drh $00c7 r7/t7 r6/t6 r5/t5 r4/t4 r3/t3 r2/t2 r1/t1 r0/t0 sc0drl address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 5 of 11)
registers register block mc68hc912dt128a ? rev 4.0 technical data motorola registers 73 $00c8 btst bspl brld sbr12 sbr11 sbr10 sbr9 sbr8 sc1bdh $00c9 sbr7 sbr6 sbr5 sbr4 sbr3 sbr2 sbr1 sbr0 sc1bdl $00ca loops woms rsrc m wake ilt pe pt sc1cr1 $00cb tie tcie rie ilie te re rwu sbk sc1cr2 $00cc tdre tc rdrf idle or nf fe pf sc1sr1 $00cd0000000rafsc1sr2 $00ce r8 t8 0 0 0 0 0 0 sc1drh $00cf r7/t7 r6/t6 r5/t5 r4/t4 r3/t3 r2/t2 r1/t1 r0/t0 sc1drl $00d0 spie spe swom mstr cpol cpha ssoe lsbf sp0cr1 $00d1 0 0 0 0 pups rdps sswai spc0 sp0cr2 $00d2 0 0 0 0 0 spr2 spr1 spr0 sp0br $00d3 spif wcol 0 modf 0 0 0 0 sp0sr $00d4 0 0 0 0 0 0 0 0 reserved $00d5 bit 7 6 5 4 3 2 1 bit 0 sp0dr $00d6 ps7 ps6 ps5 ps4 ps3 ps2 ps1 ps0 ports $00d7 dds7 dds6 dds5 dds4 dds3 dds2 dds1 dds0 ddrs $00d8?$ 00df 0 0 0 0 0 0 0 0 reserved $00e0 adr7 adr6 adr5 adr4 adr3 adr2 adr1 0 ibad $00e1 0 0 ibc5 ibc4 ibc3 ibc2 ibc1 ibc0 ibfd $00e2 iben ibie ms/sl tx/rx txak rsta 0 ibswai ibcr $00e3 tcf iaas ibb ibal 0 srw ibif rxak ibsr $00e4d7d6d5d4d3d2d1d0ibdr $00e5 0 0 0 rdpib 0 0 0 pupib ibpurd $00e6 pib7 pib6 pib5 pib4 pib3 pib2 pib1 pib0 portib $00e7 ddrib7 ddrib6 ddrib5 ddrib4 ddrib3 ddrib2 ddrib1 ddrib0 ddrib $00e8? $00eb unimplemented (4) reserved $00ec?$ 00ed 0 0 0 0 0 0 0 0 reserved $00ee 0 0 0 0 0 0 eediv9 eediv8 eedivh $00ef eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 eedivl $00f0 nobdml noshw reserved fpopen (5) 1 eeswai protlck eerc eemcr $00f1 shprot 1 bprot5 bprot4 bprot3 bprot2 bprot1 bprot0 eeprot $00f2 0 erevtn 0 0 0 etmsd etmr etmse eetst $00f3 bulkp 0 auto byte row erase eelat eepgm eeprog $00f40000000lockfeelck $00f50000000bootpfeemcr $00f6 stre revtun 0 0 0 tmsd tmr tmse feetst address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 6 of 11)
registers technical data mc68hc912dt128a ? rev 4.0 74 registers motorola $00f7 0 0 0 feeswai hven 0 eras pgm feectl $00f8 mt07 mt06 mt05 mt04 mt03 mt02 mt01 mt00 mtst0 $00f9 mt0f mt0e mt0d mt0c mt0b mt0a mt09 mt08 mtst1 $00fa mt17 mt16 mt15 mt14 mt13 mt12 mt11 mt10 mtst2 $00fb mt1f mt1e mt1d mt1c mt1b mt1a mt19 mt18 mtst3 $00fc pk7 0 0 0 pk3 pk2 pk1 pk0 portk (6) $00fd ddk7 0 0 0 ddk3 ddk2 ddk1 ddk0 ddrk (6) $00fe00000000reserved $00ff 0 0 0 0 0 pix2 pix1 pix0 ppage $0100 0 0 cswai synch tlnken slpak slprq sftres c0mcr0 $0101 0 0 0 0 0 loopb wupm clksrc c0mcr1 $0102 sjw1 sjw0 brp5 brp4 brp3 brp2 brp1 brp0 c0btr0 $0103 samp tseg22 tseg21 tseg20 tseg 13 tseg12 tseg11 tseg10 c0btr1 $0104 wupif rwrnif twrnif rerrif terrif boffif ovrif rxf c0rflg $0105 wupie rwrnie twrnie rerrie terrie boffie ovrie rxfie c0rier $0106 0 abtak2 abtak1 abtak0 0 txe2 txe1 txe0 c0tflg $0107 0 abtrq2 abtrq1 abtrq0 0 txeie2 txeie1 txeie0 c0tcr $0108 0 0 idam1 idam0 0 idhit2 idhit1 idhit0 c0idac $0109? $010d unimplemented (4) reserved $010e rxerr7 rxerr6 rxerr5 rxerr4 rxerr3 rxerr2 rxerr1 rxerr0 c0rxerr $010f txerr7 txerr6 txerr5 txerr4 txerr3 txerr2 txerr1 txerr0 c0txerr $0110 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar0 $0111 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar1 $0112 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar2 $0113 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar3 $0114 am7 am6 am5 am4 am3 am2 am1 am0 c0idmr0 $0115 am7 am6 am5 am4 am3 am2 am1 am0 c0idmr1 $0116 am7 am6 am5 am4 am3 am2 am1 am0 c0idmr2 $0117 am7 am6 am5 am4 am3 am2 am1 am0 c0idmr3 $0118 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar4 $0119 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar5 $011a ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar6 $011b ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c0idar7 $011c am7 am6 am5 am4 am3 am2 am1 am0 c0idmr4 $011d am7 am6 am5 am4 am3 am2 am1 am0 c0idmr5 $011e am7 am6 am5 am4 am3 am2 am1 am0 c0idmr6 $011f am7 am6 am5 am4 am3 am2 am1 am0 c0idmr7 address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 7 of 11)
registers register block mc68hc912dt128a ? rev 4.0 technical data motorola registers 75 $0120? $013c unimplemented (4) reserved $013d 0 0 0 0 0 0 pupcan rdpcan pctlcan0 $013e pcan7 pcan6 pcan5 pcan4 pcan3 pcan2 txcan rxcan portcan0 $013f ddcan7 ddcan6 ddcan5 ddcan4 ddcan3 ddcan2 0 0 ddrcan0 $0140? $014f foreground receive buffer 0 rxfg0 $0150? $015f transmit buffer 00 tx00 $0160? $016f transmit buffer 01 tx01 $0170? $017f transmit buffer 02 tx02 $0180? $01df unimplemented (4) reserved $01e0 reserved atd1ctl0 $01e1 reserved atd1ctl1 $01e2 adpu affc aswai djm dsgn reserved ascie ascif atd1ctl2 $01e3 0 0 0 0 s1c fifo frz1 frz0 atd1ctl3 $01e4 res10 smp1 smp0 prs4 prs3 prs2 prs1 prs0 atd1ctl4 $01e5 0 s8c scan mult cd cc cb ca atd1ctl5 $01e6 scf 0 0 0 0 cc2 cc1 cc0 atd1stat0 $01e7 ccf7 ccf6 ccf5 ccf4 ccf3 ccf2 ccf1 ccf0 atd1stat1 $01e8 sar9 sar8 sar7 sar6 sar5 sar4 sar3 sar2 atd1testh $01e9 sar1 sar0 rst tstout tst3 tst2 tst1 tst0 atd1testl $01ea?$ 01ee 0 0 0 0 0 0 0 0 reserved $01ef pad17 pad16 pad15 pad14 pad13 pad12 pad11 pad10 portad1 $01f0 bit 15 14 13 12 11 10 9 bit 8 adr10h $01f1 bit 7 bit 6 0 0 0 0 0 0 adr10l $01f2 bit 15 14 13 12 11 10 9 bit 8 adr11h $01f3 bit 7 bit 6 0 0 0 0 0 0 adr11l $01f4 bit 15 14 13 12 11 10 9 bit 8 adr12h $01f5 bit 7 bit 6 0 0 0 0 0 0 adr12l $01f6 bit 15 14 13 12 11 10 9 bit 8 adr13h $01f7 bit 7 bit 6 0 0 0 0 0 0 adr13l $01f8 bit 15 14 13 12 11 10 9 bit 8 adr14h $01f9 bit 7 bit 6 0 0 0 0 0 0 adr14l $01fa bit 15 14 13 12 11 10 9 bit 8 adr15h $01fb bit 7 bit 6 0 0 0 0 0 0 adr15l address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 8 of 11)
registers technical data mc68hc912dt128a ? rev 4.0 76 registers motorola $01fc bit 15 14 13 12 11 10 9 bit 8 adr16h $01fd bit 7 bit 6 0 0 0 0 0 0 adr16l $01fe bit 15 14 13 12 11 10 9 bit 8 adr17h $01ff bit 7 bit 6 0 0 0 0 0 0 adr17l (7) $0200 0 0 cswai synch tlnken slpak slprq sftres c2mcr0 (7) $0201 0 0 0 0 0 loopb wupm clksrc c2mcr1 (7) $0202 sjw1 sjw0 brp5 brp4 brp3 brp2 brp1 brp0 c2btr0 (7) $0203 samp tseg22 tseg21 tseg20 tseg13 tseg12 tseg11 tseg10 c2btr1 (7) $0204 wupif rwrnif twrnif rerrif terrif boffif ovrif rxf c2rflg (7) $0205 wupie rwrnie twrnie rerrie terrie boffie ovrie rxfie c2rier (7) $0206 0 abtak2 abtak1 abtak0 0 txe2 txe1 txe0 c2tflg (7) $0207 0 abtrq2 abtrq1 abtrq0 0 txeie2 txeie1 txeie0 c2tcr (7) $0208 0 0 idam1 idam0 0 idhit2 idhit1 idhit0 c2idac $0209? $020d unimplemented (4) reserved (7) $020e rxerr7 rxerr6 rxerr5 rxerr4 rxerr3 rxerr2 rxerr1 rxerr0 c2rxerr (7) $020f txerr7 txerr6 txerr5 txerr4 txerr3 txerr2 txerr1 txerr0 c2txerr (7) $0210 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar0 (7) $0211 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar1 (7) $0212 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar2 (7) $0213 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar3 (7) $0214 am7 am6 am5 am4 am3 am2 am1 am0 c2idmr0 (7) $0215 am7 am6 am5 am4 am3 am2 am1 am0 c2idmr1 (7) $0216 am7 am6 am5 am4 am3 am2 am1 am0 c2idmr2 (7) $0217 am7 am6 am5 am4 am3 am2 am1 am0 c2idmr3 (7) $0218 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar4 (7) $0219 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar5 (7) $021a ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar6 (7) $021b ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c2idar7 (7) $021c am7 am6 am5 am4 am3 am2 am1 am0 c2idmr4 (7) $021d am7 am6 am5 am4 am3 am2 am1 am0 c2idmr5 (7) $021e am7 am6 am5 am4 am3 am2 am1 am0 c2idmr6 (7) $021f am7 am6 am5 am4 am3 am2 am1 am0 c2idmr7 address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 9 of 11)
registers register block mc68hc912dt128a ? rev 4.0 technical data motorola registers 77 $0220? $023c unimplemented (4) reserved (7) $023d 0 0 0 0 0 0 pupcan rdpcan pctlcan2 (7) $023e pcan7 pcan6 pcan5 pcan4 pcan3 pcan2 txcan rxcan portcan2 (7) $023f ddcan7 ddcan6 ddcan5 ddcan4 ddcan3 ddcan2 0 0 ddrcan2 (7) $0240 ? $024f foreground receive buffer 2 rxfg2 (7) $0250 ? $025f transmit buffer 20 tx20 (7) $0260 ? $026f transmit buffer 21 tx21 (7) $0270 ? $027f transmit buffer 22 tx22 $0280- $02ff unimplemented (4) reserved $0300 0 0 cswai synch tlnken slpak slprq sftres c1mcr0 $0301 0 0 0 0 0 loopb wupm clksrc c1mcr1 $0302 sjw1 sjw0 brp5 brp4 brp3 brp2 brp1 brp0 c1btr0 $0303 samp tseg22 tseg21 tseg20 tseg 13 tseg12 tseg11 tseg10 c1btr1 $0304 wupif rwrnif twrnif rerrif terrif boffif ovrif rxf c1rflg $0305 wupie rwrnie twrnie rerrie terrie boffie ovrie rxfie c1rier $0306 0 abtak2 abtak1 abtak0 0 txe2 txe1 txe0 c1tflg $0307 0 abtrq2 abtrq1 abtrq0 0 txeie2 txeie1 txeie0 c1tcr $0308 0 0 idam1 idam0 0 idhit2 idhit1 idhit0 c1idac $0309? $030d unimplemented (4) reserved $030e rxerr7 rxerr6 rxerr5 rxerr4 rxerr3 rxerr2 rxerr1 rxerr0 c1rxerr $030f txerr7 txerr6 txerr5 txerr4 txerr3 txerr2 txerr1 txerr0 c1txerr $0310 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar0 $0311 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar1 $0312 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar2 $0313 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar3 $0314 am7 am6 am5 am4 am3 am2 am1 am0 c1idmr0 $0315 am7 am6 am5 am4 am3 am2 am1 am0 c1idmr1 $0316 am7 am6 am5 am4 am3 am2 am1 am0 c1idmr2 $0317 am7 am6 am5 am4 am3 am2 am1 am0 c1idmr3 $0318 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar4 $0319 ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar5 address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 10 of 11)
registers technical data mc68hc912dt128a ? rev 4.0 78 registers motorola $031a ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar6 $031b ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 c1idar7 $031c am7 am6 am5 am4 am3 am2 am1 am0 c1idmr4 $031d am7 am6 am5 am4 am3 am2 am1 am0 c1idmr5 $031e am7 am6 am5 am4 am3 am2 am1 am0 c1idmr6 $031f am7 am6 am5 am4 am3 am2 am1 am0 c1idmr7 $0320? $033c unimplemented (4) reserved $033d 0 0 0 0 0 0 pupcan rdpcan pctlcan1 $033e pcan7 pcan6 pcan5 pcan4 pcan3 pcan2 txcan rxcan portcan1 $033f ddcan7 ddcan6 ddcan5 ddcan4 ddcan3 ddcan2 0 0 ddrcan1 $0340? $034f foreground receive buffer 1 rxfg1 $0350? $035f transmit buffer 10 tx10 $0360? $036f transmit buffer 11 tx11 $0370? $037f transmit buffer 12 tx12 $0380- $03ff unimplemented (4) reserved = reserved or unimplemented bits. 1. port a, port b and data direct ion registers ddra, ddrb are not in map in expanded and peripheral modes. 2. port e and ddre not in the map in peripheral and expanded modes with eme set. 3. registers also not in map in peripheral mode. 4. data read at these locations is undefined. 5. the fpopen bit is available only on the 0l05h and late r mask sets. for previous masks, this bit is reserved. 6. port k and ddrk not in the map in peripheral and expanded modes with emk set. 7. mc68hc912dt128a only. locations ar e unimplemented on the mc68hc912dg128a. address bit 7 6 5 4 3 2 1 bit 0 name table 4-1 . register map (sheet 11 of 11)
mc68hc912dt128a ? rev 4.0 technical data motorola operating modes 79 technical data ? mc68hc912dt128a section 5. operating modes 5.1 contents 5.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.3 operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 5.4 background debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84 5.2 introduction eight possible operatin g modes determine the oper ating configuration of the mc68hc912dt128a. each mode has an associated default memory map and external bus configuration. 5.3 operating modes the operating mode out of reset is determined by the states of the bkgd, modb, and moda pins during reset. the smodn, modb, and moda bits in the mode register show current operating mode and provide limit ed mode switching during operation. the states of the bkgd, modb, and moda pins are latched into these bits on the rising edge of the reset signal.
operating modes technical data mc68hc912dt128a ? rev 4.0 80 operating modes motorola there are two basic type s of operating modes: normal modes ? some register s and bits are protected against accidental changes. special modes ? allow greater a ccess to protected control registers and bits for special purposes such as testing and emulation. a system development and debug feature, background debug mode (bdm), is available in all modes. in special si ngle-chip mode, bdm is active immediately after reset. 5.3.1 normal operating modes these modes provide three operati ng configurations. background debug is available in all three modes , but must first be enabled for some operations by means of a bdm background comm and, then activated. normal single-chip mode ? there are no external address and data buses in this mode. the mcu operates as a stand-alone device and all program and data resources are on-chip. external port pins normally associated with address and dat a buses can be used for general-purpose i/o. normal expanded wide mode ? this is a normal mode of operation in which the expanded bus is present with a 16-bit data bus. ports a and b are used for the 16-bit multiplexed address/data bus. table 5-1. mode selection bkgd modb moda mode port a port b 1 0 0 normal single chip g.p. i/o g.p. i/o 1 0 1 normal expanded narrow addr/data addr 1 1 0 reserved (forced to peripheral) ? ? 1 1 1 normal expanded wide addr/data addr/data 0 0 0 special single chip g.p. i/o g.p. i/o 0 0 1 special expanded narrow addr/data addr 0 1 0 special peripheral addr/data addr/data 0 1 1 special expanded wide addr/data addr/data
operating modes operating modes mc68hc912dt128a ? rev 4.0 technical data motorola operating modes 81 normal expanded narrow mod e ? this is a normal mode of operation in which the expanded bus is present with an 8-bit data bus. ports a and b are used for t he16-bit address bus. port a is used as the data bus, mu ltiplexed with addre sses. in this mode, 16-bit data is presented one byte at a time, the high byte followed by the low byte. the address is automatically incremented on the second cycle. 5.3.2 special operating modes there are three special operating modes that correspond to normal operating modes. these oper ating modes are comm only used in factory testing and system dev elopment. in addition, there is a special peripheral mode, in which an external master, such as an i.c. tester, can control the on-chip peripherals. special single-chip mode ? this mode can be used to force the mcu to active bdm mode to allow system debug through the bkgd pin. there are no external address and data buses in this mode. the mcu operates as a stand-alone device and all program and data space are on-chip . external port pins can be used for general-purpose i/o. special expanded wide mode ? this mode can be used for emulation of norm al expanded wide mode and emulation of normal single-chip mode. ports a and b are used for the 16-bit multiplexed ad dress/data bus. special expanded narrow mode ? this mode can be used for emulation of normal expanded narrow mode. ports a and b are used for the16-bit address bus. po rt a is used as the data bus, multiplexed with addresses. in this mode, 16-bit data is presented one byte at a time, the high byte followed by the low byte. the address is automatically in cremented on the second cycle. special peripheral mode ? the cpu is not acti ve in this mode. an external master can contro l on-chip peripher als for testing purposes. it is not possi ble to change to or fr om this mode without going through reset. backgro und debugging should not be used
operating modes technical data mc68hc912dt128a ? rev 4.0 82 operating modes motorola while the mcu is in special per ipheral mode as internal bus conflicts between bdm and the external master can cause improper operation of both functions. the mode register controls the mcu operating mode and various configuration options. this register is not in the map in peripheral mode smodn, modb, moda ? mode select special, b and a these bits show the current operati ng mode and reflect the status of the bkgd, modb an d moda input pins at the rising e dge of reset. read anytime. smodn may only be written if smod n = 0 (in special modes) but the first write is ignored. modb, moda may be written once if smodn = 1; anytime if smodn = 0 but the first write is ignored and in specia l peripheral and reserved modes cannot be selected. bit 7654321bit 0 smodn modb moda estr ivis ebswai emk eme reset: 0 0 0 1 1 0 1 1 special single chip reset: 0 0 1 1 1 0 1 1 special exp nar reset: 0 1 0 1 1 0 1 1 peripheral reset: 0 1 1 1 1 0 1 1 special exp wide reset: 1 0 0 1 0 0 0 0 normal single chip reset: 1 0 1 1 0 0 0 0 normal exp nar reset: 1 1 1 1 0 0 0 0 normal exp wide mode ? mode register $000b
operating modes operating modes mc68hc912dt128a ? rev 4.0 technical data motorola operating modes 83 estr ? e clock stretch enable determines if the e clock behaves as a simple free-running clock or as a bus control signal that is active onl y for external bus cycles. estr is always one in expanded m odes since it is required for address and data de-mu ltiplexing and must follow stretched cycles. 0 = e never stretches (always free running). 1 = e stretches high during exter nal access cycles and low during non-visible internal accesses (ivis = 0). normal modes: write onc e; special modes: write anytime, read anytime. ivis ? internal visibility this bit determines whether internal addr, data, r/w and lstrb signals can be s een on the external bus dur ing accesses to internal locations. in special narrow mode if this bit is set and an internal access occurs the data will appear wid e on ports a and b. this serves the same function as the emd bit of the non-multiplexed versions of the hc12 and allows for emulation. vi sibility is not available when the part is operating in a single-chip mode. 0 = no visibility of internal bus operations on external bus. 1 = internal bus oper ations are visible on external bus. normal modes: write onc e; special modes: write anytime except the first time. read anytime. ebswai ? multiplexed external bu s interface module stops in wait mode this bit controls access to the multiplexed ex ternal bus interface module during wait mode. the module will delay before shutting down in wait mode to allow for final bus activity to complete. 0 = mebi contin ues functioning during wait mode. 1 = mebi is shut down during wait mode. normal modes: write any time; special modes: write never. read anytime.
operating modes technical data mc68hc912dt128a ? rev 4.0 84 operating modes motorola emk ? emulate port k in single-chip mode portk and ddrk are always in the map regardless of the st ate of this bit. 0 = port k and ddrk registers are in the memory map. memory expansion emulation is dis abled and all pins are general purpose i/o. 1 = in expanded or periphera l mode, portk and ddrk are removed from the internal memory map. removing the registers from the map allows t he user to emulate the function of these registers externally. normal modes: write onc e; special modes: write anytime except the first time. read anytime. eme ? emulate port e in single-chip mode porte and ddre are always in the map regardless of the st ate of this bit. 0 = porte and ddre are in the memory map. 1 = if in an expanded mode, porte and ddre are removed from the internal memory map. re moving the registers from the map allows the user to emulate the function of these registers externally. normal modes: write onc e; special modes: write anytime except the first time. read anytime. 5.4 background debug mode background debug m ode (bdm) is an auxiliary operating mode that is used for system development. bdm is implemented in on-chip hardware and provides a full set of debug oper ations. some bdm commands can be executed while the cpu is op erating normal ly. other bdm commands are firmware based, and re quire the bdm firmware to be enabled and active for execution. in special single-chip m ode, bdm is enabl ed and active immediately out of reset. bdm is available in al l other operating modes, but must be enabled before it can be activated. bdm shoul d not be used in special peripheral mode because of potential bus conflicts.
operating modes background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola operating modes 85 once enabled, ba ckground mode can be made active by a serial command sent via the bkgd pin or execution of a cpu12 bgnd instruction. while back ground mode is active, the cpu can interpret special debugging commands, and r ead and write cpu registers, peripheral registers, and locations in memory. while bdm is active, t he cpu executes code loca ted in a sm all on-chip rom mapped to addresses $ff20 to $ff ff, and bdm control registers are accessible at addr esses $ff00 to $ff06. the bdm rom replaces the regular system vectors while bdm is active. while bdm is active, the user memory from $ff0 0 to $ffff is not in t he map except through serial bdm commands.
operating modes technical data mc68hc912dt128a ? rev 4.0 86 operating modes motorola
mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 87 technical data ? mc68hc912dt128a section 6. resource mapping 6.1 contents 6.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.3 internal resource mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . .87 6.4 flash eeprom mappi ng through internal memory expansion 92 6.5 miscellaneous system control register . . . . . . . . . . . . . . . . . . 96 6.6 mapping test registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 6.7 memory maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 6.2 introduction after reset, most system resources can be mapped to other addresses by writing to the approp riate contro l registers. 6.3 internal resource mapping the internal register block, ram , and eeprom have default locations within the 64k byte standard addre ss space but may be reassigned to other locations during pr ogram execution by se tting bits in mapping registers initrg, initrm, and init ee. during normal operating modes these registers can be written once. it is advisable to explicitly establish these resource locations during the initialization pha se of program execution, even if default values ar e chosen, in order to protect the registers from inadvertent modification later. writes to the mapping registers go into effect between the cycle that follows the write and t he cycle after that. to assu re that there are no
resource mapping technical data mc68hc912dt128a ? rev 4.0 88 resource mapping motorola unintended operations, a wr ite to one of these registers should be followed with a nop instruction. if conflicts occur when mapping resource s, the register block will take precedence over the other resour ces; ram or eeprom addresses occupied by the register block will not be avail able for storage. when active, bdm rom takes precedence over other resources, although a conflict between bdm rom and register space is not possible. the following table shows res ource mapping precedence. in expanded modes, all addr ess space not used by in ternal resources is by default external memory. the mc68hc912dt128a contains 128k bytes of flash eeprom nonvolatile memory which can be used to store program code or static data. this physical memory is compos ed of four 32k by te array modules, 00fee32k, 01fee32k, 10f ee32k and 11fee32k. the 32k byte array 11fee32k has a fixed location from $4000 to $7fff and $c000 to $ffff. the three 32k byte arra ys 00fee32k, 01fee32k and 10fee32k are accessible through a 16k byte program page window mapped from $8000 to $bfff. the fixed 32k byte array 11fee32k can also be accessed throug h the program page window. table 6-1. mapping precedence precedence resource 1 bdm rom (if active) 2 register space 3ram 4 eeprom 5 on-chip flash eeprom 6 external memory
resource mapping internal resource mapping mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 89 6.3.1 register block mapping after reset the 1k byte register bl ock resides at loca tion $0000 but can be reassigned to any 2k byte boundary within the standard 64k byte address space. mapping of in ternal registers is controlled by five bits in the initrg register . the register block occupies the first 1k byte of the 2k byte block. reg[15:11] ? internal register map position these bits specify the upper five bits of the 16-bit registers address. normal modes: write once; special modes: write anytime. read anytime. mmswai ? memory mapping inte rface stop in wait control this bit controls acce ss to the memory mappi ng interface when in wait mode. normal modes: write any time; special modes: write never. read anytime. 0 = memory mapping interface cont inues to functi on during wait mode. 1 = memory mapping interface a ccess is shut down during wait mode. initrg ? initialization of internal register position register $0011 bit 7654321bit 0 reg15 reg14 reg13 reg12 reg11 0 0 mmswai reset: 0 0 0 0 0 0 0 0
resource mapping technical data mc68hc912dt128a ? rev 4.0 90 resource mapping motorola 6.3.2 ram mapping the mc68hc912dt128a has 8k bytes of fully static ram that is used for storing instructions, variables, and temporary da ta during program execution. since the ram is actually implemen ted with two 4k ram arrays, any misaligned word access be tween last address of first 4k ram and first address of second 4k ram will take two cycles instead of one. after reset, ram addressing begi ns at location $2000 but can be assigned to any 8k by te boundary withi n the standard 64k byte address space. mapping of internal ram is controlled by th ree bits in the initrm register. ram[15:13] ? internal ram map position these bits specify the upper three bits of the 16-bit ram address. normal modes: write once; special modes: write anytime. read anytime. initrm ? initialization of internal ram position register $0010 bit 7654321bit 0 ram15 ram14 ram13 0 0 0 0 0 reset: 0 0 1 0 0 0 0 0
resource mapping internal resource mapping mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 91 6.3.3 eeprom mapping the mc68hc912dt128a has 2k bytes of eeprom which is activated by the eeon bit in the initee regi ster. mapping of internal eeprom is controlled by four bits in the in itee register. after reset eeprom address space begins at locati on $0800 but can be mapped to any 4k byte boundary within the standard 64k byte addre ss space. the eeprom block occupies the last 2k bytes of the 4k byte block. ee[15:12] ? internal eeprom map position these bits specify the upper four bi ts of the 16-bit eeprom address. normal modes: write once; spec ial modes: write anytime. read anytime. eeon ? internal e eprom on (enabled) read or write anytime. 0 = removes the eepro m from the map. 1 = places the on-ch ip eeprom in the memory map at the address selected by ee[15:12]. initee ? initialization of intern al eeprom position register $0012 bit 7654321bit 0 ee15 ee14 ee13 ee12 0 0 0 eeon reset:00000001
resource mapping technical data mc68hc912dt128a ? rev 4.0 92 resource mapping motorola 6.4 flash eeprom mapping through internal memory expansion the page index register or ppag e provides memory management for the mc68hc912dt128a. ppage consists of three bits to indicate which physical location is acti ve within the windows of the mc68hc912dt128a. the mc68hc912dt128a has a user?s program space window, a register space window for flash module registers, and a test program space window. the user?s program page window consis ts of 16k flash eeprom bytes. one of eight pages is viewed through this window for a total of 128k accessible flash eeprom bytes. the register space window consists of a 4-byte register block. one of four pages is viewed through this win dow for each of the 32k flash module register blocks of mc68hc912dt128a. the test mode program page window consists of 32k flash eeprom bytes. one of the four 32k byte ar rays is viewed through this window for a total 128k accessible flash eeprom bytes. this window is only available in special mode for test purposes and replaces the user?s program page window. mc68hc912dt128a has a fi ve pin port, port k, for emulation and for general purpose i/o. three pins are used to emulate the three page indices (ppage bits) and one pin is us ed as an emulation chip select. when these four pins are not used for emulation they serve as general purpose i/o pins. the fift h port k pin is used as a general purpose i/o pin. 6.4.1 program space expansion there are 128k bytes of flash e eprom for mc68h c912dt128a. with a 64k byte address space, the ppage register is needed to perform on chip memory expansion. a program space window of 16k byte pages is located from $8000 to $bfff. three page indices are used to point to one of eight differen t 16k byte pages.
resource mapping flash eeprom mapping through internal memory expansion mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 93 * the 16k byte flash in program s pace page 6 can also be accessed at a fixed location from $4000 to $7fff. the 16k byte flash in program space page 7 can also be accessed at a fixed location from $c000 to $ffff. 6.4.2 flash regi ster space expansion there are four 32k flash arra ys for mc68hc912dt128a and each requires a 4-byte register block. a register space window is used to access one of the four 4- byte blocks and the pp age register to map each one into the window. the register space window is located from $00f4 to $00f7 after reset. only two page indices are used to point to one of the four pages of the register space. table 6-2. program space page index page index 2 (ppage bit 2) page index 1 (ppage bit 1) page index 0 (ppage bit 0) 16k program space page flash array 0 0 0 16k byte page 0 00fee32k 0 0 1 16k byte page 1 00fee32k 0 1 0 16k byte page 2 01fee32k 0 1 1 16k byte page 3 01fee32k 1 0 0 16k byte page 4 10fee32k 1 0 1 16k byte page 5 10fee32k 1 1 0 16k byte page 6* 11fee32k 1 1 1 16k byte page 7* 11fee32k table 6-3. flash register space page index page index 2 (ppage bit 2) page index 1 (ppage bit 1) page index 0 (ppage bit 0) flash register space page flash array 0 0 x $00f4-$00f7 page 0 00fee32k 0 1 x $00f4-$00f7 page 1 01fee32k 1 0 x $00f4-$00f7 page 2 10fee32k 1 1 x $00f4-$00f7 page 3 11fee32k
resource mapping technical data mc68hc912dt128a ? rev 4.0 94 resource mapping motorola 6.4.3 test mode program space expansion in special mode and for test purpos es only, the 128k bytes of flash eeprom for mc68hc912dt12 8a can be accessed through a test program space window of 32k bytes. this window replaces the user?s program space window to be able to ac cess an entire array. in special mode and with romtst bit set in mi sc register, a pr ogram space is located from $8000 to $ffff. only two page indice s are used to point to one of the fo ur 32k byte arrays. these indices can be viewed as expanded addresse s x16 and x15. 6.4.4 page index re gister descriptions read and write anytime writes do not change pin state when pin configured for page index emulation output. this port is associated with page index emulation pins. when the port is not enabled to emulate page index, the port pi ns are used as general- purpose i/o. port k bit 3 is used as a general purpose i/o pin only. this register is not in the map in pe ripheral or expanded modes while the emk control bit in mo de register is set. table 6-4. test mode pr ogram space page index page index 2 (ppage bit 2) page index 1 (ppage bit 1) page index 0 (ppage bit 0) flash register space page flash array 0 0 x 32k byte array page 0 00fee32k 0 1 x 32k byte array page 1 01fee32k 1 0 x 32k byte array page 2 10fee32k 1 1 x 32k byte array page 3 11fee32k portk ? port k data register $00fc bit 7 6 5 4 3 2 1 bit 0 port pk7 0 0 0 pk3 pk2 pk1 pk0 emulation ecs 0 0 0 - pix2 pix1 pix0 reset: - 0 0 0 - - - -
resource mapping flash eeprom mapping through internal memory expansion mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 95 when inputs, these pins can be selected to be high impedance or pulled up. ecs ? emulation chip select of selected program space when this signal is active low it i ndicates that the program space is accessed. this also applies to test mode program space. an access is made if address is at the pr ogram space window and either the flash or external memory is accessed. the ecs timing is e clock high and can be stretched when accessing external memory depending on the extr0 and extr1 bits in the misc register. the ecs signal is only active when t he emk bit is set. pix[2:0] ? the content of the ppage register emulated externally. this content indicates wh ich flash module regist er space is in the memory map and which 16k byte fl ash memory is in the program space. in special mode and with romt st bit set, the content of the page index register indi cates which 32k byte flas h array is in the test program space. i read and write: anytime. this register deter mines the primary directi on for each port k pin configured as general-purpose i/o. 0 = associated pin is a high-impedance input. 1 = associated pi n is an output. this register is no t in the map in peripheral or expanded modes while the emk control bit is set. ddrk ? port k data direction register $00fd bit 7 6 5 4 3 2 1 bit 0 ddk7 0 0 0 ddk3 ddk2 ddk1 ddk0 reset: 0 0 0 0 0 0 0 0
resource mapping technical data mc68hc912dt128a ? rev 4.0 96 resource mapping motorola read and write: anytime. this register deter mines the active page viewed through mc68hc912dt128a windows. call and rtc instru ctions have a special si ngle wire mechanism to read and write this register without using an address bus. 6.5 miscellaneous system control register additional mapping and exte rnal resource controls are available. to use external resources the part must be operated in on e of the expanded modes. normal modes: write onc e; special modes: write anytime. read anytime. romtst ? flash eeprom test mode in normal modes, this bit is forced to zero. 0 = 16k window for fl ash memory is loca ted from $8000-$bfff 1 = 32k window for fl ash memory is loca ted from $8000-$ffff ppage ? (program) page index register $00ff bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 pix2 pix1 pix0 reset: 0 0 0 0 0 0 0 0 misc ? miscellaneous mapping control register $0013 bit 7654321bit 0mode romtst ndrf rfstr1 rfstr0 exstr1 exstr0 romhm romon reset: 0 0 0 0 1 1 0 0 exp mode reset: 0 0 0 0 1 1 0 1 peripheral or sc mode
resource mapping miscellaneous system control register mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 97 ndrf ? narrow data bus for register-following map space this bit enables a narrow bus feature for t he 1k byte register- following map. this is useful for accessing 8-bit peripherals and allows 8-bit and 16-bit external memory devic es to be mixed in a system. in expanded narrow (eight bit) modes, single chip modes, and peripheral mode, th is bit has no effect. 0 = makes register-fo llowing map space act as a full 16 bit data bus. 1 = makes the register-following map space act the same as an 8 bit only external data bus (data only goes through port a externally). the register-following space is mapped from $0400 to $07ff after reset, which is next to the register map. if the registers are moved this space follows. rfstr1, rfstr0 ? regi ster following stretch this two bit field determines the amount of clock stretch on accesses to the 1k byte register following m ap. it is valid regardless of the state of the ndrf bit. in single chip and peri pheral modes this bit has no meaning or effect. exstr1, exstr0 ? external access stretch this two bit field determines the amount of clock stretch on accesses to an external address space. in single chip and peripheral modes this bit has no meaning or effect. table 6-5. rfstr stretch bit definition rfstr1 rfstr0 number of e clocks stretched 00 0 01 1 10 2 11 3
resource mapping technical data mc68hc912dt128a ? rev 4.0 98 resource mapping motorola romhm ? flash eepr om only in second half of map this bit has no meaning if romon bit is clear. 0 = the 16k byte of fixed flas h eeprom in lo cation $4000-$7fff can be accessed. 1 = disables direct access to 16k byte flash eeprom from $4000-$7fff in the memo ry map. the physi cal location of this16k byte flash can still be accessed throug h the program page window. in special mode and with romtst bit set, this bit will allow overlap of the four 32k flas h arrays and overlap the four 4-byte flash register space in the same map space to be able to program all arrays at the same time. 0 = the four 32k flas h arrays are accessed with four pages for each. 1 = the four 32k flash arrays coin cide in the same space and are selected at the same time for programming. caution: bit must be cleared before readi ng any of the arrays or registers. romon ? enable flash eeprom these bits are used to enabl e the flash eeprom arrays. 0 = disables flash eepr om in the memory map. 1 = enables flash eepro m in the memory map. table 6-6. exstr stretch bit definition exstr1 exstr0 number of e clocks stretched 00 0 01 1 10 2 11 3
resource mapping mapping test registers mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 99 6.6 mapping test registers these registers are used in for testi ng the mapping logic. they can only be read and after each read they get cl eared. a write to each register will have no effect. mtst0 ? mapping test register 0 $00f8 bit 7654321bit 0 mt07 mt06 mt05 mt04 mt03 mt02 mt01 mt00 reset: 0 0 0 0 0 0 0 0 mtst1 ? mapping test register 1 $00f9 bit 7654321bit 0 mt0f mt0e mt0d mt0c mt0b mt0a mt09 mt08 reset: 00000000 mtst2 ? mapping test register 2 $00fa bit 7654321bit 0 mt17 mt16 mt15 mt14 mt13 mt12 mt11 mt10 reset:00000000 mtst3 ? mapping test register 3 $00fb bit 7654321bit 0 mt1f mt1e mt1d mt1c mt1b mt1a mt19 mt18 reset: 0 0 0 0 0 0 0 0
resource mapping technical data mc68hc912dt128a ? rev 4.0 100 resource mapping motorola 6.7 memory maps the following diagrams illus trate the memory m ap for each mode of operation immediately after reset. figure 6-1 . mc68hc912dt128a memory map after reset the following diagram illustrates the memory paging scheme. $03ff registers (mappable to any 2k space) 8k bytes ram (mappable to any 8k space) expanded normal single chip special single chip $0000 $3fff $2000 2k bytes eeprom (mappable to any 4k space) $0fff $0800 vectors vectors vectors bdm (if active) $ffff $ff00 16k page window eight 16k flash eeprom pages $bfff $8000 ext $a000 - $bfff protected boot at odd programing pages $0000 $2000 $0800 $1000 $8000 $ff00 $ffff $0400 16k fixed flash eeprom $4000 16k fixed flash eeprom $ffff $c000 $e000 - $ffff protected boot $4000 $c000
resource mapping memory maps mc68hc912dt128a ? rev 4.0 technical data motorola resource mapping 101 figure 6-2 . mc68hc912dt128a memory paging * this 32k flash accessible as pages 6 & 7 and as unpaged $4000 - $7fff & $c000 - $ffff 0 normal single chip 00 flash 32k vectors one 16k page accessible at a time (selected by ppage value = 0 to 7) $0000 $2000 $0800 $1000 $8000 $ff00 $ffff $0400 16k flash (unpaged) $4000 $c000 1234567 6 7 01 flash 32k 10 flash 32k 11 flash 32k * 16k flash (unpaged) 16k flash (paged) (8k boot) (8k boot) (8k boot) (8k boot) (8k boot) $e000
resource mapping technical data mc68hc912dt128a ? rev 4.0 102 resource mapping motorola
mc68hc912dt128a ? rev 4.0 technical data motorola bus control and input/output 103 technical data ? mc68hc912dt128a section 7. bus control and input/output 7.1 contents 7.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.3 detecting access type from external signals . . . . . . . . . . . .103 7.4 registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104 7.2 introduction internally the mc68hc 912dt128a has full 16- bit data paths, but depending upon the oper ating mode and cont rol registers, the external multiplexed bus may be 8 or 16 bits. there are cases where 8-bit and 16-bit accesses can appear on adj acent cycles using the lstrb signal to indicate 8- or 16-bit data. it is possible to have a mix of 8 and 16 bit peripherals attached to the external multiplexed bus, using the nd rf bit in the misc register while in expanded wide modes. 7.3 detecting access type from external signals the external signals lstrb , r/w , and a0 can be us ed to determine the type of bus access that is taking place. accesse s to the internal ram module are the only type of access that produce lstrb =a0=1, because the internal ram is specif ically designed to allow misaligned 16-bit accesses in a single cycle. in these cases the data for the address that was accessed is on the low half of the data bus and the data for address + 1 is on the hi gh half of the data bus.
bus control and input/output technical data mc68hc912dt128a ? rev 4.0 104 bus control and input/output motorola 7.4 registers not all registers are visible in the mc68hc 912dt128a memory map under certain conditions. in special peripheral mode the first 16 registers associated with bus expansion are removed from t he memory map. in expanded modes, some or all of port a, port b, and port e are used for expansion buses and co ntrol signals. in order to allow emulation of the single-chip functions of these ports, some of these registers must be rebuilt in an external port replacement unit. in any expanded mode, port a, and port b, are used fo r address and data lines so registers for these ports, as well as the data direction r egisters for these ports, are removed from the on-chip me mory map and become external accesses. in any expanded mode, port e pins ma y be needed for bus control (e.g., eclk, r/w ). to regain the singl e-chip functions of port e, the emulate port e (eme) control bit in the mode r egister may be set. in this special case of expanded mode and eme set, porte and ddre registers are removed from the on-chip memory map and become external accesses so port e may be rebuilt externally. table 7-1. access type vs. bus control pins lstrb a0 r/w type of access 1 0 1 8-bit read of an even address 0 1 1 8-bit read of an odd address 1 0 0 8-bit write of an even address 0 1 0 8-bit write of an odd address 0 0 1 16-bit read of an even address 111 16-bit read of an odd address (low/high data swapped) 0 0 0 16-bit write to an even address 110 16-bit write to an odd address (low/high data swapped)
bus control and input/output registers mc68hc912dt128a ? rev 4.0 technical data motorola bus control and input/output 105 bits pa[7:0] are associated res pectively with addresses addr[15:8], data[15:8] and data[7:0] , in narrow mode. when this port is not used for external addresses such as in single-chip mode, these pins can be used as general-p urpose i/o. ddra det ermines the primary direction of each pin. this register is not in the on-chip map in expanded and peripheral modes. read and wr ite anytime. this register deter mines the primary directi on for each port a pin when functioning as a general-purpose i/o port. ddra is not in the on-chip map in expanded and per ipheral modes. read and write anytime. 0 = associated pin is a high-impedance input 1 = associated pin is an output porta ? port a register $0000 bit 7654321bit 0 single chip pa7 pa6 pa5 pa4 pa3 pa2 pa1 pa0 reset:???????? expanded & periph: addr15/ data15 addr14/ data14 addr13/ data13 addr12/ data12 addr11/ data11 addr10/ data10 addr9/ data9 addr8/ data8 expanded narrow addr15/ data15/ data7 addr14/ data14/ data6 addr13/ data13/ data5 addr12/ data12/ data4 addr11/ data11/ data3 addr10/ data10/ data2 addr9/ data9/ data1 addr8/ data8/ data0 ddra ? port a data direction register $0002 bit 7654321bit 0 dda7 dda6 dda5 dda4 dda3 dda2 dda1 dda0 reset: 00000000
bus control and input/output technical data mc68hc912dt128a ? rev 4.0 106 bus control and input/output motorola bits pb[7:0] are asso ciated with addresses addr [7:0] and data[7:0] (except in narrow mode) respectively . when this port is not used for external addresses such as in si ngle-chip mode, th ese pins can be used as general-purpose i/ o. ddrb determines th e primary direction of each pin. this regi ster is not in the on-chip map in expanded and peripheral modes. read and write anytime. this register deter mines the primary directi on for each port b pin when functioning as a general-purpose i/o port. ddrb is not in the on-chip map in expanded and per ipheral modes. read and write anytime. 0 = associated pin is a high-impedance input 1 = associated pin is an output this register is associ ated with external bus control signals and interrupt inputs, incl uding data bus enable (dbe ), mode select (modb/ipipe1, moda/ipipe0) , e clock, size (lstrb ), read/write portb ? port b register $0001 bit 7654321bit 0 single chip pb7 pb6 pb5 pb4 pb3 pb2 pb1 pb0 reset: ? ? ? ? ? ? ? ? expanded & periph: addr7/ data7 addr6/ data6 addr5/ data5 addr4/ data4 addr3/ data3 addr2/ data2 addr1/ data1 addr0/ data0 expanded narrow addr7 addr6 addr5 addr4 addr3 addr2 addr1 addr0 ddrb ? port b data direction register $0003 bit 7654321bit 0 ddb7 ddb6 ddb5 ddb4 ddb3 ddb2 ddb1 ddb0 reset: 00000000 porte ? port e register $0008 bit 7654321bit 0 pe7 pe6 pe5 pe4 pe3 pe2 pe1 pe0 reset: ???????? alt. pin function dbe or eclk or cal modb or ipipe1 or cgmtst moda or ipipe0 eclk lstrb or taglo r/w irq xirq
bus control and input/output registers mc68hc912dt128a ? rev 4.0 technical data motorola bus control and input/output 107 (r/w ), irq , and xirq . when the associated pi n is not used for one of these specific functions, the pin can be used as general-purpose i/o. the port e assignment register (pear) selects the function of each pin. ddre determines the primar y direction of ea ch port e pin when configured to be general-purpose i/o. some of these pins have soft ware selectable pull-ups (dbe , lstrb , r/w , irq and xirq ). a single control bit enabl es the pull-ups for all these pins which are configured as inputs. this register is not in the map in peripheral mode or expanded modes when the eme bit is set. read and write anytime. this register deter mines the primary directi on for each port e pin configured as general-purpose i/o. 0 = associated pin is a high-impedance input 1 = associated pin is an output pe[1:0] are associated with xirq and irq and cannot be configured as outputs. these pins can be read regardless of whether the alternate interrupt functions are enabled. this register is not in the map in peripher al mode and expanded modes while the eme control bit is set. read and write anytime. ddre ? port e data direction register $0009 bit 7654321bit 0 dde7 dde6 dde5 dde4 dde3 dde2 0 0 reset: 00000000
bus control and input/output technical data mc68hc912dt128a ? rev 4.0 108 bus control and input/output motorola port e serves as general purpose i/o lines or as system and bus control signals. the pear register is used to choose between the general-purpose i/o functi ons and the alternate bus control functions. when an alternate control function is selected, the associated ddre bits are overridden. the reset condition of this regist er depends on the mode of operation because bus control signals are n eeded immediately after reset in some modes. in normal single-chip mode, no ex ternal bus control signals are needed so all of port e is conf igured for general-purpose i/o. in normal expanded modes, the reset vector is located in external memory. the dbe and e clock are requir ed for de-multiplexing address and data but lstrb and r/w are only needed by the system when there are external writable resources. therefore in normal expanded modes, the dbe and the e clock are configured for their alternate bus control functions and the othe r bits of port e are configured for general-purpose i/o. if the normal expanded system needs any other bus control signal s, pear would need to be written before any access that needed the additional signals. in special expanded modes, dbe , ipipe1, ipipe0, e, lstrb , and r/w are configured as bus-control signals. in special single chip modes, dbe , ipipe1, ipipe0, e, lstrb , r/w, and cale are configured as bus-control signals. pear ? port e assignment register $000a bit 7654321bit 0 ndbe cgmte pipoe neclk lstre rdwe cale dbene reset: 0 0 0 0 0 0 0 0 normal ex- panded reset: 0 0 1 0 1 1 0 0 special ex- panded reset: 1 1 0 1 0 0 0 0 peripheral reset: 1 0 0 1 0 0 0 0 normal sin- gle chip reset: 0 0 1 0 1 1 0 0 special sin- gle chip
bus control and input/output registers mc68hc912dt128a ? rev 4.0 technical data motorola bus control and input/output 109 in peripheral mode, the pear register is not a ccessible for reads or writes. however, the cg mte control bit is rese t to one to configure pe6 as a test output for the cgm module. ndbe ? no data bus enable normal: write once; special: writ e anytime except the first. read anytime. 0 = pe7 is used for dbe , external control of data enable on memories, or inverted e clock. 1 = pe7 is cal function if cale bit is set in pear register or general-purpose i/o otherwise. the ndbe bit has no effe ct in single chip or peripheral modes and pe7 is defaulted to the cal functi on if cale bit is set in pear register or to an i/o otherwise. cgmte ? clock generator module testing enable normal: write never; special: writ e anytime except the first time. read anytime. 0 = pe6 is gener al-purpose i/o or pipe output. 1 = pe6 is a test signal output fr om the cgm module (no effect in single chip or normal expanded modes). pipoe = 1 overrides this function and fo rces pe6 to be a pipe status output signal. pipoe ? pipe status signal output enable normal: write once; special: writ e anytime except the first time. read anytime. 0 = pe[6:5] are general- purpose i/o (if cgmte = 1, pe6 is a test output signal from the cgm module). 1 = pe[6:5] are outputs and indicate the state of the instruction queue (only effective in expanded modes). neclk ? no external e clock normal single chip: write once; spec ial single chip: write anytime; all other modes: write never. read anytime. in peripheral mode , e is an input and in all other modes, e is an output.
bus control and input/output technical data mc68hc912dt128a ? rev 4.0 110 bus control and input/output motorola 0 = pe4 is the exter nal e-clock pin subj ect to the following limitation: in single-chip modes, to get an e clock output signal, it is necessary to have estr = 0 in addition to neclk = 0. a 16-bit write to pear and mode registers can configure all three bits in one operation. 1 = pe4 is a general -purpose i/o pin. lstre ? low strobe (lstrb ) enable normal: write once; special: writ e anytime except the first time. read anytime. this bit has no effect in single-chip modes or normal expanded narrow mode. 0 = pe3 is a general -purpose i/o pin. 1 = pe3 is configur ed as the lstrb bus-control output, provided the mcu is not in single ch ip or normal expanded narrow modes. lstrb is used during external writes. after reset in normal expanded mode, lstrb is disabled. if needed, it should be enabled before external writes. external r eads do not normally need lstrb because all 16 data bits can be driven even if the mcu only needs 8 bits of data. taglo is a shared functi on of the pe3/lstrb pin. in special expanded modes with lstre set and the bdm tagging on, a zero at the falling edge of e tags the instruction wo rd low byte bei ng read into the instruction queue. rdwe ? read/write enable normal: write once; special: writ e anytime except the first time. read anytime. this bit has no ef fect in single-chip modes. 0 = pe2 is a general -purpose i/o pin. 1 = pe2 is configured as the r/w pin. in single chip modes, rdwe has no effect and pe2 is a general-purpose i/o pin. r/w is used for external writes. af ter reset in normal expanded mode, it is disabled. if needed it sh ould be enabled before any external writes.
bus control and input/output registers mc68hc912dt128a ? rev 4.0 technical data motorola bus control and input/output 111 cale ? calibration reference enable read and write anytime. 0 = calibration reference is disabled and pe7 is general purpose i/o in single chip or peripheral modes or if ndbe bit is set. 1 = calibration reference is enabled on pe7 in single chip and peripheral modes or if ndbe bit is set. dbene ? dbe or inverted e clock on pe7 normal modes: write onc e. special modes: write anytime except the first time. read anytime. dbene controls which signal is output on pe7 when ndbe control bit is cleared. the inverted e clock output can be used to latch the address for de-multiplexing. it has t he same behavior as the e clock, except it is inverted. please note t hat in the case of idle expansion bus, the ?not e clock? signal co uld stay high for many cycles. the dbene bit has no effect in si ngle chip or peripheral modes and pe7 is defaulted to the cal functi on if cale bit is set in pear register or to an i/o otherwise. 0 = pe7 pin used for dbe external control of data enable on memories in expanded m odes when ndbe = 0 1 = pe7 pin used for inverted e clock output in expanded modes when ndbe = 0 these bits select pull-up resistors for any pin in the corresponding port that is currently c onfigured as an input. this register is not in the map in peri pheral mode. read and write anytime. pupk ? pull-up port k enable 0 = port k pull-ups are disabled. 1 = enable pull-up devices for all port k input pins. pucr ? pull-up control register $000c bit 7654321bit 0 pupk pupj puph pupe 0 0 pupb pupa reset: 00010000
bus control and input/output technical data mc68hc912dt128a ? rev 4.0 112 bus control and input/output motorola pupj ? pull-up or pull-down port j enable 0 = port j resistive loads (pull- ups or pull-downs) are disabled. 1 = enable resistive load devices (pull-ups or pull-downs) for all port j input pins. puph ? pull-up or pull -down port h enable 0 = port h resistive loads (pull- ups or pull-downs) are disabled. 1 = enable resistive load devices (pull-ups or pull-downs) for all port h input pins. pupe ? pull-up port e enable 0 = port e pull-ups on pe7, pe3, pe2, pe1 and pe 0 are disabled. 1 = enable pull-up devices for port e input pins pe7, pe3, pe2, pe1 and pe0. when this bit is set port e input pins 7, 3, 2, 1 & 0 hav e an active pull- up device. pupb ? pull-up port b enable 0 = port b pull-ups are disabled. 1 = enable pull-up devices for all port b input pins. pupa ? pull-up port a enable 0 = port a pull-ups are disabled. 1 = enable pull-up devices for all port a input pins.
bus control and input/output registers mc68hc912dt128a ? rev 4.0 technical data motorola bus control and input/output 113 these bits select reduced drive for the associ ated port pins. this gives reduced power consumption and reduced rfi with a slight increase in transition time (dependi ng on loading). the reduced drive function is independent of which function is being used on a particular port. this register is not in t he map in peripheral mode. normal: write once; special: writ e anytime except the first time. read anytime. rdpk ? reduced drive of port k 0 = all port k output pi ns have full drive enabled. 1 = all port k output pins have reduced drive capability. rdpj ? reduced drive of port j 0 = all port j output pins have full drive enabled. 1 = all port j output pins hav e reduced driv e capability. rdph ? reduced drive of port h 0 = all port h output pi ns have full drive enabled. 1 = all port h output pins have reduced drive capability. rdpe ? reduced drive of port e 0 = all port e output pi ns have full drive enabled. 1 = all port e output pins have reduced drive capability. rdpb ? reduced drive of port b 0 = all port b output pi ns have full drive enabled. 1 = all port b output pins have reduced drive capability. rdpa ? reduced drive of port a 0 = all port a output pi ns have full drive enabled. 1 = all port a output pins have reduced drive capability. rdriv ? reduced drive of i/o lines $000d bit 7654321bit 0 rdpk rdpj rdph rdpe 0 0 rdpb rdpa reset:00000000
bus control and input/output technical data mc68hc912dt128a ? rev 4.0 114 bus control and input/output motorola
mc68hc912dt128a ? rev 4.0 technical data motorola flash memory 115 technical data ? mc68hc912dt128a section 8. flash memory 8.1 contents 8.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 8.3 overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 8.4 flash eeprom control bl ock . . . . . . . . . . . . . . . . . . . . . . . .116 8.5 flash eeprom arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116 8.6 flash eeprom registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.7 operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119 8.8 programming the flash eep rom . . . . . . . . . . . . . . . . . . . . . 120 8.9 erasing the flash eeprom . . . . . . . . . . . . . . . . . . . . . . . . . . 121 8.10 stop or wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121 8.11 flash protection bit fpop en . . . . . . . . . . . . . . . . . . . . . . . . .122 8.2 introduction the four flash eepr om array modules 00fee32k, 01fee32k, 10fee32k and 11fee32k for t he mc68hc912dt128a serve as electrically erasable and programmable, non-vola tile rom emulation memory. the modules can be used for program code that must either execute at high speed or is fr equently executed, such as operating system kernels and standard subroutines , or they can be used for static data which is read frequent ly. the flash eeprom m odule is ideal for program storage for single-chip applications allowing for field reprogramming.
flash memory technical data mc68hc912dt128a ? rev 4.0 116 flash memory motorola 8.3 overview each 32k flash eeprom array is ar ranged in a 16-bit configuration and may be read as either by tes, aligned words or misaligned words. access time is one bus cycle for byte and aligned word access and two bus cycles for misaligned word operations. the flash eeprom module s upports bulk erase only. each flash eeprom m odule has hardware inte rlocks which protect stored data from accide ntal corruption. an erase- and program- protected 8-kbyte block for boot routines is located at the top of each 32- kbyte array. since boot programs must be available at all times, the only useful boot block is at $e000?$ffff location. all paged boot blocks can be used as protected pr ogram space if desired. on 0l05h and later ma sk sets, an optional pr otection scheme is supported to protect all four 32-kb yte flash eeprom modules against accident program or er ase. this is achieved us ing the protection bit fpopen in eeprom eemcr (see 8.11 flash protection bit fpopen ). 8.4 flash eeprom control block a 4-byte register block for each module controls the flash eeprom operation. configuration info rmation is specified and programmed independently from the cont ents of the flash eepro m array. at reset, the 4-byte register se ction starts at addre ss $00f4 and points to the 00fee32k register block. 8.5 flash eeprom arrays after reset, a fixed 32k flash ee prom array, 11fee32k, is located from addresses $4000 to $7fff and from $c000 to $ffff. the other three 32k flash eeprom arra ys 00fee32k, 01fee32k and 10fee32k, are mapped through a 16k byte program page window located from addre sses $8000 to $bfff. the page window has eight 16k byte pages. the last two pages also map the physical location of the
flash memory flash eeprom registers mc68hc912dt128a ? rev 4.0 technical data motorola flash memory 117 fixed 32k flash eeprom array 11fe e32k. in expa nded modes, the flash eeprom arrays are turned off. see operating modes . 8.6 flash eeprom registers each 32k byte flash eeprom module has a set of registers. the register space $00f4-$00f7 is in a r egister space window of four pages. each register page of four bytes maps the register space for each flash module and each page is selected by the ppage register. see resource mapping in normal modes the lock bit c an only be written once after reset. lock ? lock register bit 0 = enable write to feemcr register 1 = disable write to feemcr register this register c ontrols the operation of the flash eeprom array. bootp cannot be c hanged when the lock c ontrol bit in the feelck register is set or if hv en or pgm or eras in the feectl register is set. feelck ? flash eeprom lock control register $00f4 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 0 0 lock reset: 0 0 0 0 0 0 0 0 feemcr ? flash eeprom module configuration register $00f5 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 0 0 bootp reset: 0 0 0 0 0 0 0 1
flash memory technical data mc68hc912dt128a ? rev 4.0 118 flash memory motorola bootp ? boot protect the boot blocks are located at $e000?$ffff and $a 000?$bfff for odd program pages for each flash eeprom module. since boot programs must be available at all time s, the only useful boot block is at $e000?$ffff location. all paged boot blocks can be used as protected program space if desired. 0 = enable erase and program of 8k byte boot block 1 = disable erase and program of 8k byte boot block this register c ontrols the programming and erasure of the flash eeprom. feeswai ? flash eeprom stop in wait control 0 = do not halt flash eeprom clock when the part is in wait mode. 1 = halt flash eeprom clock when the part is in wait mode. hven ? high-voltage enable this bit enables the charge pump to supply high voltages for program and erase operations in the array. hven can only be set if either pgm or eras are set and the proper sequence for program or erase is followed. 0 = disables high voltage to array and charge pump off 1 = enables high voltage to array and charge pump on eras ? erase control this bit configures the memory for eras e operation. eras is interlocked with the pgm bit such t hat both bits ca nnot be equal to 1 or set to1 at the same time. 0 = erase operation is not selected. 1 = erase operation selected. feectl ? flash eeprom control register $00f7 bit 7 6 5 4 3 2 1 bit 0 0 0 0 feeswai hven 0 eras pgm reset: 0 0 0 0 0 0 0 0
flash memory operation mc68hc912dt128a ? rev 4.0 technical data motorola flash memory 119 pgm ? program control this bit configures t he memory for program operation. pgm is interlocked with the eras bit such t hat both bits cannot be equal to 1 or set to1 at the same time. 0 = program operation is not selected. 1 = program operation selected. 8.7 operation the flash eeprom can c ontain program and data. on reset, it can operate as a bootstrap memory to provide the cpu with internal initialization information during the reset sequence. 8.7.1 bootstrap oper ation single-chip mode after reset, the cpu controlling t he system will begin booting up by fetching the first program address fr om address $fffe. 8.7.2 normal operation the flash eeprom allo ws a byte or aligned word read in o ne bus cycle. misaligned word read require an additional bus cycle. the flash eeprom array responds to read operations only. write operations are ignored. 8.7.3 program/erase operation an unprogrammed flash ee prom bit has a logic state of one. a bit must be programmed to change its state from one to zero. erasing a bit returns it to a logic one. the flash eeprom has a minimum program/erase life of 100 cycles. programming or erasing the flash eeprom is accomplished by a series of cont rol register writes. the flash eeprom must be complete ly erased prior to programming final data values.
flash memory technical data mc68hc912dt128a ? rev 4.0 120 flash memory motorola programming and erasing of flash lo cations cannot be performed by code being executed from the flas h memory. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. do not exceed t fpgm maximum (40 s). 8.8 programming the flash eeprom programming the flash ee prom is done on a row basis. a row consists of 32 consecutive words (64 bytes) with rows starting from addresses $xx00, $xx40, $xx80 and $xxc0. when writing a row care should be taken not to writ e data to addresse s outside of the ro w. programming is restricted to aligned word i.e. data writes to select rows/blocks for programming/erase should be to even adresses and writes to any row for programming should be to aligned words. use this step-by-step procedure to program a row of flash memory. 1. set the pgm bit. this configur es the memory for program operation and enables the latchi ng of address and data for programming. 2. write to any aligned word fl ash address within the row address range desired (with any data) to select the row. 3. wait for a time, t nvs (min. 10 s). 4. set the hven bit. 5. wait for a time, t pgs (min. 5 s). 6. write one data word (two bytes) to the next alig ned word flash address to be programmed. if boot p is asserted, an attempt to program an address in the boot block will be ignored. 7. wait for a time, t fpgm (min. 30 s). 8. repeat step 6 and 7 until all the words within the row are programmed. 9. clear the pgm bit. 10. wait for a time, t nvh (min. 5 s). 11. clear the hven bit.
flash memory erasing the flash eeprom mc68hc912dt128a ? rev 4.0 technical data motorola flash memory 121 12. after time, t rcv (min 1 s), the memory can be accessed in read mode again. this program sequence is repeated th roughout the memory until all data is programmed. for minimum ov erall programming time and least program disturb effect, the sequence should be part of an intelligent operation which it erates per row. 8.9 erasing the flash eeprom the following sequence demonstrat es the recommended procedure for erasing any of the flash eeprom array. 1. set the eras bit. 2. write to any valid address in t he flash array. the data written and the address written ar e not important. the boot block will be erased only if the contro l bit bootp is negated. 3. wait for a time, t nvs . 4. set the hven bit. 5. wait for a time, t eras . 6. clear the eras bit. 7. wait for a time, t nvhl . 8. clear the hven bit. 9. after time, t rcv , the memory can be accessed in read mode again. 8.10 stop or wait mode when stop or wait comm ands are executed, t he mcu puts the flash eeprom in stop or wait mode. in these modes the fl ash module will cease erasure or progr amming immediately. caution: it is advised not to enter stop or wait modes when program or erase operation of the flash array is in progress.
flash memory technical data mc68hc912dt128a ? rev 4.0 122 flash memory motorola 8.11 flash protection bit fpopen the fpopen bit is loca ted in eemcr ? eeprom module configuration register, bit 4. fpopen ? opens the flash ar ray for program or erase 0 = the whole flash array is protected. 1 = the whole flash array is enabled for program or erase fpopen can be read at anytime. fpopen can be written only to ?0? for protection but not to ?1? for un- protect in normal mode. fpopen can be written ?0? and ?1? in special mode only. fpopen is loaded at reset fr om eeprom shadow word bit 4. when fpopen is cleared to ?0 ?, the flash array cannot be reprogrammed in normal modes. caution: programming the nvm fpopen bit in the shadow word ($_fc0, bit 4) means that the fpopen bit in t he eemcr register will always be ?0? in normal modes. the flash array c an no longer be modified in normal modes.
mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 123 technical data ? mc68hc912dt128a section 9. eeprom memory 9.1 contents 9.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 9.3 eeprom selective write more zeros . . . . . . . . . . . . . . . . . .124 9.4 eeprom programmer? s model . . . . . . . . . . . . . . . . . . . . . . .125 9.5 eeprom control registers . . . . . . . . . . . . . . . . . . . . . . . . . . 126 9.6 program/erase operation. . . . . . . . . . . . . . . . . . . . . . . . . . . .133 9.7 shadow word mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.8 programming eedivh and eedivl registers. . . . . . . . . . . . 135 9.2 introduction the mc68hc912dt128a eeprom nonvolatile memory is arranged in a 16-bit configuration. the eeprom array may be read as either bytes, aligned words or misaligned words. access times are one bus cycle for byte and aligned word access and two bus cycles fo r misaligned word operations. programming is by byte or aligned word. attempts to program or erase misaligned words will fail. only the lower byte will be latched and programmed or erased. programming and erasing of th e user eeprom can be done in normal modes. each eeprom byte or aligned word must be erased before programming. the eeprom module supports by te, aligned word, row (32 bytes) or bulk erase, all usi ng the internal charge pump. the erased state is $ff. the e eprom module ha s hardware interlocks which protect stored data from corrupti on by accidentally enabling the program/erase voltag e. programming voltage is derived from the internal v dd supply with an in ternal charge pump.
eeprom memory technical data mc68hc912dt128a ? rev 4.0 124 eeprom memory motorola 9.3 eeprom selective write more zeros the eeprom can be programmed such th at one or multiple bits are programmed (written to a lo gic ?0?) at a time. ho wever, the user should never program any bit more than once before erasing the entire byte. in other words, the user is not allowed to over write a l ogic ?0? with another ?0?. for some applications it may be adv antageous to track more than 10k events with a single byte of eeprom by programmi ng one bit at a time. for that purpose, a special sele ctive bit programmi ng technique is available. an example is shown here. original state of byte = binary 1111:1111 (erased) first event is recorded by programming bit position 0 program write = binary 1111:1110; re sult = binary 1111:1110 second event is recorded by programming bit position 1 program write = binary 1111:1101; re sult = binary 1111:1100 third event is recorded by programming bit position 2 program write = binary 1111:1011; re sult = binary 1111:1000 fourth event is recorded by programming bi t position 3 program write = binary 1111:0111; re sult = binary 1111:0000 events five through eight are re corded in a similar fashion. note that none of the bit locations are actually programmed more than once although the byte wa s programmed eight times. when this technique is ut ilized, a program / er ase cycle is defined as multiple writes (up to eight) to a unique locati on followed by a single erase sequence.
eeprom memory eeprom programmer?s model mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 125 9.4 eeprom programmer?s model the eeprom module consists of two separately addressable sections. the first is an eight-byte memory m apped control register block used for control, testing and configuration of the eeprom array. the second section is the eeprom array itself. at reset, the eight-byte register se ction starts at address $00ec and the eeprom array is located from addresses $0800 to $0fff. registers $00ec-$00ed are reserved. read/write access to the memory array section can be enabled or disabled by the eeon control bit in the initee register ($0012). this feature allows the access of memo ry mapped resources that have lower priority than the eeprom memory ar ray. eeprom control registers can be accessed regardless of the stat e of eeon. any eeprom erase or program operation already in progress will not be affected by the change of eeon state. for in formation on re-mapping th e register block and eeprom address spac e, refer to operating modes . caution: it is strongly recomm ended to discontinue program /erase operations during wait (when eeswai=1) or stop modes since all program/erase activiti es will be terminated abruptly and considered unsuccessful. for lowest power consumption during wait mode, it is advised to turn off eepgm. the eeprom module contains an ex tra word called shadow word which is loaded at reset into t he eemcr, eedivh and eedivl registers. to program the shadow word, when in special modes (smodn=0), the noshw bit in eemc r register must be cleared. normal programming routines are used to program the shadow word which becomes accessible at address $0fc0-$0fc1 when noshw is cleared. at the next reset the sh adow word data is loaded into the eemcr, eedivh and eedivl regist ers. the shadow word can be protected from being prog rammed or erased by setting the shprot bit of eeprot register.
eeprom memory technical data mc68hc912dt128a ? rev 4.0 126 eeprom memory motorola a steady internal self-t ime clock is required to provide accurate counts to meet eeprom pr ogram/erase requirements. this clock is generated via by a programmable 10-bit prescaler register. automatic program/erase terminat ion is also provided. in ordinary situations, with crystal operating pr operly, the stead y internal self-time clock is derived from th e input clock sour ce (extali). the divider value is as in eedivh:eedivl. in limp -home mode, where the oscillator clock has malfunctioned or is unavailable, the se lf-time clock is derived from the p ll at a nominal f vcomin using a prede fined divider value of $0023. program/erase oper ation is not gua ranteed in limp- home mode. caution: it is strongly recommended that program/erase oper ation is terminated in the event of loss of cr ystal, either by the applic ation software (clearing eepgm & eelat bits) when enteri ng limp home mode or by enabling the clock monitor to generate a clock monitor reset. th is will prevent unnecessary stress on the emulated e eprom during osci llator failure. 9.5 eeprom control registers eedivh ? eeprom modulus divider $00ee bit 7654321bit 0 000000eediv9eediv8 reset: 000000? (1) ? (1) 1. loaded from shadow word. eedivl ? eeprom modulus divider $00ef bit 7654321bit 0 eediv7 eediv6 eediv5 eediv4 eediv3 eediv2 eediv1 eediv0 reset: ? (1) ? (1) ? (1) ? (1) ? (1) ? (1) ? (1) ? (1) 1. loaded from shadow word.
eeprom memory eeprom control registers mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 127 eediv[9:0] ? prescaler divider loaded from shadow word at reset. read anytime. write once in norma l modes (smodn =1 ) if eelat = 0 and anytime in special mode s (smodn =0) if eelat = 0. the prescaler divider is required to produce a self-tim e clock with a fixed frequency around 28.6 khz for the range of oscillator frequencies. the divider is set so that the o scillator frequency can be divided by a divide factor that can produce a 35 s 2 s timebase. caution: an incorrect or uninitial ized value on eedi v can result in overstress of eeprom array during program/erase operation. it is also strongly recommend not to program eeprom with osci llator frequencies less than 250 khz. the eediv value is determined by the following formula: note: int[a] denotes the round down integer value of a. program/erase cycles will not be activat ed when eediv = 0. eediv int extali (hz) x 35 6 ? 10 0.5 + [] = table 9-1. eediv selection osc freq. osc period divide factor eediv 16 mhz 62.5ns 560 $0230 8 mhz 125ns 280 $0118 4 mhz 250ns 140 $008c 2 mhz 500ns 70 $0046 1 mhz 1 s 35 $0023 500 khz 2 s 18 $0012 250 khz 4 s 9 $0009
eeprom memory technical data mc68hc912dt128a ? rev 4.0 128 eeprom memory motorola bits[7:4] are loaded at reset from the eepro m shadow word. note: the bits 5 and 4 are reserved for test purposes. these locations in shadow word should not be programmed otherwise some locations of regular eeprom array will not be more visible. nobdml ? background debug mode lockout disable 0 = the bdm lockout is enabled. 1 = the bdm lockout is disabled. loaded from shadow word at reset. read anytime. write anytime in special modes (smodn=0). noshw ? shadow word disable 0 = the shadow word is enabled and accessible at address $0fc0-$0fc1. 1 = regular eeprom arra y at address $0fc0-$0fc1. loaded from shadow word at reset. read anytime. write anytime in special modes (smodn=0). when noshw cleared, the regula r eeprom array bytes at address $0fc0 and $0fc1 are no t visible. the shado w word is accessed instead for both read and pr ogram/erase operatio ns. bits[7:4] from the high byte of t he shadow word, $0fc 0, are loaded to eemcr[7:4]. bits[1:0] from the high byte of the shadow word, $0fc0,are loaded to eedivh[1:0]. bits[7:0] from the low byte of the shadow word, $0fc1,are loaded to ee divl[7:0]. bulk program/erase only applies if shadow word is enabled. note: bit 6 from high byte of shadow word should not be programmed in order to have the full eeprom array visible. eemcr ? eeprom module configuration $00f0 bit 7654321bit 0 nobdml noshw reserved (1) fpopen (2) 1 eeswai protlck dmy reset: ? (3) ? (3) ? (3) ? (3) 1100 1. bit 5 has a test function and should not be programmed. 2. the fpopen bit is available only on the 0l05h and later mask sets. for previous masks, this bit is reserved. 3. loaded from shadow word.
eeprom memory eeprom control registers mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 129 fpopen ? opens the flash bl ock for program or erase 0 = the whole flash array is protected. 1 = the whole flash array is enable for program or erase. loaded from shadow word at rese t. read anytime. write anytime in special modes (smodn=0). writ e once ?0? is allowed in normal mode. eeswai ? eeprom stops in wait mode 0 = the module is not affe cted during wait mode 1 = the module ceases to be clocked during wait mode read and write anytime. note: the eeswai bit should be cleared if the wait mode vectors are mapped in the e eprom array. protlck ? block protect write lock 0 = block protect bits and bulk er ase protection bit can be written 1 = block protect bits are locked read anytime. write once in no rmal modes (smodn = 1), set and clear any time in spec ial modes (smodn = 0). dmy? dummy bit read and write anytime.
eeprom memory technical data mc68hc912dt128a ? rev 4.0 130 eeprom memory motorola prevents accidental writ es to eeprom. read anytime. write anytime if eepgm = 0 and protlck = 0. shprot ? shadow word protection 0 = the shadow word can be programmed and erased. 1 = the shadow word is protec ted from being programmed and erased. bprot[5:0] ? eeprom block protection 0 = associated eepr om block can be pr ogrammed and erased. 1 = associated eepr om block is protected from being programmed and erased. in normal mode, writes to eetst control bits have no effect and always read zero. the eeprom module cannot be placed in test mode inadvertently dur ing normal operation eeprot ? eeprom block protect $00f1 bit 7654321bit 0 shprot 1 bprot5 bprot4 bprot3 bprot2 bprot1 bprot0 reset: 11111111 table 9-2. 2k byte e eprom block protection bit name block protected block size bprot5 $0800 to $0bff 1024 bytes bprot4 $0c00 to $0dff 512 bytes bprot3 $0e00 to $0eff 256 bytes bprot2 $0f00 to $0f7f 128 bytes bprot1 $0f80 to $0fbf 64 bytes bprot0 $0fc0 to $0fff 64 bytes eetst ? eeprom test $00f2 bit 7654321bit 0 0 erevtn 0 0 0 etmsd etmr etmse reset: 00000000
eeprom memory eeprom control registers mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 131 . bulkp ? bulk erase protection 0 = eeprom can be bulk erased. 1 = eeprom is protected from being bulk or row erased. read anytime. write anytime if eepgm = 0 and protlck = 0. auto ? automatic shutdown of program/era se operation. eepgm is cleared automatically af ter the program/erase cycles are finished when auto is set. 0 = automatic clear of eepgm is disabled. 1 = automatic clear of eepgm is enabled. read anytime. write any time if eepgm = 0. byte ? byte and aligned word erase 0 = bulk or row erase is enabled. 1 = one byte or one al igned word erase only. read anytime. write any time if eepgm = 0. row ? row or bulk er ase (when byte = 0) 0 = erase entire eeprom array. 1 = erase only one 32-byte row. read anytime. write any time if eepgm = 0. byte and row have no ef fect when erase = 0 if byte = 1 only the lo cation specified by the address written to the programming latches will be erased . the operation will be a byte or an aligned word erase depending on the size of written data. eeprog ? eeprom control $00f3 bit 7654321bit 0 bulkp 0 auto byte row erase eelat eepgm reset: 10000000 table 9-3. erase selection byte row block size 0 0 bulk erase entire eeprom array 0 1 row erase 32 bytes 1 0 byte or aligned word erase 1 1 byte or aligned word erase
eeprom memory technical data mc68hc912dt128a ? rev 4.0 132 eeprom memory motorola erase ? erase control 0 = eeprom configurat ion for programming. 1 = eeprom configur ation for erasure. read anytime. write any time if eepgm = 0. configures the eeprom fo r erasure or programming. unless bulkp is set, erasure is by byte, aligned word, row or bulk. eelat ? eeprom latch control 0 = eeprom set up for normal reads. 1 = eeprom address and data bus latches set up for programming or erasing. read anytime. write anytime except when eepgm = 1 or eediv = 0. byte, row, erase and eelat bits can be wr itten simultaneously or in any sequence. eepgm ? program and erase enable 0 = disables program/era se voltage to eeprom. 1 = applies program/era se voltage to eeprom. the eepgm bit can be set only afte r eelat has b een set. when eelat and eepgm are set simult aneously, eepgm remains clear but eelat is set. the bulkp, auto, byte, row, erase and eelat bits cannot be changed when eepgm is se t. to complete a pr ogram or erase cycle when auto bit is cl ear, two successive writ es to clear eepgm and eelat bits are required before reading the pr ogrammed data. when the auto bit is set, eepgm is automatically cleared after the program or erase cycle completes. note that if an attempt is made to modify a protected block location t he modify cycle do es not start and the eepgm bit isn?t automatically cleared. a write to an eeprom location has no effect when eepgm is set. latched address and data cannot be modified during program or erase.
eeprom memory program/erase operation mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 133 9.6 program/erase operation a program or erase oper ation should follow the sequence below if auto bit is clear: 1. write byte, row and erase to desired value, write eelat = 1 2. write a byte or an aligned word to an eeprom address 3. write eepgm = 1 4. wait for programming, t prog or erase, t erase delay time 5. write eepgm = 0 6. write eelat = 0 if the auto bit is set, steps 4 and 5 can be replaced by a step to poll the eepgm bit until it is cleared. caution: the state machine will not start if an attempt is made to program or erase a protected location and th erefore the eepgm bit wi ll never clear on that eeprom operation. check for protected status or use a software timeout to avoid a continuous loop wh ilst polling the eepgm bit. if using a timeout, ensure steps 5 and 6 are still executed. it is possible to program/erase more bytes or words without intermediate eeprom reads, by jumping fr om step 5 to step 2.
eeprom memory technical data mc68hc912dt128a ? rev 4.0 134 eeprom memory motorola 9.7 shadow word mapping the shadow word is mapped to lo cation $_fc0 and $_fc1 when the noshw bit in eemcr register is ze ro. the value in th e shadow word is loaded to the eemc r, eedivh and eedivl after reset. table 9-4 shows the mapping of each bit from shadow word to the registers. table 9-4. shadow word mapping shadow word location register / bit $_fc0 bit 7 eemcr / nobdml $_fc0, bit 6 eemcr / noshw $_fc0, bit 5 eemcr / bit 5 (1) 1. reserved for testing. must be set to one in user application. $_fc0, bit 4 eemcr / bit 4 (1) $_fc0, bit 3:2 not mapped (2)) 2. reserved. must be set to one in user application for future compatibility. $_fc0, bit 1:0 eedivh / bit 1:0 $_fc1, bit 7:0 eedivclk / bit 7:0
eeprom memory programming eedivh and eedivl registers mc68hc912dt128a ? rev 4.0 technical data motorola eeprom memory 135 9.8 programming eedivh and eedivl registers the eedivh and eedivl regi sters must be correctly set according to the oscillator frequency before any eeprom location can be programmed or erased. 9.8.1 normal mode the eedivh and eedivl regi sters are writ e once in normal mode. upon system reset, the application program is required to write the correct divider value to eedivh and eedivl registers based on the oscillator frequency. af ter the first write, th e value in the eedivh and eedivl registers is lo cked from being overwritt en until the next reset. the eeprom is then ready for st andard program/erase routines. caution: runaway code can possibly corrupt the eedivh and eed ivl registers if they are not initialized (write once registers). 9.8.2 special mode if an existing applicat ion code with eepr om program/erase routines is fixed and the system is already oper ating at a known oscillator frequency, it is recommended to in itialize the shadow word with the corresponding eedivh and eedivl values in special mode. the shadow word initialize s eedivh and eedivl registers upon system reset to ensure software compatibility with existi ng code. initializing the eedivh and eedivl regi sters in special modes (smodn=0) is accomplished by t he following steps. 1. write correct divider value to eedivh and eedi vl registers based on the oscillato r frequency as per table 9-1 . 2. remove the shadow word protec tion by clearing shprot bit in eeprot register. 3. clear noshw bit in eemcr regist er to make the shadow word visible at $0fc0-$0fc1. 4. write noshw bit in eemcr regist er to make the shadow word visible at $0fc0-$0fc1.
eeprom memory technical data mc68hc912dt128a ? rev 4.0 136 eeprom memory motorola 5. program bits 1 and 0 of the high byte of the shadow word and bits 7 to 0 of the lo w byte of the shadow word like a regular eeprom location at address $0fc 0 and $0fc1. do not program other bits of the high byte of th e shadow word (location $0fc0); otherwise some regul ar eeprom array loca tions will not be visible. at the next reset, the s hadow values are loaded into the eedivh and eedivl r egisters. they do not require further initialization as long as the osc illator frequency of the target application is not changed. 6. protect the shadow word by setting shprot bit in eeprot register.
mc68hc912dt128a ? rev 4.0 technical data motorola resets and interrupts 137 technical data ? mc68hc912dt128a section 10. resets and interrupts 10.1 contents 10.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 10.3 exception priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 10.4 maskable interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138 10.5 latching of interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139 10.6 interrupt control and priority regist ers . . . . . . . . . . . . . . . . .141 10.7 interrupt test registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 10.8 resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143 10.9 effects of reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 10.10 register stacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 10.2 introduction cpu12 exceptions include resets and interrupts. each exception has an associated 16-bit vector, which points to the memory location where the routine that handles the e xception is located. ve ctors are stored in the upper 128 bytes of the standar d 64k byte address map. the six highest vector addresses are used for resets and non-maskable interrupt sources. the remainder of the vectors are used for maskable interrupts, and all must be initiali zed to point to the address of the appropriate service routine.
resets and interrupts technical data mc68hc912dt128a ? rev 4.0 138 resets and interrupts motorola 10.3 exception priority a hardware priority hier archy determines which reset or interrupt is serviced first when simult aneous requests are made. six sources are not maskable. the remaining sources are maskable, and any one of them can be given priority over other maskable interrupts. the priorities of the n on-maskable sources are: 1. por or reset pin 2. clock monitor reset 3. cop watchdog reset 4. unimplemented instruction trap 5. software interrupt instruction (swi) 6. xirq signal (if x bit in ccr = 0) 10.4 maskable interrupts maskable interrupt sources in clude on-chip peripheral systems and external interrupt service requests. interrupts from these sources are recognized when the global interrupt ma sk bit (i) in the ccr is cleared. the default state of the i bit out of reset is one, but it can be written at any time. interrupt sources are prio ritized by default but any one maskable interrupt source may be assigned the highest pr iority by means of the hprio register. the relative pr iorities of the other s ources remain the same. an interrupt that is assigned highest pr iority is still subject to global masking by the i bit in the ccr, or by any associated local bits. interrupt vectors are not affect ed by priority assignm ent. hprio can only be written while the i bit is set (interrupts inhibited). table 10-1 lists interrupt sources and vectors in default order of priority. before masking an interrupt by clearing the corresponding local enable bi t, it is required to set the i-bit to avoid an swi.
resets and interrupts latching of interrupts mc68hc912dt128a ? rev 4.0 technical data motorola resets and interrupts 139 10.5 latching of interrupts xirq is always level triggered and irq can be selected as a level triggered interrupt. these level tri ggered interrupt pins should only be released during the appropriate interrupt service routine. generally the interrupt service routi ne will handshake with the interrupting logic to release the pin. in this way, the mcu will never start the interrupt service sequence only to determine that there is no longer an interrupt source. in event that this does occu r the trap vector will be taken. if irq is selected as an edge triggered inte rrupt, the hold time of the level after the active edge is independent of when the interrupt is serviced. as long as the minimum hold time is met, the interrupt will be latched inside the mcu. in this ca se the irq edge interrupt latch is cleared automatically when the interrupt is serviced. all of the remaining in terrupts are latched by t he mcu with a flag bit. these interrupt flags should be cl eared during an interrupt service routine or when interr upts are masked by the i bit. by doing this, the mcu will never get an unknown interrupt source and take the trap vector.
resets and interrupts technical data mc68hc912dt128a ? rev 4.0 140 resets and interrupts motorola table 10-1. interrupt vector map vector address interrupt source ccr mask local enable hprio value to elevate $fffe, $ffff reset none none ? $fffc, $fffd clock monitor fail reset none copctl (cme, fcme) ? $fffa, $fffb cop failure reset none cop rate selected ? $fff8, $fff9 unimplemented instruction trap none none ? $fff6, $fff7 swi none none ? $fff4, $fff5 xirq x bit none ? $fff2, $fff3 irq i bit intcr (irqen) $f2 $fff0, $fff1 real time interrupt i bit rtictl (rtie) $f0 $ffee, $ffef timer channel 0 i bit tmsk1 (c0i) $ee $ffec, $ffed timer channel 1 i bit tmsk1 (c1i) $ec $ffea, $ffeb timer channel 2 i bit tmsk1 (c2i) $ea $ffe8, $ffe9 timer channel 3 i bit tmsk1 (c3i) $e8 $ffe6, $ffe7 timer channel 4 i bit tmsk1 (c4i) $e6 $ffe4, $ffe5 timer channel 5 i bit tmsk1 (c5i) $e4 $ffe2, $ffe3 timer channel 6 i bit tmsk1 (c6i) $e2 $ffe0, $ffe1 timer channel 7 i bit tmsk1 (c7i) $e0 $ffde, $ffdf timer overflow i bit tmsk2 (toi) $de $ffdc, $ffdd pulse accumulator overflow i bit pactl (paovi) $dc $ffda, $ffdb pulse accumulator input edge i bit pactl (pai) $da $ffd8, $ffd9 spi serial transfer complete i bit sp0cr1 (spie) $d8 $ffd6, $ffd7 sci 0 i bit sc0cr2 (tie, tcie, rie, ilie) $d6 $ffd4, $ffd5 sci 1 i bit sc1cr2 (tie, tcie, rie, ilie) $d4 $ffd2, $ffd3 atd0 or atd1 i bit atdxctl2 (ascie) $d2 $ffd0, $ffd1 mscan 0 wake-up i bit c0rier (wupie) $d0 $ffce, $ffcf key wake-up j or h i bit kwiej[7:0] and kwieh[7:0] $ce $ffcc, $ffcd modulus down counter underflow i bit mcctl (mczi) $cc $ffca, $ffcb pulse accumulator b overflow i bit pbctl (pbovi) $ca $ffc8, $ffc9 mscan 0 errors i bit c0rier (rwrnie, twrnie, rerrie, terrie, boffie, ovrie) $c8 $ffc6, $ffc7 mscan 0 receive i bit c0rier (rxfie) $c6 $ffc4, $ffc5 mscan 0 transmit i bit c0tcr (txeie[2:0]) $c4 $ffc2, $ffc3 cgm lock and limp home i bit pllcr (lockie, lhie) $c2 $ffc0, $ffc1 iic bus i bit ibcr (ibie) $c0 $ffbe, $ffbf mscan 1 wake-up i bit c1rier (wupie) $be
resets and interrupts interrupt control and priority registers mc68hc912dt128a ? rev 4.0 technical data motorola resets and interrupts 141 10.6 interrupt control and priority registers irqe ? irq select edge sensitive only 0 = irq configured for low-level recognition. 1 = irq configured to respond only to falling edges (on pin pe1/irq ). irqe can be read anyt ime and written once in normal modes. in special modes, irqe can be read anytime and written anytime, except the first write is ignored. irqen ? external irq enable the irq pin has an internal pull-up. 0 = external irq pin is disconnected from interrupt logic. 1 = external irq pin is connected to interrupt logic. $ffbc, $ffbd mscan 1 errors i bit c1rier (rwrnie, twrnie, rerrie, terrie, boffie, ovrie) $bc $ffba, $ffbb mscan 1 receive i bit c1rier (rxfie) $ba $ffb8, $ffb9 mscan 1 transmit i bit c1tcr (txeie[2:0]) $b8 $ffb6, $ffb7 (1) mscan 2 wake-up i bit c2rier (wupie) $b6 $ffb4, $ffb5 (1) mscan 2 errors i bit c2rier (rwrnie, twrnie, rerrie, terrie, boffie, ovrie) $b4 $ffb2, $ffb3 (1) mscan 2 receive i bit c2rier (rxfie) $b2 $ffb0, $ffb1 (1) mscan 2 transmit i bit c2tcr (txeie[2:0]) $b0 $ff80?$ffaf reserved i bit $80?$ae 1. mc68hc912dt128a only intcr ? interrupt control register $001e bit 7654321bit 0 irqeirqendly00000 reset: 01100000 table 10-1. interrupt vector map vector address interrupt source ccr mask local enable hprio value to elevate
resets and interrupts technical data mc68hc912dt128a ? rev 4.0 142 resets and interrupts motorola irqen can be read and written anytime in all modes. dly ? enable oscillator start- up delay on exit from stop the delay time of about 4096 cycles is bas ed on the xclk rate chosen. 0 = no stabilization delay impos ed on exit from stop mode. a stable external oscill ator must be supplied. 1 = stabilization delay is imposed before pr ocessing resumes after stop. dly can be read anytime and writte n once in normal modes. in special modes, dly can be r ead and written anytime. write only if i mask in ccr = 1 (int errupts inhibited) . read anytime. to give a maskable interrupt source highest priority, write the low byte of the vector address to the hprio regi ster. for example, writing $f0 to hprio would assign highest maskable interrupt prio rity to the real-time interrupt timer ($fff0). if an un-imple mented vector address or a non-i- masked vector address (value higher than $f2) is written, then irq will be the default highest priority interrupt. 10.7 interrupt test registers these registers are used in special modes for testing the interrupt logic and priority without needi ng to know which modu les and what functions are used to generate the interrupts.each bit is used to force a specific interrupt vector by writ ing it to 1.bits are named with b6 through f4 to indicate vectors $ffb6 through $fff4. these bits are also used in special modes to view that an inte rrupt caused by a module has reached the interrupt module. hprio ? highest priority i interrupt $001f bit 7654321bit 0 1 psel6 psel5 psel4 psel3 psel2 psel1 0 reset: 1 1 1 1 0 0 1 0
resets and interrupts resets mc68hc912dt128a ? rev 4.0 technical data motorola resets and interrupts 143 these registers can only be read in special modes (read in normal mode will return $00). reading t hese registers at the same time as the interrupt is changing will cause an indetermi nate value to be read. these registers can only be written in special mode. 10.8 resets there are four possible sources of reset. power-on reset (por), and external reset on the reset pin share the normal reset vector. the computer operating prop erly (cop) reset and the clock monitor reset each has a vector. entry into reset is asynchronous and does not require a clock but the mcu cannot sequenc e out of reset without a system clock. 10.8.1 power-on reset a positive transition on v dd causes a power-on reset (por). an external voltage level detector, or other external reset circuits, are the usual itst0 ? interrupt test register 0 $0018 bit 7654321bit 0 ite6 ite8 itea itec itee itf0 itf2 itf4 reset: 0 0000000 itst1 ? interrupt test register 1 $0019 bit 7654321bit 0 itd6 itd8 itda itdc itde ite0 ite2 ite4 reset: 0 0 0 0 0 0 0 0 itst2 ? interrupt test register 2 $001a bit 7654321bit 0 itc6 itc8 itca itcc itce itd0 itd2 itd4 reset: 0 0 0 0 0 0 0 0 itst3 ? interrupt test register 3 $001b bit 7654321bit 0 itb6 itb8 itba itbc itbe itc0 itc2 itc4 reset: 00000000
resets and interrupts technical data mc68hc912dt128a ? rev 4.0 144 resets and interrupts motorola source of reset in a system. the por circuit only initia lizes internal circuitry during cold starts and cannot be used to force a reset as system voltage drops. it is important to use an external low voltage rese t circuit (for example: mc34064 or mc33464) to pr event power transitions or corruption of ram or eeprom. 10.8.2 external reset the cpu distinguishes be tween internal and exter nal reset conditions by sensing whether the reset pin rises to a logic one in less than nine e- clock cycles after an internal dev ice releases reset. when a reset condition is sensed, an internal circuit drives the reset pin low and a clocked reset sequence controls when the mcu can begin normal processing. in the case of a clo ck monitor error, a 4096 cycle oscillator start-up delay is imposed before the reset recovery sequence starts (reset is driven low throughout this 4096 cycle delay). t he internal reset recovery sequence then driv es reset low for 16 to 17 cycles and releases the drive to allow reset to rise. nine e-clock cycles later the reset pin is sampled. if the pin is st ill held low, t he cpu assumes that an external reset has occurred. if the pin is high, it indica tes that the reset was initiated internally by either the cop system or the clock monitor. to prevent a cop reset from being de tected during an external reset, hold the reset pin low for at least 32 cycles. to prevent a clock monitor reset from being detected during an external reset, hold the reset pin low for at least 4096 + 32 cycles. an exte rnal rc power-up delay circuit on the reset pin is not recommended ? circui t charge time can cause the mcu to misinterpret the type of reset that has occurred. 10.8.3 cop reset the mcu includes a comput er operating properly (cop) system to help protect against software failures. w hen cop is enabled , software must write $55 and $aa (in this order) to t he coprst register in order to keep a watchdog timer from timing out. other instructions may be executed between these writes. a write of any value other than $55 or $aa or
resets and interrupts effects of reset mc68hc912dt128a ? rev 4.0 technical data motorola resets and interrupts 145 software failing to execute the sequenc e properly causes a cop reset to occur. in addition, wi ndowed cop operation can be selected. in this mode, a write to the copr st register must occur in the last 25% of the selected period. a premature wr ite will also reset the part. 10.8.4 clock monitor reset if clock frequency falls below a predetermined limit when the clock monitor is enabled, a reset occurs. 10.9 effects of reset when a reset occurs, mcu register s and control bits are changed to known start-up states, as follows. 10.9.1 operating mode and memory map operating mode and default memory mapping are determined by the states of the bkgd, moda, and modb pins during rese t. the smodn, moda, and modb bits in th e mode register reflec t the status of the mode-select inputs at the rising edge of reset. operating mode and default maps can subsequently be c hanged according to strictly defined rules. 10.9.2 clock and wat chdog control logic the cop watchdog system is enabled, with the cr[2:0 ] bits set for the longest duration time-out . the clock monitor is disabled. the rtif flag is cleared and automatic hardware interrupts are masked. the rate control bits are cleared, and must be initialized before the rti system is used. the dly control bit is set to specify an osci llator start-up delay upon recovery from stop mode.
resets and interrupts technical data mc68hc912dt128a ? rev 4.0 146 resets and interrupts motorola 10.9.3 interrupts psel is initialized in t he hprio register with t he value $f2, causing the external irq pin to have the highest i-bit interrupt priority. the irq pin is configured for level-sensitive operation (for wired-or systems). however, the interrupt mask bits in the cpu12 ccr are set to mask x- and i-related interrupt requests. 10.9.4 parallel i/o if the mcu comes out of reset in a single-chip mode, all ports are configured as general- purpose high-impedance inputs. if the mcu comes out of reset in an expanded mode, port a and port b are used for the address/data bus, and por t e pins are normally used to control the external bus (operation of port e pins can be affected by the pear register). out of reset, port j, port h, port k, por t ib, port p, port s, port t, port ad0 and port ad1 ar e all configured as general-purpose inputs. 10.9.5 central processing unit after reset, the cpu fetc hes a vector from the appropriate address, then begins executing instructions. the st ack pointer and other cpu registers are indeterminate immediately afte r reset. the ccr x and i interrupt mask bits are set to mask any interrup t requests. the s bit is also set to inhibit the stop instruction. 10.9.6 memory after reset, the internal register block is located from $0000 to $03ff, ram is at $2000 to $3fff, and eeprom is loca ted at $0800 to $0fff. in single chip mode one 32-kbyt e flash eeprom modul e is located from $4000 to $7fff and $c 000 to $ffff, and the other three 32-kbyte flash eeprom modules are accessi ble through t he program page window located from $8000 to $bfff. the first 32-kbyte flash eeprom is also accessible th rough the program page window.
resets and interrupts register stacking mc68hc912dt128a ? rev 4.0 technical data motorola resets and interrupts 147 10.9.7 other resources the enhanced capture timer (ect), pulse width modulation timer (pwm), serial communications inte rfaces (sci0 and sci1), serial peripheral interface (spi), inter-ic bus (iic), motorola scalable cans (mscan0 and mscan1) and analog-to-digital converters (atd0 and atd1) are off after reset. 10.10 register stacking once enabled, an interrupt request can be re cognized at any time after the i bit in the ccr is cleared. wh en an interrupt service request is recognized, the cpu respon ds at the completion of the instruction being executed. interrupt latency varies according to the number of cycles required to complete the in struction. some of the longer instructions can be interrupted and will resume normall y after servicing the interrupt. when the cpu begins to service an in terrupt, the instruction queue is cleared, the return address is calcul ated, and then it and the contents of the cpu register s are stacked as shown in table 10-2 . after the ccr is stacked, the i bit (and the x bit, if an xirq interrupt service request is pending) is set to prevent other interrupts from disrupting the interrupt service routine. the interrupt vector for the highest priority source that was pending at the begi nning of the interrupt sequence is fetched, and ex ecution continues at th e referenced location. at the end of the interrup t service routine, an rti instruction restores the content of all re gisters from information on the stack, and normal program execution resumes. table 10-2. stacking orde r on entry to interrupts memory location cpu registers sp ? 2 rtn h : rtn l sp ? 4 y h : y l sp ? 6 x h : x l sp ? 8 b : a sp ? 9 ccr
resets and interrupts technical data mc68hc912dt128a ? rev 4.0 148 resets and interrupts motorola if another interrupt is pendi ng at the end of an inte rrupt service routine, the register unstacking and restacking is bypassed an d the vector of the interrupt is fetched.
mc68hc912dt128a ? rev 4.0 technical data motorola i/o ports with key wake-up 149 technical data ? mc68hc912dt128a section 11. i/o ports with key wake-up 11.1 contents 11.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 11.3 key wake-up and port r egisters . . . . . . . . . . . . . . . . . . . . . . 150 11.4 key wake-up input filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 11.2 introduction the offers 16 additional i/o ports with key wake-up capability. the key wake-up feature of the mc 68hc912dt128a iss ues an interrupt that will wake up the cpu when it is in the stop or wait mode. two ports are associated with the key wa ke-up function: por t h and port j. port h and port j wake-ups are trigge red with either a rising or falling signal edge. for each pin which has an interrupt enabled, there is a path to the interrupt request signal which has no clocked devices when the part is in stop mode. this allows an active edge to bring the part out of stop. digital filtering is in cluded to prevent pulses shorter than a specified value from waking the part from stop. an interrupt is generated when a bit in the kwifh or kwifj register and its corresponding kwieh or kwiej bit ar e both set. all 16 bits/pins share the same interrupt vect or. key wake-ups can be used with the pins configured as inputs or outputs. default register addresses, as estab lished after reset, are indicated in the following descriptions. for inform ation on re-mapping the register block, refer to operating modes .
i/o ports with key wake-up technical data mc68hc912dt128a ? rev 4.0 150 i/o ports with key wake-up motorola 11.3 key wake-up and port registers read and write anytime. read and write anytime. data direction register j is associated with port j and designates each pin as an input or output. read and write anytime ddrj[7:0] ? data direction port j 0 = associated pin is an input 1 = associated pin is an output portj ? port j register $0028 bit 7654321bit 0 port pj7 pj6 pj5 pj4 pj3 pj2 pj1 pj0 kwu kwj7 kwj6 kwj5 kwj4 kwj3 kwj2 kwj1 kwj0 reset: -------- porth ? port h register $0029 bit 7654321bit 0 ph7 ph6 ph5 ph4 ph3 ph2 ph1 ph0 kwu kwh7 kwh6 kwh5 kwh4 kwh3 kwh2 kwh1 kwh0 reset: - - - - - - - - ddrj ? port j data direction register $002a bit 7654321bit 0 ddj7 ddj6 ddj5 ddj4 ddj3 ddj2 ddj1 ddj0 reset: 0 0 0 0 0 0 0 0
i/o ports with key wake-up key wake-up and port registers mc68hc912dt128a ? rev 4.0 technical data motorola i/o ports with key wake-up 151 data direction register h is associated with port h and designates each pin as an input or output . read and write anytime. ddrh[7:0] ? data direction port h 0 = associated pin is an input 1 = associated pin is an output read and write anytime. kwiej[7:0] ? key wake-up port j interrupt enables 0 = interrupt for the associated bit is disabled 1 = interrupt for the a ssociated bit is enabled read and write anytime. kwieh[7:0] ? key wake-up port h interrupt enables 0 = interrupt for the associated bit is disabled 1 = interrupt for the a ssociated bit is enabled ddrh ? port h data direction register $002b bit 7654321bit 0 ddh7 ddh6 ddh5 ddh4 ddh3 ddh2 ddh1 ddh0 reset: 0 0 0 0 0 0 0 0 kwiej ? key wake-up port j interrupt enable register $002c bit 7654321bit 0 kwiej7 kwiej6 kwiej5 kwiej4 kwiej3 kwiej2 kwiej1 kwiej0 reset: 0 0 0 0 0 0 0 0 kwieh ? key wake-up port h interrupt enable register $002d bit 7654321bit 0 kwieh7 kwieh6 kwieh5 kwieh4 kwieh3 kwieh2 kwieh1 kwieh0 reset:00000000
i/o ports with key wake-up technical data mc68hc912dt128a ? rev 4.0 152 i/o ports with key wake-up motorola read and write anytime. each flag is set by an ac tive edge on its associated input pin. this could be a rising or falling edge based on the st ate of the kwpj register. to clear the flag, write one to t he corresponding bit in kwifj. initialize this register after initializing kwpj so that illegal flags can be cleared. kwifj[7:0] ? key wake-up port j flags 0 = active edge on the associ ated bit has not occurred 1 = active edge on the associated bi t has occurred (an interrupt will occur if the associated enable bit is set). read and write anytime. each flag is set by an ac tive edge on its associated input pin. this could be a rising or falling edge based on the state of the kwph register. to clear the flag, write one to t he corresponding bit in kwifh. initialize this register after initializing kwph so that illegal flags can be cleared. kwifh[7:0] ? key wa ke-up port h flags 0 = active edge on the associ ated bit has not occurred 1 = active edge on the associated bi t has occurred (an interrupt will occur if the associat ed enable bit is set) kwifj ? key wake-up port j flag register $002e bit 7654321bit 0 kwifj7 kwifj6 kwifj5 kwifj4 kwifj3 kwifj2 kwifj1 kwifj0 reset: 00000000 kwifh ? key wake-up port h flag register $002f bit 7654321bit 0 kwifh7 kwifh6 kwifh5 kwifh4 kwifh3 kwifh2 kwifh1 kwifh0 reset: 00000000
i/o ports with key wake-up key wake-up and port registers mc68hc912dt128a ? rev 4.0 technical data motorola i/o ports with key wake-up 153 read and write anytime. it is best to clear the flags afte r initializing this register because changing the polarity of a bit c an cause the associated flag to become set. kwpj[7:0] ? key wake-up po rt j polarity selects 0 = falling edge on the associated port j pi n sets the associated flag bit in the kwifj register and a resistive pull-up device is connected to associat ed port j input pin. 1 = rising edge on the associated po rt j pin sets the associated flag bit in the kwifj register and a resistive pull-down device is connected to associ ated port j input pin. read and write anytime. it is best to clear the flags afte r initializing this register because changing the polarity of a bit c an cause the associated flag to become set. kwph[7:0] ? key wake-up port h polarity selects 0 = falling edge on the associated port h pi n sets the associated flag bit in the kwifh register and a resistive pull-up device is connected to associat ed port h input pin. 1 = rising edge on the associated po rt h pin sets the associated flag bit in the kwifh register and a resistive pull-down device is connected to associated port h input pin. kwpj ? key wake-up port j polarity register $0030 bit 7654321bit 0 kwpj7 kwpj6 kwpj5 kwpj4 kwpj3 kwpj2 kwpj1 kwpj0 reset:00000000 kwph ? key wake-up port h polarity register $0031 bit 7654321bit 0 kwph7 kwph6 kwph5 kwph4 kwph3 kwph2 kwph1 kwph0 reset: 00000000
i/o ports with key wake-up technical data mc68hc912dt128a ? rev 4.0 154 i/o ports with key wake-up motorola 11.4 key wake-up input filter the kwu input signals are fi ltered by a digital filt er which is active only during stop mode. the purpose of the filter is to prev ent single pulses shorter than a specified value from wa king the part from stop. the filter is composed of an internal o scillator and a majority voting logic. the filter oscillator starts the oscillat ion by detecting a triggering edge on an input if the co rresponding interrupt enable bit is set. the majority voting logic takes three samples of an asserted input pin at each filter oscillator perio d and if two samples are taken at the triggering level, the filter recognizes a va lid triggering level and sets the corresponding interrupt flag. in this way the majori ty voting logic rejects the short non-triggering state between two incomi ng triggering pulses. as the filter is shared wi th all kwu inputs, the fi lter considers any pulse coming from any input pin for whic h the corresponding interrupt enable bit is set. the timing specification is given for a single pulse. the time interval between the triggering edges of two following pu lses should be greater than the t kwsp in order to be consi dered as a single pulse by the filter. if this time interval is shorter than t kwsp , the majority voting logic may treat the two consecutive pulses as a single valid pulse. the filter is shared by al l the kwu pins. hence any valid triggering level on any kwu pin is seen by the filter . the timing specif ication applies to the input of the filter.
i/o ports with key wake-up key wake-up input filter mc68hc912dt128a ? rev 4.0 technical data motorola i/o ports with key wake-up 155 figure 11-1. stop key wake-up filter glitch, filtered out, no stop wake-up valid stop wake-up pulse t kwstp min. t kwsp minimum time interval between pulses to be recognized as single pulses t kwstp max.
i/o ports with key wake-up technical data mc68hc912dt128a ? rev 4.0 156 i/o ports with key wake-up motorola
mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 157 technical data ? mc68hc912dt128a section 12. clock functions 12.1 contents 12.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 12.3 clock sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158 12.4 phase-locked loop (p ll) . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 12.5 acquisition and tracking modes. . . . . . . . . . . . . . . . . . . . . . .161 12.6 limp-home and fast stop recove ry modes . . . . . . . . . . . . 163 12.7 system clock frequency fo rmulae . . . . . . . . . . . . . . . . . . . . 181 12.8 clock divider chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182 12.9 computer operating prop erly (cop) . . . . . . . . . . . . . . . . . . .185 12.10 real-time interrupt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 12.11 clock monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186 12.12 clock function registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 12.2 introduction clock generation ci rcuitry generates the inter nal and external e-clock signals as well as internal clock signals used by th e cpu and on-chip peripherals. a clock monitor circui t, a computer ope rating properly (cop) watchdog circuit, and a periodi c interrupt circuit are also incorporated into the mc68hc912dt128a.
clock functions technical data mc68hc912dt128a ? rev 4.0 158 clock functions motorola 12.3 clock sources a compatible external clock signal can be applied to the extal pin or the mcu can generate a clo ck signal using an on-chip oscillator circuit and an external crystal or ceramic resonator. the mcu uses several types of internal clock signals deriv ed from the primary clock signal: txclk clocks are used by the cpu. eclk and pclk are used by the bus interfaces, spi, pwm, atd0 and atd1. mclk is either pclk or xclk, a nd drives on-chip modules such as sci0, sci1 and ect. xclk drives on-chip m odules such as rti, co p and restart-from-stop delay time. slwclk is used as a calibration output signal. the mscan module is clocked by ext ali or sysclk, u nder control of an mscan bit. the clock monitor is clocked by extali. the bdm system is clocked by bclk or eclk, under control of a bdm bit. a slow mode clock divider is inclu ded to deliver a lower clock frequency for the sci baud rate gener ators, the ect timer module, and the rti and cop clocks. the slow clock bus frequ encies divide the crystal frequency in a programmable range of 4 to 252, wi th steps of 4. thi s is very useful for low power operation. see the clock divider chains section for further details. figure 12-1 shows some of the timing relationships.
clock functions phase-locked loop (pll) mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 159 figure 12-1. internal clock relationships 12.4 phase-locked loop (pll) the phase-locked loop (pll) of th e mc68hc912dt128a is designed for robust operation in an au tomotive environment. the allowed pll crystal or ceramic resonator reference of 0. 5 to 8mhz is selected for the wide availability of compo nents with good stability over the automotive temperature range. please refer to figure 12-6 in section clock divider chains for an overview of system clocks. note: when selecting a crystal, it is re commended to use one wi th the lowest possible frequency in order to minimise emc emissions. an oscillator design wit h reduced power consumpt ion allows for slow wait operation with a typical power supply current less than a milli- ampere. the pll circuitry can be by passed when the vddpll supply is at vss level. in this case, the pll module is powered down and the oscillator output transistor has a st ronger transconduct ance for improved drive of higher frequency resonators (as the cr ystal frequency needs to be twice the maximum bus frequency). refer to figure 3-4 in pinout and signal descriptions . t1clk t2clk t3clk t4clk int eclk pclk xclk canclk
clock functions technical data mc68hc912dt128a ? rev 4.0 160 clock functions motorola figure 12-2. pll functional diagram the pll may be used to run the mcu fr om a different time base than the incoming crystal value. it creates an integer multiple of a reference frequency. for increased flexibility, the crystal clock can be divided by values in a range of 1 ? 8 (in uni t steps) to generate the reference frequency. the pll can multiply this reference clock in a range of 1 to 64. although it is possible to set the divider to command a very high clock frequency, do not exceed the specified bus freque ncy limit for the mcu. if the pll is selected, it will cont inue to run when in wait mode resulting in more power consumpt ion than normal. to take full advantage of the reduced power consumption of wait mode, turn off the pll before going into wait. pleas e note that in this case the pll stabilization time applies. the pll operation is suspended in stop mode. after stop exit followed by the st abilization time, it resumes operati on at the same frequency, provided t he auto bit is set. a passive external loop filter must be placed on the control line (xfc pad). the filter is a sec ond-order, low-pass filter to eliminat e the vco input ripple. values of compo nents in the diagr am are dependent upon the desired vco operation. see xfc description. reduced consumption oscillator extal xtal extali pllclk reference programmable divider pdet phase detector refdv <2:0> loop programmable divider syn <5:0> cpump vco lock loop filter xfc pad up down lock detector refclk divclk slow mode programmable clock divider sldv <5:0> xclk extali 2 slwclk vddpll 2
clock functions acquisition and tracking modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 161 12.5 acquisition and tracking modes the lock detector compares the freque ncies of the vco feedback clock, divclk, and the final reference clo ck, refclk. theref ore, the speed of the lock detector is directly proportional to the final reference frequency. the circuit determines the mode of the pll and the lock condition based on this comparison. the pll filter is manually or automatically conf igurable into one of two operating modes: acquisition mode ? in acquisition m ode, the filter can make large frequency corrections to the vco. th is mode is used at pll start- up or when the pll has suffered a severe noise hit and the vco frequency is far off the desired frequency. this mode can also be desired in harsh environments when the leakage levels on the filter pin (xfc) can overcome the tracking currents of the pll charge pump. when in ac quisition mode, the acq bit in the pll control register is clear. tracking mode ? in tracking mode , the filter makes only small corrections to the frequency of the vco. the pll enters tracking mode when the vco frequency is nearly correct. the pll is automatically in tracking mode wh en not in acqui sition mode or when the acq bit is set. the pll can change the bandwidth or oper ational mode of the loop filter manually or automatically. with an i dentical filtering ti me constant, the pll bandwidth is larger in acquisition mode than in tracking by a ratio of about 3. in automatic bandwidth control mode (auto = 1), the lock detector automatically switches between acquisition and tracking modes. automatic bandwidth c ontrol mode also is us ed to determi ne when the vco clock, pllclk, is sa fe to use as the source for the base clock, sysclk. if pll lock interrupt r equests are enabled, the software can wait for an interrupt request and then check the lock bit. if cpu interrupts are disabled, software can poll the lock bit continuously (during pll start-up, usually) or at periodic intervals. in either case, when the lock bit is set, the pllclk clock is safe to use as the source
clock functions technical data mc68hc912dt128a ? rev 4.0 162 clock functions motorola for the base clock. see clock divider chains . if the vco is selected as the source for the base clock and t he lock bit is clear, the pll has suffered a severe noise hit and the software mu st take appropriate action, depending on the application. the following conditions apply when t he pll is in automatic bandwidth control mode: the acq bit is a read-only indicato r of the mode of the filter. the acq bit is set when the vco fr equency is within a certain tolerance, ? trk , and is cleared when the vco frequency is out of a certain tolerance, ? unt . see 19 electrical characteristics. the lock bit is a read-only indicator of the locked state of the pll. the lock bit is set when the vco frequency is within a certain tolerance, ? lock , and is cleared when the vco frequency is out of a certain tolerance, ? unl . see 19 electrical characteristics. cpu interrupts can occur if enabled (lockie = 1) when the lock condition changes, toggl ing the lock bit. the pll also can operate in manual mode (auto = 0). all lock features described above are active in this mode, onl y the bandwidth control is disabled. manual mode is used mainly for systems operating under harsh conditions (e.g. uncoated pcbs in automotive environments). when this is the case, the pll is likely to remain in acquisition mode. the fo llowing conditions appl y when in manual mode: acq is a writable control bit that controls t he mode of the filter. before turning on the pll in manual mode, the acq bit must be clear. in case tracking is desired (acq = 1), the software must wait a given time, tacq, after turning on the pll by setting pllon in the pll control register. this is to avoid switching to tracking mode too early while t he xfc voltage level is stil l too far away from its quiescent value corresponding to the target frequency. this operation would be very detriment al to the stabi lization time.
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 163 12.6 limp-home and fast stop recovery modes if the crystal frequency is not available due to a crystal failure or a long crystal start-up time, the mcu system clock can be supplied by the vco at its minimum oper ating frequency, f vcomin . this mode of operation is called limp-home mode and is only available when the vddpll supply voltage is at vdd level (i.e. power su pply for the pll module is present). upon power-up, the abilit y of the system to star t in limp-home mode is restricted to norma l mcu modes only. the clock monitor circuit (see section clock monitor) can detect the loss of extali, the external clock input signal, regardless of whether this signal is used as the so urce for mcu clocks or as the pll reference clock. the clock monitor contro l bits, cme and fcme, are used to enable or disable exter nal clock detection. a missing external clock may occur in the three following instances: during normal clock operation. at power-on reset. in the stop exit sequence 12.6.1 clock loss during normal operation the ?no limp-home mode ? bit, nolhm, deter mines how the mcu responds to an external cl ock loss in this case. with limp home mode disabled (n olhm bit set) and the clock monitor enabled (cme or fcme bits set), on a loss of clo ck the mcu is reset via the clock monitor reset vector. a latc h in the pll contro l section prevents the chip exiting reset in limp home mode (this is required as the nolhm bit gets cleared bu reset). only external clock activity can bring the mcu out from this reset state. once rese t has been exited, th e latch is cleared and another session, with or without limp home mode enabled, can take place. this is t he same behavior as stan dard m68hc12 circuits without pll or ope ration with vddpll at vss level. with limp home mode enabled (n olhm bit cleared) and the clock monitor enabled (cme or fc me bits set), on a lo ss of clock, the pll
clock functions technical data mc68hc912dt128a ? rev 4.0 164 clock functions motorola vco clock at its mi nimum frequency, f vcomin , is provided as the system clock, allowing the mc u to continue operating. the mcu is said to be operating in ?limp-home? mode with the forced vco clock as the system clock. pllon and bcsp (?bus clock select pll?) signals are forced high and the mcs (?module clock select?) signal is forced low. the lhome flag in the pllflg register is set to indicate that the mcu is running in limp-home mode. a change of this flag sets the limp-home interrupt flag, lhif, and if enabled by t he lhie bit, the limp-home mode interrupt is requ ested. the clock monitor is enabled irrespective of cme and fcme bit se ttings. module clocks to the rti & cop (xclk), bdm (bclk) and ect & sci (mclk) are forced to be pclk (at f vcomin ) and eclk is also equal to f vcomin . mscan clock select is unaffected. figure 12-3. clock loss durin g normal operation the clock monitor is polled each ti me the 13-stage free running counter reaches a count of 4096 xclk cycles i.e. mi d-count, hence the clock status gets checked once every 8192 xclk cycles. when the presence of an external clock is detected, the mcu exits limp-home mode, clearing the lhome flag and setting t he limp-home interr upt flag. upon leaving limp-home mode, bcsp and mcs si gnals are restored to their 0 --> 4096 limp-home (clocked by xclk) bcsp restore bcsp sysclk pllclk (limp-home) restore pllclk or extali extali 13-stage counter clock monitor fail 0 --> 4096 ab
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 165 values before the clock loss. all clocks return to their normal settings and clock monitor control is returned to the cme & fcme bits. if auto and bcsp bits were set before the clock loss (selecting the pll to provide a system clock) the sysclk ramps-up and the pll locks at the previously selected frequency. to prevent pll oper ation when the external clock frequency comes back, soft ware should clear the bcsp bit while running in limp-home mode. the two shaded regions a and b in figure 12-3 present a of code run away due to incorrect clocks on sy sclk if the mcu is clocked by extali and the p ll is not used. in region a , there is a delay between the loss of clock and its detection by the clock monitor. when the ext ali clock signal is disturbed, the clock generation circuitry may receive an out of spec signal and drive the cpu with irregular clocks. th is may lead to code runaway. in region b , as the 13-stage coun ter is free running, the count of 4096 may be reached when the amplitude of the exta li clock has not stabilized. in this case, an impr oper extali is sent to the clock generation circuitry when limp-home mode is exited . this may also cause code runaway. if the mcu is clocked by the pll, the risk of code runaway is very low, but it c an still occur under certain conditions due to irregular clocks from the clock sour ce appearing on the sysclk. caution: the cop watch dog should always be enabled in orde r to reset the mcu in case of a code runaway situation. note: it is always advisable to take additional precautions within the application software to trap such situations.
clock functions technical data mc68hc912dt128a ? rev 4.0 166 clock functions motorola 12.6.2 no clock at power-on reset the voltage level on v ddpll determines how t he mcu responds to an external clock loss in this case. with the vddpll supply vo ltage at vdd level, any reset sets the clock monitor enable bit (cme ) and the pllon bit and clears the nolhm bit. therefore, if the mcu is powered up without an external clock, limp- home mode is entered pr ovided the mcu is in a normal mode of operation. figure 12-4. no clock at power-on reset vdd power-on detector clock monitor fail extali 13-stage counter internal reset 0 --> 4096 limp-home (clocked by xclk) bcsp reset: bcsp = 0 sysclk pllclk (l.h.) extali sysclk pllclk (software check of limp-home flag) extali (slow extali) 0 --> 4096 (slow extali)
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 167 during this power up sequence, afte r the por pulse fa lling edge, the vco supplies the limp-hom e clock frequency to t he 13-stage counter, as the bcsp output is forced high and mcs is forced low. xclk, bclk and mclk are forced to be pclk, which is supplied by the vco at f vcomin . the initial period taken for the 13-st age counter to reach 4096 defines the internal reset period. if the clock monitor indi cates the presence of an external clock during the internal reset period, limp-home mode is de-asserted and the 13-stage counter is then driven by extali clock. afte r the 13-stage counter reaches a count of 4096 xclk cycles, t he internal reset is released, the 13-stage counter is reset and t he mcu exits reset normally using extali clock. however, if the crystal start-up time is longer than the initial count of 4096 xclk cycles, or in the absence of an exter nal clock, the mcu will leave the reset state in limp-hom e mode. the lhom e flag is set and lhif limp-home interrupt r equest is set, to indicate it is not operating at the desired frequency. then after yet ano ther 4096 xclk cycles followed regularly by 8192 xclk cycles (corre sponding to the 13-stage counter timing out), a che ck of the clock monitor status is performed. when the presence of an external cl ock is detected limp-home mode is exited generating a limp-home interrupt if enabled. caution: the clock monitor circuit can be misl ed by the extali clock into reporting a good signal before it has fully stabilised. under these conditions improper extali clock cycles can occur on sysclk. this may lead to a co de runaway. to ensur e that this situation does not occur, the external reset period s hould be longer than the oscillator stabilisation time - this is an application d ependent parameter. with the vddpll supply voltage at vss level, t he pll module and hence limp-home mode are di sabled, the device wil l remain effectively in a static state whilst there is no activity on ex tali. the internal reset period and mcu operation will execut e only on extali clock. note: the external clock signal must stabili se within the initial 4096 reset counter cycles.
clock functions technical data mc68hc912dt128a ? rev 4.0 168 clock functions motorola 12.6.3 stop exit and fast stop recovery stop mode is entered when a stop instruction is executed. recovery from stop depends prim arily on the state of the three status bits nolhm, cme & dly. the dly bit controls t he duration of the wait ing period between the actual exit for some key blocks (e.g . clock monitor, clock generators) and the effective exit from stop for all the rest of the mc u. dly=1 enables the 13-stage counter to generate a 4096 count dela y. dly=0 selects no delay. as the xclk is derived from t he slow mode divide r, the value in the slow register modifies the actual delay time. note: dly=0 is only recommended when t here is a good si gnal available at the extal pin (e.g. an external squar e wave source). stop mode is exited with an external reset, an external interrupt from irq or xirq, a key wake -up interrupt from port j or port h, or an mscan wake-up interrupt. figure 12-5. stop exit and fast stop recovery clock monitor fail extali 13-stage counter 0 --> 4096 limp-home (clocked by xclk) bcsp restore bcsp sysclk pllclk (l.h.) restore pllclk or extali stop (dly = 1) stop (dly = 0)
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 169 12.6.4 stop exit without limp home mode, clock monitor disabled (nolhm=1, cme=0, dly=x) if limp home mode is disabled (v ddpll =v ss or nolhm bit set) and the cme (or fcme) bit is cleared, the mcu goes into stop mode when a stop instruction is executed. if extali clock is pres ent then exit from stop will occur normally using this clock. under this condition, dly should a lways be set to allow the crystal to stabilise and minimise th e risk of code runaway. with dly=1 execution resumes after a delay of 4096 xclk cycles. note: the external clock signal should stabilise within the 4096 reset counter cycles. use of dly=0 is not recommen ded due to this requirement. 12.6.5 executing the stop in struction without limp home mode, clock monitor enabled (nolhm=1, cme=1, dly=x) if the nolhm bit and t he cme (or fcme) bits ar e set, a clock monitor failure is detected when a stop instruction is executed and the mcu resets via the clock monitor reset vector. 12.6.6 stop exit in limp home mode with delay (nolhm=0, cme=x, dly=1) if the nolhm bit is cleared, then t he cme (or fcme) bit is masked when a stop instruction is executed to pr event a clock monitor failure. when coming out of stop mode, the mcu goes into limp-home mode where cme and fcme signals are asserted. when using a crystal oscillator, a normal stop exit sequence requires the dly bit to be set to allow for the crystal stabilization period. with the 13-stage counter clocked by the vco (at f vcomin ), following a delay of 4096 xclk cycles at the limp-home fr equency, if the clock monitor indicates the pres ence of an exte rnal clock, the limp-home mode is de-asserted and the mcu exits stop normally using extali clock.
clock functions technical data mc68hc912dt128a ? rev 4.0 170 clock functions motorola where the crystal start-up time is longer than the initial count of 4096 xclk cycles, or in the absence of an external clock, the mcu recovers from stop following the 4096 count in limp-ho me mode with both the lhome flag set and the lh if limp-home interrupt request set to indicate it is not operating at the desired frequency. ea ch time the 13-stage counter reaches a count of 4096 xclk cycles, a check of the clock monitor status is performed. when the presence of an external clo ck is detected, limp-home mode is exited and the lhome flag is cleared. this sets the limp-home interrupt flag and if enabled by th e lhie bit, the limp- home mode interrupt is requested. caution: the clock monitor circuit can be misled by extali clock into reporting a good signal before it has fully st abilised. under these conditions, improper extali clock cycles can occur on sysclk. this may lead to a code runaway. 12.6.7 stop exit in limp home mode without delay ( fast stop recovery) (nolhm=0, cme=x, dly=0) fast stop recovery refers to any exit from stop using dly=0. if the nolhm bit is cleared, then t he cme (or fcme) bit is masked when a stop instruction is executed to pr event a clock monitor failure. when coming out of stop mode, the mcu goes into limp-home mode where cme and fcme signals are asserted. when using a crystal oscillator, it is possible to exit stop with the dly bit cleared. in this case, stop is de-asserted without delay and the mcu will execute software in limp-home mode, giving th e crystal oscillator time to stablise. caution: this mode is not recomm ended since the risk of the clock monitor detecting incorrect clocks is high.
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 171 each time the 13-stage counter reaches a count of 4096 xclk cycles (every 8192 cycles), a che ck of the clock monitor st atus is performed. if the clock monitor indicates the pres ence of an external clock limp-home mode is de-asserted, the lhome fl ag is cleared and the limp-home interrupt flag is set. upon leav ing limp-home mode, bcsp and mcs are restored to their values before the loss of clock, and all clocks return to their previous frequencies. if auto and bcsp were set before the clock loss, the sysclk ramps-up and the pll locks at t he previously selected frequency. to prevent pll operation when t he external clock frequency comes back, the software should clear t he bcsp bit while r unning in limp-home mode. when using an external clo ck, i.e. a square wave source, it is possible to exit stop with the dly bit cleare d. in this case the lhome flag is never set and stop is de -asserted without delay. 12.6.8 pseudo-stop pseudo-stop is a low pow er mode similar to stop where the external oscillator is allowed to run (at redu ced amplitude) whilst the rest of the part is in stop. this increases t he current consumption over stop mode by the amount of cu rrent in the oscillator, but reduces wear and mechanical stress on the crystal. if the pstp bit in the pllcr register is set, the mc u goes into pseudo- stop mode when a stop in struction is executed. pseudo-stop mode is exited the same as stop with an external reset, an external interrupt fr om irq or xirq, a key wake-up interrupt from port j or port h, or an mscan wake-up interrupt. the effect of the dly bit is the same as noted above in stop exit and fast stop recovery .
clock functions technical data mc68hc912dt128a ? rev 4.0 172 clock functions motorola 12.6.9 pseudo-stop exit in li mp home mode with delay (nolhm=0, cme=x, dly=1) when coming out of pseudo-stop mode with the no lhm bit cleared and the dly bit set, the mcu goes in to limp-home mode (regardless of the state of the cm e or fcme bits). the vco supplies the li mp-home clock frequen cy to the 13-stage counter (xclk). the bcsp output is forced high and mcs is forced low. after the 13-stage count er reaches a count of 4096 xclk cycles, a check of the clock monitor is perfor med and as the crystal oscillator was kept running due to the pseudo- stop mode, the mcu exits stop normally, using the extali clock. in the case where a crystal failure occurred during pseudo-st op, then the mcu exits stop using the limp home clock (f vcomin ) with both the lhome fl ag set and the lhif limp- home interrupt request set to indicate it is not operating at the desired frequency. each time the 13-stage counter reac hes a count of 4096 xclk cycles, a check of the clock monitor is perform ed. if the clock monitor indicates the presence of an ex ternal clock, limp-home mode is de-asserted, the lhome flag is cleared and the lhif limp-home interrupt request is set to indicate a return to normal operation using extali clock. 12.6.10 pseudo-stop exit in limp home mode without delay ( fast stop recovery) (nolhm=0, cme=x, dly=0) if pseudo-stop is exited with the nolh m bit set to 0 an d the dly bit is cleared then the exit fr om pseudo-stop is acco mplished without delay as in fast stop recovery. caution: where pseudo-stop recovers usi ng the limp home clock the vco - which has been held in stop - must be restarted in order to supply the limp home frequency. this restart, which occurs at a high frequency and ramps toward the limp home frequency, is almost immediately supplied to the cpu before it ma y have reached the steady state frequency. it is possible that the initial clock fr equency may be high enough to cause the cpu to function incorrectly with a resultant risk of code runaway.
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 173 12.6.11 pseudo-stop exit without limp home m ode, clock monitor enabled (nolhm=1, cme=1, dly=x) if the nolhm bit is set and the cm e (or fcme) bits are set, a clock monitor failure is detected when a st op instruction is executed and the mcu resets via the clock monitor reset vector. 12.6.12 pseudo-stop exit without limp home m ode, clock monitor disabled (nolhm=1, cme=0, dly=1) if nolhm is set to 1 and the cme a nd fcme bits are cleared, the limp home clock is not used. in this mode, crystal activity is the only method by which the device may recover from pseudo-stop. the device will start execution with the extali clock following 4096 xclk cycles. (nolhm=1, cme=0, dly=0) if nolhm is set to 1 and the cme a nd fcme bits are cleared, the limp home clock is not used. in this mode, crystal activity is the only method by which the device may recover from pseudo-stop. the device will start execution with the extal i clock following 16 xclk cycles. caution: due to switching of the clock this configuration is not recommended. 12.6.13 summary of stop and pseudo-stop mode ex it conditions table 12-1 and table 12-2 summarise the exit conditions from stop and pseudo-stop modes using interr upt, key-interrupt and xirq. a short reset pulse shoul d not be used to exit stop or pseudo-stop mode because limp home mode is aut omatically entered after reset (when v ddpll =v dd ). the reset wakeup pulse mu st be longer than the oscillator startup time (as in power on reset) in order to remove the risk of code runaway.
clock functions technical data mc68hc912dt128a ? rev 4.0 174 clock functions motorola .. table 12-1. summary of stop mode exit conditions mode conditions summary stop exit without limp home mode, clock monitor disabled nolhm=1 cme=0 dly=x oscillator must be stable wit hin 4096 xclk cycles. xclk can be modified by slow divider register. use of dly=0 only recommended with external clock. executing the stop instruction without limp home mode, clock monitor enabled nolhm=1 cme=1 dly=x when a stop instruction is executed the mcu resets via the clock monitor reset vector. stop exit in limp home mode with delay nolhm=0 cme=x dly=1 oscillator must be stable within 4096 f vcomin cycles or there is a possibility of code runaway as the clock monitor circuit can be misled by extali clock into reporting a good signal before it has fully stabilised stop exit in limp home mode without delay (fast stop recovery) nolhm=0 cme=x dly=0 this mode is only recommended for use with an external clock source. table 12-2. summary of p seudo stop mode exit conditions mode conditions summary pseudo-stop exit in limp home mode with delay nolhm=0 cme=x dly=1 cpu exits stop in limp home mo de and oscillator running. if the oscillator fails during pseudo-stop and then recovers there is a possibility of code runaway as the clock monitor circuit can be misled by extali clock into reporting a good signal before it has fully stabilised pseudo-stop exit in limp home mode without delay (fast stop recovery) nolhm=0 cme=x dly=0 this mode is not recommended as it is possible that the initial vco clock frequency may be high enough to cause code runaway. pseudo-stop exit without limp home mode, clock monitor enabled nolhm=1 cme=1 dly=x when a stop instruction is executed the mcu resets via the clock monitor reset vector. pseudo-stop exit without limp home mode, clock monitor disabled, with delay nolhm=1 cme=0 dly=1 oscillator starts operation following 4096 xclk cycles (actual controlled by slow mode divider). pseudo-stop exit without limp home mode, clock monitor disabled, without delay nolhm=1 cme=0 dly=0 this mode is only recommended for use with an external clock source.
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 175 12.6.14 pll regi ster descriptions read anytime, write anytime, except when bcsp = 1 (pll selected as bus clock). if the pll is on, the count in the loop di vider (synr) register effectively multiplies up the bus frequency fr om the pll refe rence frequency by synr + 1. internally, sysclk runs at twice the bus frequency. caution should be used not to exceed the maximum ra ted operating frequency for the cpu. read anytime, write anyti me, except when bcsp = 1. the reference divider bits provides a finer granularity for the pll multiplier steps. the reference fr equency is divided by refdv + 1. always reads zero, exc ept in test modes. bit 7654321bit 0 0 0 syn5 syn4 syn3 syn2 syn1 syn0 reset: 00000000 synr ? synthesizer register $0038 bit 7654321bit 0 00000refdv2refdv1refdv0 reset: 0 0 0 0 0 0 0 0 refdv ? reference divider register $0039 bit 7654321bit 0 tstout7 tstout6 tstout5 tstout4 tstout3 tstout2 tstout1 tstout0 reset: 0 0 0 0 0 0 0 0 cgtflg ? clock generator test register $003a
clock functions technical data mc68hc912dt128a ? rev 4.0 176 clock functions motorola read anytime, refer to eac h bit for write conditions. lockif ? pll lock interrupt flag 0 = no change in lock bit. 1 = lock condition has changed, either from a locked state to an unlocked state or vice versa. to clear the flag, write one to this bit in pllflg. cl eared in limp-home mode. lock ? locked phas e lock loop circuit regardless of the bandwidth contro l mode (automatic or manual): 0 = pll vco is not within the des ired tolerance of the target frequency. 1 = after the phase lock l oop circuit is turned on, indi cates the pll vco is within the desired tole rance of the target frequency. write has no effect on lock bit. this bit is cleare d in limp-home mode as the lock detector c annot operate without t he reference frequency. lhif ? limp-home interrupt flag 0 = no change in lhome bit. 1 = lhome condition has changed, either entered or exited limp- home mode. to clear the flag, write one to this bit in pllflg. lhome ? limp-home mode status 0 = mcu is operating normally, wi th extali clock available for generating clocks or as pll reference. 1 = loss of reference clock. cgm delivers pll vco limp-home frequency to the mcu. for limp-home mode, see limp-home and fast stop recovery modes . bit 7654321bit 0 lockiflock0000lhiflhome reset: 00000000 pllflg ? pll flags $003b
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 177 read and write anytime . exceptions are list ed below for each bit. lockie ? pll lock interrupt enable 0 = pll lock interrupt is disabled 1 = pll lock interrupt is enabled forced to 0 when vddpll=0. pllon ? phase lock loop on 0 = turns the pll off. 1 = turns on the phase lock loop circui t. if auto is se t, the pll will lock automatically. cannot be cleared when bcsp = 1 (pll selected as bus clock). forced to 0 when vddpll is at vss level. in limp-home mode, the output of pllon is forced to 1, but the pllon bit reads the latched value. auto ? automatic bandwidth control 0 = automatic mode control is disabled and the pll is under software control, using acq bit. 1 = automatic mode con trol is enabled. acq bit is read only. automatic bandwidth control sele cts either the high bandwidth (acquisition) mode or the low bandwidth (tracking) mode depending on how close to the desired freque ncy the vco is running. see electrical specifications . bit 7654321bit 0 lockie pllon auto acq 0 pstp lhie nolhm reset: 0 ? (1) 10000 ? (2) pllcr ? pll control register $003c 1. set when vddpll power supply is high. forced to 0 when vddpll is low. 2. cleared when vddpll power supply is high. forced to 1 when vddpll is low.
clock functions technical data mc68hc912dt128a ? rev 4.0 178 clock functions motorola acq ? not in acquisition if auto = 1 (acq is read only) 0 = pll vco is not within the des ired tolerance of the target frequency. the loop filter is in high bandwidth, acquisition mode. 1 = after the phase lock l oop circuit is turned on, indi cates the pll vco is within the desired tole rance of the target frequency. the loop filter is in lo w bandwidth, tracking mode. if auto = 0 0 = high bandwidth pll loop selected 1 = low bandwidth pll loop selected pstp ? pseudo- stop enable 0 = pseudo-stop oscilla tor mode is disabled 1 = pseudo-stop osci llator mode is enabled in pseudo-stop mode, the oscillator is still r unning while the mcu is maintained in stop m ode. this allows for a faster stop recovery and reduces the mechanical stress and aging of the resonator in case frequent stop conditions at the expense of a sl ightly increased power consumption. lhie ? limp-home interrupt enable 0 = limp-home inte rrupt is disabled 1 = limp-home inte rrupt is enabled forced to 0 when vddpll is at vss level. nolhm ?no limp-home mode 0 = loss of reference clock forc es the mcu in limp-home mode. 1 = loss of reference clock caus es standard clock monitor reset. read anytime; normal modes: wr ite once; special modes: write anytime. forced to 1 when vddpll is at vss level.
clock functions limp-home and fast stop recovery modes mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 179 read and write anytime . exceptions are list ed below for each bit. bcsp and bcss bits dete rmine the clock used by the main system including the cpu and buses. bcsp ? bus clock select pll 0 = sysclk is derived from the crystal clock or from slwclk. 1 = sysclk source is the pll. cannot be set when pllon = 0. in limp-home mode, the output of bcsp is forced to 1, but the b csp bit reads the latched value. bcss ? bus clock select slow 0 = sysclk is derived from the crystal clock extali. 1 = sysclk source is the slow clock slwclk. this bit has no effect when bcsp is set. mcs ? module clock select 0 = m clock is the same as pclk. 1 = m clock is derived from slow clock slwclk. this bit determines t he clock used by the ect module and the baud rate generators of the scis. in limp-home mode , the output of mcs is forced to 0, but the mcs bit reads the latched value. bit 7654321bit 0 0 bcsp bcss 0 0 mcs 0 0 reset: 00000000 clksel ? clock generator clock select register $003d
clock functions technical data mc68hc912dt128a ? rev 4.0 180 clock functions motorola read and write anytime. a write to this register changes the slwclk frequency with minimum delay (less than one slwclk cycl e), thus allowi ng immediate tune- up of the performance versus po wer consumption for the modules using this clock. the frequency divide ratio is 2 times (slow), hence the divide range is 2 to 126 ( not on first pass products). when slow = 0, the divider is bypass ed. the generation of e, p and m clocks further divides sl wclk by 2. hence, t he final ratio of bus to extali frequency is prog rammable to 2, 4, 8, 12, 16, 20, ..., 252, by steps of 4. slwclk is a 50% duty cycle signal. bit 7654321bit 0 0 0 sldv5 sldv4 sldv3 sldv2 sldv1 sldv0 reset: 00000000 slow ? slow mode divider register $003e
clock functions system clock frequency formulae mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 181 12.7 system clock frequency formulae see figure 12-6 : slwclk = extali / ( 2 x slow ) slow = 1,2,..63 slwclk = extali slow = 0 pllclk = 2 x extali x (synr + 1) / (refdv + 1) eclk = sysclk / 2 xclk = slwclk / 2 pclk = sysclk / 2 bclk (1) = extali / 2 boolean equations: sysclk = (bcsp & pllclk) | (bcsp & bcss & extali) | (bcsp & bcss & slwclk) mclk = (pclk & mcs ) | (xclk & mcs) mscan system = ( extali & clksrc) | (sysclk & clksrc) bdm system = (bclk & clksw) | (eclk & clksw) note: during limp-home m ode pclk, eclk, bclk, mclk and xclk are supplied by vco (pllclk). 1. if sysclk is slower than extali (bcss= 1, bcsp=0, slow>0), bclk becomes eclk.
clock functions technical data mc68hc912dt128a ? rev 4.0 182 clock functions motorola 12.8 clock divider chains figure 12-6 , figure 12-7 , figure 12-8 , and figure 12-9 summarize the clock divider chains for t he various peripherals on the mc68hc912dt128a. figure 12-6. clock generation chain reduced consumption oscillator phase lock loop extal xtal 0:0 sysclk to buses, spi, pwm, atd0, atd1 to rti, cop bcsp bcss slow mode clock divider extali extali extali slwclk pllclk 0:1 bcsp bcss 1:x bcsp bcss mcs = 0 mcs = 1 2 2 to mscan clksrc = 1 tclks t clock generator e and p clock generator pclk eclk xclk to sci0, sci1, ect to cpu sync mclk to bdm 2 sync to cal to clock monitor clksrc = 0 clksw = 0 clksw = 1
clock functions clock divider chains mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 183 bus clock select bits bcsp and bcss in the clock select register (clksel) determine which clock dr ives sysclk for the main system including the cpu and buses . bcss has no effect if bcsp is set. during the transition, the clock se lect output will be held low and all cpu activity will cease until the trans ition is complete. the module clock select bit mcs deter mines the clock used by the ect module and the baud rate generators of the scis . in limp-home mode, the output of mcs is forced to 0, but the mcs bit reads the latched value. it allows normal operati on of the serial and time r subsystems at a fixed reference frequen cy while allowing the cpu to operate at a higher, variable frequency. figure 12-7. clock chain fo r sci0, sci1, rti, cop xclk sc0bd modulus divider: 1, 2, 3, 4, 5, 6,...,8190, 8191 sci0 receive baud rate (16x) sci0 transmit baud rate (1x) bits: rtr2, rtr1, rtr0 to rti bits: cr2, cr1, cr0 to cop 16 sci1 receive baud rate (16x) sci1 transmit baud rate (1x) 16 0:0:0 0:0:1 0:1:0 0:1:1 1:0:0 1:0:1 1:1:0 1:1:1 2 2 2 2 2 2 0:0:0 0:0:1 0:1:0 0:1:1 1:0:0 1:0:1 1:1:0 1:1:1 4 4 4 2 4 2 4 register: copctl register: rtictl sc1bd modulus divider: 1, 2, 3, 4, 5, 6,...,8190, 8191 register: rtictl bit:rtbyp 2048 mclk
clock functions technical data mc68hc912dt128a ? rev 4.0 184 clock functions motorola figure 12-8. clock chain for ect bits: pr2, pr1, pr0 mclk pamod paclk pulse acc low byte paclk/256 pulse acc high byte paclk/65536 (paov) gate logic bits: paen, clk1, clk0 ten register: pactl register: tmsk2 paen 0:0:0 0:0:1 2 0:1:0 2 0:1:1 2 1:0:0 2 1:0:1 2 1:1:0 2 1:1:1 2 bits: mcpr1, mcpr0 mcen register: mcctl 0:0 0:1 4 1:0 2 1:1 2 0:x:x 1:0:0 1:0:1 1:1:0 1:1:1 to timer main counter (tcnt) modulus down counter port t7 prescaled mclk
clock functions computer operating properly (cop) mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 185 figure 12-9. clock chain for m scan, spi, atd0 , atd1 and bdm 12.9 computer oper ating properly (cop) the cop or watchdog timer is an added check that a program is running and sequencing properly. when the cop is being used, software is responsible for keeping a free running watchdog timer fr om timing out. if the watchdog timer times out it is an indication that t he software is no longer being executed in the intended sequence; thus a system reset is initiated. three control bits allow selection of seve n cop time-out periods. when cop is e nabled, sometime during the selected period the program must write $55 an d $aa (in this order) to the coprst register. if the program fails to do this the part will rese t. if any val ue other than $55 or $aa is written, the part is reset. pclk bits : spr2, spr1, spr0 spi bit rate 5-bit modulus counter (pr0-pr4) to atd0 and atd1 bkgd bdm bit clock: receive: detect falling edge, count 12 e clocks, sample input transmit 1: detect falling edge, count 6 e clocks while output is high impedance, drive out 1 e cycle pulse high, high imped- ance output again transmit 0: detect falling edge, drive out low, count 9 e clocks, drive out 1 e cycle pulse high, high impedance output pin synchronizer logic bkgd in bkgd out bkgd direction 2 0:0:0 0:0:1 0:1:0 0:1:1 1:0:0 1:0:1 1:1:0 1:1:1 2 2 2 2 2 2 2 2 register: sp0br mscan clock clksrc extali sysclk clksw eclk bclk
clock functions technical data mc68hc912dt128a ? rev 4.0 186 clock functions motorola in addition, window ed cop operation can be se lected. in this mode, writes to the coprst regi ster must occur in the la st 25% of the selected period. a premature write will also reset the part. 12.10 real-time interrupt there is a real time ( periodic) interrupt avai lable to the user. this interrupt will occur at on e of seven selected rate s. an interrupt flag and an interrupt enable bit are associated wi th this function. there are three bits for the rate select. 12.11 clock monitor the clock monitor circuit is based on an internal resistor-capacitor (rc) time delay. if no extali clock edges are detected within this rc time delay, the clock monitor can optio nally generate a syst em reset. the clock monitor function is enabled/disa bled by the cme control bit in the copctl register. this time -out is based on an rc delay so that the clock monitor can operate without any extali clock. clock monitor time-outs are shown in table 12-3 . the corresponding extali clock period with an ideal 50% duty cycle is twice this time-out value. table 12-3. clock monitor time-outs supply range 5 v +/? 10% 2?20 s
clock functions clock function registers mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 187 12.12 clock function registers all register addresses shown reflect the reset state. registers may be mapped to any 2k byte space. rtie ? real time interrupt enable read and write anytime. 0 = interrupt requests from rti are disabled. 1 = interrupt will be requeste d whenever rtif is set. rswai ? rti and cop st op while in wait write once in normal modes, an ytime in special modes. read anytime. 0 = allows the rti and cop to continue running in wait. 1 = disables both the rti and co p whenever the part goes into wait. rsbck ? rti and co p stop while in ba ckground debug mode write once in normal modes, an ytime in special modes. read anytime. 0 = allows the rti and cop to continue running while in background mode. 1 = disables both t he rti and cop when the part is in background mode. this is useful for emulation. rtbyp ? real time interr upt divider chain bypass write not allowed in normal modes, anytime in special modes. read anytime. 0 = divider chain functions normally. 1 = divider chain is by passed, allows faster testing (the divider chain is normally xclk divided by 2 13 , when bypassed becomes xclk divided by 4). bit 7654321bit 0 rtie rswai rsbck reserved rtbyp rtr2 rtr1 rtr0 reset: 00000000 rtictl ? real-time interrupt control register $0014
clock functions technical data mc68hc912dt128a ? rev 4.0 188 clock functions motorola rtr2, rtr1, rtr0 ? real-time interrupt rate select read and write anytime. rate select for real-time interrupt . the clock used for this module is the xclk. rtif ? real time interrupt flag this bit is cleared aut omatically by a write to th is register with this bit set. 0 = time-out has not yet occurred. 1 = set when the time -out period is met. table 12-4. real time interrupt rates rtr2 rtr1 rtr0 divide x by: time-out period x = 125 khz time-out period x = 500 khz time-out period x = 2.0 mhz time-out period x = 8.0 mhz 0 0 0 off off off off off 001 2 13 65.536 ms 16.384 ms 4.096 ms 1.024 ms 010 2 14 131.72 ms 32.768 ms 8.196 ms 2.048 ms 011 2 15 263.44 ms 65.536 ms 16.384 ms 4.096 ms 100 2 16 526.88 ms 131.72 ms 32.768 ms 8.196 ms 101 2 17 1.05 s 263.44 ms 65.536 ms 16.384 ms 110 2 18 2.11 s 526.88 ms 131.72 ms 32.768 ms 111 2 19 4.22 s 1.05 s 263.44 ms 65.536 ms bit 7654321bit 0 rtif0000000 reset: 00000000 rtiflg ? real time interrupt flag register $0015
clock functions clock function registers mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 189 cme ? clock monitor enable read and write anytime. if fcme is set, this bit has no meaning nor effect. 0 = clock monitor is disabled. sl ow clocks and stop instruction may be used. 1 = slow or stopped clocks (incl uding the stop instruction) will cause a clock reset sequenc e or limp-home mode. see limp- home and fast stop recovery modes . on reset cme is 1 if vddpll is high cme is 0 if vddpll is low. note: the vddpll-dependent reset operation is not im plemented on first pass products. in this case the stat e of cme on reset is 0. fcme ? force clock monitor enable write once in normal modes, an ytime in special modes. read anytime. in normal modes, when this bit is set, the clock monitor function cannot be disabled until a reset occurs. 0 = clock monitor follows the state of the cme bit. 1 = slow or stopped clocks will c ause a clock reset sequence or limp-home mode. see limp-home and fast stop recovery modes . bit 7654321bit 0 cme fcme fcmcop wcop disr cr2 cr1 cr0 reset: 0/1 0 0 0 0 1 1 1 normal reset: 0/1 0 0 0 1 1 1 1 special copctl ? cop control register $0016
clock functions technical data mc68hc912dt128a ? rev 4.0 190 clock functions motorola fcmcop ? force clock monitor reset or cop watchdog reset writes are not allowed in normal modes, anytime in special modes. read anytime. if disr is set, th is bit has no effect. 0 = normal operation. 1 = a clock monitor failure reset or a cop failure reset is forced depending on the state of cme and if cop is enabled. wcop ? window cop mode write once in normal modes, an ytime in special modes. read anytime. 0 = normal cop operation 1 = window cop operation when set, a write to the coprst regi ster must occur in the last 25% of the selected period. a premature write will also reset the part. as long as all writes occur during this window, $55 can be written as often as desired. once $aa is written the time-out logic restarts and the user must wait until the next window before writ ing to coprst. please note, there is a fixed time uncertainty about the exact cop counter state when reset, as the initial prescale clock divider in the rti section is not cl eared when the cop coun ter is cleared. this means the effective window is reduced by this uncertainty. table 12- 5 below shows the exact duration of this window for the seven available cop rates. cme cop enabled forced reset 0 0 none 0 1 cop failure 1 0 clock monitor failure 11 both (1) 1. highest priority inte rrupt vector is serviced.
clock functions clock function registers mc68hc912dt128a ? rev 4.0 technical data motorola clock functions 191 disr ? disable resets from cop watchdog and clock monitor writes are not allowed in normal modes, anytime in special modes. read anytime. 0 = normal operation. 1 = regardless of other control bi t states, cop and clock monitor will not generate a system reset. cr2, cr1, cr0 ? cop watchdog timer rate select bits these bits select the cop time- out rate. the clock used for this module is the xclk. write once in normal modes, an ytime in special modes. read anytime. table 12-5. cop watchdog rates cr2 cr1 cr0 divide xclk by 8.0 mhz xclk time-out window cop enabled: window start (1) window end effective window (2) 0 0 0 off off off off off 001 2 13 1.024 ms -0/+0.256 ms 0.768 ms 0.768 ms 0% (3) 010 2 15 4.096 ms -0/+0.256 ms 3.072 ms 3.840 ms 18.8 % 011 2 17 16.384 ms -0/+0.256 ms 12.288 ms 16.128 ms 23.4 % 100 2 19 65.536 ms -0/+1.024 ms 49.152 ms 64.512 ms 23.4 % 101 2 21 262.144 ms -0/+1.024 ms 196.608 ms 261.120 ms 24.6 % 110 2 22 524.288 ms -0/+1.024 ms 393.216 ms 523.264 ms 24.8 % 111 2 23 1.048576 ms -0/+1.024 ms 786.432 ms 1.047552 s 24.9 % 1. time for writing $55 following previous co p restart of time-out logic due to writing $aa. 2. please refer to wcop bit description above. 3. window cop cannot be used at this rate.
clock functions technical data mc68hc912dt128a ? rev 4.0 192 clock functions motorola always reads $00. writing $55 to this address is the first step of the cop watchdog sequence. writing $aa to this address is t he second step of the cop watchdog sequence. other instruct ions may be executed between these writes but both must be complete d in the correct order prior to time-out to avoid a watchdog reset. writing anything other than $55 or $aa causes a cop reset to occur. bit 7654321bit 0 bit 7654321bit 0 reset: 00000000 coprst ? arm/reset cop timer register $0017
oscillator contents mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 193 13.1 contents 13.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 13.3 mc68hc912dt128a oscilla tor specification . . . . . . . . . . . .194 13.4 mc68hc912dx128c colpitts oscilla tor specification . . . . . . 197 13.5 mc68hc912dx128p pierc e oscillator specificat ion . . . . . . . 212 13.2 introduction the oscillator implementati on on the original 0.65 (non-suffix) hc12 d- family is a ?colpitts oscillator with translated ground?. this design was carried over to the first 0.5 devices (a-suffix), up to the 0l05h mask set, and is described in section 13.3 mc68hc912dt1 28a oscillator specification . in this section of the document, the term mc68hc912dt128a refers only to the mc68hc 912dt128a and mc68hc912dg128a devices. on mask set 1l05h, the colpitts osci llator was updated , primarily to improve its performance. to maximi se the benefit of this change, different external component valu es are required. however, the oscillator will perform at least as well as the mc68hc912dt128a version with the same component s. this implementation and the changes are described in section 13.4 mc68hc912dx128c colpitts oscillator specification . in this section of the document, the term mc68hc912dx128c refers only to the mc68hc912dt128c and mc68hc912dg128c devices. in order to make the hc12 d-family oscillator options more flexible, a pierce oscillator configuratio n has been implemented on the 2l05h technical data ? mc68hc912dt128a section 13. oscillator
oscillator technical data mc68hc912dt128a ? rev 4.0 194 oscillator motorola mask set. this implementat ion, described in section 13.5 mc68hc912dx128p pierce o scillator specification , utilises the automatic level control ci rcuit to provide a lowe r power oscillator than traditional pierce o scillators based on simple in verter circuits. in this section of the document, the term mc68hc912dx128p refers only to the mc68hc912dt128p and mc68h c912dg128p devices. in the following sections, each parti cular oscillator implementation is described in detail. refer to the appr opriate sections for the mask set being used and optimum exte rnal component selection. 13.3 mc68hc912dt128a os cillator specification this section applies to the 0l05h mask se t and all previous mc68hc912dt128a versions. 13.3.1 mc68hc912dt128a oscillator design architecture the colpitts oscillator ar chitecture is shown in figure 13-1 . the component configuration for this oscillator is the same as all previous mc68hc912dt128a configurations.
oscillator mc68hc912dt128a osc illator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 195 figure 13-1. mc68hc912dt128a colpitts oscillat or architecture alc + - ota + - cflt rflt en bias resonator c x-ex c x-vss buf rflt cflt 2 gm extal xtal resd
oscillator technical data mc68hc912dt128a ? rev 4.0 196 oscillator motorola 13.3.2 mc68hc912dt128a oscillator design guidelines proper and robust operation of the o scillator circuit requires excellent board layout design practice. poor la yout of the appl ication board can contribute to emc susceptibility, noise generation, slow starting oscillators, and reaction to noise on the clock input buff er. in addition to published errata for the mc68hc 912dt128a, the following guidelines must be followed or fail ure in operation may occur. minimize capacitance to vss on extal pin ? the colpitts oscillator architecture is sensitiv e to capacitance in parallel with the resonator (from extal to vss). follow these techniques: i. remove ground plane from all layers around resonator and extal route ii. observe a minimum spacing from the extal trace to all other traces of at leas t three times the design rule minimum (until the mi crocontroller?s pin pitch prohibits this guideline) iii. where possible, use xtal as a shield between extal and vss iv. keep extal capacitanc e to less than 1pf (2pf absolute maximum) shield all oscillator com ponents from all noisy traces (while observing above guideline). keep the vsspll pin and the vss reference to the oscillator as identical as possible . impedance between these signals must be minimum. observe best pract ice supply bypassing on all mcu power pins. the oscillator?s supply reference is vdd, not vdpll. account for xtal?vss and extal?xtal parasitics in component values. note: an increase in the extal ? xtal parasitic as a result of reducing extal ? vss parasitic is acceptable provided component value is reduced by the appr opriate value. minimize xtal and extal routing lengths to reduce emc issues.
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 197 note: extal and xtal routing resistan ces are less important than capacitances. using minimum width tr aces is an acceptable trade-off to reduce capacitance. 13.4 mc68hc912dx12 8c colpitts oscill ator specification this section applies to t he 1l05h mask set, whic h refers to the newest set of cgm improvements (to the mc68hc912dt128a) wit h the colpitts oscillator configuration enabled. the name for these devices is mc68hc912dx128c. 13.4.1 mc68hc912dx128c oscillator desi gn architecture the colpitts oscillator ar chitecture is shown in figure 13-2 . the component configuration for this oscillator is the same as all previous mc68hc912dt128a configurati ons, although the recommended component values may be different.
oscillator technical data mc68hc912dt128a ? rev 4.0 198 oscillator motorola figure 13-2. mc68hc912dx128c colp itts oscillator architecture there are the following pr imary differences betw een the previous (?a?) and new (?c?) colpitts oscillator configurations: hysteresis was added to the clock in put buffer to reduce sensitivity to noise internal parasitics were reduc ed from extal to vss to increase oscillator gain margin. alc + - ota + - cflt rflt en bias resonator c x-ex c x-vss buf rflt cflt 2 gm extal xtal resd
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 199 the bias current to the amplifier was optimized for less variation over process. the input esd resistor from extal to the gate of the oscillator amplifier was changed to provi de a parallel path, reducing parasitic phase shift in the oscillator. 13.4.1.1 clock bu ffer hysteresis the input clock buffer uses an oper ational transconductance amplifier (labeled ?ota? in the figure above) followed by a di gital buffer to amplify the input signal on the extal pin into a full-swing clo ck for use by the clock generation section of the microcontroller. ther e is an internal r-c filter (composed of co mponents rflt2 and cflt2 in the figure above), which creates the dc value to whic h the extal signal is compared. in this manner, the clock input buffer can track changes in the extal bias voltage due to process vari ation as well as exter nal factors such as leakage. because the purpose of the clock input buffer is to amplify relatively low- swing signals into a full-r ail output, the gain of t he ota is very high. in the configuration shown, this means t hat very small levels of noise can be coupled onto the i nput of the clock buffe r resulting in noise amplification. to remedy this issue, hysteresis was added to the ota so that the circuit could still provide the tolerance to leakage and the high gain required without the noise sensit ivity. approximately 150m v of hysteresis was added with a maximum hysteresis over process variation of 350mv. as such, the clock input buffe r will not respond to input signals until they exceed the hysteresis level. at th is point, the inpu t signal due to oscillation will dominate the total input waveform and narrow clock pulses due to noise will be eliminated. this circuit will limit the overall performance of the oscillator block only in cases where the amplitude of os cillation is less than the level of hysteresis. the minimum amplitude of o scillation is expected to be in excess of 750mv and the maximum hyst eresis is expected to be less than 350mv, providing a factor of safety in excess of two.
oscillator technical data mc68hc912dt128a ? rev 4.0 200 oscillator motorola 13.4.1.2 internal parasitic reduction any oscillator circuit?s gain marg in is reduced when a low ac-impedance (low resistance or high capacitance) is placed in pa rallel with the resonator. in the colpitts oscillato r configuration, this impedance is dominated by the parasit ic capacitance from t he extal pin to vss. since this capacitance is large comp ared to the shunt capacitance of the resonator, the gain margin in a colpitts configuration is less than in other configurations. to remedy this issue, the internal circuits were optimized for lower capacitance. this should increase the gain margin and allow more robust operation over pr ocess, temperature a nd voltage vari ation. to maximize the benefit of th is change, different exte rnal component values are required. however, the oscillator will function at least as well as the mc68hc912dt128a version wit h the same components. 13.4.1.3 bias curren t process optimization for proper oscillation, the gain margin of the oscillator must exceed one or the circuit will not o scillate. due to the sens itive gain margin of the colpitts configuration, process va riance in the bias current (which controls the gain of the amplifier) can cause the gain margin to be much lower than typical. this can be as a resu lt of either too much or too little current. to reduce the process sensitivity of t he gain, the material of the device that sets the bias current was changed to a material with tighter process and temperature control. as a result, the tran sconductance and ibias variances are more limited t han in the prev ious design.
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 201 13.4.1.4 input esd resist or path modification to satisfy the condition of oscillation, the oscillator circ uit must not only provide the correct amount of gain but also the correct amount of phase shift. in the colpitts configuration, the phase shift due to parasitics in the input path to the gate of the transc onductance amplifier must be as low as possible. in the origi nal configuration, the par asitic capacitance of the clock input buffer (ota), automatic loop control circuit (alc), and input resistors (rflt and rflt2) reacted with the input resistance to cause a large phase shift. to reduce the phase shift, the input esd resi stor (marked resd in the figure above) was changed from a single path to the input circuitry (the alc and the ota) and oscillator tr ansconductance amplifier (marked gm in the figure above) to a parallel path. in this configuration, the only capacitance causing a phase shift on t he input to the transconductance device is due to the transc onductance device itself. 13.4.2 mc68hc912dx128c oscillator circui t specifications 13.4.2.1 negative resistance margin negative resistance marg in (nrm) is a figure of merit commonly used to qualify an oscillator ci rcuit with a given resona tor. nrm is an indicator of how much additional resistance in series with the resonator is tolerable while still maintaining oscilla tion. this figure is usually expected to be a multiple of the nominal "maximum" rate d esr of the resonator to allow for variation and degr adation of the resonator. currently, many systems are optimiz ed for nrm by ad justing the load capacitors until nrm is maximized. this method may not achieve the best overall nrm because the optimiz ation method is empirical and not analytical. that is, the method only achieves the best nrm for the particular sample set of microcontrollers, res onators, and board values tested. the figure below shows the anticipated nr m for a nominal 4mhz resonator given the expected proce ss variance of the microcontroller (d60a), board, and crystal (excluding es r). in this case, the value of load capacitors providing the optim um nrm for a best- case situation
oscillator technical data mc68hc912dt128a ? rev 4.0 202 oscillator motorola yield an unacceptable nr m for a worst-case sit uation (the slope of the nrm vs. capacitance curve is very steep, indicating severe sensitivity to small variations). if the nrm opt imization happened to be performed on a best-case sample set, there coul d be unexpected sensitivity at worst- case. nrm measurement techni ques can also generat e misleading results when applied to automati c level control (alc) st yle oscillator circuits such as the d60x/dx128x. many nr m methods slowly increase series resistance until oscillation stops. al c-style oscillators reduce the gain of the oscillator circui t after start-up to reduce curr ent, so if the oscillator tends to have more gain than optimum it will be more tolerant of additional resistance after start-up than it will during the start-up process. this means that nrm figures may be optimistic unless the method verifies the nrm value by attempting to start the oscillator with the additional resistance in-place. wo rse, this phenomenon exaggerates the difference between best- and worst-case nrm curves. negative resistance margin vs. capacitance 10 100 1000 68 56 47 39 33 27 22 18 15 13 10 8 capacitance negative resistance margin wcs ty p ty p bcs
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 203 13.4.2.2 gain margin the gain margin of the o scillator indicates the am ount the gain of the oscillator can vary while maintaini ng oscillation. s pecifically, gain margin is: gain margin = min(gain/minimum required gain, maximum allowed gain/gain) just like nrm, gain margin may be dominated by either too much or too little oscillator gain a nd an increase in gain may not increase gain margin. gain margin is theoretically related to nrm since the maximum allowed gain is (approximately) in versely proportiona l to esr, and the minimum required gain is (approximately) proporti onal to esr, leaving gain margin (approx imately) inversely proportional to esr. the preferred method for specifying th e oscillator, give n a set of load capacitor values, is to dete rmine the maximum allowed while maintaining a worst-case gain marg in of 2. since gain margin is proportional to esr, this means the empirica lly measured nrm at the worst-case point would be approx imately twice the maximum allowed esr. however, since typical nr m is likely to be higher and most measurement techniques do not account for alc effects, actual nrm measurements are likely to be much higher. 13.4.2.3 optimizi ng component values the maximum esr possible (given a worst- case gain margin of 2) is not the optimum operat ing point. in some cases, the frequency accuracy of the oscillator is important and in other cases satisfying the traditional nrm measurement tec hnique is important. if frequency accuracy is important , the total load capacitance (the combination of the load capacitors and their a ssociated parasitics) should be equal (or close to equal) to the rat ed load capacitance of the resonator. provided the resultant load capacitors yield a maximum allowed esr greater than the maxi mum esr of the crystal (while maintaining the worst case gain marg in of 2), this is an acceptable operating point. if the maximum al lowed esr is not high enough, the closest possible components with high enough esr should be chosen.
oscillator technical data mc68hc912dt128a ? rev 4.0 204 oscillator motorola similarly, if meeting a tr aditional nrm optimization criteria is important, then the components determ ined by this method are acceptable if the same components yiel d a maximum allowed esr greater than the maximum esr of the cryst al while maintaining the worst case gain margin of 2. there is no guaran tee that component s chosen through traditional nrm optimizat ion techniques wi ll yield acceptable results across all expected variations. 13.4.2.4 key parameters the following items are of critical importance to the operation of the oscillator: extal ? xtal capacitor value ? the value of the component plus external (board) parasitic in excess of 0. 1pf between extal and xtal. xtal ? vss capacitor value ? the value of t he component plus external (board) parasitic in excess of 1.0pf bet ween xtal and vss. maximum shunt capacitance ? the maximum value of the resonator?s shunt capac itance (c0) plus t he external (board) parasitics in excess of 1pf from exta l to vss. vddpll setting ? the voltage applied to the vddpll pin (logic 1 means vddpll is tied to the same potential as vdd). resonator frequency ? the frequency of o scillation of the resonator. maximum esr ? the maximum effectiv e series resistance (esr) of the resonator. this figur e must include any increases due to ageing, power dissipation, temperature, process variation or particle contamination.
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 205 13.4.3 important information for calculating component values before attempting to apply the informati on in section 13.4.2.4 key parameters , the following data from the resonator vendor is required: resonator frequency (f) maximum esr (r , esr, or r1) maximum shunt capacitance (c0) load capacitance (cl) ? this is not th e external component values but rather t he capacitance applied in parallel with the resonator during th e tuning procedure. 13.4.3.1 how to use this information the following tables provide maxi mum esr vs. com ponent value for various frequencies. this table should be used in the following manner: 1. choose the set of component va lues corresponding to the correct maximum shunt c apacitance (equa l to the sum of extal?vss parasitics in excess of 1pf, plus the c0 of the resonator) and vddpll setting. 2. determine the range of compone nts for which the maximum esr is greater than the absolute maximum esr of the resonator (including ageing, power dissipat ion, temperature, process variation or particle contamination). 3. within this range, choose the extal?xtal capacitance closest to (c extal?xtal = 2*cl ? 1pf). 4. if the ideal component is betw een two valid component values (the maximum esr is sufficient for both component values), then choose the component with the highest maximum esr or choose an available component betw een the two listed values. 5. choose the size of the xtal ?vss capacitance equal to the closest available size to (c xtal?vss = 0.82*c extal?xtal ).
oscillator technical data mc68hc912dt128a ? rev 4.0 206 oscillator motorola 6. if the frequency of the crystal falls between listed values, determine the appropriate com ponent for the li sted frequency values on either side and extrapolate. 7. the maximum allowed capacitor is the highest listed component, and the minimum allo wed capacitor is the lowest listed component. ?na? or ?not allowed? means t he listed component is not valid or allowed for the giv en frequency, shunt capacitance, and vddpll setting. 13.4.3.2 general specifications the following limitations apply to every system: ceramic resonators with in tegrated components should not be used, as they are designed for pierce-configured oscillators. series cut resonators should not be used. use parall el cut instead. the load capacitance should be 12pf or higher, preferably greater than 15pf.
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 207 table 13-1. mc68hc912dx128c extal ? xtal capacitor values vs. maximum esr, shunt capacitance, and vddpll setting maximum esr vs. extal?xtal capacitor value, 1mhz resonators shunt capacitance (pf) (vddpll=vdd) 3 1570 2080 2620 2700 1870 1140 630 170 5 1460 1890 2340 2010 1370 830 460 120 7 1350 1730 2100 1550 1050 630 350 90 10 1210 1520 1600 1100 740 440 240 60 c extal-xtal (pf) 100pf 82pf 68pf 56pf 47pf 39pf 33pf 27pf 22pf 18pf maximum esr vs. extal?xtal capac itor value, 2mhz resonators shunt capacitance (pf) (vddpll=vdd) 3 360 480 620 780 940 1100 1080 730 440 240 5 340 450 570 700 830 950 800 530 320 170 7 320 410 520 630 740 830 620 410 250 130 10 290 370 450 550 620 600 440 290 170 90 c extal-xtal (pf) 100pf 82pf 68pf 56pf 47pf 39pf 33pf 27pf 22pf 18pf maximum esr vs. extal?xtal capa citor value, 4mhz resonators shunt capacitance (pf) (vddpll=vdd) 3 210 255 290 335 370 340 175 80 5 190 225 254 290 310 255 130 60 7 170 200 227 250 270 200 100 45 10 145 170 190 205 205 140 70 25 shunt capacitance (pf) (vddpll=0) 3 250 300 350 400 440 325 165 75 5 225 265 305 340 345 245 120 55 7 200 235 265 295 270 190 90 40 10 175 200 220 240 195 135 65 20 c extal-xtal (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf
oscillator technical data mc68hc912dt128a ? rev 4.0 208 oscillator motorola maximum esr vs. extal?xtal capa citor value, 8mhz resonators shunt capacitance (pf) (vddpll=vdd) 3 40 50 60 70 80 90 95 90 5 35 45 50 60 70 75 80 70 7 30 40 45 50 60 65 65 10 25 30 35 40 45 50 shunt capacitance (pf) (vddpll=0) 3 50 60 70 85 95 105 115 104 5 40 50 60 70 80 90 95 75 7 35 45 55 60 70 75 80 60 10 35 40 45 50 55 60 c extal-xtal (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf maximum esr vs. extal?xtal capacitor value, 10mhz resonators shunt capacitance (pf) (vddpll=0) 3 25 35 40 50 55 65 70 70 5 25 30 35 40 50 55 60 7 20 25 30 35 40 45 10 15 20 25 30 35 c extal-xtal (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf maximum esr vs. extal?xtal capacitor value, 16mhz resonators shunt capacitance (pf) (1) (vddpll=0) 3 5 7 10 c extal-xtal (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf = not allowed 1. please refer to point 1 in 13.4.3.1 how to use this information for important information regarding shunt ca- pacitance.
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 209 13.4.4 mc68hc912dx128c dc blocking capaci tor guidelines due to the placement of the res onator from extal to vss and the nature of the microcontrolle r?s inputs, there will be a dc bias voltage of approximately (vdd?2v) ac ross the pins of the resonator. for some resonators, this can hav e long-term reliability i ssues. to remedy this situation, a dc-blocking capacitor can be plac ed in series with the crystal, as shown in figure 13-3 . the value of the dc-blocking capac itor should be between 0.1 and 10nf, with a preferred valu e of 1nf. this capaci tor must be connected as shown in figure 13-3 . if connected thus, all other oscillator specifications and guidel ines continue to apply.
oscillator technical data mc68hc912dt128a ? rev 4.0 210 oscillator motorola figure 13-3. mc68hc912dx128c crystal with dc blocking capacitor alc + - ota + - cflt rflt en bias resonator c x-ex c x-vss buf rflt cflt 2 gm extal xtal resd c dc 1nf dc- b locking ca p acito r
oscillator mc68hc912dx128c colpitts oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 211 13.4.5 mc68hc912dx128c oscillator desi gn guidelines proper and robust operation of the o scillator circuit requires excellent board layout design practice. poor la yout of the appl ication board can contribute to emc susceptibility, noise generation, slow starting oscillators, and reaction to noise on the clock input buff er. in addition to published errata for the mc68hc 912dt128a, the following guidelines must be followed or fail ure in operation may occur. minimize capacitance to vss on extal pin ? the colpitts oscillator architecture is sensitiv e to capacitance in parallel with the resonator (from extal to vss). follow these techniques: i. remove ground plane from all layers around resonator and extal route ii. observe a minimum spacing from the extal trace to all other traces of at leas t three times the design rule minimum (until the mi crocontroller?s pin pitch prohibits this guideline) iii. where possible, use xtal as a shield between extal and vss iv. keep extal capacitanc e to less than 1pf (2pf absolute maximum) shield all oscillator com ponents from all noisy traces (while observing above guideline). keep the vsspll pin and the vss reference to the oscillator as identical as possible . impedance between these signals must be minimum. observe best pract ice supply bypassing on all mcu power pins. the oscillator?s supply reference is vdd, not vddpll. account for xtal ? vss and extal ? xtal parasitics in component values. the specified compon ent values assume a maximum parasitic ca pacitance of 1pf and 0.1pf, respectively. note: an increase in the extal?xtal para sitic as a resu lt of reducing extal?vss parasitic is acceptab le provided component value is reduced by the appr opriate value.
oscillator technical data mc68hc912dt128a ? rev 4.0 212 oscillator motorola minimize xtal and extal routing lengths to reduce emc issues. note: extal and xtal routing resistan ces are less important than capacitances. using minimum width tr aces is an acceptable trade-off to reduce capacitance. 13.5 mc68hc912dx128p pier ce oscillator specification this section applies to t he 2l05h mask set, whic h refers to the newest set of cgm fixes (to the mc68hc912d t128a) with the pie rce oscillator configuration enabled. the name for these devices is mc68hc912dx128p. 13.5.1 mc68hc912dx128p oscillator design architecture the pierce oscillator arch itecture is shown in figure 13-4 . the component configuration for this oscillator is diffe rent to all previous mc68hc912dt128a configurat ions and the recommended components may be different. please note carefully the connection of external capacitors and the resonator in this diagram.
oscillator mc68hc912dx128p pierce oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 213 figure 13-4. mc68hc912dx128p pi erce oscillator architecture there are the following primary di fferences between the previous colpitts (?a?) and new pierce ( ?p?) oscillator configurations: oscillator architecture was cha nged from colpitts to pierce. hysteresis was added to the clock in put buffer to reduce sensitivity to noise. the bias current to the amplifie r was optimized for less process variation. alc + - ota + - rfeedback en bias resonator c ex-vss c x-vss buf rflt cflt 2 gm extal xtal resd
oscillator technical data mc68hc912dt128a ? rev 4.0 214 oscillator motorola the input esd resistor from extal to the gate of the oscillator amplifier was changed to provi de a parallel path, reducing parasitic phase shift in the oscillator. 13.5.1.1 oscillator architecture change from colpitts to pierce the primary difference from the ?a ? to the ?p? versions of the mc68hc912dx128 is the archit ecture, or configurati on, of the oscillator. the previous version (?a?) is connected in colpitts configuration, where the resonator is connected bet ween the extal pin and vss. this configuration causes the relatively large parasitics fr om extal to vss react in parallel with the resonator , decreasing gain margin in some corners. the pierce c onfiguration places the much-lower extal to xtal parasitic capacitances in para llel with the reso nator, providing a much larger gain margin across process, temperature and voltage variance. implementation of the pie rce architecture requir ed the replacement of the previous p-type, non -inverting source-follo wer amplifier with an n- type, inverting, traditional amplifie r. additionally, t he extal biasing circuit on the colpitts configurat ions was replaced with a feedback resistor from xtal to extal to achieve self-bias. parametric differences from the ?a? to the ?p? versions of the oscillator include: phase shift from extal to xt al ? the phase shift on the ?p? version will be approxim ately 180 degrees ( vs. approximately 0 degrees on the ?a? vers ion) due to the require ment of an inverting amplifier in the pierce configuration). dc offset of oscillation on ex tal and xtal ? the dc offset of the extal and xtal nodes on the ?p? version will be approximately 0.7?1.0v ( vs. approximately vdd?2v and vdd?1v, respectively, on the ?a? ve rsion) due to the different bias requirements of the n- type inverting amplifier. amplitude of oscill ation ? the amplitude of oscillation may be slightly lower on the ?p? versio n than the ?a? vers ion due to using the same amplitude level control (alc ) circuit for both architectures. the ci rcuit responds slightly differently to the different dc offsets in the two arch itectures, resulting in slightly
oscillator mc68hc912dx128p pierce oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 215 lower amplitude for the pierce. the amplitude will still be sufficient for robust operation across pr ocess, temperature, and voltage variance. 13.5.1.2 clock bu ffer hysteresis the input clock buffer uses an oper ational transconductance amplifier (labeled ?ota? in the figure above) followed by a di gital buffer to amplify the input signal on the extal pin into a full-swing clo ck for use by the clock generation section of the microcontroller. ther e is an internal r-c filter (composed of co mponents rflt2 and cflt2 in the figure above), which creates the dc value to whic h the extal signal is compared. in this manner, the clock input buffer can track ch anges in the extal dc offset voltage due to process variatio n as well as external factors such as leakage. because the purpose of the clock input buffer is to amplify relatively low- swing signals into a full-r ail output, the gain of t he ota is very high. in the configuration shown, this means t hat very small levels of noise can be coupled onto the i nput of the clock buffe r resulting in noise amplification. to remedy this issue, hysteresis was added to the ota so that the circuit could still provide the tolerance to leakage and the high gain required without the noise sensit ivity. approximately 150m v of hysteresis was added with a maximum hysteresis over process variation of 350mv. as such, the clock input buffe r will not respond to input signals until they exceed the hysteresis level. at th is point, the inpu t signal due to oscillation will dominate the total input waveform and narrow clock pulses due to noise will be eliminated. this circuit will limit the overall performance of the oscillator block only in cases where the amplitude of os cillation is less than the level of hysteresis. the minimum amplitude of o scillation is expected to be in excess of 750mv and the maximum hyst eresis is expected to be less than 350mv, providing a factor of safety in excess of two.
oscillator technical data mc68hc912dt128a ? rev 4.0 216 oscillator motorola 13.5.1.3 bias curren t process optimization for proper oscillation, the gain margin of the oscillator must exceed one or the circuit wil l not oscillate. process variance in the bias current (which controls the gain of the amplifier) can cause the gain margin to be much lower than typical. this can be as a resu lt of either too much or too little current. to reduce the process sensitivity of t he gain, the material of the device that sets the bias current was changed to a material with tighter process and temperature control. as a result, the tran sconductance and ibias variances are more limited than in the pr evious design. 13.5.1.4 input esd resist or path modification to satisfy the condition of oscillation, the oscillator circ uit must not only provide the correct amount of gain but also the correct amount of phase shift. in the pierce conf iguration, the pha se shift due to parasitics in the input path to the gate of the transc onductance amplifier must be as low as possible. in the origi nal configuration, the par asitic capacitance of the clock input buffer (ota), automatic loop control circuit (alc), and input resistor (rflt) reacted with the input resistance to cause a large phase shift. to reduce the phase shift, the input esd resi stor (marked resd in the figure above) was changed from a single path to the input circuitry (the alc and the ota) and oscillator tr ansconductance amplifier (marked gm in the figure above) to a parallel path. in this configuration, the only capacitance causing a phase shift on t he input to the transconductance device is due to the transc onductance device itself.
oscillator mc68hc912dx128p pierce oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 217 13.5.2 mc68hc912dx128p oscillator circuit specifications 13.5.2.1 negative resistance margin negative resistance marg in (nrm) is a figure of merit commonly used to qualify an oscillator ci rcuit with a given resona tor. nrm is an indicator of how much additional resistance in series with the resonator is tolerable while still maintaining oscilla tion. this figure is usually expected to be a multiple of the nominal "maximum" rate d esr of the resonator to allow for variation and degr adation of the resonator. currently, many systems are optimiz ed for nrm by ad justing the load capacitors until nrm is maximized. this method may not achieve the best overall nrm because the optimiz ation method is empirical and not analytical. that is, the method only achieves the best nrm for the particular sample set of microcontrollers, res onators, and board values tested. the figure below shows the anticipated nr m for a nominal 4mhz resonator given the expected proce ss variance of the microcontroller (d60a), board, and crystal (excluding es r). in this case, the value of load capacitors providing the optim um nrm for a best- case situation yield an unacceptable nr m for a worst-case sit uation (the slope of the nrm vs. capacitance curve is very steep, indicating severe sensitivity to small variations). if the nrm opt imization happened to be performed on a best-case sample set, there coul d be unexpected sensitivity at worst- case. negative resistance margin vs. capacitance 10 100 1000 68 56 47 39 33 27 22 18 15 13 10 8 capacitance negative resistance margin wcs ty p ty p bcs
oscillator technical data mc68hc912dt128a ? rev 4.0 218 oscillator motorola nrm measurement techni ques can also generat e misleading results when applied to automati c level control (alc) st yle oscillator circuits such as the d60x/dx128x. many nr m methods slowly increase series resistance until oscillation stops. al c-style oscillators reduce the gain of the oscillator circui t after start-up to reduce curr ent, so if the oscillator tends to have more gain than optimum it will be more tolerant of additional resistance after start-up than it will during the start-up process. this means that nrm figures may be optimistic unless the method verifies the nrm value by attempting to start the oscillator with the additional resistance in-place. wo rse, this phenomenon exaggerates the difference between best- and worst-case nrm curves. 13.5.2.2 gain margin the gain margin of the o scillator indicates the am ount the gain of the oscillator can vary while maintaini ng oscillation. s pecifically, gain margin is: gain margin = min(gain/minimum required gain, maximum allowed gain/gain) just like nrm, gain margin may be dominated by either too much or too little oscillator gain a nd an increase in gain may not increase gain margin. gain margin is theoretically related to nrm since the maximum allowed gain is (approximately) in versely proportiona l to esr, and the minimum required gain is (approximately) proporti onal to esr, leaving gain margin (approx imately) inversely proportional to esr. the preferred method for specifying th e oscillator, give n a set of load capacitor values, is to determi ne the maximum allowed esr while maintaining a worst-case gain marg in of 2. since gain margin is proportional to esr, this means the empirica lly measured nrm at the worst-case point would be approx imately twice the maximum allowed esr. however, since typical nr m is likely to be higher and most measurement techniques do not account for alc effects, actual nrm measurements are likely to be much higher.
oscillator mc68hc912dx128p pierce oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 219 13.5.2.3 optimizi ng component values the maximum esr possible (given a worst- case gain margin of 2) is not the optimum operat ing point. in some cases, the frequency accuracy of the oscillator is important and in other cases satisfying the traditional nrm measurement tec hnique is important. if frequency accuracy is important , the total load capacitance (the combination of the load capacitors and their a ssociated parasitics) should be equal (or close to equal) to the rat ed load capacitance of the resonator. provided the resultant load capacitors yield a maximum allowed esr greater than the maxi mum esr of the crystal (while maintaining the worst case gain marg in of 2), this is an acceptable operating point. if the maximum al lowed esr is not high enough, the closest possible components with high enough esr should be chosen. similarly, if meeting a tr aditional nrm optimization criteria is important, then the components determ ined by this method are acceptable if the same components yiel d a maximum allowed esr greater than the maximum esr of the cryst al while maintaining the worst case gain margin of 2. there is no guaran tee that component s chosen through traditional nrm optimizat ion techniques wi ll yield acceptable results across all expected variations. 13.5.2.4 key parameters the following items are of critical importance to the operation of the oscillator: extal?vss capac itor value ? the value of the component plus external (board) parasitic in excess of 1. 0pf between extal and vss. xtal?vss capacitor value ? the value of t he component plus external (board) parasitic in excess of 1.0pf bet ween xtal and vss. maximum shunt capacitance ? the maximum value of the resonator?s shunt capac itance (c0) plus t he external (board) parasitics in excess of 0.1pf from extal to xtal.
oscillator technical data mc68hc912dt128a ? rev 4.0 220 oscillator motorola vddpll setting ? the voltage applied to the vddpll pin (logic 1 means vddpll is tied to the same potential as vdd). resonator frequency ? the frequency of o scillation of the resonator. maximum esr ? the maximum effectiv e series resistance (esr) of the resonator. this figur e must include any increases due to ageing, power dissipation, temperature, process variation or particle contamination. 13.5.3 important information for calculating component values before attempting to apply the informati on in section 13.5.2.4 key parameters , the following data from the resonator vendor is required: resonator frequency (f) maximum esr (r , esr, or r1) maximum shunt capacitance (c0) load capacitance (cl) ? this is not th e external component values but rather t he capacitance applied in parallel with the resonator during th e tuning procedure. 13.5.3.1 how to use this information the following tables provide maxi mum esr vs. com ponent value for various frequencies. this table should be used in the following manner: 1. choose the set of component va lues corresponding to the correct maximum shunt c apacitance (equa l to the sum of extal?xtal parasitics in excess of 0.1pf, pl us the c0 of the resonator) and vddpll setting. 2. determine the range of compone nts for which the maximum esr is greater than the absolute maximum esr of the resonator (including ageing, power dissipat ion, temperature, process
oscillator mc68hc912dx128p pierce oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 221 variation or particle contamination). 3. within this range, choose the extal?vss capacitance closest to (c extal?vss = 2*cl ? 10pf). 4. if the ideal component is betw een two valid component values (the maximum esr is sufficient for both component values), then choose the component with the highest maximum esr or choose an available component betw een the two listed values. 5. choose the size of the xt al?vss capacitance equal to extal?vss capacitance. 6. if the frequency of the crystal falls between listed values, determine the appropriate com ponent for the li sted frequency values on either side and extrapolate. 7. the maximum allowed capacitor is the highest listed component, and the minimum allo wed capacitor is the lowest listed component. ?na? or ?not allowed? means t he listed component is not valid or allowed for the giv en frequency, shunt capacitance, and vddpll setting. 13.5.3.2 general specifications the following limitations apply to every system: ceramic resonators with in tegrated components must have the integrated components accounted for in th e total component value. series cut resonators should not be used. use parall el cut instead. the load capacitance should be 12pf or higher, preferably greater than 15pf.
oscillator technical data mc68hc912dt128a ? rev 4.0 222 oscillator motorola table 13-2. mc68hc912dx128p extal?vss, xtal?vss capac itor values vs. maximum esr, shunt capacitance, and vddpll setting maximum esr vs. extal?vss or xtal?vss capacitor value, 1mhz resonators shunt capacitance (pf) (vddpll=0) 3 4400 5500 6700 8100 8500 6350 3700 2250 5 3800 4650 5400 5350 4000 2900 1650 1000 7 3300 3950 4150 3100 2300 1650 950 550 10 2700 2900 2300 1700 1200 850 500 300 c extal-vss (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf maximum esr vs. extal?vss or xtal?vss capacitor value, 2mhz resonators shunt capacitance (pf) (vddpll=0) 3 1100 1425 1750 2200 2700 3200 3975 3925 5 975 1225 1500 1825 2150 2475 2350 1825 7 850 1050 1275 1525 1750 1925 1375 1050 10 725 875 1025 1175 1325 1050 725 550 c extal-vss (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf maximum esr vs. extal?vss or xtal?vss capacitor value, 4mhz resonators shunt capacitance (pf) (vddpll=vdd) 3 270 350 440 560 700 850 1100 1310 5 240 310 380 470 570 680 850 970 7 210 270 320 400 480 550 670 740 10 180 220 260 320 370 420 490 520 shunt capacitance (pf) (vddpll=0) 3 250 330 410 520 660 800 1040 1230 5 230 290 350 440 540 640 800 910 7 200 250 300 370 450 520 630 700 10 170 210 250 300 350 400 450 500 c extal-vss (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf
oscillator mc68hc912dx128p pierce oscillator specification mc68hc912dt128a ? rev 4.0 technical data motorola oscillator 223 maximum esr vs. extal?vss or xtal?vss capacitor value, 8mhz resonators shunt capacitance (pf) (vddpll=vdd) 3 60 80 100 130 165 200 270 325 5 55 70 85 110 135 165 210 250 7 50 60 75 95 115 135 170 195 10 40 50 60 75 90 105 125 145 shunt capacitance (pf) (vddpll=0) 3 60 75 95 125 155 190 255 305 5 50 65 80 105 130 155 200 235 7 45 55 70 90 105 125 160 185 10 40 45 55 70 85 95 120 130 c extal-vss (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf maximum esr vs. extal?vss or xtal? vss capacitor value, 10mhz resonators shunt capacitance (pf) (vddpll=0) 3 35 45 60 80 100 120 165 200 5 30 40 50 65 80 100 125 150 7 25 35 45 55 65 80 100 120 10 20 30 35 40 50 60 70 80 c extal-vss (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf maximum esr vs. extal?vss or xtal? vss capacitor value, 16mhz resonators shunt capacitance (pf) (1) (vddpll=0) 3 10 15 20 30 35 50 60 5 10 15 20 25 30 45 7 10 15 20 30 35 10 20 c extal-vss (pf) 47pf 39pf 33pf 27pf 22pf 18pf 13pf 10pf 1. please refer to point 1 in 13.5.3.1 how to use this information for important information regarding shunt ca- pacitance.
oscillator technical data mc68hc912dt128a ? rev 4.0 224 oscillator motorola 13.5.4 mc68hc912dx128p guidelines proper and robust operation of the o scillator circuit requires excellent board layout design practice. poor la yout of the appl ication board can contribute to emc susceptibility, noise generation, slow starting oscillators, and reaction to noise on the clock input buff er. in addition to published errata for the mc68hc 912dt128a, the following guidelines must be followed or fail ure in operation may occur. minimize capacitance betw een extal and xtal traces ? the pierce oscillator architecture is sensitive to capacitance in parallel with the resonator (from extal to xtal). to reduce this capacitance, run a shield tr ace (connected to vss) between extal and xtal as far as possible. shield all oscillator com ponents from all noisy traces. if the vss used for shielding is not identi cal to the oscillator reference, it must be consider ed a noisy signal. keep the vsspll pin and the vss reference to the oscillator as identical as possible . impedance between these signals must be minimum. observe best pract ice supply bypassing on all mcu power pins. the oscillator?s supply reference is vdd, not vddpll. account for xtal ? vss and extal ? vss parasitics in component values. the specified compon ent values assume a maximum parasitic capacitance of 1pf for these pins. note: an increase in the extal?vss or xt al?vss parasitic as a result of reducing extal?xtal paras itic is acceptable provided the component values are reduced by the appropriate value. minimize xtal and extal routing lengths to reduce emc issues. note: extal and xtal routing resistan ces are less important than capacitances. using minimum width tr aces is an acceptable trade-off to reduce capacitance.
mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 225 technical data ? mc68hc912dt128a section 14. pulse width modulator 14.1 contents 14.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 14.3 pwm register descriptions . . . . . . . . . . . . . . . . . . . . . . . . . .229 14.4 pwm boundary cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240 14.2 introduction the pulse-width modulat or (pwm) subsystem provides four independent 8-bit pwm waveforms or two 16-bit pwm waveforms or a combination of one 16-bit and tw o 8-bit pwm waveforms. each waveform channel has a programm able period and a programmable duty-cycle as well as a dedicated counter . a flexible clock select scheme allows four different clock sources to be used with the c ounters. each of the modulators can cr eate independent, continuou s waveforms with software-selectable duty rates from 0 percent to 10 0 percent. the pwm outputs can be programmed as left-aligned out puts or center-aligned outputs. the period and duty registers are double buffered so that if they change while the channel is enabl ed, the change will not ta ke effect until the counter rolls over or the channel is disabled. if t he channel is not enabled, then writes to the period and/or duty regi ster will go directly to the latches as well as the buffer, t hus ensuring that the pwm output will always be either the old waveform or the new waveform, not some variation in between. a change in duty or period can be forced into immedi ate effect by writing the new value to the duty and/or period register s and then writing to the counter. this causes the counter to reset and the new duty and/or period values to be latched. in addition, since the counter is readable it is
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 226 pulse width modulator motorola possible to know where t he count is with respec t to the dut y value and software can be used to make adjus tments by turning the enable bit off and on. the four pwm channel outputs shar e general-purpose port p pins. enabling pwm pins takes precedenc e over the general -purpose port. when pwm are not in use, the po rt pins may be used for discrete input/output. figure 14-1. block diagram of pwm left-aligned output channel gate pwcntx 8-bit compare = pwdtyx 8-bit compare = pwperx up /down from port p data register to pin driver ppolx clock source (eclk or scaled eclk) (clock edge sync) reset centr = 0 mux mux s r q q pwper pwdty pwenx ppol = 0 ppol = 1 sync
pulse width modulator introduction mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 227 figure 14-2. block di agram of pwm center-a ligned output channel gate pwcntx 8-bit compare = pwdtyx 8-bit compare = pwperx reset from port p data register to pin driver ppolx clock source (eclk or scaled eclk) (clock edge sync) up /down centr = 1 mux mux t q q pwdty pwenx ppol = 1 ppol = 0 (duty cycle) (period) pwper 2 (pwper ? pwdty) 2 pwdty sync
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 228 pulse width modulator motorola figure 14-3. pwm clock sources 8-bit down counter pclk2 mux pclk3 mux clock to pwm channel 2 clock to pwm channel 3 2 pwscnt1 8-bit scale register pwscal1 clock b clock s1** **clock s1 = (clock b)/2, (clock b)/4, (clock b)/6,... (clock b)/512 2 0:0:0 0:0:1 0:1:0 0:1:1 1:0:0 1:0:1 1:1:0 1:1:1 2 2 2 2 2 2 0:0:0 0:0:1 0:1:0 0:1:1 1:0:0 1:0:1 1:1:0 1:1:1 8-bit down counter pclk0 mux pclk1 mux clock to pwm channel 0 clock to pwm channel 1 2 pwscnt0 8-bit scale register pwscal0 clock a clock s0* *clock s0 = (clock a)/2, (clock a)/4, (clock a)/6,... (clock a)/512 register: bits: pckb2, pckb0 pckb1, = 0 = 0 bits: pcka2, pcka0 pcka1, pwpres psbck limbdm eclk psbck is bit 0 of pwctl register. internal signal limbdm is one if the mcu is in background debug mode.
pulse width modulator pwm register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 229 14.3 pwm register descriptions read and write anytime. con23 ? concatenate pw m channels 2 and 3 when concatenated, c hannel 2 becomes the high-orde r byte and channel 3 becomes the low-order by te. channel 2 out put pin is used as the output for this 16-bit pwm (bit 2 of por t p). channel 3 clock- select control bits determines t he clock source. channel 3 output pin becomes a general purpose i/o. 0 = channels 2 and 3 are separate 8-bit pwms. 1 = channels 2 and 3 are concatenated to create one 16-bit pwm channel. con01 ? concatenate pw m channels 0 and 1 when concatenated, c hannel 0 becomes the high-orde r byte and channel 1 becomes the low-order by te. channel 0 out put pin is used as the output for this 16-bit pwm (bit 0 of por t p). channel 1 clock- select control bits determine the clock source. channel 1 output pin becomes a general purpose i/o. 0 = channels 0 and 1 are separate 8-bit pwms. 1 = channels 0 and 1 are concatenated to create one 16-bit pwm channel. pcka2 ? pcka0 ? prescaler for clock a clock a is one of two clock sour ces which may be used for channels 0 and 1. these three bits determine the rate of clock a, as shown in table 14-1 . pckb2 ? pckb0 ? prescaler for clock b clock b is one of two clock sour ces which may be used for channels 2 and 3. these three bits determine the rate of clock b, as shown in table 14-1 . pwclk ? pwm clocks and concatenate $0040 bit 7 6 5 4 3 2 1 bit 0 con23 con01 pcka2 pcka1 pcka0 pckb2 pckb1 pckb0 reset: 0 0 0 0 0 0 0 0
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 230 pulse width modulator motorola read and write anytime. pclk3 ? pwm channel 3 clock select 0 = clock b is the clo ck source for channel 3. 1 = clock s1 is the cl ock source for channel 3. pclk2 ? pwm channel 2 clock select 0 = clock b is the clo ck source for channel 2. 1 = clock s1 is the cl ock source for channel 2. pclk1 ? pwm channel 1 clock select 0 = clock a is the clo ck source for channel 1. 1 = clock s0 is the clo ck source for channel 1. pclk0 ? pwm channel 0 clock select 0 = clock a is the clo ck source for channel 0. 1 = clock s0 is the clo ck source for channel 0. if a clock select is changed while a pwm signal is being generated, a truncated or stretched pulse may occur duri ng the transition. the following four bits apply in left-ali gned mode only: table 14-1. clock a and clock b prescaler pcka2 (pckb2) pcka1 (pckb1) pcka0 (pckb0) value of clock a (b) 000 p 001 p 2 010 p 4 011 p 8 100 p 16 101 p 32 110 p 64 111p 128 pwpol ? pwm clock select and polarity $0041 bit 7 6 5 4 3 2 1 bit 0 pclk3 pclk2 pclk1 pclk0 ppol3 ppol2 ppol1 ppol0 reset: 0 0 0 0 0 0 0 0
pulse width modulator pwm register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 231 ppol3 ? pwm channel 3 polarity 0 = channel 3 output is low at the beginning of the period; high when the duty c ount is reached. 1 = channel 3 output is high at the beginning of the period; low when the duty c ount is reached. ppol2 ? pwm channel 2 polarity 0 = channel 2 output is low at the beginning of the period; high when the duty c ount is reached. 1 = channel 2 output is high at the beginning of the period; low when the duty c ount is reached. ppol1 ? pwm channel 1 polarity 0 = channel 1 output is low at the beginning of the period; high when the duty c ount is reached. 1 = channel 1 output is high at the beginning of the period; low when the duty c ount is reached. ppol0 ? pwm channel 0 polarity 0 = channel 0 output is low at the beginning of the period; high when the duty c ount is reached. 1 = channel 0 output is high at the beginning of the period; low when the duty c ount is reached. depending on the polarity bit, the duty register s may contain the count of either the high time or the low time. if the polarity bit is zero and left alignment is selected, the duty registers contai n a count of the low time. if the polarity bit is one, the duty register s contain a count of the high time.
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 232 pulse width modulator motorola setting any of the pwen x bits causes the asso ciated port p line to become an output regardless of the state of the associated data direction register (ddrp) bit. this does not change the state of the data direction bit. when pwenx returns to zero, the data direction bit controls i/o direction. on the front end of the pwm channel, the scaler clock is enabled to the pwm circuit by the pwenx enable bit being high. when all four pwm channels are disabled, the prescaler counter shuts off to save power. there is an edge-synchroni zing gate circuit to guarantee that the clock will only be enabled or disabled at an edge. read and write anytime. pwen3 ? pwm channel 3 enable the pulse modulat ed signal will be av ailable at port p, bit 3 when its clock source begins its next cycle. 0 = channel 3 is disabled. 1 = channel 3 is enabled. pwen2 ? pwm channel 2 enable the pulse modulat ed signal will be av ailable at port p, bit 2 when its clock source begins its next cycle. 0 = channel 2 is disabled. 1 = channel 2 is enabled. pwen1 ? pwm channel 1 enable the pulse modulat ed signal will be av ailable at port p, bit 1 when its clock source begins its next cycle. 0 = channel 1 is disabled. 1 = channel 1 is enabled. pwen0 ? pwm channel 0 enable the pulse modulat ed signal will be av ailable at port p, bit 0 when its clock source begins its next cycle. 0 = channel 0 is disabled. 1 = channel 0 is enabled. pwen ? pwm enable $0042 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 pwen3 pwen2 pwen1 pwen0 reset: 0 0 0 0 0 0 0 0
pulse width modulator pwm register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 233 pwpres is a free-running 7-bit counter. read any time. write only in special mode (smod = 1). read and write anytime. a write will cause the scaler counter pwscnt0 to load the pwscal0 value unless in special mode with discal = 1 in the pwtst register. pwm channels 0 and 1 can select clock s0 (scaled) as its input clock by setting the control bi t pclk0 and pclk1 respec tively. clock s0 is generated by dividing clock a by the va lue in the pwscal0 register + 1 and dividing again by tw o. when pwscal0 = $ff, clock a is divided by 256 then divided by two to generate clock s0. pwscnt0 is a down-counter that, upon reaching $00, loads the value of pwscal0. read any time. pwpres ? pwm prescale counter $0043 bit 7 6 5 4 3 2 1 bit 0 0 bit 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 pwscal0 ? pwm scale register 0 $0044 bit 7 6 5 4 3 2 1 bit 0 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 pwscnt0 ? pwm scale counter 0 value $0045 bit 7 6 5 4 3 2 1 bit 0 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 234 pulse width modulator motorola read and write anytime. a write will cause the scaler counter pwscnt1 to load the pwscal1 value unless in special mode with discal = 1 in the pwtst register. pwm channels 2 and 3 can select clock s1 (scaled) as its input clock by setting the control bi t pclk2 and pclk3 respec tively. clock s1 is generated by dividing clock b by the va lue in the pwscal1 register + 1 and dividing again by tw o. when pwscal1 = $ff, clock b is divided by 256 then divided by two to generate clock s1. pwscnt1 is a down-counter that, upon reaching $00, loads the value of pwscal1. read any time. read and write anytime. a write will cause the pw m counter to reset to $00. in special mode, if di scr = 1, a write does no t reset the pwm counter. pwscal1 ? pwm scale register 1 $0046 bit 7 6 5 4 3 2 1 bit 0 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 pwscnt1 ? pwm scale counter 1 value $0047 bit 7 6 5 4 3 2 1 bit 0 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 pwcntx ? pwm channel counters bit 7 6 5 4 3 2 1 bit 0 pwcnt0 bit 7 6 5 4 3 2 1 bit 0 $0048 pwcnt1 bit 7 6 5 4 3 2 1 bit 0 $0049 pwcnt2 bit 7 6 5 4 3 2 1 bit 0 $004a pwcnt3 bit 7 6 5 4 3 2 1 bit 0 $004b reset: 0 0 0 0 0 0 0 0
pulse width modulator pwm register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 235 the pwm counters are not reset w hen pwm channels ar e disabled. the counters must be reset prior to a new enable. each counter may be read any time without affecting the count or the operation of the corresponding pwm cha nnel. writes to a counter cause the counter to be reset to $00 and fo rce an immediate load of both duty and period registers with new values . to avoid a truncated pwm period, write to a counter while the counter is disabled. in left-aligned output mode, resetting the counter and st arting the waveform output is controlled by a match be tween the period register and the value in the counter. in center-aligned output m ode the counters operate as up/down counters, where a match in period changes the counter direction. the duty register changes the state of the outpu t during the period to determine the duty. when a channel is enabled, the associated pwm counter starts at the count in the pwcntx register usin g the clock select ed for that channel. in special mode, when discp = 1 and configur ed for left-aligned output, a match of period does not rese t the associated pwm counter. read and write anytime. the value in the period register deter mines the period of the associated pwm channel. if written while the c hannel is enabled, t he new value will not take effect until the existing period terminates, forcing the counter to reset. the new period is then latched and is used until a new period value is written. reading this regi ster returns the most recent value written. to start a new period immedi ately, write the new period value pwperx ? pwm channel period registers bit 7 6 5 4 3 2 1 bit 0 pwper0 bit 7 6 5 4 3 2 1 bit 0 $004c pwper1 bit 7 6 5 4 3 2 1 bit 0 $004d pwper2 bit 7 6 5 4 3 2 1 bit 0 $004e pwper3 bit 7 6 5 4 3 2 1 bit 0 $004f reset: 1 1 1 1 1 1 1 1
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 236 pulse width modulator motorola and then write the counter forcing a new period to start with the new period value. period = channel-clock-period (pwper + 1) (centr = 0) period = channel-clock-period (2 pwper) (centr = 1) read and write anytime. the value in each duty regi ster determines the du ty of the associated pwm channel. when the dut y value is equal to t he counter value, the output changes state. if the register is writ ten while the channel is enabled, the new value is held in a bu ffer until the c ounter rolls over or the channel is disabl ed. reading this regist er returns the most recent value written. if the duty register is greater than or equal to the value in the period register, there will be no duty change in state. if t he duty register is set to $ff the output will always be in the state which would normally be the state opposite the ppolx value. left-aligned-output mo de (centr = 0): duty cycle = [(pwdtyx+1) / (pwperx+1)] 100% (ppolx = 1) duty cycle = [(pwperx ? pwdtyx) / (pwperx+1)] 100% (ppolx = 0) center-aligned-output mode (centr = 1): duty cycle = [(pwperx ? pwdtyx) / pwperx] 100% (ppolx = 0) duty cycle = [pwdtyx / pwperx] 100% (ppolx = 1) pwdtyx ? pwm channel duty registers bit 7 6 5 4 3 2 1 bit 0 pwdty0 bit 7 6 5 4 3 2 1 bit 0 $0050 pwdty1 bit 7 6 5 4 3 2 1 bit 0 $0051 pwdty2 bit 7 6 5 4 3 2 1 bit 0 $0052 pwdty3 bit 7 6 5 4 3 2 1 bit 0 $0053 reset: 1 1 1 1 1 1 1 1
pulse width modulator pwm register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 237 read and write anytime. pswai ? pwm halts while in wait mode 0 = allows pwm main clock generat or to continue while in wait mode. 1 = halt pwm main clock generator when the part is in wait mode. centr ? center-aligned output mode to avoid irregularities in the pwm output mode, writ e the centr bit only when pwm channel s are disabled. 0 = pwm channels operate in left-aligned output mode 1 = pwm channels operate in center-aligned output mode rdpp ? reduced drive of port p 0 = all port p output pins have normal drive capability. 1 = all port p output pins have reduced drive capability. pupp ? pull-up port p enable 0 = all port p pins have an ac tive pull-up dev ice disabled. 1 = all port p pins have an active pull- up device enabled. psbck ? pwm stops wh ile in background mode 0 = allows pwm to conti nue while in background mode. 1 = disable pwm input clock when the part is in background mode. pwctl ? pwm control register $0054 bit 7 6 5 4 3 2 1 bit 0 0 0 0 pswai centr rdpp pupp psbck reset: 0 0 0 0 0 0 0 0
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 238 pulse width modulator motorola read anytime but write only in sp ecial mode (smodn = 0). these bits are available only in special m ode and are rese t in normal mode. discr ? disable reset of channel counter on write to channel counter 0 = normal operation. write to pwm channel counter will reset channel counter. 1 = write to pwm channel counter does not reset c hannel counter. discp ? disable co mpare count period 0 = normal operation 1 = in left-aligned output mode, match of period does not reset the associated pwm counter register. discal ? disable load of scale-counters on write to the associated scale-registers 0 = normal operation 1 = write to pwscal0 and pw scal1 does not load scale counters pwtst ? pwm special mode register (?test?) $0055 bit 7 6 5 4 3 2 1 bit 0 discr discp discal 0 0 0 0 0 reset: 0 0 0 0 0 0 0 0
pulse width modulator pwm register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola pulse width modulator 239 portp can be read anytime. pwm functions share port p pins 3 to 0 and take prec edence over the general-purpose port when enabled. when configured as input, a read will return the pi n level. for port bits 7 to 4 it will r ead zero because there are no available external pins. when configured as output, a read will return t he latched output data. for port bits 7 to 4 it will read the last value written. a write will drive associated pins only if configured for output and the corresponding pwm channel is not enabled. after reset, all pins are general -purpose, high-i mpedance inputs. ddrp determines pin direction of po rt p when used for general-purpose i/o. ddrp[7:4] ? this bits served as me mory locations since there are no corresponding port pins. ddrp[3:0] ? data dire ction port p pin 0-3 0 = i/o pin configured as high impedance input 1 = i/o pin configured for output. portp ? port p data register $0056 bit 7 6 5 4 3 2 1 bit 0 pp7 pp6 pp5 pp4 pp3 pp2 pp1 pp0 pwm ? ? ? ? pwm3 pwm2 pwm1 pwm0 reset: ? ? ? ? ? ? ? ? ddrp ? port p data direction register $0057 bit 7 6 5 4 3 2 1 bit 0 ddp7 ddp6 ddp5 ddp4 ddp3 ddp2 ddp1 ddp0 reset: 0 0 0 0 0 0 0 0
pulse width modulator technical data mc68hc912dt128a ? rev 4.0 240 pulse width modulator motorola 14.4 pwm boundary cases the boundary conditions fo r the pwm channel duty registers and the pwm channel period register s cause these results: table 14-2. pwm left-al igned boundary conditions pwdtyx pwperx ppolx output $ff > $00 1 low $ff > $00 0 high pwperx ? 1 high pwperx ? 0 low ? $00 1 high ? $00 0 low table 14-3. pwm center-a ligned boundary conditions pwdtyx pwperx ppolx output $00 > $00 1 low $00 > $00 0 high pwperx ? 1 high pwperx ? 0 low ? $00 1 high ?$000low
mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 241 technical data ? mc68hc912dt128a section 15. enhanced capture timer 15.1 contents 15.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 15.3 enhanced capture timer modes of operation . . . . . . . . . . . . 247 15.4 timer register description s . . . . . . . . . . . . . . . . . . . . . . . . . . 251 15.5 timer and modulus counter operation in different modes . . 275 15.2 introduction the hc12 enhanced captur e timer module has th e features of the hc12 standard timer modu le enhanced by additional features in order to enlarge the fiel d of applications, in parti cular for automotive abs applications. the additional features permi t the operation of this timer module in a mode similar to t he input control timer implemented on mc68hc11nb4. these additional f eatures are: 16-bit buffer register for f our input captur e (ic) channels. four 8-bit pulse accumulators with 8-bit buffer registers associated with the four buffered ic channels. configurable also as two 16-bit pulse accumulators. 16-bit modulus down-counter with 4-bit prescaler. four user selectable delay coun ters for input noise immunity increase. main timer prescaler extended to 7-bit.
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 242 enhanced capture timer motorola this design specificati on describes the standard timer as well as the additional features. the basic timer consists of a 16-bit, software -programmable counter driven by a prescaler. this ti mer can be used for many purposes, including input waveform measur ements while simultaneously generating an output waveform. pu lse widths can vary from microseconds to many seconds. a full access for the counter regi sters or the input capture/output compare registers should take place in one clock cycle. accessing high byte and low byte separately for all of these registers may not yield the same result as acce ssing them in one word.
enhanced capture timer introduction mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 243 figure 15-1. timer bl ock diagram in latch mode 16 bit main timer pt1 comparator tc0h hold register pt0 pt3 pt2 pt4 pt5 pt6 pt7 edg0 edg1 edg2 edg3 mux prescaler m clock 16-bit load register 16-bit modulus 0 reset edg0 edg1 edg2 edg4 edg5 edg3 edg6 edg7 1, 2, ..., 128 1, 4, 8, 16 16-bit free-running latch underflow main timer prescaler tc0 capture/compare register comparator tc1 capture/compare register comparator tc2 capture/compare register comparator tc3 capture/compare register comparator tc4 capture/compare register comparator tc5 capture/compare register comparator tc6 capture/compare register comparator tc7 capture/compare register pin logic pin logic pin logic pin logic pin logic pin logic pin logic pin logic delay counter delay counter delay counter delay counter m clock tc1h hold register tc2h hold register tc3h hold register mux mux mux pa0h hold register pac0 0 reset pa1h hold register pac1 0 reset pa2h hold register pac2 0 reset pa3h hold register pac3 write $0000 to modulus counter iclat, latq, bufen (force latch) latq (mdc latch enable) down counter
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 244 enhanced capture timer motorola figure 15-2. timer block diagram in queue mode 16 bit main timer pt1 comparator tc0h hold register pt0 pt3 pt2 pt4 pt5 pt6 pt7 edg0 edg1 edg2 edg3 mux prescaler m clock 16-bit load register 16-bit modulus 0 reset edg0 edg1 edg2 edg4 edg5 edg3 edg6 edg7 1, 2, ..., 128 1, 4, 8, 16 16-bit free-running latch0 main timer prescaler tc0 capture/compare register comparator tc1 capture/compare register comparator tc2 capture/compare register comparator tc3 capture/compare register comparator tc4 capture/compare register comparator tc5 capture/compare register comparator tc6 capture/compare register comparator tc7 capture/compare register pin logic pin logic pin logic pin logic pin logic pin logic pin logic pin logic delay counter delay counter delay counter delay counter m clock tc1h hold register tc2h hold register tc3h hold register mux mux mux pa0h hold register pac0 0 reset pa1h hold register pac1 0 reset pa2h hold register pac2 0 reset pa3h hold register pac3 latch1 latch3 latch2 latq , bufen (queue mode) read tc3h hold register read tc2h hold register read tc1h hold register read tc0h hold register down counter
enhanced capture timer introduction mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 245 figure 15-3. 8-bit pulse ac cumulators block diagram host cpu data bus pt0 load holding register and reset pulse accumulator 0 0 edg3 edg2 edg1 edg0 edge detector delay counter interrupt interrupt pt1 edge detector delay counter pt2 edge detector delay counter pt3 edge detector delay counter 8-bit pac0 (pacn0) pa0h holding register 0 8-bit pac1 (pacn1) pa1h holding register 0 8-bit pac2 (pacn2) pa2h holding register 0 8-bit pac3 (pacn3) pa3h holding register
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 246 enhanced capture timer motorola figure 15-4. 16-bit pulse accumulators block diagram edge detector 8-bit pac2 intermodule bus 8-bit pac3 pt7 pt0 m clock divide by 64 clock select clk0 clk1 4:1 mux to tcnt counter paclk paclk / 256 paclk / 65536 prescaled mclk (tmsk2 bits pr2-pr0) interrupt mux (pamod) edge detector paca delay counter (pacn3) (pacn2) 8-bit pac0 8-bit pac1 interrupt pacb (pacn1) (pacn0)
enhanced capture timer enhanced capture timer modes of operation mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 247 figure 15-5. block diagram fo r port7 with output compar e / pulse accumulator a figure 15-6. c3f-c0f in terrupt flag setting 15.3 enhanced capture timer modes of operation the enhanced capture timer has 8 i nput capture, output compare (ic/oc) channels same as on the hc12 standard timer (timer channels tc0 to tc7). when channels are select ed as input capture by selecting the iosx bit in tios register, they are calle d input capture (ic) channels. pulse accumulator a pad (om7=1 or ol7=1) or (oc7m7 = 1) oc7 ptn edge detector delay counter 16-bit main timer tcn input capture reg. tcnh i.c. holding reg. bufen ? latq ? tfmod set cnf interrupt
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 248 enhanced capture timer motorola four ic channels are the same as on the standard timer with one capture register which memorizes the timer value captured by an action on the associated input pin. four other ic channels, in addition to the capture register, have also one buffer called holdin g register. this per mits to memorize two different timer values without gener ation of any interrupt. four 8-bit pulse accumulato rs are associated with the four buffered ic channels. each pulse accumulator has a holdin g register to memorize their value by an acti on on its external input. each pair of pulse accumulators can be used as a 16-bit pulse accumulator. the 16-bit modulus down-counter can control the transfer of the ic registers contents and the pulse accumu lators to the respective holding registers for a given period, every time th e count reaches zero. the modulus down-counter can also be used as a stand-alone time base with periodic inte rrupt capability. 15.3.1 ic channels the ic channels are com posed of four standard ic registers and four buffered ic channels. an ic register is empty when it has been read or latched into the holding register. a holding register is empty when it has been read. 15.3.1.1 non-bu ffered ic channels the main timer value is memorized in th e ic register by a valid input pin transition. if the corr esponding novwx bit of the icovw register is cleared, with a new occurrence of a c apture, the contents of ic register are overwritten by the new value. if the corresponding novw x bit of the icovw r egister is set, the capture register cannot be written unless it is empty. this will prevent the captured value to be overwr itten until it is read.
enhanced capture timer enhanced capture timer modes of operation mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 249 15.3.1.2 buffered ic channels there are two modes of operations for the buffered ic channels. ic latch mode: when enabled (latq=1), the main timer value is memorized in the ic register by a valid input pin transition. the value of the buffered ic register is latched to its holding register by the modulus counter for a given period when the count reaches zero, by a write $0000 to the modulus counter or by a write to iclat in the mcctl register. if the corresponding novwx bit of the icovw regist er is cleared, with a new occurrence of a capture, the cont ents of ic register are overwritten by the new value. in case of latching, the contents of its holding register are overwritten. if the corresponding novwx bit of the icovw register is set, the capture register or its holding r egister cannot be written by an event unless they are empty (see ic channels ). this will prev ent the captured value to be overwritten until it is read or latched in the holding register. ic queue mode: when enabled (latq=0), the main timer value is memorized in the ic register by a valid input pin transition. if the corresponding novw x bit of the icovw regist er is cleared, with a new occurrence of a captur e, the value of the ic r egister will be transferred to its holding register and the ic register memori zes the new timer value. if the corresponding novwx bit of the icovw register is set, the capture register or its holding r egister cannot be written by an event unless they are empty (see ic channels ). in queue mode, read s of holding regi ster will latch the corresponding pulse accumulator value to its holding register.
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 250 enhanced capture timer motorola 15.3.2 pulse accumulators there are four 8-bit pulse accumulators with four 8-bi t holding registers associated with the four ic buffe red channels. a pul se accumulator counts the number of active edge s at the input of its channel. the user can prevent 8-bit pulse accu mulators counting further than $ff by pacmx control bit in icsys ($ab). in this case a va lue of $ff means that 255 counts or more have occurred. each pair of pulse accumulators can be used as a 16-bit pulse accumulator. there are two modes of operation for the pulse accumulators. 15.3.2.1 pulse accumulator latch mode the value of the pulse accumulator is transferred to its holding register when the modulus down- counter reaches zero, a write $0000 to the modulus counter or when the force latch control bit iclat is written. at the same time the pulse accumulator is cleared. 15.3.2.2 pulse accumulator queue mode when queue mode is enabled, reads of an input capt ure holding register will transfer the contents of the a ssociated pulse accumulator to its holding register. at the same time the pulse accumulator is cleared. 15.3.3 modulus down-counter the modulus down-counter can be used as a ti me base to generate a periodic interrupt. it can also be used to latch the values of the ic registers and the pulse accumulato rs to their holding registers. the action of latching ca n be programmed to be periodic or only once.
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 251 15.4 timer register descriptions input/output pins default to general- purpose i/o lines un til an internal function which uses that pin is specifically ena bled. the timer overrides the state of the ddr to force the i/o state of each associated port line when an output compare using a port line is enabled. in these cases the data direction bits will hav e no affect on these lines. when a pin is assigned to output an on -chip peripheral f unction, writing to this portt bit does not affect the pin but the data is stored in an internal latch such that if the pi n becomes available for general-purpose output the driven level will be the last value writ ten to the portt bit. read or write anytime. ios[7:0] ? input capt ure or output compar e channel configuration 0 = the corresponding channel acts as an input capture 1 = the corresponding channel acts as an output compare. read anytime but will al ways return $00 (1 stat e is transient). write anytime. tios ? timer input capture/output compare select $0080 bit 7 6 5 4 3 2 1 bit 0 ios7 ios6 ios5 ios4 ios3 ios2 ios1 ios0 reset: 0 0 0 0 0 0 0 0 cforc ? timer compare force register $0081 bit 7 6 5 4 3 2 1 bit 0 foc7 foc6 foc5 foc4 foc3 foc2 foc1 foc0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 252 enhanced capture timer motorola foc[7:0] ? force output co mpare action for channel 7-0 a write to this register with the corresponding data bit(s) set causes the action which is programmed for output compare ?n? to occur immediately. the action taken is the same as if a successful comparison had just taken place with the tcn register except the interrupt flag d oes not get set. read or write anytime. the bits of oc7m correspond bit-for- bit with the bits of timer port (portt). setting the oc 7mn will set the corr esponding port to be an output port regardless of the st ate of the ddrt n bit when the corresponding tiosn bit is set to be an output compare. this does not change the state of the ddr t bits. at successful oc7, for eachbit that is set in oc7m, the corresponding data bit in oc7d is stored to the corresponding bit of the timer port. note: oc7m has priority over output action on timer port enabled by omn and oln bits in tct l1 and tctl2. if an oc7m bit is set, it prevents the action of corresponding om and ol bits on the se lected timer port. read or write anytime. the bits of oc7d corres pond bit-for-bit with t he bits of timer port (portt). when a successful oc7 com pare occurs, for each bit that is set in oc7m, the corresponding data bit in oc7d is stored to the corresponding bit of the timer port. oc7m ? output compare 7 mask register $0082 bit 7 6 5 4 3 2 1 bit 0 oc7m7 oc7m6 oc7m5 oc7m4 oc7m3 oc7m2 oc7m1 oc7m0 reset: 0 0 0 0 0 0 0 0 oc7d ? output compare 7 data register $0083 bit 7 6 5 4 3 2 1 bit 0 oc7d7 oc7d6 oc7d5 oc7d4 oc7d3 oc7d2 oc7d1 oc7d0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 253 when the oc7mn bit is set, a succe ssful oc7 action will override a successful oc[6:0] compare action durin g the same cycle; therefore, the ocn action taken will depend on the corresponding oc7d bit. the 16-bit main timer is an up counter. a full access for the counter register should take place in one clock cycle. a separate read/write for high byte and lo w byte will give a different result than accessing them as a word. read anytime. write has no meaning or effect in the normal mode; only writable in special modes (smodn = 0). the period of the first count after a write to the tcnt registers may be a different size because the write is not synchronized wi th the prescaler clock. read or write anytime. ten ? timer enable 0 = disables the main timer, incl uding the counter. can be used for reducing power consumption. 1 = allows the timer to function normally. if for any reason the timer is not active, there is no 64 clock for the pulse accumulator since the e 64 is generated by the timer prescaler. tcnt ? timer count register $0084?$0085 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 tscr ? timer system control register $0086 bit 7 6 5 4 3 2 1 bit 0 ten tswai tsbck tffca reset: 0 0 0 0 0 0 0 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 254 enhanced capture timer motorola tswai ? timer module stops while in wait 0 = allows the timer module to continue running during wait. 1 = disables the timer module when the mcu is in the wait mode. timer interrupts cannot be used to get the mcu out of wait. tswai also affects pulse accumu lators and modulus down counters. tsbck ? timer and modulus counte r stop while in background mode 0 = allows the timer and modulus c ounter to continue running while in background mode. 1 = disables the timer and modulus counter whenever the mcu is in background mode. this is useful for emulation. tbsck does not stop th e pulse accumulator. tffca ? timer fast flag clear all 0 = allows the timer flag clea ring to function normally. 1 = for tflg1($8e), a read from an i nput capture or a write to the output compare channel ($90?$9f) causes the corresponding channel flag, cnf, to be clear ed. for tflg2 ($8f), any access to the tcnt regist er ($84, $85) clear s the tof flag. any access to the pacn3 and pacn2 registers ($a2, $a3) clears the paovf and paif flags in the paflg register ($a1). any access to the pacn1 and pacn0 registers ($a4, $a5) clears the pbovf flag in the pbflg register ($b1). any access to the mccnt register ($b6, $b7) clears the mczf flag in the mcflg register ($a7). this ha s the advantage of eliminating software overhead in a separate clear sequence. extra care is required to avoid accidental flag clearing due to unintended accesses.
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 255 read or write anytime. omn ? output mode oln ? output level these eight pairs of control bits are encoded to spec ify the output action to be taken as a result of a successf ul ocn compare. when either omn or oln is one, the pin associated with ocn becomes an output tied to ocn regardless of t he state of the associated ddrt bit. note: to enable output action by omn and oln bits on timer port, the corresponding bit in oc 7m should be cleared. to operate the 16-bit pulse accumu lators a and b (paca and pacb) independently of input c apture or output compar e 7 and 0 respectively the user must set the corresponding bits iosn = 1, omn = 0 and oln = 0. oc7m7 or oc7m0 in the oc7m register must also be cleared. tqcr ? reserved $0087 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 tctl1 ? timer control register 1 $0088 bit 7 6 5 4 3 2 1 bit 0 om7 ol7 om6 ol6 om5 ol5 om4 ol4 reset: 0 0 0 0 0 0 0 0 tctl2 ? timer control register 2 $0089 bit 7 6 5 4 3 2 1 bit 0 om3 ol3 om2 ol2 om1 ol1 om0 ol0 reset: 0 0 0 0 0 0 0 0 table 15-1. compare result output action omn oln action 0 0 timer disconnected from output pin logic 0 1 toggle ocn output line 1 0 clear ocn output line to zero 1 1 set ocn output line to one
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 256 enhanced capture timer motorola read or write anytime. edgnb, edgna ? input capture edge control these eight pairs of control bits configure the i nput capture edge detector circuits. read or write anytime. the bits in tmsk1 correspond bit-for-bit with the bits in the tflg1 status register. if cleared, the corresponding flag is di sabled from causing a hardware interrupt. if set, the co rresponding flag is enabled to cause a hardware interrupt. read or write anytime. c7i?c0i ? input captur e/output compare ?x ? interrupt enable. tctl3 ? timer control register 3 $008a bit 7 6 5 4 3 2 1 bit 0 edg7b edg7a edg6b edg6a edg5b edg5a edg4b edg4a reset: 0 0 0 0 0 0 0 0 tctl4 ? timer control register 4 $008b bit 7 6 5 4 3 2 1 bit 0 edg3b edg3a edg2b edg2a edg1b edg1a edg0b edg0a reset: 0 0 0 0 0 0 0 0 table 15-2. edge detector circuit configuration edgnb edgna configuration 0 0 capture disabled 0 1 capture on rising edges only 1 0 capture on falling edges only 1 1 capture on any edge (rising or falling) tmsk1 ? timer interrupt mask 1 $008c bit 7 6 5 4 3 2 1 bit 0 c7i c6i c5i c4i c3i c2i c1i c0i reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 257 read or write anytime. toi ? timer overflow interrupt enable 0 = interrupt inhibited 1 = hardware interrupt re quested when tof flag set pupt ? timer port pu ll-up resistor enable this enable bit controls pull-up re sistors on the time r port pins when the pins are conf igured as inputs. 0 = disable pull-up resistor function 1 = enable pull-up resistor function rdpt ? timer port drive reduction this bit reduces the effective output driver size which can reduce power supply current and gener ated noise depending upon pin loading. 0 = normal output drive capability 1 = enable output drive reduction function tcre ? timer count er reset enable this bit allows the timer counter to be reset by a successful output compare 7 event. this mode of operat ion is similar to an up-counting modulus counter. 0 = counter reset inhibi ted and counter free runs 1 = counter reset by a successful output compare 7 if tc7 = $0000 and tcre = 1, tcnt will stay at $0000 continuously. if tc7 = $ffff an d tcre = 1, tof will never be set when tcnt is reset from $ffff to $0000. pr2, pr1, pr0 ? timer prescaler select these three bits specify the number of 2 stages that are to be inserted between the module clock and the main timer counter. tmsk2 ? timer interrupt mask 2 $008d bit 7 6 5 4 3 2 1 bit 0 toi 0 pupt rdpt tcre pr2 pr1 pr0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 258 enhanced capture timer motorola the newly selected prescale factor wi ll not take effect until the next synchronized edge where all presca le counter stages equal zero. tflg1 indicates when inte rrupt conditions have oc curred. to clear a bit in the flag register, write a one to the bit. use of the tfmod bit in the icsys r egister ($ab) in conjunction with the use of the icovw register ($aa) allo ws a timer interrupt to be generated after capturing two values in the c apture and holding r egisters instead of generating an interrupt for every capture. read anytime. write used in the cl earing mechanism (set bits cause corresponding bits to be cleared). writi ng a zero will not affect current status of the bit. when tffca bit in tscr r egister is set, a read from an input capture or a write into an output compare channel ($90?$9f) will cause the corresponding channel flag cnf to be cleared. c7f?c0f ? input capture/outp ut compare channel ?n? flag. table 15-3. pres caler selection pr2 pr1 pr0 prescale factor 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 tflg1 ? main timer interrupt flag 1 $008e bit 7 6 5 4 3 2 1 bit 0 c7f c6f c5f c4f c3f c2f c1f c0f reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 259 tflg2 indicates when inte rrupt conditions have oc curred. to clear a bit in the flag register , set the bit to one. read anytime. write used in clea ring mechanism (set bits cause corresponding bits to be cleared). any access to tcnt will clear tflg2 register if the tffca bit in tscr register is set. tof ? timer overflow flag set when 16-bit free-running timer overflows from $ffff to $0000. this bit is cleared automa tically by a write to the tflg2 register with bit 7 set. (see also tc re control bit explanation.) tflg2 ? main timer interrupt flag 2 $008f bit 7 6 5 4 3 2 1 bit 0 tof 0 0 0 0 0 0 0 reset: 0 0 0 0 0 0 0 0 tc0 ? timer input capture/output compare register 0 $0090?$0091 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc1 ? timer input capture/output compare register 1 $0092?$0093 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc2 ? timer input capture/output compare register 2 $0094?$0095 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc3 ? timer input capture/output compare register 3 $0096?$0097 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 260 enhanced capture timer motorola depending on the tios bit fo r the correspondi ng channel, these registers are used to latch the va lue of the free-ru nning counter when a defined transition is sensed by the corres ponding input capture edge detector or to trigger an output action fo r output compare. read anytime. write anyti me for output compare function. writes to these registers have no me aning or effect during i nput capture. all timer input capture/output compare registers are reset to $0000. 16-bit pulse accumulator a (paca) is formed by cascading the 8-bit pulse accumulators pac3 and pac2. when paen is set, the p aca is enabled. the paca shares the input pin with ic7. read: any time write: any time tc4 ? timer input capture/output compare register 4 $0098?$0099 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc5 ? timer input capture/output compare register 5 $009a?$009b bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc6 ? timer input capture/output compare register 6 $009c?$009d bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc7 ? timer input capture/output compare register 7 $009e?$009f bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 pactl ? 16-bit pulse accumulator a control register $00a0 bit 7 6 5 4 3 2 1 bit 0 0 paen pamod pedge clk1 clk0 paovi pai reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 261 paen ? pulse accumulator a system enable 0 = 16-bit pulse accumulator a s ystem disabled. 8-bit pac3 and pac2 can be enabled when their re lated enable bits in icpacr ($a8) are set. pulse accumulator input edge flag (paif) function is disabled. 1 = pulse accumulator a system enabled. the tw o 8-bit pulse accumulators pac3 and pac2 ar e cascaded to form the paca 16-bit pulse accumulator. when paca in enabled, the pacn3 and pacn2 registers c ontents are respectively the high and low byte of the paca. pa3en and pa2en contro l bits in icpacr ($a8) have no effect. pulse accumulator input edge fl ag (paif) functi on is enabled. paen is independent from ten. with timer disabled, the pulse accumulator can still function unless pulse a ccumulator is disabled. pamod ? pulse accumulator mode 0 = event counter mode 1 = gated time accumulation mode pedge ? pulse accumulator edge control for pamod bit = 0 (event counter mode). 0 = falling edges on pt7 pin caus e the count to be incremented 1 = rising edges on pt7 pin cause the count to be incremented for pamod bit = 1 (gated ti me accumulation mode). 0 = pt7 input pin hi gh enables m divided by 64 clock to pulse accumulator and the trailing fall ing edge on pt7 sets the paif flag. 1 = pt7 input pin low enables m divided by 64 clock to pulse accumulator and the trailing ri sing edge on pt7 sets the paif flag. if the timer is not active (ten = 0 in tscr), there is no divide-by-64 since the e 64 clock is generated by the timer prescaler. pamod pedge pin action 0 0 falling edge 0 1 rising edge 1 0 div. by 64 clock enabled with pin high level 1 1 div. by 64 clock enabled with pin low level
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 262 enhanced capture timer motorola clk1, clk0 ? clock select bits if the pulse accumulator is disabl ed (paen = 0), the prescaler clock from the timer is alwa ys used as an input clo ck to the timer counter. the change from one selected clock to the other happens immediately after thes e bits are written. paovi ? pulse accumulator a overflow interrupt enable 0 = interrupt inhibited 1 = interrupt requeste d if paovf is set pai ? pulse accumulator i nput interrupt enable 0 = interrupt inhibited 1 = interrupt reques ted if paif is set read or write anytime. w hen the tffca bit in the t scr register is set, any access to the pacnt r egister will clear all the flags in the paflg register. paovf ? pulse accumulator a overflow flag set when the 16-bit pulse accumu lator a overflows from $ffff to $0000,or when 8-bit pulse accumulato r 3 (pac3) overflows from $ff to $00. this bit is cleared automat ically by a write to the paflg register with bit 1 set. clk1 clk0 clock source 0 0 use timer prescaler clock as timer counter clock 0 1 use paclk as input to timer counter clock 1 0 use paclk/256 as timer counter clock frequency 11 use paclk/65536 as timer counter clock frequency paflg ? pulse accumulator a flag register $00a1 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 0 paovf paif reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 263 paif ? pulse accumulator input edge flag set when the selected edge is detected at the pt7 input pin. in event mode the event edge tri ggers paif and in gated time accumulation mode the trailing edge of the gate si gnal at the pt7 i nput pin triggers paif. this bit is cleared by a write to the paflg regi ster with bit 0 set. any access to the pacn3, pacn2 regi sters will clear al l the flags in this register when tffca bit in register tscr($86) is set. read or write any time. the two 8-bit pulse accumulators p ac3 and pac2 are cascaded to form the paca 16-bit pulse accumulator. when paca in enabled (paen=1 in pactl, $a0) the pacn3 and pacn2 registers contents are respectively the high and low byte of the paca. when pacn3 overflows from $ff to $00, the interrupt flag paovf in paflg ($a1) is set. full count register access should take place in one clock cycle. a separate read/write for high byte and low byte will gi ve a different result than accessing them as a word. read or write any time. pacn3, pacn2 ? pulse accumulators count registers $00a2, $00a3 bit 7 6 5 4 3 2 1 bit 0 $00a2 bit 7 6 5 4 3 2 1 bit 0 pacn3 (hi) $00a3 bit 7 6 5 4 3 2 1 bit 0 pacn2 (lo) reset: 0 0 0 0 0 0 0 0 pacn1, pacn0 ? pulse accumulato rs count registers $00a4, $00a5 bit 7 6 5 4 3 2 1 bit 0 $00a4 bit 7 6 5 4 3 2 1 bit 0 pacn1 (hi) $00a5 bit 7 6 5 4 3 2 1 bit 0 pacn0 (lo) reset: 0 0 0 0 0 0 0 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 264 enhanced capture timer motorola the two 8-bit pulse accumulators p ac1 and pac0 are cascaded to form the pacb 16-bit pulse accumulator. when pacb in enabled, (pben=1 in pbctl, $b0) the pacn1 and pacn0 registers contents are respectively the high and low byte of the pacb. when pacn1 overflows from $ff to $00, the interrupt flag pbovf in pbflg ($b1) is set. full count register access should take place in one clock cycle. a separate read/write for high byte and low byte will gi ve a different result than accessing them as a word. read or write any time. mczi ? modulus counter un derflow interrupt enable 0 = modulus counter interrupt is disabled. 1 = modulus counter interrupt is enabled. modmc ? modulus mode enable 0 = the counter counts once from the value wr itten to it and will stop at $0000. 1 = modulus mode is enabled. when the c ounter reaches $0000, the counter is loaded with the latest va lue written to the modulus count register. note: for proper operation, t he mcen bit should be cl eared before modifying the modmc bit in order to rese t the modulus c ounter to $ff. rdmcl ? read modulus down-counter load 0 = reads of the modulus count register will return the present value of the c ount register. 1 = reads of the modulus count regi ster will return the contents of the load register. mcctl ? 16-bit modulus down-counter control register $00a6 bit 7 6 5 4 3 2 1 bit 0 mczi modmc rdmcl iclat flmc mcen mcpr1 mcpr0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 265 iclat ? input capture for ce latch action when input capture latch mode is enabled (latq and bufen bit in icsys ($ab) are set), a write one to this bit im mediately forces the contents of the inpu t capture registers tc0 to tc3 and their corresponding 8-bit pulse accumu lators to be la tched into the associated holding registers. the pulse accumulators will be automatically cleared when the latch action occurs. writing zero to this bit has no effec t. read of this bit will return always zero. flmc ? force load register into t he modulus counter count register this bit is active on ly when the modulus down-counter is enabled (mcen=1). a write one into this bit loads the load regist er into the modulus counter count register. this al so resets the modulus counter prescaler. write zero to this bit has no effect. when modmc=0, counter starts counting and stops at $0000. read of this bit will return always zero. mcen ? modulus down -counter enable 0 = modulus count er disabled. 1 = modulus counter is enabled. when mcen=0, the counter is preset to $ffff. this will prevent an early interrupt flag when the m odulus down-counter is enabled. mcpr1, mcpr0 ? modulus counter prescaler select these two bits specify the division rate of the modulus counter prescaler. the newly selected prescaler division ra te will not be effective until a load of the load regi ster into the modulus counter count register occurs. mcpr1 mcpr0 prescaler division rate 00 1 01 4 10 8 11 16
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 266 enhanced capture timer motorola read: any time write: only for clearing bit 7 mczf ? modulus counter underflow interrupt flag the flag is set when the modu lus down-counter reaches $0000. a write one to this bi t clears the flag. writ e zero has no effect. any access to the mccnt register will clear t he mczf flag in this register when tffca bit in register tscr($86) is set. polf3 ? polf0 ? first input capture polarity status this are read only bits. write to these bits has no effect. each status bit gives the polarity of the first edge which has caused an input capture to occur af ter capture latch has been read. each polfx corresponds to a timer portx input. 0 = the first input capture has been caused by a falling edge. 1 = the first input capture has been caused by a rising edge. the 8-bit pulse accumulators pac 3 and pac2 can be enabled only if paen in patcl ($a0) is cleared. if paen is set, pa3en and pa2en have no effect. the 8-bit pulse accumulators pac 1 and pac0 can be enabled only if pben in pbtcl ($b0) is cleared. if pben is set, pa1en and pa0en have no effect. read or write any time. mcflg ? 16-bit modulus down-counter flag register $00a7 bit 7 6 5 4 3 2 1 bit 0 mczf 0 0 0 polf3 polf2 polf1 polf0 reset: 0 0 0 0 0 0 0 0 icpar ? input control pulse accumulators register $00a8 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 pa3en pa2en pa1en pa0en reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 267 paxen ? 8-bit pulse ac cumulator ?x? enable 0 = 8-bit pulse accumu lator is disabled. 1 = 8-bit pulse accu mulator is enabled. read or write any time. if enabled, after detection of a vali d edge on input captur e pin, the delay counter counts the pre-selected nu mber of m clock (module clock) cycles, then it will generate a pulse on its output. the pulse is generated only if the level of input signal, after the preset delay, is the opposite of the level before the trans ition.this will avoid re action to narrow input pulses. after counting, the counter wi ll be cleared automatically. delay between two active edges of the input signal period should be longer than the sele cted counter delay. dlyx ? delay counter select read or write any time. dlyct ? delay counter control register $00a9 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 0 dly1 dly0 reset: 0 0 0 0 0 0 0 0 dly1 dly0 delay 0 0 disabled (bypassed) 0 1 256m clock cycles 1 0 512m clock cycles 1 1 1024 m clock cycles icovw ? input control overwrite register $00aa bit 7 6 5 4 3 2 1 bit 0 novw7 novw6 novw5 novw4 novw3 novw2 novw1 novw0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 268 enhanced capture timer motorola an ic register is empty when it has been read or latche d into the holding register. a holding register is em pty when it has been read. novwx ? no input capture overwrite 0 = the contents of the related capt ure register or holding register can be overwritten when a new in put capture or latch occurs. 1 = the related capture register or holding regi ster cannot be written by an event unless they are empty (see ic channels ). this will prevent the capt ured value to be over written until it is read or latched in th e holding register. read: any time write: may be written once (smodn= 1). writes are always permitted when smodn=0. shxy ? share input action of input capt ure channels x and y 0 = normal operation 1 = the channel input ?x? causes t he same action on the channel ?y?. the port pin ?x? and the corresponding edge detector is used to be active on the channel ?y?. tfmod ? timer flag-setting mode use of the tfmod bit in the icsys register ($ab) in conjunction with the use of the ic ovw register ($aa) allows a timer interrupt to be generated after capturi ng two values in th e capture and holding registers instead of gen erating an interrupt for every capture. by setting tfmod in queue mode, wh en novw bit is set and the corresponding capture an d holding registers ar e emptied, an input capture event will first update the related input capture register with icsys ? input control system control register $00ab bit 7 6 5 4 3 2 1 bit 0 sh37 sh26 sh15 sh04 tfmod pacmx bufen latq reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 269 the main timer contents. at the next event the tcn data is transferred to the tcnh register , the tcn is updated and th e cnf interrupt flag is set. see figure 15-6 . in all other inpu t capture cases the interrupt flag is set by a valid external event on ptn. 0 = the timer flags c3f?c 0f in tflg1 ($8e) are set when a valid input capture transition on the corresponding port pin occurs. 1 = if in queue mode (bufen=1 and latq=0), the timer flags c3f?c0f in tflg1 ($8e) are se t only when a latch on the corresponding holding register occurs. if the queue mode is not engaged, the timer flags c3f?c0f are set the same way as for tfmod=0. pacmx ? 8-bit pulse accu mulators maximum count 0 = normal operation. when the 8-bit pulse accumulator has reached the value $ff, with t he next active edge, it will be incremented to $00. 1 = when the 8-bit pulse accumula tor has reached the value $ff, it will not be incremented fu rther. the value $f f indicates a count of 255 or more. bufen ? ic buffer enable 0 = input capture and pulse accu mulator holding registers are disabled. 1 = input capture and pulse accu mulator holding registers are enabled. the latching mode is defined by latq control bit. write one into iclat bit in mc ctl ($a6), when latq is set will produce latching of input capture and pulse accumulators registers into thei r holding registers. latq ? input control lat ch or queue mode enable the bufen control bit should be set in order to enable the ic and pulse accumulators holding regi sters. otherwise latq latching modes are disabled. write one into iclat bit in mcc tl ($a6), when latq and bufen are set will produce latching of i nput capture and pulse accumulators registers into thei r holding registers.
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 270 enhanced capture timer motorola 0 = queue mode of input capture is enabled. the main timer value is memorized in the ic register by a valid input pin transition. with a new occurrence of a capture, the val ue of the ic register will be transferred to its holding register and the ic register memorizes the new timer value. 1 = latch mode is enabled. la tching function occurs when modulus down-counter r eaches zero or a zero is written into the count register mccnt (see buffered ic channels ). with a latching event the content s of ic regist ers and 8-bit pulse accumulators are transfe rred to their holding registers. 8-bit pulse accumula tors are cleared. read: any time write: only in spec ial mode (smod = 1). tcbyp ? main timer divider chain bypass 0 = normal operation 1 = for testing only. the 16-bit free- running timer count er is divided into two 8-bit halves and the prescaler is bypassed. the clock drives both halves directly. when the high byte of timer c ounter tcnt ($84) overflows from $ff to $00, the tof flag in tflg 2 ($8f) will be set. read: any time (inputs return pin leve l; outputs return data register contents) timtst ? timer test register $00ad bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 0 tcbyp 0 reset: 0 0 0 0 0 0 0 0 portt ? timer port data register $00ae bit 7 6 5 4 3 2 1 bit 0 port pt7 pt6 pt5 pt4 pt3 pt2 pt1 pt0 timer i/oc7 i/oc6 i/oc5 i/oc4 i/oc3 i/oc2 i/oc1 i/oc0 reset: - - - - - - - -
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 271 write: data stored in an in ternal latch (drives pins only if configured for output) since the output compar e 7 shares the pin wi th pulse accumulator input, the only way for pulse ac cumulator to receive an independent input from output compare 7 is se tting both om7 & ol7 to be zero, and also oc7m7 in oc7m register to be zero. oc7 is still able to reset the counter if enabled while pt7 is used as input to pulse accumulator. portt can be read anytime. when conf igured as an i nput, a read will return the pin level. w hen configured as an output, a read will return the latched output data. note: writes do not change pin state when the pin is configured for timer output. the minimum pulse width for pulse accumulator input should always be greater than the width of two modul e clocks due to input synchronizer circuitry. the minimum pulse width for the input capture should always be greater than the width of tw o module clocks due to input synchronizer circuitry. read or write any time. 0 = configures the corres ponding i/o pin for input only 1 = configures the corr esponding i/o pin for output. the timer forces the i/o state to be an output for each timer port line associated with an enabled output comp are. in these cases the data direction bits will not be changed, but have no effect on the direction of these pins. the ddrt will revert to controll ing the i/o direction of a pin when the associated timer ou tput compare is disabled. input captures do not overri de the ddrt settings. ddrt ? data direction register for timer port $00af bit 7 6 5 4 3 2 1 bit 0 ddt7 ddt6 ddt5 ddt4 ddt3 ddt2 ddt1 ddt0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 272 enhanced capture timer motorola read or write any time. 16-bit pulse accumulator b (pacb) is formed by cascading the 8-bit pulse accumulators pac1 and pac0. when pben is set, the p acb is enabled. the pacb shares the input pin with ic0. pben ? pulse accumulator b system enable 0 = 16-bit pulse accumulator syst em disabled. 8-bit pac1 and pac0 can be enabled when t heir related e nable bits in icpacr ($a8) are set. 1 = pulse accumulator b system enabled. the tw o 8-bit pulse accumulators pac1 and pac0 are cascaded to form the pacb 16-bit pulse accumulator. when pacb in enabled, the pacn1 and pacn0 registers cont ents are respectively the high and low by te of the pacb. pa1en and pa0en control bits in icpacr ($a8 ) have no effect. pben is independent from ten. with timer disabled, the pulse accumulator can still function unless pulse a ccumulator is disabled. pbovi ? pulse accumulator b overflow interrupt enable 0 = interrupt inhibited 1 = interrupt requeste d if pbovf is set read or write any time. pbctl ? 16-bit pulse accumulator b control register $00b0 bit 7 6 5 4 3 2 1 bit 0 0 pben 0 0 0 0 pbovi 0 reset: 0 0 0 0 0 0 0 0 pbflg ? pulse accumulator b flag register $00b1 bit 7 6 5 4 3 2 1 bit 0 0 0 0 0 0 0 pbovf 0 reset: 0 0 0 0 0 0 0 0
enhanced capture timer timer register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 273 pbovf ? pulse accumulator b overflow flag this bit is set when t he 16-bit pulse accumula tor b overflows from $ffff to $0000, or when 8-bit puls e accumulator 1 (pac1) overflows from $ff to $00. this bit is cleared by a write to the pbflg regi ster with bit 1 set. any access to the pacn1 and pacn0 registers will cl ear the pbovf flag in this register when tffca bit in regi ster tscr($86) is set. read: any time write: has no effect. these registers are used to latch t he value of the co rresponding pulse accumulator when the related bits in register icpar ($a8) are enabled (see pulse accumulators ). read or write any time. a full access for the counter register should take place in one clock cycle. a separate read/write for high byte and low byte will give differ ent result than accessing them as a word. if the rdmcl bit in mc ctl register is clear ed, reads of the mccnt register will return the present value of the count regist er. if the rdmcl pa3h?pa0h ? 8-bit pulse accumulators holding registers $00b2?$00b5 bit 7 6 5 4 3 2 1 bit 0 $00b2 bit 7 6 5 4 3 2 1 bit 0 pa3h $00b3 bit 7 6 5 4 3 2 1 bit 0 pa2h $00b4 bit 7 6 5 4 3 2 1 bit 0 pa1h $00b5 bit 7 6 5 4 3 2 1 bit 0 pa0h reset: 0 0 0 0 0 0 0 0 mccnt ? modulus down-counter count register $00b6, $00b7 bit 7 6 5 4 3 2 1 bit 0 $00b6 bit 15 14 13 12 11 10 9 bit 8 mccnth $00b7 bit 7 6 5 4 3 2 1 bit 0 mccntl reset: 1 1 1 1 1 1 1 1
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 274 enhanced capture timer motorola bit is set, reads of the mccnt will return t he contents of the load register. if a $0000 is written into mccnt an d modulus counter while latq and bufen in icsys ($ab) r egister are set, the input capture and pulse accumulator registers will be latched. with a $0000 write to the mccnt, the modulus counte r will stay at zero and does not set the mczf fl ag in mcflg register. if modulus mode is enab led (modmc=1), a write to this address will update the load register with the value written to it . the count regi ster will not be updated wi th the new value until t he next counter underflow. the flmc bit in mcctl ($ a6) can be used to immediately update the count register with the new val ue if an immediat e load is desired. if modulus mode is not enabled (modmc =0), a write to this address will clear the prescaler and will immediatel y update the counter register with the value writt en to it and down-counts once to $0000. tc0h ? timer input capture holding register 0 $00b8?$00b9 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc1h ? timer input capture holding register 1 $00ba?$00bb bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc2h ? timer input capture holding register 2 $00bc?$00bd bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0 tc3h ? timer input capture holding register 3 $00be?$00bf bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 bit 7 6 5 4 3 2 1 bit 0
enhanced capture timer timer and modulus counter operation in different modes mc68hc912dt128a ? rev 4.0 technical data motorola enhanced capture timer 275 read: any time write: has no effect. these registers are used to latch the value of the input capture registers tc0 ? tc3. the corresponding iosx bits in tios ($80) should be cleared (see ic channels ). 15.5 timer and modulus counte r operation in different modes stop: timer and modulus coun ter are off since clocks are stopped. bgdm: timer and modulus coun ter keep on running, unless tsbck (reg$86, bit5 ) is set to one. wait: counters keep on running, unless tswai in tscr ($86) is set to one. normal: timer and modulus counter keep on running, unless ten in tscr($86) respectively mcen in mcctl ($a6) are cleared. ten=0: all 16-bit timer operati ons are stopped, can only access the registers. mcen=0: modulus c ounter is stopped. paen=1: 16-bit pulse accumulator a is active. paen=0: 8-bit pulse accumulators 3 and 2 can be enabled. (see icpar) pben=1: 16-bit pulse accumulator b is active. pben=0: 8-bit pulse accumulato rs 1 and 0 can be enabled. (see icpar)
enhanced capture timer technical data mc68hc912dt128a ? rev 4.0 276 enhanced capture timer motorola
mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 277 technical data ? mc68hc912dt128a section 16. multiple serial interface 16.1 contents 16.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 16.3 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278 16.4 serial communication inte rface (sci) . . . . . . . . . . . . . . . . . .278 16.5 serial peripheral interface (spi) . . . . . . . . . . . . . . . . . . . . . . .289 16.6 port s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 16.2 introduction the multiple serial interface (msi) module consists of three independent serial i/o sub-systems: two serial communication interfaces (sci0 and sci1) and the serial peri pheral interface (spi). ea ch serial pin shares function with the gener al-purpose port pins of port s. the sci subsystems are nrz type systems that are compatible with standard rs-232 systems. these sci systems have a new single wire operation mode which allows the unused pin to be available as general-purpose i/o. the spi subsystem, which is co mpatible with the m68hc11 spi, includes new features such as ss output and bidi rectional mode.
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 278 multiple serial interface motorola 16.3 block diagram figure 16-1. multiple se rial interface block diagram 16.4 serial communic ation interface (sci) two serial communication inte rfaces are available on the mc68hc912dt128a. these ar e nrz format (one st art, eight or nine data, and one stop bit) asynchronous communication systems with independent internal baud ra te generation circuitry and sci transmitters and receivers. they can be configured fo r eight or nine data bits (one of which may be designated as a parity bit, odd or even). if enabled, parity is generated in hardware for transmi tted and received data. receiver parity errors are flagged in hardwar e. the baud rate generator is based on a modulus counter, allowing flexib ility in choosing baud rates. there is a receiver wake-up fe ature, an idle line dete ct feature, a loop-back mode, and various error detection f eatures. two port pins for each sci provide the external interface fo r the transmitted data (txd) and the received data (rxd). for a faster wake-up out of wait mode by a received sci message, both sci have the capabilit y of sending a receiver interrupt, if enabled, when raf (receiver active flag) is set. for compatibility with other m68hc12 products, this feature is ac tive only in wait mode and is disabled when vddpll supply is at v ss level. ps0 ps1 ps2 ps3 ps4 ps5 ps6 ps7 sci0 sci1 spi ddrs/ioctlr port s i/o drivers msi rxd0 txd0 rxd1 txd1 miso/siso mosi/momi sck cs /ss hc12a4 msi block
multiple seri al interface serial communication interface (sci) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 279 figure 16-2. serial communi cations interf ace block diagram rx baud rate tx baud rate mclk divider 10-11 bit shift reg msb txd buffer/scxdrl txmtr control scxcr2/sci ctl 2 scxcr1/sci ctl 1 scxsr1/int status data recovery 10-11 bit shift reg txd buffer/scxdrl scxbd/select lsb rxd txd pin control / ddrs / port s wake-up logic scxcr1/sci ctl 1 scxsr1/int status scxcr2/sci ctl 2 int request logic msb lsb int request logic sci receiver sci transmitter baud rate clock to internal logic data bus parity detect parity generator hc12a4 sci block
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 280 multiple serial interface motorola 16.4.1 data format the serial data format requir es the following conditions: an idle-line in the high state bef ore transmission or reception of a message. a start bit (logic zero), transmitt ed or received, that indicates the start of each character. data that is transmitted or receiv ed least significant bit (lsb) first. a stop bit (logic one), us ed to indicate the end of a frame. (a frame consists of a start bit, a characte r of eight or nine data bits and a stop bit.) a break is defined as the transmission or reception of a logic zero for one frame or more. this sci supports hardware par ity for transmit and receive. 16.4.2 sci baud rate generation the basis of the sci baud rate generator is a 13-bit modulus counter. this counter gives the generator the flexibilit y necessary to achieve a reasonable level of i ndependence from the c pu operating frequency and still be able to produce standard bau d rates with a minimal amount of error. the clock s ource for the generator comes from the m clock. table 16-1. baud rate generation desired sci baud rate br divisor for m = 4.0 mhz br divisor for m = 8.0 mhz 110 2273 4545 300 833 2273 600 417 833 1200 208 417 2400 104 208 4800 52 104 9600 26 52 14400 17 35 19200 13 26 38400 ? 13
multiple seri al interface serial communication interface (sci) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 281 16.4.3 sci regist er descriptions control and data register s for the sci subsystem are described below. the memory address indica ted for each register is the default address that is in use after reset. both sci have identical control registers mapped in two blocks of eight bytes. scxbdh and scxbdl are considered together as a 16-bit baud rate control register. read any time. write sbr[12:0] anytime . low order byte must be written for change to take effect. write sbr [15:13] only in special modes. the value in sbr[12:0] determines t he baud rate of the sci. the desired baud rate is determined by the following formula: which is equivalent to: br is the value writt en to bits sbr[12:0] to establish baud rate. note: the baud rate generator is disabled until te or re bit in scxcr2 register is set for the first time af ter reset, and/or th e baud rate generator is disabled when sbr[12:0] = 0. btst ? reserved for test function bspl ? reserved for test function brld ? reserved fo r test function sc0bdh/sc1bdh ? sci baud rate control register $00c0/$00c8 bit 7654321bit 0 btst bspl brld sbr12 sbr11 sbr10 sbr9 sbr8 high reset: 0 0 0 0 0 0 0 0 sc0bdl/sc1bdl ? sci baud rate control register $00c1/$00c9 bit 7654321bit 0 sbr7 sbr6 sbr5 sbr4 sbr3 sbr2 sbr1 sbr0 low reset: 0 0 0 0 0 1 0 0 sci baud rate mclk 16 br -------------------- = br mclk 16 sci baud rate ----------------------------------------------- - =
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 282 multiple serial interface motorola read or write anytime. loops ? sci loop mode/s ingle wire mode enable 0 = sci transmit and receiv e sections operate normally. 1 = sci receive section is disc onnected from the rxd pin and the rxd pin is available as general purpose i/o. the receiver input is determined by t he rsrc bit. the tr ansmitter output is controlled by the associated d drs bit. both the transmitter and the receiver must be enabl ed to use the loop or the single wire mode. if the ddrs bit associ ated with the txd pin is set during the loops = 1, the txd pin outputs the sci waveform. if the ddrs bit associated with the txd pin is clear during the loops = 1, the txd pin becomes high (idle line stat e) for rsrc = 0 and high impedance for rsrc = 1. refer to table 16-2 . woms ? wired-or mode for serial pins this bit controls the two pins (txd and rxd) associat ed with the scix section. 0 = pins operate in a normal m ode with both high and low drive capability. to affect the rxd bit, that bi t would have to be configured as an output (via dd rs0/2) which is the single wire case when using the sci. woms bit still affects general- purpose output on txd and rxd pi ns when scix is not using these pins. 1 = each pin operates in an open drain fashion if that pin is declared as an output . sc0cr1/sc1cr1 ? sci control register 1 $00c2/$00ca bit 7654321bit 0 loops woms rsrc m wake ilt pe pt reset:00000000
multiple seri al interface serial communication interface (sci) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 283 rsrc ? receiver source when loops = 1, the rsrc bit det ermines the in ternal feedback path for the receiver. 0 = receiver input is connected to the transmitter inte rnally (not txd pin) 1 = receiver input is connected to the txd pin m ? mode (select character format) 0 = one start, eight data, one stop bit 1 = one start, ei ght data, ninth da ta, one stop bit wake ? wake-up by address mark/idle 0 = wake up by idle line recognition 1 = wake up by address ma rk (last data bit set) ilt ? idle line type determines which of two types of id le line detection w ill be used by the sci receiver. 0 = short idle line mode is enabled. 1 = long idle line mode is detected. in the short mode, the sci circuitr y begins counting ones in the search for the idle line conditi on immediately after the start bit. this means that the stop bit and any bits that were ones before the stop bit could be counted in that string of ones, resulting in earlier recognition of an idle line. table 16-2. loop mode functions loops rsrc ddrs1(3) woms function of port s bit 1/3 0 x x x normal operations 1 0 0 0/1 loop mode without txd output(txd = high impedance) 1 0 1 1 loop mode with txd output (cmos) 1 0 1 1 loop mode with txd output (open-drain) 11 0 x single wire mode without txd output (the pin is used as receiver input only, txd = high impedance) 11 1 0 single wire mode with txd output (the output is also fed back to receiver input, cmos) 1 1 1 1 single wire mode for the receiving and transmitting(open-drain)
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 284 multiple serial interface motorola in the long mode, the sci circuitry does not begin counting ones in the search for the idle line condition unt il a stop bit is received. therefore, the last byte?s stop bi t and preceding ?1? bits do not affect how quickly an idle line conditi on can be detected. pe ? parity enable 0 = parity is disabled. 1 = parity is enabled. pt ? parity type if parity is enabled, this bit deter mines even or odd parity for both the receiver and t he transmitter. 0 = even parity is selected. an even number of o nes in the data character causes the parity bit to be zero and an odd number of ones causes the parity bit to be one. 1 = odd parity is se lected. an odd number of ones in the data character causes the parity bi t to be zero and an even number of ones causes the parity bit to be one. read or write anytime. tie ? transmit interrupt enable 0 = tdre interrupts disabled 1 = sci interrupt will be requested whenever the tdre status flag is set. tcie ? transmit comple te interrupt enable 0 = tc interrupts disabled 1 = sci interrupt will be requested whenever the tc status flag is set. sc0cr2/sc1cr2 ? sci control register 2 $00c3/$00cb bit 7654321bit 0 tie tcie rie ilie te re rwu sbk reset:00000000
multiple seri al interface serial communication interface (sci) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 285 rie ? receiver interrupt enable 0 = rdrf and or interrupts disabl ed, raf interrupt in wait mode disabled 1 = sci interrupt wil l be requested whenever the rdrf or or status flag is set, or when raf is set while in wait mode with vddpll high. ilie ? idle line interrupt enable 0 = idle interrupts disabled 1 = sci interrupt will be requested whenever t he idle status flag is set. te ? transmitter enable 0 = transmitt er disabled 1 = sci transmit logic is enabled and the txd pi n (port s bit 1/bit 3) is dedicated to the transmi tter. the te bit can be used to queue an idle preamble. re ? receiver enable 0 = receiver disabled 1 = enables the sci receive circuitry. rwu ? receiver wake-up control 0 = normal sci receiver 1 = enables the wake-up function and inhibits further receiver interrupts. normally hardwar e wakes the receiver by automatically clearing this bit. sbk ? send break 0 = break generator off 1 = generate a break code (at le ast 10 or 11 contiguous zeros). as long as sbk remains set the tr ansmitter will s end zeros. when sbk is changed to zero, the current frame of all zeros is finished before the txd line goes to the idle state. if sbk is toggled on and off, the transmitter will send only 10 (o r 11) zeros and then revert to mark idle or sending data.
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 286 multiple serial interface motorola the bits in these regist ers are set by various conditions in the sci hardware and are automatically cl eared by special acknowledge sequences. the receive related flag bits in scxsr1 (rdrf, idle, or, nf, fe, and pf) are al l cleared by a read of the scxsr1 register followed by a read of th e transmit/receive dat a register low byte. however, only those bits which were set when scxsr1 was read will be cleared by the subseque nt read of the tran smit/receive data register low byte. the tr ansmit related bits in scxsr1 (tdre and tc) are cleared by a read of the scxsr1 register followed by a write to the transmit/receive dat a register low byte. read anytime (used in auto cl earing mechanism). write has no meaning or effect. tdre ? transmit data register empty flag new data will not be transmitted un less scxsr1 is read before writing to the transmit dat a register. reset sets this bit. 0 = scxdr busy 1 = any byte in the trans mit data register is tran sferred to the serial shift register so new data may now be written to the transmit data register. tc ? transmit complete flag flag is set when the transmitter is idle (no data, pr eamble, or break transmission in progress). clear by reading scxsr1 with tc set and then writing to scxdr. 0 = transmitter busy 1 = transmitt er is idle sc0sr1/sc1sr1 ? sci status register 1 $00c4/$00cc bit 7654321bit 0 tdre tc rdrf idle or nf fe pf reset:11000000
multiple seri al interface serial communication interface (sci) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 287 rdrf ? receive data register full flag once cleared, idle is not set again until the rxd line has been active and becomes idle again. rdrf is set if a received character is ready to be read from scxdr. clear the rdrf flag by r eading scxsr1 with rdrf set and then reading scxdr. 0 = scxdr empty 1 = scxdr full idle ? idle line detected flag receiver idle line is detected (the receipt of a minimum of 10/11 consecutive ones). this bi t will not be set by t he idle line condition when the rwu bit is set. once clea red, idle will not be set again until after rdrf has been set (after the line has been active and becomes idle again). 0 = rxd line is idle 1 = rxd line is active or ? overrun error flag new byte is ready to be transferred from the re ceive shift register to the receive data register and the receive data register is already full (rdrf bit is set). data transfer is inhibited until this bit is cleared. 0 = no overrun 1 = overrun detected nf ? noise error flag set during the same cycle as the rdrf bit but not set in the case of an overrun (or). 0 = unanimous decision 1 = noise on a valid start bit, any of the data bi ts, or on the stop bit fe ? framing error flag set when a zero is detected where a stop bit was expec ted. clear the fe flag by reading scxsr1 with fe set and then reading scxdr. 0 = stop bit detected 1 = zero detected rather than a stop bit
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 288 multiple serial interface motorola pf ? parity error flag indicates if received data?s parity ma tches parity bit. this feature is active only when parity is enabled. the ty pe of parity tested for is determined by the pt (par ity type) bit in scxcr1. 0 = parity correct 1 = incorrect parity detected read anytime. write has no meaning or effect. raf ? receiver active flag this bit is controlled by the receiver front end. it is set during the rt1 time period of the start bit search. it is clear ed when an idle state is detected or when the receiver circ uitry detects a false start bit (generally due to noise or baud rate mismatch). 0 = a character is not being received 1 = a character is being received if enabled with rie = 1, raf se t generates an interrupt when vddpll is high while in wait mode. sc0sr2/sc1sr2 ? sci status register 2 $00c5/$00cd bit 7654321bit 0 0 000000raf reset: 00000000 sc0drh/sc1drh ? sci data register high $00c6/$00ce bit 7654321bit 0 r8t8000000 reset: ? ? ? ? ? ? ? ? sc0drl/sc1drl ? sci data register low $00c7/$00cf bit 7654321bit 0 r7/t7 r6/t6 r5/t5 r4/t4 r3/t3 r2/t2 r1/t1 r0/t0 reset: ????????
multiple seri al interface serial peripheral interface (spi) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 289 r8 ? receive bit 8 read anytime. write has no meaning or affect. this bit is the ninth se rial data bit received when the sci system is configured for nine-data-bit operation. t8 ? transmit bit 8 read or write anytime. this bit is the ninth seri al data bit transmitted when the sci system is configured for nine-data-bit operat ion. when using 9-bit data format this bit does not have to be written for each data word. the same value will be transmitt ed as the ninth bit until this bit is rewritten. r7/t7?r0/t0 ? receive/transmit data bits 7 to 0 reads access the eight bits of the read-only sci receive data register (rdr). writes access the eight bits of the write-only sci transmit data register (tdr). scxdrl:scxdrh form the 9-bit data word for the sci. if the sci is bei ng used with a 7- or 8-bi t data word, only scxdrl needs to be accessed. if a 9-bit fo rmat is used, t he upper register should be written firs t to ensure that it is tr ansferred to the transmitter shift register with the lower register. 16.5 serial peripheral interface (spi) the serial peripheral interface allows the mc68h c912dt128a to communicate synchronously with peripheral devices and other microprocessors. the spi system in the mc68hc912dt128a can operate as a master or as a slave. the spi is also capable of interprocessor communi cations in a multiple master system. when the spi is enabled, al l pins that are defined by the configuration as inputs will be inputs regardless of the state of the ddrs bits for those pins. all pins that are defined as spi outputs will be outputs only if the ddrs bits for those pins are set. any spi output w hose corresponding ddrs bit is cleared can be used as a general-purpose input. a bidirectional serial pin is possible using t he ddrs as the direction control.
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 290 multiple serial interface motorola 16.5.1 spi baud rate generation the e clock is input to a divider series and the re sulting spi clock rate may be selected to be e di vided by 2, 4, 8, 16, 32, 64, 128 or 256. three bits in the sp0br regist er control the spi clo ck rate. this baud rate generator is activated only when spi is in the master mode and serial transfer is taking place. ot herwise this divider is disabled to save power. 16.5.2 spi operation in the spi system t he 8-bit data register in t he master and t he 8-bit data register in the slave ar e linked to form a distribut ed 16-bit register. when a data transfer operation is performed, this 16-bi t register is serially shifted eight bit po sitions by the sck clock fr om the master so the data is effectively exchanged between the master and the slave. data written to the sp0dr register of the master becomes the output data for the slave and data read from the sp0dr register of the master after a transfer operation is the i nput data from the slave.
multiple seri al interface serial peripheral interface (spi) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 291 figure 16-3. serial peri pheral interface block diagram a clock phase control bit (cpha) and a clock polarity control bit (cpol) in the sp0cr1 register select one of four possi ble clock formats to be used by the spi system. the cpol bi t simply selects non-inverted or inverted clock. the cpha bit is used to accommodate two fundamentally different pr otocols by shifting the clock by one half cycle or no phase shift. pin control logic 8-bit shift register read data buffer shift control logic clock logic spi control sp0sr spi status register sp0dr spi data register spif wcol modf divider select sp0br spi baud rate register 2 4 8 16 32 64 128 256 spi interrupt internal bus mcu p clock (same as e rate) s m m s m s spr2 spr1 spr0 request spie spe mstr cpol cpha lsbf lsbf pups rds swom spc0 ssoe spe clock mstr swom miso ps4 sck ps6 ss ps7 mosi ps5 hc12 spi block sp0cr1 spi control register 1 sp0cr2 spi control register 2
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 292 multiple serial interface motorola figure 16-4. spi clock format 0 (cpha = 0) t l begin end sck (cpol=0) sample i change o sel ss (o) transfer sck (cpol=1) msb first (lsbf=0): lsb first (lsbf=1): msb lsb lsb msb bit 5 bit 2 bit 6 bit 1 bit 4 bit 3 bit 3 bit 4 bit 2 bit 5 bit 1 bit 6 change o sel ss (i) (mosi pin) (miso pin) (master only) (mosi/miso) t t if next transfer begins here for t t , t l , t l minimum 1/2 sck t i t l hc12 spi clock form 0
multiple seri al interface serial peripheral interface (spi) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 293 figure 16-5. spi clock format 1 (cpha = 1) 16.5.3 ss output available in master mode only, ss output is enabled wi th the ssoe bit in the sp0cr1 register if th e corresponding ddrs is set. the ss output pin will be connected to the ss input pin of the external slave device. the ss output automatically goes low fo r each transmission to select the external device and it goes high during each idling state to deselect external devices. t l t t for t t , t l , t l minimum 1/2 sck t i t l if next transfer begins here begin end sck (cpol=0) sample i change o sel ss (o) transfer sck (cpol=1) msb first (lsbf=0): lsb first (lsbf=1): msb lsb lsb msb bit 5 bit 2 bit 6 bit 1 bit 4 bit 3 bit 3 bit 4 bit 2 bit 5 bit 1 bit 6 change o sel ss (i) (mosi pin) (miso pin) (master only) (mosi/miso) hc12 spi clock form 1 table 16-3. ss output selection ddrs7 ssoe master mode slave mode 00ss input with modf feature ss input 01 reserved ss input 1 0 general-purpose output ss input 11 ss output ss input
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 294 multiple serial interface motorola 16.5.4 bidirectional mode (momi or siso) in bidirectional m ode, the spi uses only one se rial data pin for external device interface. the mstr bit decides which pin to be used. the mosi pin becomes serial data i/o (momi) pin for the master mode, and the miso pin becomes serial data i/o (siso) pin for the slave mode. the direction of each serial i/o pi n depends on the corr esponding ddrs bit. 16.5.5 register descriptions control and data register s for the spi subsystem are described below. the memory address indica ted for each register is the default address that is in use after reset. for more information refer to operating modes . read or write anytime. spie ? spi interrupt enable 0 = spi interrupts are inhibited figure 16-6. normal m ode and bidirectional mode when spe=1 master mode mstr=1 slave mode mstr=0 normal mode spc0=0 swom enables open drain output. swom enables open drain output. bidirectional mode spc0=1 swom enables open drain output. ps4 becomes gpio. swom enables open drain output. ps5 becomes gpio. spi mo mi ddrs5 serial out serial in spi si so serial in serial out ddrs4 spi momi ps4 ddrs5 serial out serial in spi ps5 siso ddrs4 serial in serial out sp0cr1 ? spi control register 1 $00d0 bit 7654321bit 0 spie spe swom mstr cpol cpha ssoe lsbf reset: 0 0 0 0 0 1 0 0
multiple seri al interface serial peripheral interface (spi) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 295 1 = hardware interrupt sequence is requested each time the spif or modf status flag is set spe ? spi system enable 0 = spi internal hardware is init ialized and spi system is in a low- power disabled state. 1 = ps[4:7] are dedicat ed to the spi function when modf is set, spe always reads zero. sp0cr1 must be written as part of a mode fault recovery sequence. swom ? port s wired-or mode controls not only spi output pins but also the gener al-purpose output pins (ps[4:7]) which are not used by spi. 0 = spi and/or ps[4:7] output buffers operate normally 1 = spi and/or ps[4:7 ] output buffers behave as open-drain outputs mstr ? spi master /slave mode select 0 = slave mode 1 = master mode when modf is set, mstr alwa ys reads zero. sp0cr1 must be written as part of a mode fault reco very sequence. cpol, cpha ? spi clock polarity, clock phase these two bits are used to specify the clock fo rmat to be used in spi operations. when the clock polarity bit is cleared and dat a is not being transferred, the sck pin of the ma ster device is lo w. when cpol is set, sck idles high. see figure 16-4 and figure 16-5 . ssoe ? slave select output enable the ss output feature is enabled only in t he master mode by asserting the ssoe and ddrs7. lsbf ? spi lsb first enable 0 = data is transferred mo st significant bit first 1 = data is transferred l east significant bit first normally data is transferred most si gnificant bit first.this bit does not affect the position of the msb and lsb in the data register. reads and writes of the data register will always have msb in bit 7.
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 296 multiple serial interface motorola read or write anytime. pups ? pull-up port s enable 0 = no internal pul l-ups on port s 1 = all port s input pi ns have an active pull- up device. if a pin is programmed as output, the pu ll-up device becomes inactive rdps ? reduce drive of port s 0 = port s output dr ivers operate normally 1 = all port s output pins have reduced drive capability for lower power and less noise sswai ? serial interf ace stop in wait mode 0 = serial interface clock operates normally 1 = halt serial interface cl ock generation in wait mode spc0 ? serial pin control 0 this bit decides serial pin configurations wi th mstr control bit. sp0cr2 ? spi control register 2 $00d1 bit 7654321bit 0 0 0 0 0 pups rdps sswai spc0 reset: 0 0 0 0 1 0 0 0 pin mode spc0 (1) 1. the serial pin control 0 bit enables bidirectional configurations. mstr miso (2) 2. slave output is enabled if ddrs4 = 1, ss = 0 and mstr = 0. (#1, #3) mosi (3) 3. master output is enabled if ddrs5 = 1 and mstr = 1. (#2, #4) sck (4) 4. sck output is enabled if ddr s6 = 1 and mstr = 1. (#2, #4) ss (5) 5. ss output is enabled if ddrs7 = 1, ssoe = 1 and mstr = 1. (#2, #4) #1 normal 0 0 slave out slave in sck in ss in #2 1 master in master out sck out ss i/o #3 bidirectional 1 0 slave i/o gpi/o sck in ss in #4 1 gpi/o master i/o sck out ss i/o
multiple seri al interface serial peripheral interface (spi) mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 297 read anytime. write anytime. at reset, e clock divi ded by 2 is selected. spr[2:0] ? spi clock ( sck) rate select bits these bits are used to spec ify the spi clock rate. read anytime. write has no meaning or effect. spif ? spi interrupt request spif is set after the eighth sck cyc le in a data tr ansfer and it is cleared by reading the sp 0sr register (with spif set) followed by an access (read or write) to the spi data register. sp0br ? spi baud rate register $00d2 bit 7654321bit 0 0 0 0 0 0 spr2 spr1 spr0 reset: 0 0 0 0 0 0 0 0 table 16-4. spi clock rate selection spr2 spr1 spr0 e clock divisor frequency at e clock = 4 mhz frequency at e clock = 8 mhz 0 0 0 2 2.0 mhz 4.0 mhz 0 0 1 4 1.0 mhz 2.0 mhz 0 1 0 8 500 khz 1.0 mhz 0 1 1 16 250 khz 500 khz 1 0 0 32 125 khz 250 khz 1 0 1 64 62.5 khz 125 khz 1 1 0 128 31.3 khz 62.5 khz 1 1 1 256 15.6 khz 31.3 khz sp0sr ? spi status register $00d3 bit 7654321bit 0 spifwcol0modf0000 reset: 00000000
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 298 multiple serial interface motorola wcol ? write coll ision status flag the mcu write is disabled to av oid writing over the data being transferred. no interrupt is gener ated because the er ror status flag can be read upon completi on of the transfer that was in progress at the time of the error. automatica lly cleared by a read of the sp0sr (with wcol set) followed by an a ccess (read or write) to the sp0dr register. 0 = no write collision 1 = indicates that a serial trans fer was in progress when the mcu tried to write new data in to the sp0dr data register. modf ? spi mode error interrupt status flag this bit is set automatically by spi ha rdware if the mstr control bit is set and the slave select input pin be comes zero. this condition is not permitted in normal operati on. in the case where ddrs bit 7 is set, the ps7 pin is a general- purpose output pin or ss output pin rather than being dedicated as the ss input for the sp i system. in this special case the mode fault function is inhi bited and modf remains cleared. this flag is automaticall y cleared by a read of the sp0sr (with modf set) foll owed by a write to the sp0cr1 register. read anytime (normally only after spif flag set). wr ite anytime (see wcol write collision flag). reset does not affect this address. this 8-bit register is bo th the input and output register for spi data. reads of this register are double buffered but writes cause data to written directly into the serial shif ter. in the spi syst em the 8-bit data register in the master and the 8-bit data r egister in the sl ave are linked by the mosi and miso wires to form a distributed 16-bi t register. when a data transfer operation is performed, this 16-bi t register is serially shifted eight bit po sitions by the sck clock fr om the master so the data is effectively exchanged between the master and the slav e. note that sp0dr ? spi data register $00d5 bit 7654321bit 0 bit 7654321bit 0
multiple seri al interface port s mc68hc912dt128a ? rev 4.0 technical data motorola multiple se rial interface 299 some slave devices are very simple and either accept data from the master without retu rning data to the ma ster or pass data to the master without requiring dat a from the master. 16.6 port s in all modes, port s bits ps[7:0] can be used for either general-purpose i/o, or with the sci and spi subsystems. duri ng reset, port s pins are configured as high-impedance inputs (ddrs is cleared). read anytime (inputs retu rn pin level; outputs re turn pin driver input level). write data stored in internal latch (drives pi ns only if configured for output). writes do not ch ange pin state when pin co nfigured for spi or sci output. after reset all bits are conf igured as general-purpose inputs. port s shares function with the on-chip serial systems (spi and sci0/1). read or write anytime. after reset, all general-purpose i/o are configured for input only. 0 = configure the correspondi ng i/o pin for input only 1 = configure the corr esponding i/o pin for output ports ? port s data register $00d6 bit 7654321bit 0 ps7 ps6 ps5 ps4 ps3 ps2 ps1 ps0 msi ss cs sck mosi momi miso siso txd1 rxd1 txd0 rxd0 reset:-------- ddrs ? data direction register for port s $00d7 bit 7654321bit 0 dds7 dds6 dds5 dds4 dds3 dds2 dds1 dds0 reset: 0 0 0 0 0 0 0 0
multiple serial interface technical data mc68hc912dt128a ? rev 4.0 300 multiple serial interface motorola dds2, dds0 ? data directio n for port s bit 2 and bit 0 if the sci receiver is configur ed for two-wire sci operation, corresponding port s pins will be input regardless of the state of these bits. dds3, dds1 ? data directio n for port s bit 3 and bit 1 if the sci transmitter is confi gured for two-wire sci operation, corresponding port s pins will be output regardless of the state of these bits. dds[6:4] ? data direction for port s bits 6 through 4 if the spi is enabled and expects the corresponding port s pin to be an input, it will be an input regardless of the stat e of the ddrs bit. if the spi is enabled and ex pects the bit to be an output, it will be an output only if the ddrs bit is set. dds7 ? data direction for port s bit 7 in spi slave mode, ddrs7 has no me aning or effect; the ps7 pin is dedicated as the ss input. in spi master mode, ddrs7 determines whether ps7 is an error detect input to the spi or a general-purpose or slave select output line. note: if mode fault error occurs bits 5, 6 and 7 are fo rced to zero.
mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 301 technical data ? mc68hc912dt128a section 17. inter ic bus 17.1 contents 17.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 17.3 iic features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302 17.4 iic system configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 17.5 iic protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 17.6 iic register descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 17.7 iic programming examples . . . . . . . . . . . . . . . . . . . . . . . . . .318 17.2 introduction the inter-ic bus (iic or i 2 c) is a two-wire, bidire ctional serial bus that provides a simple, efficient method of data exchange between devices. being a two-wire device, the iic minimizes the need for large numbers of connections between devices, and eliminates the need for an address decoder. this bus is suitable for applic ations requiring occasional communications over a short distanc e between a number of devices. it also provides flexibility, allowing additional devices to be connected to the bus for further expansion and system development. the interface is designed to operate up to 100kbps with maximum bus loading and timing. the device is capable of operating at higher baud rates, up to a maximum of clo ck/20, with reduced bus loading. the maximum communication l ength and the number of devices that can be connected are limited by a ma ximum bus capacitance of 400pf.
inter ic bus technical data mc68hc912dt128a ? rev 4.0 302 inter ic bus motorola 17.3 iic features the iic module has the fo llowing key features: compatible with i 2 c bus standard multi-master operation software programmable for one of 64 different serial clock frequencies software selectable acknowledge bit interrupt driven byte -by-byte data transfer arbitration lost interrupt with automatic mode switching from master to slave calling address iden tification interrupt start and stop signal generation/detection repeated start signal generation acknowledge bit generation/detection bus busy detection eight-bit general purpose i/o port a block diagram of the iic module is shown in figure 17-1 .
inter ic bus iic features mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 303 figure 17-1. iic block diagram input sync in/out data shift register address compare scl sda interrupt addr & control data clock control start, stop & arbitration con tr ol ctrl_reg freq_reg addr_reg status_reg data_reg addr_decode data_mux
inter ic bus technical data mc68hc912dt128a ? rev 4.0 304 inter ic bus motorola 17.4 iic system configuration the iic system uses a serial data line (sda) and a se rial clock line (scl) for data transfer. all devices c onnected to it must have open drain or open collector outputs. logic ?and? function is exercised on both lines with external pull-up resistors, the value of these resistors is system dependent. 17.5 iic protocol normally, a standard communication is composed of four parts: start signal, slave address transmission, data transfer and st op signal. they are described brie fly in the following sect ions and illustrated in figure 17- 2 . figure 17-2. iic transmission signals scl sda start signal ack bit 12345678 msb lsb 12345678 msb lsb stop signal no scl sda 1234567 8 msb lsb 1 2 5 678 msb lsb repeated 34 9 9 ad7 ad6 ad5 ad4 ad3 ad2 ad1 r/w xxx d7 d6 d5 d4 d3 d2 d1 d0 calling address read/ data byte ad7 ad6 ad5 ad4 ad3 ad2 ad1 r/w ad7 ad6 ad5 ad4 ad3 ad2 ad1 r/w new calling address 99 xx ack bit write start signal start signal ack bit calling address read/ write stop signal no ack bit read/ write
inter ic bus iic protocol mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 305 17.5.1 start signal when the bus is free, i.e. no mast er device is engaging the bus (both scl and sda lines are at logical high), a ma ster may initiate communication by sending a st art signal. as shown in figure 17-2 , a start signal is defined as a high-to-l ow transition of sda while scl is high. this signal denotes the beginning of a new data tr ansfer (each data transfer may contain several bytes of data) and wakes up all slaves. 17.5.2 slave address transmission the first byte of data transfer immediat ely after the start signal is the slave address transmitted by the mast er. this is a seven-bit calling address followed by a r/w bit. the r/w bit tells the slave the desired direction of data transfer. 1 = read transfer, the slave transmits data to the master. 0 = write transfer, the master transmits data to the slave. only the slave with a calling address that matc hes the one transmitted by the master will respond by sendi ng back an acknowledge bit. this is done by pulling the sda low at the 9th clock (see figure 17-2 ). slave address - no two slaves in the system may have the same address. if the iic is master, it must not tr ansmit an address that is equal to its own sl ave address. the iic cannot be master and slave at the same time. if however arbitration is lost during an address cycle the iic will revert to slave mode and operate correctly even if it is being addressed by another master. 17.5.3 data transfer once successful slave addressing is achieved, the data transfer can proceed byte-by-byte in a dire ction specified by the r/w bit sent by the calling master. note: all transfers that come after an a ddress cycle are refe rred to as data transfers, even if they carry sub-address info rmation for the slave device.
inter ic bus technical data mc68hc912dt128a ? rev 4.0 306 inter ic bus motorola each data byte is 8 bits long. da ta may be changed on ly while scl is low and must be held stable while scl is high as shown in figure 17-2 . there is one clock pulse on scl fo r each data bit, the msb being transferred first. each data byte ha s to be followed by an acknowledge bit, which is signalled fr om the receiving device by pulling the sda low at the ninth clock. so one complete data byte transfer needs nine clock pulses. if the slave receiver does not a cknowledge the master, the sda line must be left high by the slave. the master can then generate a stop signal to abort the data transfer or a start signal (re peated start) to commence a new calling. if the master receiver does not ackn owledge the slave transmitter after a byte transmission, it m eans 'end of data' to t he slave, so the slave releases the sda line fo r the master to generat e stop or start signal. 17.5.4 stop signal the master can terminat e the communication by generating a stop signal to free the bus. however, the master may generate a start signal followed by a calling comm and without generati ng a stop signal first. this is called r epeated start. a stop signa l is defined as a low- to-high transition of sda while scl at logical ?1? (see figure 17-2 ). the master can generate a stop even if the slave has generated an acknowledge at which point the slave must release the bus. 17.5.5 repeated start signal as shown in figure 17-2 , a repeated start signal is a start signal generated without first gene rating a stop signa l to terminate the communication. this is us ed by the master to communicate with another slave or with the same slave in different mode (transmit/receive mode) without releas ing the bus.
inter ic bus iic protocol mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 307 17.5.6 arbitration procedure iic is a true multi-master bus that allows more than one master to be connected on it. if two or more masters try to control the bus at the same time, a clock synchroniza tion procedure determines the bus clock, for which the low period is equal to the longes t clock low period and the high is equal to the shortest one among the masters. the relative priority of the contending masters is determined by a data arbitration procedure, a bus master loses arbitration if it tr ansmits logic ?1? wh ile another master transmits logic ?0?. the lo sing masters immediately switch over to slave receive mode and stop dr iving sda output. in th is case the transition from master to slave mode does not generate a st op condition. meanwhile, a status bit is set by hardware to indi cate loss of arbitration. 17.5.7 clock synchronization since wire-and logic is performed on scl line, a high-to -low transition on scl line affects all the devices connected on the bus. the devices start counting their low period and once a devic e's clock has gone low, it holds the scl line low until the cl ock high state is reached. however, the change of low to high in this device clock may not change the state of the scl line if another device clock is sti ll within its low period. therefore, synchronized clock scl is held low by the device with the longest low period. devi ces with shorter low pe riods enter a high wait state during this time (see figure 17-3 ). when all devices concerned have counted off their lo w period, the synchroni zed clock scl line is released and pulled high. there is then no differ ence between the device clocks and the state of the scl line and all the devices start counting their high periods. the first device to complete its high period pulls the scl line low again.
inter ic bus technical data mc68hc912dt128a ? rev 4.0 308 inter ic bus motorola figure 17-3. iic cl ock synchronization 17.5.8 handshaking the clock synchronization mechanism can be used as a handshake in data transfer. slave devices may hol d the scl low after completion of one byte transfer (9 bits). in such ca se, it halts the bus clock and forces the master clock into wait states un til the slave releases the scl line. 17.5.9 clock stretching the clock synchronization mechanism ca n be used by sl aves to slow down the bit rate of a tr ansfer. after the master has driven scl low the slave can drive scl low for the requir ed period and then re lease it. if the slave scl low period is greater than the master scl low period then the resulting scl bu s signal low period is stretched. scl1 scl2 scl internal counter reset wait start counting high period
inter ic bus iic register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 309 17.6 iic register descriptions . read and write anytime this register contains the address the iic will respond to when addressed as a slave; note that it is not the address sent on the bus during the address transfer adr7?adr1 ? slave address bit 1 to bit 7 contain the specific slave address to be used by the iic module. the default mode of iic is slave mode for an address match on the bus. read and write anytime ibc5?ibc0 ? iic bu s clock rate 5?0 this field is used to pr escale the clock for bit rate selection. the bit clock generator is implemented as a prescaled shift register - ibc5-3 select the prescaler divider and ibc2 -0 select the sh ift register tap point. the ibc bits ar e decoded to give the tap and prescale values as shown in table 17-1 . note: at 8 mhz system bus fr equency, the iic bus frequen cy will slow down by as much as 5%. however, the communica tions rate of the iic system will be automatically adjust ed to a slower rate. ibad ? iic bus address register $00e0 bit 7654321bit 0 adr7 adr6 adr5 adr4 adr3 adr2 adr1 0 reset: 00000000 ibfd ? iic bus frequency divider register $00e1 bit 7654321bit 0 00 ibc5 ibc4 ibc3 ibc2 ibc1 ibc0 reset: 0 0 0 0 0 0 0 0
inter ic bus technical data mc68hc912dt128a ? rev 4.0 310 inter ic bus motorola the number of clocks from the fall ing edge of scl to the first tap (tap[1]) is defined by the values shown in t he scl2tap column of table 17-1 , all subsequent tap point s are separated by 2 ibc5-3 as shown in the tap2tap column in table 17-1 . the scl tap is used to generated the scl period and the sda tap is us ed to determine the delay from the falling edge of scl to sda changing, the sda hold time. the serial bit clock frequency is equal to the cpu clock frequency divided by the di vider shown in table 17-2 . the equation used to generate the divider values from the ibfd bits is: scl divider = 2 x ( scl2tap + [ ( scl_tap -1 ) x tap2tap ] + 2 ) the sda hold delay is equal to the cpu clock per iod multiplied by the sda hold value shown in figure 17-2 . the equation used to generate the sda hold value from the ibfd bits is: sda hold = scl2tap + [ ( sda_tap - 1 ) x tap2tap ] + 3 table 17-1. iic tap and prescale values ibc2-0 (bin) scl tap (clocks) sda tap (clocks) ibc5-3 (bin) scl2tap (clocks) tap2tap (clocks) 000 5 1 000 4 1 001 6 1 001 4 2 010 7 2 010 6 4 011 8 2 011 6 8 100 9 3 100 14 16 101 10 3 101 30 32 110 12 4 110 62 64 111 15 4 111 126 128
inter ic bus iic register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 311 table 17-2. iic divider and sda hold values ibc5-0 (hex) scl divider (clocks) sda hold (clocks) ibc5-0 (hex) scl divider (clocks) sda hold (clocks) 00 20 7 20 160 17 01 22 7 21 192 17 02 24 8 22 224 33 03 26 8 23 256 33 04 28 9 24 288 49 05 30 9 25 320 49 06 34 10 26 384 65 07 40 10 27 480 65 08 28 7 28 320 33 09 32 7 29 384 33 0a 36 9 2a 448 65 0b 40 9 2b 512 65 0c 44 11 2c 576 97 0d 48 11 2d 640 97 0e 56 13 2e 768 129 0f 68 13 2f 960 129 10 48 9 30 640 65 11 56 9 31 768 65 12 64 13 32 896 129 13 72 13 33 1024 129 14 80 17 34 1152 193 15 88 17 35 1280 193 16 104 21 36 1536 257 17 128 21 37 1920 257 18 80 9 38 1280 129 19 96 9 39 1536 129 1a 112 17 3a 1792 257
inter ic bus technical data mc68hc912dt128a ? rev 4.0 312 inter ic bus motorola read and write anytime iben ? iic bus enable this bit controls the software reset of the entire iic module. 0 = the module is reset and disabled. this is the power-on reset situation. when low the iic system is held in reset but registers can still be accessed. 1 = the iic system is en abled. this bit must be set before any other ibcr bits have any effect. if the iic module is enabled in th e middle of a byte transfer the interface behaves as follows: slave mode ignores the current transfer on the bus and starts operatin g whenever a subsequent start condition is detected. master mode will not be aware that the bus is busy, hence if a start cycle is initia ted then the current bus cycle may become corrupt. this would ultimately result in either the current bus master or the iic module losing ar bitration, after which bus operation would return to normal. note: to prevent glitches fr om appearing on the sda & scl lines during reset of the iic module, set po rtib bit 6 & 7 to 1 befo re clearing the iben bit. 1b 128 17 3b 2048 257 1c 144 25 3c 2304 385 1d 160 25 3d 2560 385 1e 192 33 3e 3072 513 1f 240 33 3f 3840 513 table 17-2. iic divider and sda hold values ibc5-0 (hex) scl divider (clocks) sda hold (clocks) ibc5-0 (hex) scl divider (clocks) sda hold (clocks) ibcr ? iic bus control register $00e2 bit 7654321bit 0 iben ibie ms/sl tx/rx txak rsta 0 ibswai reset: 00000000
inter ic bus iic register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 313 ibie ? iic bus interrupt enable 0 = interrupts from the iic module are disabled. note that this does not clear any currently pending interrupt condition. 1 = interrupts from the iic modu le are enabled. an iic interrupt occurs provided the ibif bit in the status r egister is also set. ms/sl ? master/slave mode select bit upon reset, this bit is cleared. w hen this bit is chang ed from 0 to 1, a start signal is generated on the bus, and the master mode is selected. when this bit is changed from 1 to 0, a stop signal is generated and the operation mode changes from master to slave. ms/sl is cleared without generating a stop signal when the master loses arbitration. 0 = slave mode 1 = master mode tx/rx ? transmit/receiv e mode select bit this bit selects the di rection of master and slave transfers. when addressed as a slave this bit should be set by software according to the srw bit in the status register. in master mode this bit should be set according to the type of transf er required. theref ore, for address cycles, this bit will always be high. 0 = receive 1 = transmit txak ? transmit a cknowledge enable this bit specifies th e value driven onto sd a during acknowledge cycles for both master and slave receiver s. note that values written to this bit are only used when the iic is a receiver, not a transmitter. 0 = an acknowledge sig nal will be sent out to the bus at the 9th clock bit after receiving one byte data 1 = no acknowledge si gnal response is sent (i.e. acknowledge bit = 1)
inter ic bus technical data mc68hc912dt128a ? rev 4.0 314 inter ic bus motorola rsta ? re peat start writing a 1 to this bit will generate a repeated star t condition on the bus, provided it is the current bus master. this bit w ill always be read as a low. attempting a repeated star t at the wrong time , if the bus is owned by another master, will result in loss of arbitration. 1 = generate repeat start cycle ibswai ? iic st op in wait mode 0 = iic module operates normally 1 = halt clock generation of iic module in wait mode this status register is read-only with exception of bit 1 (ibif) and bit 4 (ibal), which are software clearable tcf ? data transferring bit while one byte of data is be ing transferred, th is bit is cleared. it is set by the falling edge of the 9th clock of a byte transfer. 0 = transfer in progress 1 = transfer complete iaas ? addressed as a slave bit when its own specific address (iic bus address register) is matched with the calling addres s, this bit is set. the cpu is interrupted provided the ibie is set. then th e cpu needs to c heck the srw bit and set its tx/rx mode accordingly. writing to the iic bus control register clears this bit. 0 = not addressed 1 = addressed as a slave ibb ? iic bus busy bit this bit indicates the status of the bus. when a start signal is detected, the ibb is set. if a stop signal is detected, it is cleared. 0 = bus is idle 1 = bus is busy ibsr ? iic bus status register $00e3 bit 7654321bit 0 tcf iaas ibb ibal 0 srw ibif rxak reset: 10000000
inter ic bus iic register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 315 note: if, after trying to generat e a start signal and neit her the ibb nor ibal bits are set after seve ral cycles, the iic s hould be disabled and re- enabled with iben bit. ibal ? arbitration lost the arbitration lost bit (ibal) is set by hardware wh en the arbitration procedure is lost. arbitration is lo st in the followin g circumstances: 1. sda sampled as lo w when the master dr ives a high during an address or data transmit cycle. 2. sda sampled as a low when the master drives a high during the acknowledge bit of a data receive cycle. 3. a start cycle is attemp ted when the bus is busy. 4. a repeated start cycle is requested in slave mode. 5. a stop condition is detected wh en the master di d not request it. this bit must be clear ed by software, by writing a one to it. note: if, after trying to generat e a start signal and neit her the ibb nor ibal bits are set after seve ral cycles, the iic s hould be disabled and re- enabled with iben bit. srw ? slave read/write when iaas is set this bi t indicates the value of the r/w command bit of the calling address se nt from the master. caution: this bit is only valid when the iic is in slave mode, a complete address transfer has occurred with an address match and no other transfers have been initiated. checking this bit, the cpu can select slave transmit/receive mode according to the command of the master. 0 = slave receive, mast er writing to slave 1 = slave transmit, mast er reading from slave
inter ic bus technical data mc68hc912dt128a ? rev 4.0 316 inter ic bus motorola ibif ? iic bus interrupt flag the ibif bit is set w hen an interrupt is pendi ng, which will cause a processor interrupt request provided ib ie is set. ibif is set when one of the following events occurs: 1. complete one byte tr ansfer (set at the falling edge of the 9th clock). 2. receive a calling address that matches its own specific address in slave receive mode. 3. arbitration lost. this bit must be cl eared by software, writing a one to it, in the interrupt routine. rxak ? received acknowledge the value of sda during the acknow ledge bit of a bus cycle. if the received acknowledge bit (rxak) is low, it i ndicates an acknowledge signal has been received after t he completion of 8 bits data transmission on the bus. if rxak is high, it means no acknowledge signal is detected at the 9th clock. 0 = acknowledge received 1 = no acknowledge received . read and write anytime in master transmit mode, when data is written to the ibdr a data transfer is initiated. the most signi ficant bit is sent first. in master receive mode, reading this register initiates next by te data receiving. in slave mode, the same functions are available af ter an address match has occurred. note: in master transmit mode, the first byte of data written to ibdr following assertion of ms/sl is used for the address tr ansfer and should comprise of the calling addres s (in position d7-d1) concat enated with the required r/w bit (in position d0). ibdr ? iic bus data i/o register $00e4 bit 7654321bit 0 d7 d6 d5 d4 d3 d2 d1 d0 high reset: 0 0 0 0 0 0 0 0
inter ic bus iic register descriptions mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 317 read and write anytime rdpib - reduced drive of port ib 0 = all port ib output pins have full drive enabled. 1 = all port ib output pins have reduced drive capability. pupib - pull-up port ib enable 0 = port ib pull-ups are disabled. 1 = enable pull-up devices for port ib input pins [7:6]. pull-ups for port ib input pi ns [5:0] are always enabled. read and write anytime. iic functions scl and sda share port ib pi ns 7 and 6 and take precedence over the gener al-purpose port when iic is enabled. the scl and sda output buffers behave as open-drain outputs. when port is configured as input, a read will return the pin level. port bits 5 through 0 have internal pull ups when configured as inputs so they will read ones. when configured as output, a read will return t he latched output data. port bits 5 through 0 will read the last value writ ten. a write will drive associated pins only if configur ed for output and iic is not enabled. port bits 5 through 0 do not have available external pins for mc68hc912dt128a. ibpurd ? pull-up and reduced drive for port ib $00e5 bit 7654321bit 0 000rdpib000pupib reset:00000000 portib ? port data ib register $00e6 bit 7654321bit 0 pib7 pib6 pib5 pib4 pib3 pib2 pib1 pib0 iicsclsda------ reset:--------
inter ic bus technical data mc68hc912dt128a ? rev 4.0 318 inter ic bus motorola read and write anytime ddrib[7:2]? port ib [7:2] data direction each bit determines the primary direction for eac h pin configured as general-purpose i/o. 0 = associated pin is a high-impedance input. 1 = associated pi n is an output. ddrib[5:0] ? these bits served as memory locations since there are no corresponding external port pins for mc68hc912dt128a. 17.7 iic programming examples 17.7.1 initialization sequence reset will put the iic bus control regi ster to its defaul t status. before the interface can be us ed to transfer serial data, an initialization procedure must be carried out, as follows: 1. update the frequency divider r egister (ibfd) and select the required division ratio to obtai n scl frequency from system clock. 2. update the iic bus address regi ster (ibad) to define its slave address. 3. set the iben bit of the iic bus control register (ibcr) to enable the iic interface system. 4. modify the bits of the iic bus control regi ster (ibcr) to select master/slave mode, transmit/ receive mode and interrupt enable or not. ddrib ? data direction for port ib register $00e7 bit 76 5 4 3 2 1bit 0 ddrib7 ddrib6 ddrib5 ddrib4 d drib3 ddrib2 ddrib1 ddrib0 reset: 0 0 0 0 0 0 0 0
inter ic bus iic programming examples mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 319 17.7.2 generation of start after completion of the initializati on procedure, seri al data can be transmitted by selecting the 'master tr ansmitter' mode. if the device is connected to a multi-master bus syst em, the state of the iic bus busy bit (ibb) must be test ed to check whether th e serial bus is free. if the bus is free (ibb=0) , the start condition and the first byte (the slave address) can be sent. the data written to the data register comprises the slave calling address and the lsb set to indicate t he direction of transfer required from the slave. the bus free time (i.e., the time between a st op condition and the following start condition) is built into the hardwa re that generates the start cycle. depending on the relative frequencies of the system clock and the scl period it may be necessary to wait until the iic is busy after writing the calling a ddress to the ibdr bef ore proceeding with the following instructions. thi s is illustrated in the following example. an example of a program which generates the start signal and transmits the first byte of data (slave address) is shown below: 17.7.3 post-transfe r software response transmission or reception of a byte will set the dat a transferring bit (tcf) to 1, which indicates one byte co mmunication is finished. the iic bus interrupt bit (ibif) is set also; an in terrupt will be generat ed if the interrupt function is enabled during initialization by sett ing the ibie bit. software must clear the ibif bit in the interrupt rout ine first. the tcf bit will be cleared by reading from t he iic bus data i/o regi ster (ibdr) in receive mode or writing to ibdr in transmit mode. software may service the iic i/o in the main program by monitoring the ibif bit if the interrupt function is disabled. note that polling should chflag brset ibsr,#$20,* ;wait for ibb flag to clear txstart bset ibcr,#$30 ;set transmit and master mode ;i.e. generate start condition movb calling,ibdr ;transmit the calling ;address, d0=r/w ibfree brclr ibsr,#$20,* ;wait for ibb flag to set
inter ic bus technical data mc68hc912dt128a ? rev 4.0 320 inter ic bus motorola monitor the ibif bit ra ther than the tcf bit si nce their operation is different when arbi tration is lost. note that when an interrupt occurs at the end of the address cycle the master will always be in tran smit mode, i.e. the addr ess is transmitted. if master receive mode is r equired, indica ted by r/w bit in ibdr, then the tx/rx bit should be toggl ed at this stage. during slave mode address cycles (ia as=1) the srw bit in the status register is read to det ermine the direction of the subsequent transfer and the tx/rx bit is programmed accordingl y. for slave mode data cycles (iaas=0) the srw bit is not valid, the tx/rx bit in the control register should be read to deter mine the direction of the current transfer. the following is an example of a software response by a 'master transmitter' in the in terrupt routine (see figure 17-4 ). 17.7.4 generation of stop a data transfer ends with a stop signal generated by the 'master' device. a master transmitter can si mply generate a stop signal after all the data has been transmitt ed. the following is an example showing how a stop condition is generated by a master transmitter. if a master receiver want s to terminate a data transfe r, it must inform the slave transmitter by not acknowledgi ng the last byte of data which can isr bclr ibsr,#$02 ;clear the ibif flag brclr ibcr,#$20,slave ;branch if in slave mode brclr ibcr,#$10,receive ;branch if in receive mode brset ibsr,#$01,end ;if no ack, end of transmission transmit movb databuf,ibdr ;transmit next byte of data mastx tst txcnt ;get value from the ;transmiting counter beq end ;end if no more data brset ibsr,#$01,end ;end if no ack movb databuf,ibdr ;transmit next byte of data dec txcnt ;decrease the txcnt bra emastx ;exit end bclr ibcr,#$20 ;generate a stop condition emastx rti ;return from interrupt
inter ic bus iic programming examples mc68hc912dt128a ? rev 4.0 technical data motorola inter ic bus 321 be done by setting the transmit ack nowledge bit (txak) before reading the 2nd last byte of dat a. before reading the last byte of data, a stop signal must be generated first. the foll owing is an example showing how a stop signal is generated by a master receiver. 17.7.5 generation of repeated start at the end of data transfer, if the master still wa nts to communicate on the bus, it can generate another start signal followed by another slave address without first generating a st op signal. a program example is as shown. 17.7.6 slave mode in the slave interrupt service routin e, the module addressed as slave bit (iaas) should be tested to check if a calling of its own address has just been received (see figure 17-4 ). if iaas is set, so ftware should set the transmit/receive mode select bit (tx/rx bit of ibcr) a ccording to the r/w command bit (srw). writi ng to the ibcr clears the iaas automatically. note that the only time iaas is read as set is from the interrupt at the end of the add ress cycle where an address match occurred, interrupts resulting from subsequent data transfers will have iaas cleared. a data transfer may now be initiated by writing information to ibdr, for slave transmits, or dum my reading from ibdr, in slave masr dec rxcnt ;decrease the rxcnt beq enmasr ;last byte to be read movb rxcnt,d1 ;check second last byte dec d1 ;to be read bne nxmar ;not last or second last lamar bset ibcr,#$08 ;second last, disable ack ;transmitting bra nxmar enmasr bclr ibcr,#$20 ;last one, generate ?stop? signal nxmar movb ibdr,rxbuf ;read data and store rti restart bset ibcr,#$04 another start (restart) movb calling,ibdr ;transmit the calling address ;d0=r/w
inter ic bus technical data mc68hc912dt128a ? rev 4.0 322 inter ic bus motorola receive mode. the slave will drive scl low in-between by te transfers, scl is released when the ibdr is accessed in the required mode. in slave transmitter routine, the received ack nowledge bit (r xak) must be tested before transmitting the next byte of data. setting rxak means an 'end of data' signal from the master receiver, af ter which it must be switched from transmitter mode to receiver mode by software. a dummy read then releases the scl line so t hat the master c an generate a stop signal. 17.7.7 arbitration lost if several masters try to engage the bus simultaneously, only one master wins and the others lose arbitration. the devices which lost arbitration are immediately switched to slave re ceive mode by the hardware. their data output to the sda li ne is stopped, but scl is still generated until the end of the byte during whic h arbitration was lost. an interrupt occurs at the falling edge of the ninth clock of this transfer with ibal=1 and ms/sl =0. if one master attempts to st art transmission while the bus is being engaged by another master, t he hardware will inhibit the transmission; switch the ms/sl bit from 1 to 0 wi thout generating stop condition; generate an interrupt to cpu and set the ibal to indicate that the attempt to engage the bus is failed. when considering these cases, the slave service routi ne should test the ibal first and the software should clear the ibal bit if it is set.
inter ic bus technical data mc68hc912dt128a ? rev 4.0 323 inter ic bus motorola figure 17-4. flow-char t of typical iic interrupt routine clear master mode ? tx/rx ? last byte transmitted ? rxak=0 ? end of addr cycle (master rx) ? write next byte to ibdr switch to rx mode dummy read from ibdr generate stop signal read data from ibdr and store set txak =1 generate stop signal 2nd last byte to be read ? last byte to be read ? arbitration lost ? clear ibal iaas=1 ? iaas=1 ? srw=1 ? tx/rx ? set tx mode write data to ibdr set rx mode dummy read from ibdr ack from receiver ? tx next byte read data from ibdr and store switch to rx mode dummy read from ibdr rti yn y y y y y y y y y n n n n n n n n n y tx rx rx tx (write) (read) n ibif address transfer data transfer
inter ic bus technical data mc68hc912dt128a ? rev 4.0 324 inter ic bus motorola
mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 325 technical data ? mc68hc912dt128a section 18. mscan controller 18.1 contents 18.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 18.3 external pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326 18.4 message storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 18.5 identifier acceptance filter . . . . . . . . . . . . . . . . . . . . . . . . . . .332 18.6 interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335 18.7 protocol violation protecti on. . . . . . . . . . . . . . . . . . . . . . . . . . 337 18.8 low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338 18.9 timer link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 18.10 clock system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343 18.11 memory map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 18.12 programmer?s model of message storage . . . . . . . . . . . . . . .346 18.13 programmer?s model of control registers . . . . . . . . . . . . . . . 351 18.2 introduction the mc68hc912dt128a has three identical mscan12 modules, identified as can0, can1 and can2. the mc68hc 912dg128a has two: can0 and can1. t he information to foll ow describes one mscan unless specifically noted and register locations specifically relate to can0. can1 registers ar e located 512 bytes fr om can0, and on the mc68hc912dt128a, can2 registers are located 256 bytes from can0.
mscan controller technical data mc68hc912dt128a ? rev 4.0 326 mscan controller motorola the mscan12 is the specific implem entation of the mo torola scalable can (mscan) concept targeted for the motorola m68hc12 microcontroller family. the module is a communica tion controller impl ementing the can 2.0 a/b protocol as defined in the bosch specific ation dated september 1991. the can protocol was prim arily, but not only, de signed to be used as a vehicle serial data bus, meeting the s pecific requirements of this field: real-time processing, re liable operation in t he emi environment of a vehicle, cost-effectivene ss and required bandwidth. mscan12 utilizes an advanced buf fer arrangement resulting in a predictable real-time behavior and si mplifies the application software. 18.3 external pins the mscan12 uses 2 external pins , 1 input (rxcan) and 1 output (txcan). the txcan output pin represents the logic level on the can: 0 is for a dominant state, an d 1 is for a recessive state. rxcan is on bit 0 of port can, txc an is on bit 1. the remaining six pins of port can are controlled by r egisters in the mscan12 address space (see mscan12 port can contro l register (pctlcan) and mscan12 port can data direct ion register (ddrcan) ). a typical can system with mscan12 is shown in figure 18-1 below. each can station is connected physi cally to the can bus lines through a transceiver chip. the transceiver is capable of driving the large current needed for the can and has current protection, against defected can or defected stations.
mscan controller message storage mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 327 figure 18-1. the can system 18.4 message storage mscan12 facilitates a sophistic ated message storage system which addresses the requirements of a br oad range of network applications. 18.4.1 background modern application layer software is built upon two fundamental assumptions: 1. any can node is ab le to send out a stream of scheduled messages without releasing th e bus between two messages. such nodes will arbitrate for the bus right af ter sending the previous message and wi ll only release the bus in case of lost arbitration. 2. the internal messa ge queue within any ca n node is organized such that if more than one messa ge is ready to be sent, the highest priority message will be sent out first. transceiver mscan12 can system can station 1 can station 2 can station n can txcan rxcan ..... controller
mscan controller technical data mc68hc912dt128a ? rev 4.0 328 mscan controller motorola above behavior can not be achieved with a single tr ansmit buffer. that buffer must be reloaded right after the previous message has been sent. this loading process la sts a definite amount of time and has to be completed within the inte r-frame sequence (ifs) in order to be able to send an uninterrupted stream of messages . even if this is feasible for limited can bus sp eeds it requires that t he cpu reacts with short latencies to the transmit interrupt. a double buffer scheme w ould de-couple the re-l oading of the transmit buffers from the act ual message sending and as such reduces the reactiveness requirement s on the cpu. problems may arise if the sending of a message would be finis hed just while the cpu re-loads the second buffer, no buffer would then be ready fo r transmission and the bus would be released. at least three transmit buffers are required to meet the first of above requirements under all ci rcumstances. the mscan1 2 has three transmit buffers. the second requirement calls for some so rt of internal prioritizing which the mscan12 implem ents with the local prio rity concept described below. 18.4.2 receive structures the received messages ar e stored in a two stage input fifo. the two message buffers are mapped using a ping-pong arrangement into a single memory area (see figure 18-2 ). while the background receive buffer (rxbg) is exclus ively associated to the mscan12, the foreground receive buffer (rxfg) is address ed by the cpu12. this scheme simplifies the handler software as only one address area is applicable for the receive process. both buffers have a size of 13 byte s to store the can control bits, the identifier (standard or extended) and the data cont ents (for details see programmer?s model of message storage ). the receiver full flag (rxf) in the mscan12 re ceiver flag register (crflg) (see mscan12 receiver fl ag register (crflg) ) signals the
mscan controller message storage mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 329 status of the foreground receive buf fer. when the buffer contains a correctly received message with matching identifier this flag is set. after the mscan12 successfully received a message into the background buffer and if t he message passes the fi lter, it copies the content of rxbg into rxfg (1) , sets the rxf flag, and emits a receive interrupt to the cpu (2) . a new message (which may follow immediately after the ifs field of the can frame) will be received into rxbg. the over-writing of the backg round buffer is independent of the identifier filter function. the user?s receive handler has to read the received message from rxfg and to reset the rxf flag in order to acknow ledge the interrupt and to release the foreground buffer. an overrun condition occurs wh en both the fo reground and the background receive message buffers ar e filled with correctly received messages with accepted identifiers and a further correctly received message with accepted identifier is received fr om the bus. the latter message will be discarded and an error interrupt with overrun indication will occur if enabled. as l ong as both buff ers remain filled, the mscan12 is able to transmit mess ages but it w ill discard all incoming messages. note: the mscan12 will receive its ow n messages into the background receive buffer rxbg but will not overwrite rx fg and will not emit a receive interrupt nor will it ackn owledge (ack) its ow n messages on the can bus. the exception to this rule is that when in loop-back mode mscan12 will treat it s own messages exactly like all other incoming messages. 1. only if the rxf flag is not set. 2. the receive interrupt will occur only if no t masked. a polling scheme can be applied on rxf also.
mscan controller technical data mc68hc912dt128a ? rev 4.0 330 mscan controller motorola figure 18-2. user model fo r message buffer organization 18.4.3 transmit structures the mscan12 has a triple transmit buf fer scheme in order to allow multiple messages to be set up in advance and to achieve an optimized real-time performance. the three bu ffers are arranged as shown in figure 18-2 . all three buffers have a 13 byte data st ructure similar to the outline of the receive buffers (see programmer?s model of message storage ). an additional transmit buffer priority regi ster (tbpr) contai ns an 8-bit so rxfg rxbg tx0 rxf txe prio tx1 txe prio tx2 txe prio mscan12 cpu bus
mscan controller message storage mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 331 called local priority field (prio) (see transmit buffer priority registers (tbpr) ). in order to trans mit a message, the cpu12 has to identify an available transmit buffer which is indicated by a set tr ansmit buffer empty (txe) flag in the mscan12 transmitter flag register (ctflg) (see mscan12 transmitter flag register (ctflg) ). the cpu12 then stores the identifier, the cont rol bits and the data content into one of the transmit buffers. finally, the buffer has to be flagged as being ready for transmission by clearing the txe flag. the mscan12 will then schedule the message fo r transmission and will signal the successful tran smission of the buffer by setting the txe flag. a transmit interrupt will be emitted (1) when txe is set and this can be used to drive the ap plication software to re-load the buffer. in case more th an one buffer is scheduled for transmission when the can bus becomes available for arbitr ation, the mscan12 uses the local priority setting of the three buffers fo r prioritizing. for this purpose every transmit buffer has an 8-bit local pr iority field (prio). the application software sets this field when the message is set up. the local priority reflects the priority of this partic ular message relati ve to the set of messages being emitted fr om this node. the lowest binary value of the prio field is defined to be the highest priority. the internal scheduling process take s places whenever the mscan12 arbitrates for the bus. this is also the case after the occurrence of a transmission error. when a high priority mess age is scheduled by the application software it may become necessary to abort a lower priority me ssage being set up in one of the three transmit buffers. as messages that are already under transmission can not be aborted, t he user has to request the abort by setting the correspon ding abort request flag (abtrq) in the transmission control register (ctc r). the mscan12 grants the request, if possible, by setting the co rresponding abort request acknowledge (abtak) and the txe flag in order to release the buffer and by emitting 1. the transmit interrupt will occur only if not masked. a polling scheme can be applied on txe also.
mscan controller technical data mc68hc912dt128a ? rev 4.0 332 mscan controller motorola a transmit interrupt. the transmit interr upt handler software can tell from the setting of t he abtak flag whethe r the message was actually aborted (abtak=1) or sent in the meantime (abtak=0). 18.5 identifier acceptance filter a very flexible programmable generic identifier acceptance filter has been introduced in order to reduce the cpu interrupt loading. the filter is programmable to operate in four different modes: two identifier acceptanc e filters, each to be applied to the full 29 bits of the identifier and to the following bits of the can frame: rtr, ide, srr. this mode implements a two filters for a full length can 2.0b compliant extended identifier. figure 18-3 shows how the first 32-bit filter bank (cidar0?3, cidmr0?3) produces a filter 0 hit. simi larly, the second fi lter bank (cidar4?7, cidmr4?7) produces a filter 1 hit. four identifier acceptance filters, each to be applied to a) the 11 bits of the identifier and the rtr bit of can 2.0a messages or b) the 14 most significant bits of t he identifier of can 2.0b messages. figure 18-4 shows how the first 32-bi t filter bank (cidar0?3, cidmr0?3) produces filter 0 and 1 hi ts. similarly, the second filter bank (cidar4?7, cidmr4?7) produ ces filter 2 and 3 hits. eight identifier acceptance filters, each to be applied to the first 8 bits of the identifier. this mode implements eight independent filters for the first 8 bit of a can 2.0a comp liant standard identifier or of a can 2.0b comp liant extended identifier. figure 18-5 shows how the first 32-bit filter bank (cidar0?3, cidm r0?3) produces filter 0 to 3 hits. similarly, the second filter bank (cidar4?7, cidmr4?7) produces filter 4 to 7 hits. closed filter. no can message will be copied into the foreground buffer rxfg, and the rxf fl ag will never be set.
mscan controller identifier acceptance filter mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 333 figure 18-3. 32-bit maskable identifier acceptance filters figure 18-4. 16-bit m askable acceptance filters cidmr2 id28 id21 id20 id15 id14 id7 id6 rtr id10 id3 id2 ide am7 idr0 idr0 idr1 idr1 idr2 idr3 am0 am7 am0 am7 am7 am0 am0 ac7 ac0 ac7 ac0 ac7 ac0 ac7 ac0 cidmro cidmr1 cidmr3 cidar3 cidar2 cidar1 cidaro id accepted (filter 0 hit) id28 id21 id20 id15 id14 id7 id6 rtr id10 id3 id2 ide am7 idr0 idr0 idr1 idr1 idr2 idr3 am0 am7 am0 ac7 ac0 ac7 ac0 cidmro cidmr1 cidar1 cidaro id accepted (filter 0 hit) id accepted (filter 1 hit) am7 am0 am7 am0 ac7 ac0 ac7 ac0 cidmr2 cidmr3 cidar3 cidar2
mscan controller technical data mc68hc912dt128a ? rev 4.0 334 mscan controller motorola figure 18-5. 8-bit m askable acceptance filters the identifier acceptance register s (cidar0?7) defi ne the acceptable patterns of the standard or exten ded identifier (id10?id0 or id28?id0). any of these bits can be marked don? t care in the identifier mask registers (cidmr0?7). a filter hit is indicated to the application software by a set rxf (receive buffer full flag, see mscan12 receiver fl ag register (crflg) ) and id28 id21 id20 id15 id14 id7 id6 rtr id10 id3 id2 ide am7 idr0 idr0 idr1 idr1 idr2 idr3 am0 ac7 ac0 cidmro cidaro id accepted (filter 0 hit) am7 am0 ac7 ac0 cidmr1 cidar1 am7 am0 ac7 ac0 cidmr2 cidar2 id accepted (filter 1 hit) id accepted (filter 2 hit) am7 am0 ac7 ac0 cidmr3 cidar3
mscan controller interrupts mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 335 three bits in the identifier a cceptance control register (see mscan12 identifier acceptance control register (cidac) ). these identifier hit flags (idhit2?0) clearly i dentify the filter sect ion that caused the acceptance. they simplify the application software ?s task to identify the cause of the receiver interrupt. in case that more than one hit occurs (two or more filters match) th e lower hit has priority. a hit will also cause a re ceiver interrupt if enabled. 18.6 interrupts the mscan12 supports four inte rrupt vectors mapped onto eleven different interrupt sources, any of which can be individually masked (for details see mscan12 receiver fl ag register (crflg) to mscan12 transmitter contro l register (ctcr) ): transmit interrupt : at least one of the th ree transmit buffers is empty (not scheduled) and can be loaded to schedule a message for transmission. the txe flags of the empty message buffers are set. receive interrupt : a message has been successfully received and loaded into the foregr ound receive buffer. this interrupt will be emitted immediately after receiv ing the eof symbol. the rxf flag is set. wake-up interrupt : an activity on the can bus occurred during mscan12 internal sleep mode. error interrupt : an overrun, error or warning condition occurred. the receiver flag regi ster (crflg) will indicate one of the following conditions: ? overrun: an overrun conditi on as described in receive structures has occurred. ? receiver warning : the receive error counter has reached the cpu warning limit of 96. ? transmitter warning : the transmit error counter has reached the cpu warning limit of 96.
mscan controller technical data mc68hc912dt128a ? rev 4.0 336 mscan controller motorola ? receiver error passive : the receive error counter has exceeded the error passive limit of 127 and mscan12 has gone to error passive state. ? transmitter error passive : the transmit error counter has exceeded the error passive limit of 127 and mscan12 has gone to error passive state. ? bus off : the transmit error count er has exceeded 255 and mscan12 has gone to busoff state. 18.6.1 interrupt acknowledge interrupts are directly associated with one or more status flags in either the mscan12 receiver flag regist er (crflg) or the mscan12 transmitter flag register (ctflg). interrupts are pending as long as one of the corresponding flags is set. the flags in above registers must be reset within the interrupt handler in order to handshake the interrupt. the flags are reset through writing a 1 to the corresponding bit position. a flag can not be cleared if the respec tive condition st ill prevails. note: bit manipulation instructio ns (bset) shall not be used to clear interrupt flags. 18.6.2 interrupt vectors the mscan12 supports four inte rrupt vectors as shown in table 18-1 . the vector addresses and t he relative interrupt pr iority are dependent on the chip integrati on and to be defined.
mscan controller protocol violation protection mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 337 18.7 protocol violation protection the mscan12 will protect the user from accident ally violating the can protocol through programming errors . the protection logic implements the following features: the receive and transmit error counters cannot be written or otherwise manipulated. all registers which control the configuration of the mscan12 can not be modified while the mscan12 is on-line. the sftres bit in cmcr0 (see mscan12 module control register (cmcr0) ) serves as a lock to prot ect the following registers: ? mscan12 module control register 1 (cmcr1) ? mscan12 bus timing register 0 and 1 (cbtr0, cbtr1) ? mscan12 identifier acceptance control register (cidac) ? mscan12 identifier accept ance registers (cidar0?7) ? mscan12 identifier mask registers (cidmr0?7) the txcan pin is forced to rece ssive when the mscan12 is in any of the low power modes. table 18-1. mscan12 interrupt vectors function source local mask global mask wake-up wupif wupie i bit error interrupts rwrnif rwrnie twrnif twrnie rerrif rerrie terrif terrie boffif boffie ovrif ovrie receive rxf rxfie transmit txe0 txeie0 txe1 txeie1 txe2 txeie2
mscan controller technical data mc68hc912dt128a ? rev 4.0 338 mscan controller motorola 18.8 low power modes the mscan12 has three modes wit h reduced power consumption compared to normal mode. in sl eep and soft_reset mode, power consumption is reduced by stopping all clocks except those to access the registers. in power_down mode, all clocks are stopped and no power is consumed. the wai and stop instructions put t he mcu in low power consumption stand-by modes. table 18-2 summarizes the comb inations of mscan12 and cpu modes. a particular combinat ion of modes is entered for the given settings of the bits cswai, slpak, and s ftres. for all modes, an mscan wake-up interrupt can occu r only if slpak=wupie=1. while the cpu is in wait mode, the mscan12 can be operated in normal mode and emit interrupts (registe rs can be accessed via background debug mode). table 18-2. mscan12 vs . cpu oper ating modes mscan mode cpu mode stop wait run power_down cswai = x (1) slpak = x sftres = x 1. x means don?t care. cswai = 1 slpak = x sftres = x sleep cswai = 0 slpak = 1 sftres = 0 cswai = x slpak = 1 sftres = 0 soft_reset cswai = 0 slpak = 0 sftres = 1 cswai = x slpak = 0 sftres = 1 normal cswai = 0 slpak = 0 sftres = 0 cswai = x slpak = 0 sftres = 0
mscan controller low power modes mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 339 18.8.1 mscan12 sleep mode the cpu can request the ms can12 to enter this low-power mode by asserting the slprq bit in the mo dule configuration register (see figure 18-6 ). the time when t he mscan12 will then enter sleep mode depends on its cu rrent activity: if there are one or more me ssage buffers are scheduled for transmission (txex = 0), the mscan will continue to transmit until all transmit message buffers ar e empty (txex = 1, transmitted successfully or aborted) and then goes into sleep mode if it is receiving, it continues to receive a nd goes into sleep mode as soon as the can bus next becomes idle if it is neither transmitting nor rece iving, it will immediately go into sleep mode the application software must avoi d setting up a transmission (by clearing one or more txe flag(s)) and imm ediately request sleep mode (by setting slprq). it will then depend on the exact sequence of operations whether the ms can12 will start trans mitting or go into sleep mode directly. during sleep mode, the slpak flag is set. the application software should use slpak as a handshake indication for the request (slprq) to go into sleep mode. when in sleep mode, the mscan12 stops its internal clocks. clocks to allow register accesses will still run. the txcan pin will stay in recessive state. if rxf=1, the message can be read and rxf can be cleared. however, if the ms can12 is in bus-off state, it stops counting 128*11 consecutive recessive bits due to the stopped clocks. likewise, copying of rxbg into rxfg will not take place while in sleep mode. it is possible to access the transmit buffers and to clear the txe flags. no message abort will take place while in sleep mode. the mscan12 will leave sl eep mode (wake-up) when bus activity occurs or the mcu clears the slprq bit or the mcu sets sftres.
mscan controller technical data mc68hc912dt128a ? rev 4.0 340 mscan controller motorola note: the mcu cannot clear the slprq bit before the mscan12 is in sleep mode (slpak = 1). after wake-up, the mscan12 waits fo r 11 consecutive recessive bits to synchronize to the bus. as a consequen ce, if the mscan 12 is woken-up by a can frame, this frame will not be receiv ed. the receive message buffers (rxbg and rxfg) will contain messages if they were received before sleep mode was entered. pend ing copying of rxbg and rxfg, as well as pending message aborts and pending message transmissions, will now be executed. if the mscan12 is still in bus-off state after sleep mode was left, it continues c ounting the 128*11 consecutive recessive bits. figure 18-6. sleep req uest / acknowledge cycle mscan12 sleeping slprq = 1 slpak = 1 mscan12 running slprq = 0 slpak = 0 sleep request slprq = 1 slpak = 0 mcu mscan12 mcu or mscan12
mscan controller low power modes mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 341 18.8.2 mscan12 soft_reset mode in soft_reset mode, the mscan12 is stopped. registers can still be accessed. this mode is used to init ialize the module c onfiguration, bit timing, and t he can message filter. see mscan12 module control register (cmcr0) for a complete descrip tion of the soft_reset mode. when setting the sftres bit, th e mscan12 immediately stops all ongoing transmissions and receptions, potentially c ausing the can protocol violations. the user is responsible to take care that the mscan12 is not active when soft_reset mo de is entered. the recommended procedure is to bri ng the mscan12 in to sleep mode before the sftres bit is set. 18.8.3 mscan12 power_down mode the mscan12 is in po wer_down mode when the cpu is in stop mode or the cpu is in wait mode and the cswai bit is set (see mscan12 module control register (cmcr0) ). when entering the power_down mode, the mscan12 immediately stops all ongoing transmissions and re ceptions, potentially causing can protocol violations. the user is responsible to take care that the mscan12 is not acti ve when power_down mode is entered. the recommended procedure is to bri ng the mscan12 in to sleep mode before the stop instructi on (or the wai instruction, if cswai is set) is executed. to protect the can bus system from fa tal consequences of violations to above rule, the mscan12 wi ll drive the txcan pin into recessive state. in power_down mode, no registers can be accessed.
mscan controller technical data mc68hc912dt128a ? rev 4.0 342 mscan controller motorola 18.8.4 programmable wake-up function the mscan12 can be progra mmed to apply a low-pa ss filter function to the rxcan input li ne while in sleep mode (see control bit wupm in the module control register, mscan12 module control register (cmcr0) ). this feature can be used to protect the mscan12 from wake-up due to short glitches on the c an bus lines. such glitch es can result from electromagnetic inferenc e within noisy environments. 18.9 timer link the mscan12 will generat e a timer signal whenev er a valid frame has been received. because the can spec ification defines a frame to be valid if no errors occurred before the eof field has been transmitted successfully, the timer si gnal will be generated ri ght after the eof. a pulse of one bit time is generated. as the mscan12 receiver engine receives also the frames being sent by itself, a timer signal will also be generated after a successful transmission. the previously described timer sig nal can be routed into the on-chip timer module (ect). under the contro l of the timer link enable (tlnken) bit in the cmcr0, this signal will be connected to the ect timer channel m input (1) . after ect timer has been programmed to capture rising edge events, it can be used under software control to generate 16-bit time stamps which can be stored with the received message. 1. the timer channel being used for the timer link for can0 is channel 4 and for can1 is channel 5.
mscan controller clock system mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 343 18.10 clock system figure 18-7 shows the structure of t he mscan12 clo ck generation circuitry. with this flexible cl ocking scheme the mscan12 is able to handle can bus rates ra nging from 10 kb ps up to 1 mbps. figure 18-7. clocking scheme the clock source bit (clksrc) in the mscan12 module control register (cmcr1) (see mscan12 bus timing register 0 (cbtr0) ) defines whether the mscan12 is c onnected to the output of the crystal oscillator (extali) or to the system clock (sysclk). the clock source has to be chosen such that the ti ght oscillator tolerance requirements (up to 0.4%) of the can protocol ar e met. additionally, for high can bus rates (1 mbps), a 50% duty cycle of the clock is required. for microcontrollers without the cgm module, cgmcanclk is driven from the crystal o scillator (extali). a programmable prescaler is used to generate out of mscanclk the time quanta (tq) clock. a time quantum is the atom ic unit of time handled by the mscan12. a bit time is subdivided into three segments (1) : sync_seg: this segment has a fixed length of one time quantum. signal edges are expected to happen within this section. 1. for further explanation of the under-lying co ncepts please refer to is o/dis 11519-1, section 10.3. mscan12 cgm sysclk extali cgmcanclk prescaler (1...64) time quanta clock clksrc clksrc
mscan controller technical data mc68hc912dt128a ? rev 4.0 344 mscan controller motorola time segment 1: this segmen t includes the prop_seg and the phase_seg1 of the c an standard. it can be programmed by setting the parameter tseg1 to consist of 4 to 16 time quanta. time segment 2: this segment represents t he phase_seg2 of the can standard. it can be programmed by setting the tseg2 parameter to be 2 to 8 time quanta long. the synchronization jump width can be programmed in a range of 1 to 4 time quanta by setti ng the sjw parameter. above parameters can be set by progr amming the bus ti ming registers (cbtr0?1, see mscan12 bus timing r egister 0 (cbtr0) and mscan12 bus timing r egister 1 (cbtr1) ). it is the user?s responsibil ity to make sure that his bit time settings are in compliance with the can standard. figure 18-9 gives an overview on the can conforming segment settings and the related parameter values. figure 18-8. segments within the bit time sync _seg time segment 1 time seg. 2 1 4 ... 16 2 ... 8 8... 25 time quanta = 1 bit time nrz signal sample point (single or triple sampling) (prop_seg + phase_seg1) (phase_seg2) transmit point
mscan controller memory map mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 345 18.11 memory map the mscan12 occupies 128 bytes in the cpu12 memory space. the background receive buffer can on ly be read in test mode. figure 18-9. can standard compli ant bit time segment settings time segment 1 tseg1 time segment 2 tseg2 synchron. jump width sjw 5 .. 10 4 .. 9 2 1 1 .. 2 0 .. 1 4 .. 11 3 .. 10 3 2 1 .. 3 0 .. 2 5 .. 12 4 .. 11 4 3 1 .. 4 0 .. 3 6 .. 13 5 .. 12 5 4 1 .. 4 0 .. 3 7 .. 14 6 .. 13 6 5 1 .. 4 0 .. 3 8 .. 15 7 .. 14 7 6 1 .. 4 0 .. 3 9 .. 16 8 .. 15 8 7 1 .. 4 0 .. 3 figure 18-10. msc an12 memory map $0100 control registers 9 bytes $0108 $0109 reserved 5 bytes $010d $010e error counters 2 bytes $010f $0110 identifier filter 16 bytes $011f $0120 reserved 29 bytes $013c $013d port can registers 3 bytes $013f $0140 foreground receive buffer $014f $0150 transmit buffer 0 $015f $0160 transmit buffer 1 $016f $0170 transmit buffer 2 $017f
mscan controller technical data mc68hc912dt128a ? rev 4.0 346 mscan controller motorola 18.12 programmer?s model of message storage the following section deta ils the organization of the receive and transmit message buffers and the associated control registers. for reasons of programmer interface simplificati on the receive and transmit message buffers have the same outline. each message buf fer allocates 16 bytes in the memory map containing a 13 by te data structure. an additional transmit buffer priority register (tbpr ) is defined for t he transmit buffers. figure 18-11. message buffer organization address (1) 1. x is 4, 5, 6, or 7 dep ending on which buffer rxfg, tx0, tx1, or tx2 respectively. register name 01x0 identifier register 0 01x1 identifier register 1 01x2 identifier register 2 01x3 identifier register 3 01x4 data segment register 0 01x5 data segment register 1 01x6 data segment register 2 01x7 data segment register 3 01x8 data segment register 4 01x9 data segment register 5 01xa data segment register 6 01xb data segment register 7 01xc data length register 01xd transmit buffer priority register (2) 2. not applicable for receive buffers 01xe unused 01xf unused
mscan controller programmer?s model of message storage mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 347 18.12.1 message buffer outline figure 18-12 shows the common 13 byte da ta structure of receive and transmit buffers for ex tended identifiers. th e mapping of standard identifiers into the idr registers is shown in figure 18-13 . all bits of the 13 byte data structure ar e undefined out of reset. note: the foreground receive buffer can be read anyti me but can not be written. the transmit buffers c an be read or written anytime. figure 18-12. receive/t ransmit message buffer extended identifier addr (1) registerr/wbit 7654321bit 0 $01x0 idr0 r id28 id27 id26 id25 id24 id23 id22 id21 w $01x1 idr1 r id20 id19 id18 srr (1) ide (1) id17 id16 id15 w $01x2 idr2 r id14 id13 id12 id11 id10 id9 id8 id7 w $01x3 idr3 r id6 id5 id4 id3 id2 id1 id0 rtr w $01x4 dsr0 r db7 db6 db5 db4 db3 db2 db1 db0 w $01x5 dsr1 r db7 db6 db5 db4 db3 db2 db1 db0 w $01x6 dsr2 r db7 db6 db5 db4 db3 db2 db1 db0 w $01x7 dsr3 r db7 db6 db5 db4 db3 db2 db1 db0 w $01x8 dsr4 r db7 db6 db5 db4 db3 db2 db1 db0 w $01x9 dsr5 r db7 db6 db5 db4 db3 db2 db1 db0 w $01xa dsr6 r db7 db6 db5 db4 db3 db2 db1 db0 w $01xb dsr7 r db7 db6 db5 db4 db3 db2 db1 db0 w $01xc dlr r dlc3 dlc2 dlc1 dlc0 w 1. x is 4, 5, 6, or 7 depending on which buffer rxfg, tx0, tx1, or tx2 respectively.
mscan controller technical data mc68hc912dt128a ? rev 4.0 348 mscan controller motorola 18.12.2 identifier registers (idrn) the identifiers consist of either 11 bits (id10?id0) for the standard, or 29 bits (id28?id0) for the extended format. id10/28 is the most significant bit and is transmitted firs t on the bus during the arbitration procedure. the priority of an identifier is defined to be highest for the smallest binary number. srr ? substitute remote request this fixed recessive bit is used only in extended format. it must be set to 1 by the user for transmission bu ffers and will be st ored as received on the can bus for receive buffers. ide ? id extended this flag indicates whet her the extended or standa rd identifier format is applied in this buffer. in case of a receive buffer t he flag is set as being received and indica tes to the cpu how to process the buffer identifier registers. in case of a transmit buffer the flag indicates to the mscan12 what type of identifier to send. 0 = standard format (11-bit) 1 = extended format (29-bit) figure 18-13. standard identifier mapping addr (1) registerr/wbit 7654321bit 0 $01x0 idr0 r id10 id9 id8 id7 id6 id5 id4 id3 w $01x1 idr1 r id2 id1 id0 rtr ide(0) w $01x2 idr2 r w $01x3 idr3 r w 1. x is 4, 5, 6, or 7 depending on which buf fer rxfg, tx0, tx1, or tx2 respectively.
mscan controller programmer?s model of message storage mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 349 rtr ? remote tran smission request this flag reflects the st atus of the remote transmission request bit in the can frame. in case of a rece ive buffer it indicates the status of the received frame and allows to support the tr ansmission of an answering frame in software. in case of a transmit buffer this flag defines the setting of t he rtr bit to be sent. 0 = data frame 1 = remote frame 18.12.3 data length register (dlr) this register keeps t he data length field of the can frame. dlc3 ? dlc0 ? data length code bits the data length code contai ns the number of bytes (data byte count) of the respective mess age. at transmission of a remote frame, the data length code is transmitted as programm ed while the number of transmitted bytes is always 0. the data byte count ranges from 0 to 8 for a data frame. table 18-3 shows the effect of setting the dlc bits. table 18-3. data length codes data length code data byte count dlc3 dlc2 dlc1 dlc0 00000 00011 00102 00113 01004 01015 01106 01117 10008
mscan controller technical data mc68hc912dt128a ? rev 4.0 350 mscan controller motorola 18.12.4 data segment registers (dsrn) the eight data segment registers cont ain the data to be transmitted or being received. the number of bytes to be transmitted or being received is determined by the data leng th code in the corresponding dlr. 18.12.5 transmit buffer pr iority registers (tbpr) prio7 ? prio0 ? local priority this field defines the lo cal priority of the associated message buffer. the local priority is used for the inte rnal prioritizing process of the mscan12 and is defined to be highest fo r the smallest binary number. the mscan12 implements the foll owing internal priorization mechanism: all transmission buffers with a cl eared txe flag par ticipate in the priorisation right before the so f (start of frame) is sent. the transmission buffer with the lowe st local priority field wins the priorisation. in case of more than one buffer ha ving the same lowest priority the message buffer with the lower index number wins. note: to ensure data integrity, no registers of the tr ansmit buffers shall be written while the associ ated txe flag is cleared. to ensure data integrity, no register s of the receive buffer shall be read while the rxf flag is cleared. bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 tbpr (1) 1. x is 5, 6, or 7 depending on which buffer tx0, tx1, or tx2 respectively. r prio7 prio6 prio5 prio4 prio3 prio2 prio1 prio0 $01xd w reset - - - - - - - -
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 351 18.13 programmer?s mode l of control registers 18.13.1 overview the programmer?s model ha s been laid out for maximum simplicity and efficiency. 18.13.2 mscan12 module cont rol register (cmcr0) cswai ? can stops in wait mode 0 = the module is not affe cted during wait mode. 1 = the module ceases to be clocked during wait mode. synch ? synchronized status this bit indicates whet her the mscan12 is synchronized to the can bus and as such can participate in the co mmunication process. 0 = mscan12 is not sync hronized to the can bus 1 = mscan12 is synchr onized to the can bus tlnken ? timer enable this flag is used to establish a link between the mscan12 and the on- chip timer (see timer link ). 0 = the port is connected to the timer input. 1 = the mscan12 timer signal out put is connected to the timer input. slpak ? sleep m ode acknowledge this flag indicates whether the ms can12 is in module internal sleep mode. it shall be used as a handshak e for the sleep mode request (see mscan12 sleep mode ). 0 = wake-up ? the mscan12 is not in sleep mode. 1 = sleep ? the mscan12 is in sleep mode. bit 7654321bit 0 cmcr0 r 0 0 cswai synch tlnken slpak slprq sftres $0100 w reset 0 0 1 0 0 0 0 1
mscan controller technical data mc68hc912dt128a ? rev 4.0 352 mscan controller motorola slprq ? sleep request this flag allows to reques t the mscan12 to go into an internal power- saving mode (see mscan12 sleep mode ). 0 = wake-up ? the mscan12 will function normally. 1 = sleep request ? the mscan12 will go into sleep mode when the can bus is idle, i.e. the module is not receiving a message and all transmi t buffers are empty. sftres? soft_reset when this bit is set by the cpu, the mscan12 immedi ately enters the soft_reset state. any ongoing transmission or reception is aborted and synchronization to the bus is lost. the following registers will go into and stay in the same state as out of hard reset: cmcr0, crflg, crier, ctflg, ctcr. the registers cmcr1, cbtr0, cb tr1, cidac, cidar0?3, cidmr0?3 can only be written by the cpu when the mscan12 is in soft_reset state. the values of the error counters are not affected by soft_reset. when this bit is cleared by the cpu, the mscan 12 will try to synchronize to the can bus: if t he mscan12 is not in busoff state it will be synchroniz ed after 11 recessive bits on the bus; if the mscan12 is in busoff state it cont inues to wait for 128 occurrences of 11 recessive bits. clearing sftres and writi ng to other bits in cmcr0 must be in separate instructions. 0 = normal operation 1 = mscan12 in soft_reset state.
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 353 18.13.3 mscan12 module cont rol register (cmcr1) loopb ? loop back self test mode when this bit is set the mscan 12 performs an internal loop back which can be used for self test opera tion: the bit stream output of the transmitter is fed back to the rece iver. the rxcan input pin is ignored and the txcan output goes to the recessive state (1). note that in this state the mscan12 ignores the bit s ent during the ack slot of the can frame acknowledge fi eld to insure proper reception of its own message and will treat mess ages being received while in transmission as received me ssages from remote nodes. 0 = normal operation 1 = activate loop back self test mode wupm ? wake-up mode this flag defines whether the integr ated low-pass filter is applied to protect the mscan12 from spurious wake-ups (see programmable wake-up function ). 0 = mscan12 will wake up t he cpu after any recessive to dominant edge on the can bus. 1 = mscan12 will wake up the cpu only in case of dominant pulse on the bus which has a length of at least approximately t wup . clksrc ? mscan 12 clock source this flag defines which clock sour ce the mscan12 module is driven from (only for system with cgm module; see clock system , figure 18-7 ). 0 = the mscan12 clock source is extali. 1 = the mscan12 clock source is sysclk, twice the frequency of eclk. note: the cmcr1 register can onl y be written if the sft res bit in cmcr0 is set. bit 7654321bit 0 cmcr1r00000 loopb wupm clksrc $0101 w reset 0 0 0 00000
mscan controller technical data mc68hc912dt128a ? rev 4.0 354 mscan controller motorola 18.13.4 mscan12 bus timi ng register 0 (cbtr0) sjw1, sjw0 ? synchronization jump width the synchronization jump width defi nes the maximum number of time quanta (tq) clock cycles by whic h a bit may be shortened, or lengthened, to achieve resynchron ization on data transitions on the bus (see table 18-4 ). brp5 ? brp0 ? b aud rate prescaler these bits determine the time quanta ( tq) clock, which is used to build up the individual bi t timing, according to table 18-5 . note: the cbtr0 register can only be writte n if the sftres bit in cmcr0 is set. bit 7654321bit 0 cbtr0 r sjw1 sjw0 brp5 brp4 brp3 brp2 brp1 brp0 $0102 w reset 0 0 0 0 0 0 0 0 table 18-4. synchronization jump width sjw1 sjw0 synchronization jump width 0 0 1 tq clock cycle 0 1 2 tq clock cycles 1 0 3 tq clock cycles 1 1 4 tq clock cycles table 18-5. baud rate prescaler brp5 brp4 brp3 brp2 brp1 brp0 prescaler value (p) 000000 1 000001 2 000010 3 000011 4 :::::: : :::::: : 111111 64
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 355 18.13.5 mscan12 bus timi ng register 1 (cbtr1) samp ? sampling this bit determines the number of samples of the serial bus to be taken per bit time. if se t three samples per bit are taken, the regular one (sample point) and two preceding sa mples, using a majority rule. for higher bit rates samp should be cleared, which means that only one sample will be taken per bit. 0 = one sample per bit. 1 = three samples per bit (1) . tseg22 ? tseg10 ? time segment time segments within the bit time fix the number of clock cycles per bit time, and the location of the sample point. time segment 1 (tseg1) and time segment 2 (tseg2) are programmable as shown in table 18-7 . bit 7654321bit 0 cbtr1 r samp tseg22 tseg21 tseg20 t seg13 tseg12 tseg11 tseg10 $0103 w reset 0 0 0 0 0 0 0 0 1. in this case phase_seg1 must be at least 2 timequanta. table 18-6. time segment syntax sync_seg system expects transitions to occur on the bus during this period. transmit point a node in transmit mode will transfer a new value to the can bus at this point. sample point a node in receive mode will sample th e bus at this point. if the three samples per bit option is selected then this point marks the position of the third sample. table 18-7. time segment values tseg13 tseg12 tseg11 tseg10 time segment 1 tseg22 tseg21 tseg20 time segment 2 0 0 0 0 1 tq clock cycle 0 0 0 1 tq clock cycle 0 0 0 1 2 tq clock cycles 0 0 1 2 tq clock cycles 0 0 1 0 3 tq clock cycles . . . . 0 0 1 1 4 tq clock cycles . . . . . . . . . 1 1 1 8 tq clock cycles .... . 1 1 1 1 16 tq clock cycles
mscan controller technical data mc68hc912dt128a ? rev 4.0 356 mscan controller motorola the bit time is determined by the oscillator frequen cy, the baud rate prescaler, and the number of time quanta (tq) clock cycles per bit (as shown above). note: the cbtr1 register can only be writte n if the sftres bit in cmcr0 is set. 18.13.6 mscan12 receiver flag register (crflg) all bits of this regist er are read and clear onl y. a flag can be cleared by writing a 1 to the corresponding bi t position. a flag can only be cleared when the condition which caused the se tting is no more valid. writing a 0 has no effect on the fl ag setting. every flag has an associated interrupt enable flag in the crier register. a hard or soft reset will clear the register. wupif ? wake-up interrupt flag if the mscan12 detects bus activity while it is in sleep mode, it clears the slpak bit in the cmcr0 register; the wupif bi t will then be set. if not masked, a wake-up interrupt is pending while this flag is set. 0 = no wake-up activity has bee n observed while in sleep mode. 1 = mscan12 has det ected activity on the bus and requested wake-up. rwrnif ? receiver wa rning interrupt flag this bit will be set w hen the mscan12 goes in to warning status due to the receive error counter ( rec) exceeding 96 and neither one of the error interrupt flags or the bus-off interrupt flag is set (1) . if not masked, an error interrupt is pen ding while this flag is set. 0 = no receiver warning status has been reached. 1 = mscan12 went into receiver warning status. bit 7654321bit 0 crflg r wupif rwrnif twrnif rerri f terrif boffif ovrif rxf $0104 w reset 0 0 0 00000 1. rwrnif = (96 < rec) & rerrif & terrif & boffif
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 357 twrnif ? transmitter wa rning interrupt flag this bit will be set w hen the mscan12 goes in to warning status due to the transmit error counter (tec) exceeding 96 and neither one of the error interrupt flags or the bus-off interrupt flag is set (1) . if not masked, an error interrupt is pen ding while this flag is set. 0 = no transmitter warning status has been reached. 1 = mscan12 went into transmitter warning status. rerrif ? receiver error passive interrupt flag this bit will be set when th e mscan12 goes into error passive status due to the receive error counter (rec) exceeding 127 and the bus- off interrupt flag is not set (2) . if not masked, an error interrupt is pending while this flag is set. 0 = no receiver error pa ssive status has been reached. 1 = mscan12 went in to receiver erro r passive status. terrif ? transmitter error passive interrupt flag this bit will be set when th e mscan12 goes into error passive status due to the transmit error counter (tec) exceeding 127 and the bus- off interrupt flag is not set (3) . if not masked, an error interrupt is pending while this flag is set. 0 = no transmitter error passi ve status has been reached. 1 = mscan12 went in to transmitter error passive status. boffif ? busoff interrupt flag this bit will be set when the msc an12 goes into busoff status, due to the transmit error counter exc eeding 255. it ca nnot be cleared before the mscan12 has monitor ed 128*11 consecutive recessive bits on the bus. if not masked, an er ror interrupt is pending while this flag is set. 0 = no busoff stat us has been reached. 1 = mscan12 went in to busoff status. 1. twrnif = (96 < tec) & rerrif & terrif & boffif 2. rerrif = (128 < rec < 255) & boffif 3. terrif = (128 < tec < 255) & boffif
mscan controller technical data mc68hc912dt128a ? rev 4.0 358 mscan controller motorola ovrif ? overrun interrupt flag this bit will be set when a data overrun conditi on occurred. if not masked, an error interrupt is pen ding while this flag is set. 0 = no data overrun has occurred. 1 = a data overrun has been detected. rxf ? receive buffer full the rxf flag is set by the mscan12 when a new message is available in the foreground receive buffer. this flag indicates whether the buffer is loaded with a correct ly received message. after the cpu has read that message from the re ceive buffer the rxf flag must be handshaked (cleared) in or der to release the buf fer. a set rxf flag prohibits the exchange of the background rece ive buffer into the foreground buffer. if not masked, a receive interrupt is pending while this flag is set. 0 = the receive buffer is released (not full). 1 = the receive buffer is full . a new message is available. note: the crflg register is held in the reset state if t he sftres bit in cmcr0 is set. 18.13.7 mscan12 receiver interrup t enable regi ster (crier) wupie ? wake-up interrupt enable 0 = no interrupt will be generated from this event. 1 = a wake-up event will result in a wake-up interrupt. rwrnie ? receiver wa rning interrupt enable 0 = no interrupt will be generated from this event. 1 = a receiver warn ing status event will resu lt in an error interrupt. twrnie ? transmitter wa rning interrupt enable 0 = no interrupt will be generated from this event. 1 = a transmitter warning status event will result in an error interrupt. bit 7654321bit 0 crier r wupie rwrnie twrnie rerrie t errie boffie ovrie rxfie $0105 w reset 00000000
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 359 rerrie ? receiver error passive interrupt enable 0 = no interrupt will be generated from this event. 1 = a receiver error pa ssive status event will result in an error interrupt. terrie ? transmitter erro r passive interrupt enable 0 = no interrupt will be generated from this event. 1 = a transmitter error passive stat us event will resu lt in an error interrupt. boffie ? busoff interrupt enable 0 = no interrupt will be generated from this event. 1 = a busoff event will resu lt in an error interrupt. ovrie ? overrun interrupt enable 0 = no interrupt will be generated from this event. 1 = an overrun event will re sult in an error interrupt. rxfie ? receiver full interrupt enable 0 = no interrupt will be generated from this event. 1 = a receive buffer full (successf ul message reception) event will result in a receive interrupt. note: the crier register is held in the reset state if the sftres bit in cmcr0 is set.
mscan controller technical data mc68hc912dt128a ? rev 4.0 360 mscan controller motorola 18.13.8 mscan12 transmitte r flag register (ctflg) the abort acknowledge flags are read only. the transmi tter buffer empty flags are read and clear only. a flag can be cleared by writing a1 to the corresponding bit position. writing a zero has no effect on the flag setting. the transmitter buffer empty flags each have an associated interrupt enable flag in the ctcr register. a hard or soft reset will reset the register. abtak2 ? abtak0 ? abort acknowledge this flag acknowledges that a me ssage has been ab orted due to a pending abort request from the cpu. after a particular message buffer has been flagged empty, th is flag can be used by the application software to identif y whether the message has been aborted successfully or has been sent in the meantime. the flag is reset implicitly whenev er the associated txe flag is set to 0. 0 = the massage has no t been aborted, thus has been sent out. 1 = the message ha s been aborted. txe2 ? txe0 ?transmi tter buffer empty this flag indicates that the asso ciated transmit message buffer is empty, thus not scheduled for transmi ssion. the cpu must handshake (clear) the flag after a message has been set up in the transmit buffer and is due for transmi ssion. the mscan12 will set the flag after the message ha s been sent successfully . the flag will also be set by the mscan12 when th e transmission request was successfully aborted due to a pending abo rt request ( mscan12 transmitter contro l register (ctcr) ). if not masked, a transmit interrupt is pending while this flag is set. clearing this flag will also clear the corresponding a bort acknowledge flag (abtak, see above). setting this flag will clear the corresponding abort request flag (abtrq, mscan12 transmitter control register (ctcr) ). bit 7654321bit 0 ctflg r 0 abtak2 abtak1 abtak0 0 txe2 txe1 txe0 $0106 w reset 0 0 0 00111
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 361 0 = the associated message buffer is full (loaded wi th a message due for transmission). 1 = the associated message buffer is empty (not scheduled). note: the ctflg register is held in the re set state if the sftres bit in cmcr0 is set. 18.13.9 mscan12 transmitter control register (ctcr) abtrq2 ? abtrq0 ? abort request the cpu sets this bit to request that an already scheduled message buffer (txe = 0) shall be abort ed. the mscan12 will grant the request when the message is not already under transmission. when a message is aborted t he associated txe and the abort acknowledge flag (abtak, see mscan12 transmitter fl ag register (ctflg) ) will be set and an txe interrupt will o ccur if enabled. th e cpu can not reset abtrqx. abtrqx is reset im plicitly whenever the associated txe flag is set. 0 = no abort request. 1 = abort request pending. note: the software must not clear one or mo re of the txe flags in ctfgl and simultaneously set the res pective abtrq bit(s). txeie2 ? txeie0 ? transmitt er empty interrupt enable 0 = no interrupt will be generated from this event. 1 = a transmitter empty (transmit buffer available for transmission) event will result in a tr ansmitter empty interrupt. note: the ctcr register is held in the reset state if t he sftres bit in cmcr0 is set. bit 7654321bit 0 ctcr r 0 abtrq2 abtrq1 abtrq0 0 txeie2 txeie1 txeie0 $0107 w reset 0 0 0 00000
mscan controller technical data mc68hc912dt128a ? rev 4.0 362 mscan controller motorola 18.13.10 mscan12 identi fier acceptance control register (cidac) idam1 ? idam0 ? identifier a cceptance mode the cpu sets these flags to define the i dentifier acceptance filter organization (see identifier acceptance filter ). table 18-7 summarizes the different setti ngs. in filter closed mode no messages will be accepted such th at the foreground buffer will never be reloaded. idhit2 ? idhit0 ? i dentifier acceptance hit indicator the mscan12 sets these flags to indi cate an identifier acceptance hit (see identifier acceptance filter ). table 18-7 summarizes the different settings. the idhit indicators ar e always related to the message in the foreground buffer. w hen a message gets copied from the background to the foreground buffer the indicators are updated as well. note: the cidac register can onl y be written if the s ftres bit in cmcr0 is set. bit 7654321bit 0 cidac r 0 0 idam1 idam0 0 idhit2 idhit1 idhit0 $0108 w reset 0 0 0 00000 table 18-8. identifier acceptance mode settings idam1 idam0 identif ier acceptance mode 0 0 two 32 bit acceptance filters 0 1 four 16 bit acceptance filters 1 0 eight 8 bit acceptance filters 1 1 filter closed table 18-9. identifier acceptance hit indication idhit2 idhit1 idhit0 iden tifier acceptance hit 0 0 0 filter 0 hit 0 0 1 filter 1 hit 0 1 0 filter 2 hit 0 1 1 filter 3 hit 1 0 0 filter 4 hit 1 0 1 filter 5 hit 1 1 0 filter 6 hit 1 1 1 filter 7 hit
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 363 18.13.11 mscan12 receive error counter (crxerr) this register reflec ts the status of the msc an12 receive error counter. the register is read only. 18.13.12 mscan12 transmit error counter (ctxerr) this register reflects t he status of the mscan12 transmit error counter. the register is read only. note: both error counters must only be read when in sleep or soft_reset mode. 18.13.13 mscan12 iden tifier acceptance registers (cidar0?7) on reception each message is writ ten into the ba ckground receive buffer. the cpu is only signalled to read the me ssage however, if it passes the criteria in the identi fier acceptance and identifier mask registers (accepted); ot herwise, the message will be overwritten by the next message (dropped). the acceptance registers of the ms can12 are applied on the idr0 to idr3 registers of in coming messages in a bit by bit manner. for extended identifiers all four acceptance and mask registers are applied. for standard i dentifiers only the fi rst two (cidmr0/1 and cidar0/1) are applied. in the latter ca se it is required to program the three last bits (am2 ? am0) in the mask register cidmr1 to ?don?t care?. bit 7654321bit 0 crxerr r rxerr7 rxerr6 rxerr5 rxerr4 rxerr3 rxerr2 rxerr1 rxerr0 $010e w reset 0 0 0 0 0 0 0 0 bit 7654321bit 0 ctxerr r txerr7 txerr6 txerr5 txe rr4 txerr3 txerr2 txerr1 txerr0 $010f w reset 0 0 0 0 0 0 0 0
mscan controller technical data mc68hc912dt128a ? rev 4.0 364 mscan controller motorola ac7 ? ac0 ? acc eptance code bits ac7 ? ac0 comprise a user defined sequence of bits with which the corresponding bits of th e related identifier regi ster (idrn) of the receive message buffer are compared. the result of this comparison is then masked with the corres ponding identifier mask register. note: the cidar0?7 registers can only be wr itten if the sftres bit in cmcr0 is set. figure 18-14. identifier ac ceptance registers (1st bank) bit 7654321bit 0 cidar0 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $0110 w cidar1 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $0111 w cidar2 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $0112 w cidar3 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $0113 w reset-------- figure 18-15. identifier acce ptance regist ers (2nd bank) bit 7654321bit 0 cidar4 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $0118 w cidar5 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $0119 w cidar6 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $011a w cidar7 r ac7 ac6 ac5 ac4 ac3 ac2 ac1 ac0 $011b w reset - - - - ----
mscan controller programmer?s model of control registers mc68hc912dt128a ? rev 4.0 technical data motorola mscan controller 365 18.13.14 mscan12 i dentifier mask r egisters (cidmr0?7) the identifier mask register specifies which of the corres ponding bits in the identifier acceptance register are relevant for acc eptance filtering. am7 ? am0 ? acceptance mask bits if a particular bit in th is register is cleared this indicates that the corresponding bit in the identifier acceptance register must be the same as its identifier bit, before a match wi ll be detected. the message will be accepted if all such bits match. if a bit is set, it indicates that the state of the corresponding bit in the identifier acceptance register will not affect whether or not the message is accepted. 0 = match corresponding acceptance c ode register and identifier bits. 1 = ignore corresponding accept ance code r egister bit. note: the cidmr0?7 registers can only be wr itten if the sf tres bit in cmcr0 is set. figure 18-16. identifier mask registers (1st bank) bit 7654321bit 0 cidmr0 r am7 am6 am5 am4 am3 am2 am1 am0 $0114 w cidmr1 r am7 am6 am5 am4 am3 am2 am1 am0 $0115 w cidmr2 r am7 am6 am5 am4 am3 am2 am1 am0 $0116 w cidmr3 r am7 am6 am5 am4 am3 am2 am1 am0 $0117 w reset-------- figure 18-17. ident ifier mask regi sters (2nd bank) bit 7654321bit 0 cidmr4 r am7 am6 am5 am4 am3 am2 am1 am0 $011c w cidmr5 r am7 am6 am5 am4 am3 am2 am1 am0 $011d w cidmr6 r am7 am6 am5 am4 am3 am2 am1 am0 $011e w cidmr7 r am7 am6 am5 am4 am3 am2 am1 am0 $011f w reset--------
mscan controller technical data mc68hc912dt128a ? rev 4.0 366 mscan controller motorola 18.13.15 mscan12 port can c ontrol register (pctlcan) the following bits control pins 7 thro ugh 2 of port can when they are implemented externally. pupcan ? pull-up enable port can 0 = pull mode dis abled for port can. 1 = pull mode enabled for port can. rdpcan ? reduced drive port can 0 = reduced drive dis abled for port can. 1 = reduced drive enabled for port can. 18.13.16 mscan12 port can da ta register (portcan) port bits 7 to 2 will read zero w hen configured as inputs because they are not implement ed externally. when configured as output, port bits 7 to 2 will read the last value written. reading bits 1 and 0 returns the value of the txcan and rxcan pins, respectively. 18.13.17 mscan12 port can data direction regi ster (ddrcan) ddcan7 ? ddcan2 ? this bits served as memory locations since there are no correspondi ng external port pins. bit 7654321bit 0 pctlcanr000000 pupcan rdpcan $013d w reset 0 0 0 0 0 0 0 0 bit 7654321bit 0 portcan r pcan7 pcan6 pcan5 pcan4 pcan3 pcan2 txcan rxcan $013e w reset ----- bit 7654321bit 0 ddrcan r ddcan7 ddcan6 ddcan5 ddcan4 ddcan3 ddcan2 00 $013f w reset 0 0000000
mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 367 technical data ? mc68hc912dt128a section 19. analog-to-digital converter 19.1 contents 19.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 19.3 modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369 19.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370 19.5 atd operational modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372 19.6 atd operation in different mcu modes . . . . . . . . . . . . . . . . 373 19.7 general purpose digital input port operation . . . . . . . . . . . .375 19.8 application considerations . . . . . . . . . . . . . . . . . . . . . . . . . . .376 19.9 atd registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 19.2 introduction the mc68hc912dt128a has two identical atd m odules identified as atd0 and atd1. except for the v dda and v ssa analog supply voltage, all pins are duplicated and indexed wi th ?0? or ?1? in the following description. an ?x? indicates either ?0? or ?1?. the atd module is an 8-channel, 10-bit or 8-bit, multiplexed-input, successive-approximation analog-to-dig ital converter. it does not require external sample and hold circ uits because of the type of charge redistribution technique used. the atd converter timing can be synchronized to the system pclk. the atd module consists of a 16- word (32-byte) memory-mapped control register block used for control, testing and configuration.
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 368 analog-to-digital converter motorola 19.2.1 features ? 8/10 bit resolution ? 10 s, 10-bit single conversion time ? sample and transfer buffer amplifier ? programmable sample time ? left/right justified result data ? conversion completion interrupt ? analog input mult iplexer for 8 anal og input channels ? analog/digital inpu t pin multiplexing ? 1, 4, 8 conversi on sequence lengths ? continuous conversion mode ? multiple channel scans figure 19-1. analog-to-digi tal converter block diagram mode and timing controls atd 0 atd 1 atd 2 atd 3 atd 4 atd 5 atd 6 atd 7 sar rc dac array and comparator internal bus v dda v ssa v rlx v rhx clock select/prescale analog mux and sample buffer amp port ad data input register anx7/padx7 anx6/padx6 anx5/padx5 anx4/padx4 anx3/padx3 anx2/padx2 anx1/padx1 anx0/padx0 reference supply hc12 atd block
analog-to-digital converter modes of operation mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 369 19.3 modes of operation analog to digital conversions are pe rformed in a variety of different programmable sequences referred to as conversion modes. each conversion mode is defined by: how many a/d conversions (one, f our or eight) are performed in a sequence which analog input channels ar e examined during a sequence the sample time length whether sequences are perform ed continuously or not result register assignments the modes are defined by the settings of three control bits (in atdctl5) mult controls whether the s equence examines a single analog input channel or scans a num ber of different channels scan determines if sequences are performed continuously sc determines if we are perfor ming a special conversion i.e. converting v rl , v rh , (v rl +v rh )/2 (usually used for test purposes). and three contro l values cc/cb/ca (in atdctl5) define the input channel(s) to be examined s8c/s1c (in atdctl3/5) define the number of conversions in a sequence smp0/smp1 (in atdctl4) define t he length of the sample time. sequences are initiated or halted by writing to control registers atdctl4 and atdctl5. for the continuous sequence modes, co nversions will not stop until another non-continuous conver sion sequence is initiated and finishes the atd is powered do wn (adpu control bit) the atd is reset
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 370 analog-to-digital converter motorola wait is executed (if the aswa i bit is activated) stop is executed. the mcu can discover when result dat a is available in the result registers with an interrupt on seq uence complete or by polling the conversion complete flags the scf bit is set after the co mpletion of each sequence. the ccf bit associated with each re sult register is set when that register is loaded with result data. note: atd conversion modes should not be confused with mcu operating modes such as stop, wait, idle, run, debug, and special (test) modes or with module defined operating modes such as power down, fast flag clear, 8-bit reso lution, 10-bit resolution, interrupt enable, clock prescaler setting, and freeze modes; and finally do not confuse with module result data formats such as right justify mode and left justify mode. 19.4 functional description 19.4.1 analog input multiplexer the analog input multiplexer selects one of the 8 exte rnal analog input channels to generate an analog sample. the input analog signals are unipolar and must fall within the potential r ange of vssa to vdda (analog electronics supply potentials). 19.4.2 sample bu ffer amplifier a sample amplifier is used to buffe r the input analog signal so that a storage node can be quickly char ged to the sample potential.
analog-to-digital converter functional description mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 371 19.4.3 sample and hold stage a sample and hold (s/h) stage accept s the analog signal from the input multiplexer and stores it as a capacitor char ge on a storage node in the module. the sample process uses a three stage approach: 1. the input signal is samp led onto a sample capacitor (for 2 module clocks). 2. the sample amplifier quickly c harges the storage node with a copy of the sample capacitor potential (for 4 module clocks). 3. the input signal is connected directly to the storage node to complete the sample for high accu racy (for 2, 4, 8 or 16 module clocks). longer sample times allo w accurate measurement of higher impedance sources. this charge redistribution method el iminates the need for external sample-and-hold circuitry. 19.4.4 analog-to-digit al converter submodule the analog-to-digital (a/d) machine uses a successive approximation a/d architecture to perform analog to digital conversi ons. the resolution of the a/d converter is se lectable at either 8 or 10 bits. it functions by comparing the stored analog sample potential wit h a series of digitally generated analog potentials (using cdac & rdac arra ys). by following a binary search algorithm, the converter quickly locates the approximating potential that is nearest to the sampled pot ential. at the end of the conversion pr ocess (10 module clocks for 8-bit, 12 module clocks for 10-bit), the successive approximation r egister (sar) contains the nearest appr oximation to the samp led signal, given the resolution of the a/d co nverter, and is transfe rred to the appropriate results register in the selected format. 19.4.5 clock prescaler function to keep the atd module clock with in the specified frequency range (note: there is a mini mum and maximum frequency), a clock prescaler function is available. this function divides the system pclk by a
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 372 analog-to-digital converter motorola programmable constant in order to generate the at d module?s internal clock. one additional benefit of the prescaled clo ck feature is that it allows the user further control ov er the sample per iod (note that changing the module clock also affects conversion time). the prescaler is based on a 5 bit modul us counter and divides the pclk by an integer value be tween 1 and 32. the final clock frequency is obtained with a further division by 2. the internal atd module clock and the system pclk have a direct phase relationship, however the at d module operates as if it is effectively asynchronous to mcu bus clock cycles. 19.5 atd operational modes 19.5.1 power down mode the atd module can be power ed down under program control. this is done by turning the clock signals off to the digital electronics of the module and eliminating th e quiescent current dr aw of the analog electronics. power down control is implem ented in one of three ways. 1. using the adpu bit in co ntrol register atdctl2. 2. when stop instruction is execut ed, the module will power down for the duration of the stop function. 3. if the module wait enable bi t (aswai) is set and a wait instruction is executed, the module will power down for the duration of the wait function. note that the reset default for the adp u bit is zero. therefore, when this module is reset, it is rese t into the power down state. once the command to power down has been re ceived, the atd module aborts any conversion sequence in progress and ente rs lower power mode. when the module is powered up again, the bi as settings in the analog electronics must be given time to stabilize before conversions
analog-to-digital converter atd operation in dif ferent mcu modes mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 373 can be performed. note that poweri ng up the module does not reset the module since the register file is not initialized. in power down mode, the control and result regi sters are still accessible. 19.5.2 idle mode idle mode for the atd module is def ined as the stat e where the atd module is powered up and ready to perform an a/d conversion, but not actually performing a conversion at the present time. access to all control, status, and re sult registers is available. the module is consuming near maximum power. note: when not active, the sample- and-hold and analog-to-digital sub- modules disable the clocks at their inputs to conserve power. the analog electronics still draw quiescent current. 19.5.3 run mode run mode for the atd m odule is defined as t he state where the atd module is powered up and currently performing an a/d conversion. complete assess to all con trol, status and result registers is available. the module is consum ing maximum power. 19.6 atd operation in different mcu modes 19.6.1 stop mode asserting stop causes the atd module to power down. the digital clocks are disabled and the analog quiescent current draw is turned off; this places the module into its power down state and is equivalent to clearing the adpu control bit in atdctl2.
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 374 analog-to-digital converter motorola 19.6.2 wait mode if the aswai control bi t in atdctl2 is set, then the atd responds to wait mode. if the aswai control bi t is clear, then th e atd ignores the wait signal. the atd response to the wa it mode is to power down the module. in this mode, the mcu does not have access to the control, status or result registers. 19.6.3 background d ebug (atd freeze) mode when debugging an applicati on, it is useful to have the atd pause when a breakpoint is enc ountered. to accommodate this, there are two freeze bits in the atdctl3 regist er used to select one of three responses: 1. the atd module may ignor e the freeze request. 2. it may respond to the freeze r equest by finish ing the current conversion and ?freezing? before starting the next sample period. 3. it may respond by im mediately ?freezing?. control and timing logic is static al lowing the register contents and timing position to be remembered indefinitel y. the analog electronics remains powered up; however, internal le akage may compromise the accuracy of a frozen conversion depending on the l ength of the freeze period. when the bdm signal is negated clock ac tivity resumes. access to the atd register file is possible during the ?frozen? period. 19.6.4 module reset the atd module is reset on two different events. 1. in the case of a system reset. 2. if the rst bit in the atdtest regist er is activated. the single difference between the two events is t hat the rst bit event does not reset the adpu bit to its rese t state value - i. e. the module is not reset into a powered down state a nd will be returned to an idle state.
analog-to-digital converter general purpose digital input port operation mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 375 the atd module reset function pl aces the module back into an initialized state. if the module is performing a conv ersion sequence, both the current conversion and t he sequence are te rminated. the conversion complete flags are cl eared and any pending interrupts are cancelled. note that the control, test, and status registers are initialized on reset; the initia lized register state is defi ned in the register description section of this specification. note that when the mo dule powers up via a wait signal that the atd is not reset; atd operation proceeds as it was prior to entering the wait. freezing the module does no t cause it to be reset. if a freeze mode is entered and defines that the current conversion be terminated, then this is done and the module will be idle afte r exiting the freeze state, but the module is not initialized. powering the module up (using the a dpu bit) does not cause the module to reset since the register file is not initialized. finally, writing to control register atdctl4/5 does not cause the module to be reset; the current conversion and sequence will be terminated and new ones started; the conversi on complete flags and pending interrupts will be cleared. this is a restart operation rather than a reset operation because the register file is not reinitialized. 19.7 general purpose digi tal input port operation there is one digital, 8-bit, inpu t-only port associated with the atd module. it is accessed through the 8- bit port data register (portadx). since the port pins are used only as inputs, in normal operating modes, no data direction r egister is availa ble for this port. the input channel pins ca n be used to read anal og and digital data. as analog inputs, they are mu ltiplexed and sampled to supply signals to the a/d converter. as digital inputs, they supply input data buffers that can be accessed through the digital port r egisters. analog signals present on the input pins at the digital sampling time t hat don?t meet the v il or v ih specification will return unknown digital values. a read of portadx may affect the accuracy of an in progress sample period but will not affect an in progress a/d conversion.
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 376 analog-to-digital converter motorola 19.8 application considerations note that the a/d converter?s accura cy is limited by the accuracy of the reference potentials. noise on the refer ence potentials will result in noise on the digital output dat a stream: the referenc e potential lines do not reject reference noise. the reference potential pins must have a low ac impedance path back to the source. a large bypass capacito r (100nf or larger) will suffice in most cases. in extreme cases, in ductors and/or ferr ite beads may be necessary if high frequency noise is present. series resistance is not advisable since the atd module draw s current from t he reference. a potential drop across any series resi stance would result in gain and offset errors in the digital data output stream unless the reference potential was sensed at the reference inpu t pin and any potential drop compensated for. for best performance, the analog inputs s hould have a low ac impedance at the input pins to shunt noi se current coupled onto the input node away from the a/d i nput. this can be acco mplished by placing a capacitor with good high frequency characteristi cs between the input pin and v ssa . the size of this capacitor is application dependent; larger capacitors will lower the ac imped ance and be more effective at shunting away noise cu rrent. however, the in put analog signal has its own dynamic characteristics which the a/d converter is being used to track. these, along with the source impedance of th e signal driver, must also be considered when choosing the c apacitor size to avoid rolling off any high frequency com ponents of interest. if the input signal contains exce ssive high frequen cy conducted noise, then a series resistance may be us ed with the capacitor to generate a one pole, low pass ant i-aliasing filter. 19.9 atd registers control and data register s for the atd modules are described below. both atds have identical control registers mapped in two blocks of 16 bytes.
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 377 19.9.1 atd control regist ers 0 &1 (atdctl0, atdctl1) writes to this register will abort current conversion sequence. read or write any time. write: write to this register has no meaning. read: special mode only. 19.9.2 atd control regist ers 2 & 3 (atdctl2, atdctl3) the atd control registers 2 & 3 are used to select the power up mode, fast flag clear mode, wait mode, 16 channel mode, interr upt control, and freeze control. writes to these re gisters will not abo rt the current conversion sequence nor start a new sequence. read: any time write: any time (except for bit 0 ? ascif, read: any time, write: not allowed) adpu ? atd disable / power down 0 = disable and power down the atd 1 = normal atd functionality atd0ctl0/atd1ctl0 ? reserved $0060/$01e0 bit 7654321bit 0 reset: 00000000 atd0ctl1/atd1ctl1 ? reserved $0061/$01e1 bit 7654321bit 0 reset: 0 0 0 0 0 0 0 0 atd0ctl2/atd1ctl2 ? atd control register 2 $0062/$01e2 bit 7654321bit 0 adpu affc aswai djm reserved reserved ascie ascif reset: 0 0 0 0 0 0 0 0
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 378 analog-to-digital converter motorola this bit provides program on/off cont rol over the atd module allowing reduced mcu power consumption wh en the atd is not being used. when reset to zero, the adpu bit aborts any conversion sequence in progress. because the analog elec tronics is tur ned off when powered down, the atd requires a recovery time period wh en adpu bit is enabled. affc ? atd fast conversi on complete flag clear 0 = atd flag clearing operates nor mally (read the st atus register before reading the result regist er to clear the associated ccf bit). 1 = changes all atd co nversion complete flags to a fast clear sequence. any access to a result register (atd0?7) will cause the associated ccf flag to clear automatical ly if it was set at the time. operating normally means that the status register must be read after the conversion complete flag has been set before that flag can be reset. after the status register read, a read to the associated result register causes its conversion complete flag in the status register to be cleared. the scf flag is cleared when a new conversion sequence is begun by writing to control register atdctl4/5. in applications where the atd module is polled to determine if an atd conversion is complete, this feature provides a convenient way of clearing the status register conversion complete flag. in applications where atd interrupts are used to signal conversion completion, the precondition of read ing the status register can be eliminated using fast co nversion complete flag clear mode. in this mode, any access to a result regi ster will cause its associated conversion complete flag in the status register to be cleared. the scf flag is cleared after the first ( any) result register is read. aswai ? atd stop in wait mode 0 = atd continues to run wh en the mcu is in wait mode 1 = atd stops to save power when the mcu is in wait mode the wait function allows the mcu to selectiv ely halt and power down the atd module. if the aswai bit is set and the m cu, then the atd module immediately halts operation and powers down. when wait is
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 379 exited, the atd module powers up and continues operation. the module is not reset; the register file is not reinitialized; the conversion sequence is not restarted. when the module comes out of wa it, it is recommended that a stabilization delay ( t sr ) is allowed before new conversions are started. djm ? result register data justification mode 0 = left justified mode 1 = right ju stified mode for 10-bit resolution, left justifi ed mode maps a result register into data bus bits 6 through 15; bit 15 is the msb. in right justified mode, the result registers m aps onto data bus bits 0 through 9; bit 9 is the msb. for 8-bit resolution, left justified mode maps a result into the high byte (bits 8 though 15; bit 15 is the msb). ri ght justified maps a result into the low byte (bits 0 throu gh 7; bit 7 is the msb). table 19-1 summarizes the result dat a formats available and how they are set up usin g the control bits. table 19-2 illustrates left justified outp ut codes for an input signal range between 0 and 5.1 volts. res10 djm result data formats description and bus bit mapping 0 0 1 1 0 1 0 1 8-bit/left justified - bits 8-15 8-bit/right justified - bits 0-7 10-bit/left justified - bits 6-15 10-bit/right justified - bits 0-9 table 19-1. result data formats available
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 380 analog-to-digital converter motorola ascie ? atd sequence comp lete interrupt enable 0 = disables atd interrupt 1 = enables atd interr upt on sequence complete the sequence complete interrupt f unction signals th e mcu when a conversion sequence is complete. at this time, the result registers contain the result data generated by the conversion s equence. if this interrupt function is disabled, then the conversion complete flags must be polled to determine when a conv ersion or a conversion sequence is complete. note that reset clears pending interrupts. ascif ? atd sequence complete interrupt flag 0 = no atd sequence complete interrupt occurred 1 = atd sequence complete interrupt occurred the sequence complete inte rrupt flag. this flag is not cleared until the interrupt is serviced (by reading the result data in such a way that the conversion complete flag is clear ed), a new conversion sequence is initiated, or the module is reset. this bit is not writ able in any mode. input signal vrl = 0 volts vrh = 5.12 volts 8-bit codes 10-bit codes 5.120 volts 5.100 5.080 2.580 2.560 2.540 0.020 0.000 ff ff fe 81 80 7f 01 00 ffc0 ff00 fe00 8100 8000 7f00 0100 0000 table 19-2. left justif ied atd output codes
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 381 read: any time write: any time s1c ? conversion sequence lengt h (least significant bit) this control bit works with control bit s8c in atdctl5 in determining how many conversion are performed per sequence. when the s1c bit is set, a sequenc e length of 1 is defined. however, if the s8c bit is also set, the s8c bit takes precedence. for sequence length coding information see the description for s8c bit in atdctl5. fifo ? result r egister fifo mode 0 = result registers maps to the conversion sequence 1 = result registers do not map to the conversion sequence in normal operation, the a/d conversion results map into the result registers based on the conversion se quence; the result of the first conversion appears in the fi rst result register, t he second result in the second result register, and so on. in fifo mode the result register counter is not reset at the beg inning or ending of a conversion sequence; conversion re sults are placed in consecutive result registers between sequences. the re sult register counter wraps around when it reaches the end of th e result register file. the conversion counter value in at dstat0 can be used to determine where in the result register file, the next conversion result will be placed. the results register coun ter is initialized to zero on three events: on reset, the beginni ng of a normal (non-fif o) conversion sequence, and the end of a normal (non-fifo) conversion sequenc e. therefore, the reset bit in regist er atdtest1 can be toggled to zero the result register counter; any sequence allowe d to complete normally will zero the result register counter; a new sequence (non-fifo) initiated with a write to atdctl4/5 followed by a write to atdctl3 to set the fifo bit will start a fifo sequence with the result register initialized. atd0ctl3/atd1ctl3 ? atd control register 3 $0063/$01e3 bit 7654321bit 0 0000s1cfifofrz1frz0 reset: 0 0 0 0 0 0 0 0
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 382 analog-to-digital converter motorola finally, which result registers hold valid data can be tracked using the conversion complete flags. fast fl ag clear mode may or may not be useful in a particular applic ation to track valid data. frz1, frz0 ? backgr ound debug freeze enable background debug freeze function al lows the atd mo dule to pause when a breakpoint is encountered. table 19-3 shows how frz1 and frz0 determine the atd?s response to a breakpoint. when bdm is deasserted, the atd module continue s operating as it was before the breakpoint occurred. 19.9.3 atdctl4 atd co ntrol register 4 atd control register 4 is used to se lect the internal atd clock frequency (based on the system clock) , select the length of the third phase of the sample period, and set the resolution of the a/d conversion (i.e. 8-bits or 10-bits). all writes to this regi ster have an immediate effect. if a conversion is in progre ss, the entire conversi on sequence is aborted. a write to this register (or atdctl5) initiates a new conversion sequence. table 19-3. atd response to background debug enable frz1 frz0 atd response 0 0 continue conversions in active background mode 01 reserved 1 0 finish current conversion, then freeze 1 1 freeze when bdm is active atd0ctl4/atd1ctl4 ? atd control register 4 $0064/$01e4 bit 7654321bit 0 res10 smp1 smp0 prs4 prs3 prs2 prs1 prs0 reset: 00000001
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 383 res10 ? a/d resolution select 0 = 8-bit reso lution selected 1 = 10-bit resolution selected this bit determines the re solution of the a/d conv erter: 8-bits or 10- bits. the a/d converter has the a ccuracy of a 10-bit converter. however, if low resolution is adequate, the conversion can be speeded up by select ing 8-bit resolution. smp[1:0] ? sample time select these two bits select the length of the third phase of the sample period (in internal atd cl ock cycles) which occurs after the buffered sample and transfer. during this phase, the external analog signal is connected directly to t he storage node for final charging and improved accuracy. note that the atd clock period is itself a function of the prescaler value (bits prs0?4). table 19-4 lists the lengths available for the third sample phase. prs[4:0] ? atd clock prescaler the binary prescaler value (0 to 31 ) plus one (1 to 32) becomes the divide-by-factor for a modulus counter used to prescale the system pclk frequency. the resu lting scaled clock is further divided by 2 before the atd internal clock is gener ated. this clock is used to drive the s/h and a/d machines. note that the maximum atd clock frequency is half of the system clock. the default prescaler value is 00001 which resu lts in a default atd clock frequency that is quarter of the system clock i.e. with 8mhz bus the atd module clock is 2mhz. table 19-5 illustrates the divide- by operation and the appr opriate range of syst em clock frequencies. table 19-4. final sample time selection smp1 smp0 final sample time 0 0 2 a/d clock periods 0 1 4 a/d clock periods 1 0 8 a/d clock periods 1 1 16 a/d clock periods
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 384 analog-to-digital converter motorola 19.9.4 atdctl5 atd co ntrol register 5 atd control register 5 determines the type of conversion sequence and the analog input channels sampled. all writes to this register have an immediate effect. if a conversion is in progress, the entire conversion sequence is aborted. a write to this r egister (or atdctl4) initiates a new conversion sequence (scf an d ccf bits are reset). s8c / s1c ? conver sion sequence length s8c: bit position: 6, atdctl5 s1c: bit position: 3, atdctl3 the s8c/s1c bits define the l ength of a conv ersion sequence . table 19-6 lists the coding combinations. table 19-5. clock prescaler values prescale value total divisor max pclk (1) 1. maximum conversion frequency is 2 mhz. maximum pclk divisor value will become maximum conversion rate that can be used on this atd module. min pclk (2) 2. minimum conversion frequency is 500 khz. minimum pclk divisor value will become minimum conversion rate that this atd can perform. 00000 24 mhz 1 mhz 00001 48 mhz 2 mhz 00010 68 mhz 3 mhz 00011 88 mhz 4 mhz 00100 10 8 mhz 5 mhz 00101 12 8 mhz 6 mhz 00110 14 8 mhz 7 mhz 00111 16 8 mhz 8 mhz 01xxx do not use 1xxxx atd0ctl5/atd1ctl5 ? atd control register 5 $0065/$01e5 bit 7654321bit 0 0 s8c scan mult sc cc cb ca reset: 00000000
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 385 the result register assignments made to a conversion sequence follow a few simple rules. normally, the first result is placed in the first register; the second result is placed in the second register, and so on. table 19- 7 presents the result register assi gnments for the various conversion lengths that are normally made. if fifo mode is used, the result register assignments differ. the re sults are placed in consecutive registers between conversion sequence s; the result register mapping wraps around when the end of the register file is reached. scan ? continuous conv ersion sequence mode 0 = perform a conversion sequ ence and return to idle mode 1 = perform conversion sequences continuously (scan mode) the scan mode bit controls whether or not conversion sequences are performed continuously or not. if this c ontrol bit is 0, a write to control register 4 or 5 will initiate a conversion sequence; the conversion sequence will be executed; the sequenc e complete flag (scf) will be set, and the module will return to id le mode. in this mode, the module remains powered up bu t no conversions are per formed; the module waits for the next conversi on sequence to be initiated. if this control bit is 1, a single c onversion sequence initia tion will result in a continuously executed conver sion sequence. when a conversion sequence completes, t he sequence complete flag (scf) is set and a new sequence is immediatel y begun. the conversion mode characteristics of each sequence ar e identical. if a new conversion s8c s1c number of conversions per sequence 00 4 01 1 1x 8 table 19-6. conversion sequence length coding number of conversions per sequence result register assignment 1 adr0 4 adr0 through adr3 8 adr0 through adr7 table 19-7. result register a ssignment for different conversion sequences
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 386 analog-to-digital converter motorola mode is required, the existi ng continuous sequence must be interrupted, the control regist ers modified, and a new conversion sequence initiated. mult ? multi-channel sample mode 0 = sample only t he specified channel 1 = sample across many channels when mult is 0, the atd sequence controller samples only from the specified analog inpu t channel for an entir e conversion sequence. the analog channel is selected by channel selection code (control bits cc/cb/ca located in atdctl5). when mult is 1, the atd seq uence controller samples across channels. the number of channels sampled is determined by the sequence length va lue (s8c, s1c control bi ts). the first analog channel examined is determined by channel selection code (cc, cb, ca control bits); su bsequent channels sampled in the sequence are determined by incr ementing the channel selection code. sc ? special channel conversion mode 0 = perform a/d conversi on on an analog input channel 1 = perform special c hannel a/d conversion sc determines if the atd module performs a/d conversions on any of the analog input cha nnels (normal operation) or whether it performs a conversion on one of the defin ed, special channels. the special channels are normally used to te st the a/d machine and include converting the high and low refer ence potentials for the module. the control bits cc/cb/ca are used to indicate which special channel is to be converted. table 19-8. special channel conversion select coding cc cb ca special expected channel digital result code 0xx reserved ? 100 vrh $ff 1 0 1 vrl $00 1 1 0 (vrh + vrl)/2 $7f 111 reserved ?
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 387 table 19-8 lists the special channels. th e last column in the table denote the expected digital code that should be generated by the special conversion fo r 8-bit resolution. cc, cb, ca ? analog input channel select code these bits select the analog input channel(s). table 19-9 lists the coding used to select the various analog input channels. in the case of single channel scans (mult=0), this selection code specifies the channel for conversion. in the case of multi-channel scans (mult=1), this selection code repr esents the first channel to be examined in the conversion sequence. subsequent channels are determined by incrementing the channel selection code; selection codes that reach the maximum value wrap ar ound to the minimum value. note that for special conversi on mode, bits cc/cb/ca have a different function. instead of spec ifying the analog i nput channel, they identify which special channel conv ersion is to take place. (see table 19-8 .) a summart of the channels converted and t he associated result locations for multiple cha nnel scans can be found in table 19-10 . table 19-9. analog input channel select coding cc cb ca analog input channel 000 ad0 001 ad1 010 ad2 011 ad3 100 ad4 101 ad5 110 ad6 111 ad7
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 388 analog-to-digital converter motorola table 19-10. multichannel mode r esult register a ssignment (mult=1) 4 channel conversion, external channels (s8c = 0, sc = 0) cc 0 000 1 111 cb 0 011 0 011 ca 0 101 0 101 adr0 an0 an1 an2 an3 an4 an5 an6 an7 adr1 an1 an2 an3 an4 an5 an6 an7 an0 adr2 an2 an3 an4 an5 an6 an7 an0 an1 adr3 an3 an4 an5 an6 an7 an0 an1 an2 s1c bit must be clear. 4 channel conversion, internal sources (s8c = 0, sc = 1) cc0000 1 111 cb0011 0 011 ca0101 0 101 adr0 vrh vrl mid adr1 vrh vrl mid adr2 vrh vrl mid adr3 vrh vrl mid shaded cells are reserved mid = (vrh + vrl) / 2 s1c bit must be clear.
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 389 8 channel conversion, external channels (s8c = 1, sc = 0) cc 0 0001111 cb 0 0110011 ca 0 1010101 adr0 an0 an1 an2 an3 an4 an5 an6 an7 adr1 an1 an2 an3 an4 an5 an6 an7 an0 adr2 an2 an3 an4 an5 an6 an7 an0 an1 adr3 an3 an4 an5 an6 an7 an0 an1 an2 adr4 an4 an5 an6 an7 an0 an1 an2 an3 adr5 an5 an6 an7 an0 an1 an2 an3 an4 adr6 an6 an7 an0 an1 an2 an3 an4 an5 adr7 an7 an0 an1 an2 an3 an4 an5 an6 8 channel conversion, internal sources (s8c = 1, sc = 1) cc 0 0001111 cb 0 0110011 ca 0 1010101 adr0 vrh vrl mid adr1 vrh vrl mid adr2 vrh vrl mid adr3 vrh vrl mid adr4 vrh vrl mid adr5 vrl mid vrh adr6 mid vrh vrl adr7 vrh vrl mid shaded cells are reserved mid = (vrh + vrl) / 2 notes: 1) for compatibility with the mc68hc912dg128, ca , cb, cc bits must be ?0? where masked on the mc68hc912dg128. this is shown above in bold text. 2) when mult = 0, all four bits (sc, cc, cb, and ca) must be specified and a conversion sequence consists of four or eight consecutive conversions of the single specified channel. 3) when s8c = 0 and s1c = 1, all four bits (sc, cc, cb, and ca) must be specified and a conversion sequence consists of one conversion of the single specified channel. table 19-10. multichannel m ode result register assi gnment (mult=1) (continued)
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 390 analog-to-digital converter motorola 19.9.5 atdstat a/ d status register the atd status registers contain t he conversion complete flags and the conversion sequence counter. the status registers are read-only . scf ? sequence complete flag this flag is set upon completion of a conversion sequence. if conversion sequences are continuous ly performed (scan=1), the flag is set after each one is comp leted. how this flag is cleared depends on the setting of the fast flag clear bit. when affc=0, scf is cleared when a new conversion sequence is initia ted (write to register atdctl4/5). when affc=1 , scf is cleared after reading the first (any) result register. cc[2:0] ? conversion counter this 3-bit value represents the contents of the re sult register counter; the result register counter points to the result re gister that will receive the result of the current conversion. if not in fifo m ode, the register counter is initialized to zero when a new conv ersion sequence is begun. if in fifo mode, the register c ounter is not init ialized. the result register count wraps around when its maximum value is reached. ccf[7:0] ? conversi on complete flags a conversion complete flag is set at the end of each conversion in a conversion sequence. the flags are a ssociated with the conversion position in a sequence and the result regist er number. therefore, ccf0 is set when the first conversi on in a sequence is complete and atd0stat0/atd1stat0 ? atd status register $0066/$01e6 bit 7654321bit 0 scf 0 0 0 0 cc2 cc1 cc0 reset:00000000 atd0stat1/atd1stat1 ? atd status register $0067/$01e7 bit 7654321bit 0 ccf7 ccf6 ccf5 ccf4 ccf3 ccf2 ccf1 ccf0 reset: 0 0 0 0 0 0 0 0
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 391 the result is available in result register adr0; ccf 1 is set when the second conversion in a sequence is complete and the result is available in adr1, and so forth. the conversion complete flags are cleared depending on the setting of the fast flag cl ear bit (affc in atdctl2). when affc=0, the status register containing the conv ersion complete flag must be read as a precondition before t he flag can be cleared. t he flag is actually cleared during a subsequent access to the result register. this provides a convenient method for clearing the conv ersion complete flag when the user is polling the atd module; it ensures the user is signaled as to the avai lability of new data and avoids having to have the user clear t he flag explicitly. when affc=1, the conversion comple te flags are cleared when their associated result registers are read; reading the status register is not a necessary condition in order to clear them. this is the easiest method for cleari ng the conversion complete flags which is useful when the atd module signals conversion completion with an interrupt. the conversion complete flags are norm ally read only; in special (test) mode they can be written. note: when atdctl4/5 register is written, the scf fl ags and all ccfx flags are cleared; any pending interr upt request is canceled.
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 392 analog-to-digital converter motorola 19.9.6 atdtest module tes t register (atdtest) the test registers implement various special (test) modes used to test the atd module. the re set bit in atdtest1 is always read/write . the sar (successive approxi mation register) can a lways be read but only written in special (test) mode. the functions implemented by the test registers are reserved for factory test. sar[9:0] ? successive approximation register this ten bit value represents t he contents of t he ad machine?s successive approximation register. this value can always be read. it can only be written in special (t est) mode. note that atdtest0 acts as a ten bit register since the entire sar is read/written when accessing this address. rst ? test mode reset bit 0 = no reset 1 = reset the atd module when set, this bit causes the atd m odule to reset itself. this sets all registers to their reset state (note the reset stat e of the reset bit is zero), the current conversion and conversion sequenc e are aborted, pending interrupts are clear ed, and the module is placed in an idle mode. atd0testh/atd1testh ? atd test register $0068/$01e8 bit 7654321bit 0 sar9 sar8 sar7 sar6 sar5 sar4 sar3 sar2 reset: 0 0 0 0 0 0 0 0 atd0testl/atd1testl ? atd test register $0069/$01e9 bit 7654321bit 0 sar1 sar0 rst 0 0 0 0 0 reset: 0 0 0 0 0 0 0 0
analog-to-digital converter atd registers mc68hc912dt128a ? rev 4.0 technical data motorola analog-to-digital converter 393 resetting to idle mode defines the onl y exception of the reset control bit condition to the system reset c ondition. the reset control bit does not initialize the adpu bit to its reset condition and therefore does not power down the module. this except allows the module to remain active for other test operations. 19.9.7 portad port data register the input data port associated with the atd module is input-only. the port pins are shared wi th the analog a/d inputs. padx[7:0] ? port ad data input bits reset: these pins reflect t he state of the input pins. the atd input ports may be used for general purpose digital input. when the port data registers are read, they contain the digital levels appearing on the input pins at the time of the r ead. input pins with signal potentials not meeting v il or v ih specifications will have an indeterminate value. use of any port pin for digital inpu t does not preclude the use of any other port pin for analog input. writes to this register have no meaning at any time. portad0/portad1 ? port ad data input register $006f/$01ef bit 7654321bit 0 padx7 padx6 padx5 padx4 padx3 padx2 padx1 padx0 reset: --------
analog-to-digital converter technical data mc68hc912dt128a ? rev 4.0 394 analog-to-digital converter motorola 19.9.8 adrx a/d conversion result registers (adr0-15) the a/d conversion result s are stored in 8 resu lt registers. these registers are designat ed adr0 through adr7. the result data is formatted using t he djm control bit in atdctl2. for 8-bit result data, the result data ma ps between the high (l eft justified) and low (right justified) order bytes of the result r egister. for 10-bit result data, the result data maps between bits 6-15 (left justif ied) and bits 0-9 (right justified) of the result register. these registers are normally read-only. adrx0h ? a/d converter result register 0 $0070/$01f0 adrx0l ? a/d converter result register 0 $0071/$01f1 adrx1h ? a/d converter result register 1 $0072/$01f2 adrx1l ? a/d converter result register 1 $0073/$01f3 adrx2h ? a/d converter result register 2 $0074/$01f4 adrx2l ? a/d converter result register 2 $0075/$01f5 adrx3h ? a/d converter result register 3 $0076/$01f6 adrx3l ? a/d converter result register 3 $0077/$01f7 adrx4h ? a/d converter result register 4 $0078/$01f8 adrx4l ? a/d converter result register 4 $0079/$01f9 adrx5h ? a/d converter result register 5 $007a/$01fa adrx5l ? a/d converter result register 5 $007b/$01fb adrx6h ? a/d converter result register 6 $007c/$01fc adrx6l ? a/d converter result register 6 $007d/$01fd adrx7h ? a/d converter result register 7 $007e/$01fe adrx7l ? a/d converter result register 7 $007f/$01ff adrxxh bit 15654321bit 8 adrxxl bit 7bit 6000000 reset: 00000000
mc68hc912dt128a ? rev 4.0 technical data motorola development support 395 technical data ? mc68hc912dt128a section 20. development support 20.1 contents 20.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 20.3 instruction queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395 20.4 background debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .397 20.5 breakpoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 20.6 instruction tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 20.2 introduction development support involves complex intera ctions between mc68hc912dt128a resources and ex ternal development systems. the following section concerns in struction queue an d queue tracking signals, background debug mode, and instruction tagging. 20.3 instruction queue the cpu12 instructio n queue provides at least three bytes of program information to the cpu when instru ction execution b egins. the cpu12 always completely finishes executi ng an instruction before beginning to execute the next instruction. st atus signals ipipe[1:0] provide information about data movement in the queue and indicate when the cpu begins to execute instructions. this makes it possible to monitor cpu activity on a cycle-by-cycle basis for debugging. information available on the ipipe[1:0] pins is time multiplexed. external circuitry can latch data movement informat ion on rising edges of the e-clock signal; execution start informat ion can be latched on falling edges. table 20-1 shows the meaning of data on the pins.
development support technical data mc68hc912dt128a ? rev 4.0 396 development support motorola program information is fetched a few cycl es before it is used by the cpu. in order to monitor cyc le-by-cycle cpu activity, it is necessary to externally reconstruc t what is happening in the instruction queue. internally the mcu only needs to buffer the data from program fetches. for system debug it is necessary to keep the data and its associated address in the reconstructed inst ruction queue. the raw signals required for reconstruction of the queue are addr, data, r/w , eclk, and status signals ipipe[1:0]. the instruction queue consists of tw o 16-bit queue stages and a holding latch on the input of the first st age. to advance the queue means to move the word in the first stage to the second stage and move the word from either the holding latch or t he data bus input buffe r into the first stage. to start even (or odd) instruct ion means to exec ute the opcode in the high-order (or low-orde r) byte of the second st age of the instruction queue. table 20-1. ipipe decoding data movement ? ipipe[1:0] captured at rising edge of e clock (1) 1. refers to data that was on the bus at the previous e falling edge. ipipe[1:0] mnemonic meaning 0:0 ? no movement 0:1 lat latch data from bus 1:0 ald advance queue and load from bus 1:1 all advance queue and load from latch execution start ? ipipe[1:0] captured at falling edge of e clock (2) 2. refers to bus cycle starti ng at this e falling edge. ipipe[1:0] mnemonic meaning 0:0 ? no start 0:1 int start interrupt sequence 1:0 sev start even instruction 1:1 sod start odd instruction
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 397 20.4 background debug mode background debug mode (b dm) is used for syst em development, in- circuit testing, field testing, and programming. bdm is implemented in on-chip hardware and provides a full set of debug options. because bdm control logic does not reside in the c pu, bdm hardware commands can be executed while t he cpu is operating normally. the control logic generally uses c pu dead cycles to execute these commands, but can steal cycles fro m the cpu when necessary. other bdm commands are firmware based, and r equire the cpu to be in active background mode for executio n. while bdm is acti ve, the cpu executes a firmware program located in a sma ll on-chip rom that is available in the standard 64-kbyte me mory map only while bdm is active. the bdm control logic communicates with an external host development system serially, via the bkgd pin. this single-wire approach minimizes the number of pins needed for development support. 20.4.1 enabling bdm firmware commands bdm is available in all operating mo des, but must be made active before firmware commands can be executed. bdm is enabled by setting the enbdm bit in the bdm st atus register via t he single wire interface (using a hardware command; writ e_bd_byte at $ff01). bdm must then be activated to map bdm r egisters and rom to addresses $ff00 to $ffff and to put the mcu in active background mode. after the firmware is enabled, bdm can be acti vated by the hardware background command, by the bdm tagging me chanism, or by the cpu bgnd instruction. an attempt to activate bdm before firmware has been enabled causes the mcu to resu me normal instruction execution after a brief delay. bdm becomes active at the nex t instruction b oundary following execution of the bdm background command, but tags activate bdm before a tagged instru ction is executed.
development support technical data mc68hc912dt128a ? rev 4.0 398 development support motorola in special single-chip mode, backg round operation is enabled and active immediately out of reset. this active case replaces the m68hc11 boot function, and allows programming a system with blank memory. while bdm is active, a set of bd m control regist ers are mapped to addresses $ff00 to $ff06. the bdm control logic us es these registers which can be read anytime by bdm logi c, not user programs. refer to bdm registers for detailed descriptions. some on-chip peripherals have a bdm control bit which allows suspending the peripheral function duri ng bdm. for example, if the timer control is enabled, the timer count er is stopped while in bdm. once normal program flow is continued, the timer c ounter is re-enabled to simulate real-time operations. 20.4.2 bdm serial interface the bdm serial interface requires the external controller to generate a falling edge on the bkgd pin to indicate the st art of each bi t time. the external controller provides this fa lling edge whether data is transmitted or received. bkgd is a pseudo-open-drain pin t hat can be driven either by an external controller or by the mcu. data is transferred msb first at 16 bdmclk cycles per bit ( nominal speed). the inte rface times out if 512 bdmclk cycles occur between fa lling edges from the host. the hardware clears the co mmand register when a time-out occurs. the bkgd pin can receive a high or lo w level or transmi t a high or low level. the following diagrams show ti ming for each of these cases. interface timing is synchronous to m cu clocks but asynch ronous to the external host. the internal clock signal is shown for reference in counting cycles. figure 20-1 shows an external host transmitt ing a logic one or zero to the bkgd pin of a target mc68hc 912dt128a mcu. the host is asynchronous to the target so there is a 0-to-1 cycle del ay from the host- generated falling edge to wher e the target perceives the beginning of the bit time. ten target b cycles later, the target sens es the bit level on the bkgd pin. typically the host acti vely drives the pseudo-open-drain
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 399 bkgd pin during host-to-target tran smissions to speed up rising edges. since the target does not drive the bkgd pi n during this period, there is no need to treat the line as an open-drain signal during host-to-target transmissions. figure 20-1. bdm host to target serial bit timing figure 20-2. bdm tar get to host serial bit timing (logic 1) 10 cycles bdmclk (target mcu) host transmit 1 target senses bit earliest start of next bit synchronization uncertainty perceived start of bit time host transmit 0 hc12a4 bdm host to target tim 10 cycles bdmclk (target mcu) earliest start of next bit bkgd pin perceived start of bit time 10 cycles host samples bkgd pin host drive to bkgd pin target mcu speedup pulse r-c rise high-impedance high-impedance high-impedance hc12a4 bdm target to host tim 1
development support technical data mc68hc912dt128a ? rev 4.0 400 development support motorola figure 20-2 shows the host receiving a logic one from the target mc68hc912dt128a mcu. since the host is asynchronous to the target mcu, there is a 0-to-1 cycle delay from t he host-generated falling edge on bkgd to the perceived st art of the bit time in the target mcu. the host holds the bkgd pin low long enough for the ta rget to recognize it (at least two target b cycl es). the host must rel ease the low drive before the target mcu drives a brief ac tive-high speed-up pulse seven cycles after the perceived start of the bit time. the host should sample the bit level about ten cycles afte r it started the bit time. figure 20-3. bdm target to h ost serial bit timing (logic 0) 10 cycles bdmclk (target mcu) earliest start of next bit bkgd pin perceived start of bit time 10 cycles host samples bkgd pin host drive to bkgd pin target mcu drive and speedup pulse high-impedance speedup pulse hc12a4 bdm target to host tim 0
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 401 figure 20-3 shows the host receiving a logic zero from the target mc68hc912dt128a mcu. since the host is asynchronous to the target mcu, there is a 0-to-1 cycle delay from t he host-generated falling edge on bkgd to the start of th e bit time as perceived by the target mcu. the host initiates the bit ti me but the target mc68 hc912dt128a finishes it. since the target wants t he host to receive a logi c zero, it drives the bkgd pin low for 13 bdmc lk cycles, then briefly dr ives it high to speed up the rising edge. the host samples the bit leve l about ten cycles after starting the bit time. 20.4.3 bdm commands the bdm command set cons ists of two types: hardware and firmware. hardware commands allow target system memory to be read or written.target system memory includes all memory that is accessible by the cpu12 including eeprom, on-chip i/o and control registers, and external memory that is connected to the target hc12 mcu.hardware commands are implemented in hardw are logic and do not require the hc12 mcu to be in bdm mode for execution.the control logic watches the cpu12 buses to find a free bus cy cle to execute the command so the background access does not disturb t he running application programs. if a free cycle is not found within 128 bdmclk cycles, the cpu12 is momentarily frozen so the control logic can steal a cycle.commands implemented in bdm contro l logic are listed in table 20-2 .
development support technical data mc68hc912dt128a ? rev 4.0 402 development support motorola the second type of bdm commands are called firmware commands implemented in a small rom within the hc12 mcu.the cpu must be in background mode to execute firmware commands. the usual way to get to background mode is by the har dware command background. the bdm rom is located at $ff20 to $ffff while bdm is active. there are also seven bytes of bdm register s located at $ff00 to $ff06 while bdm is active. the cpu execut es code in the bdm fi rmware to perform the requested operation. the bdm firmware watches for serial commands table 20-2. hardware commands (1) command opcode (hex) data description background 90 none enter background mode if firmware enabled. read_bd_byte (1) e4 16-bit address 16-bit data out read from memory with bdm in map (may steal cycles if external access) data for odd address on low byte, data for even address on high byte. read_bd_word (1) ec 16-bit address 16-bit data out read from memory with bdm in map (may steal cycles if external access). mu st be aligned access. read_byte e0 16-bit address 16-bit data out read from memory with bdm out of map (may steal cycles if external access) data for odd address on low byte, data for even address on high byte. read_word e8 16-bit address 16-bit data out read from memory with bdm out of map (may steal cycles if external access). must be aligned access. write_bd_byte (1) c4 16-bit address 16-bit data in write to memory with bdm in map (may steal cycles if external access) data for odd address on low byte, data for even address on high byte. write_bd_word (1) cc 16-bit address 16-bit data in write to memory with bdm in map (may steal cycles if external access). must be aligned access. write_byte c0 16-bit address 16-bit data in write to memory with bdm out of map (may steal cycles if external access) data for odd address on low byte, data for even address on high byte. write_word c8 16-bit address 16-bit data in write to memory with bdm out of map (may steal cycles if external access). mu st be aligned access. 1. use these commands only for reading/writing to bdm locations . the bdm firmware rom and bdm registers are not nor- mally in the hc12 mcu memory map . since these locations have the same addresses as some of the normal application memory map, there needs to be a way to decide which phys ical locations are being accessed by the hardware bdm com- mands . this gives rise to needing separate memory access commands for the bdm locations as opposed to the normal application locations . in logic, this is accomplished by momentarily enabl ing the bdm memory resources, just for the access cycles of the read_bd and write_bd commands . this logic allows the debugging system to unobtrusively access the bdm locations even if the application program is running out of the same memory area in the normal application memory map .
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 403 and executes them as they are rece ived. the firmware commands are shown in table 20-3 . each of the hardware a nd firmware bdm commands start with an 8-bit command code (opcode). depending upon the commands, a 16-bit address and/or a 16-bit data word is required as indicate d in the tables by the command. all the read comm ands output 16-bits of data despite the byte/word implicat ion in the command name. the external host should wait 150 bdmclk cycles for a non-intrusive bdm command to execut e before another command is sent. this delay includes 128 bdmclk cycles for the ma ximum delay for a free cycle.for data read commands, the host must in sert this delay between sending the address and attempti ng to read the data.in the case of a write command, the host must delay after t he data portion, be fore sending a new command, to be sure the write ha s finished. the external host should delay about 32 target bdmclk cycles between a firmware read command and the dat a portion of these commands. this allows the bdm firmware to execut e the instructions needed to get the requested data into the bdm shifter register. the external host should delay about 32 target bdmclk cycles after the data portion of firmware write co mmands to allow bd m firmware to table 20-3. bdm firmware commands command opcode (hex) data description read_next 62 16-bit data out x = x + 2; read next word pointed to by x read_pc 63 16-bit data out read program counter read_d 64 16-bit data out read d accumulator read_x 65 16-bit data out read x index register read_y 66 16-bit data out read y index register read_sp 67 16-bit data out read stack pointer write_next 42 16-bit data in x = x + 2; write next word pointed to by x write_pc 43 16-bit data in write program counter write_d 44 16-bit data in write d accumulator write_x 45 16-bit data in write x index register write_y 46 16-bit data in write y index register write_sp 47 16-bit data in write stack pointer go 08 none go to user program trace1 10 none execute one user instruction then return to bdm taggo 18 none enable tagging and go to user program
development support technical data mc68hc912dt128a ? rev 4.0 404 development support motorola complete the requested write operation before a new serial command disturbs the bdm shifter register. the external host should delay about 64 target bdmclk cycles after a trace1 or go command bef ore starting any new serial command. this delay is needed because the bdm shifter regi ster is used as a temporary data holding regi ster during the exit sequence to user code. bdm logic retains control of the internal buses unt il a read or write is completed.if an operation can be completed in a si ngle cycle, it does not intrude on normal cpu12 operation.however, if an operation requires multiple cycles, cpu12 cloc ks are frozen until the operation is complete. 20.4.4 bdm lockout the access to the mcu resources by bdm may be prevented by enabling the bdm lockout feature. when enabled, the bdm lockout mechanism prevents the bdm from being active. in this case the bdm rom is disabled and does not app ear in the mcu memory map. the bdm lockout is e nabled by clearing no bdml bit of eemcr register. the nobdml bit is loaded at reset from the shadow word of eeprom module. modifying the state of the nobdml and corresponding eeprom shadow bit is only possible in special modes. please refer to eeprom memory for nobdml information. 20.4.4.1 enabling the bdm lockout enabling the bdm lockout feature is only possi ble in special modes (smodn=0) and is accompli shed by the following steps. 1. remove the shadow word protec tion by clearing shprot bit in eeprot register. 2. clear noshw bit in eemcr regist er to make the shadow word visible at $0fc0-$0fc1. 3. program bit 7 of the high byte of the shadow word like a regular eeprom location at address $0f c0 (write $7f into address $0fc0). do not program other bi ts of the high byte of the
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 405 shadow word (location $0fc0) ; otherwise some regular eeprom array locations will not be visible. at the next reset, the high byte of the shadow wo rd is loaded into the eemcr register. nobdml bit in eemcr will be cl eared and bdm will not be operational. 4. protect the shadow word by setting shprot bit in eeprot register. 20.4.4.2 disabli ng the bdm lockout disabling the bdm lock out is only possible in special modes (smodn=0) except in s pecial single chip. follow the same steps as for enabling the bdm lockout, but erase the shadow word. at the next reset, the high byte of shadow word is loaded into the eemcr register. nobdml bit in eemcr will be set and bdm becomes operational. note: when the bdm lockout is enabled it is not possible to run code from the reset vector in spec ial single chip mode. 20.4.5 bdm registers seven bdm registers ar e mapped into the st andard 64-kbyte address space when bdm is active . mapping is shown in table 20-4 . the content of the instru ction register is deter mined by the type of background command being executed.the status register indicates bdm operating conditions. the shift register contains data being received or transmitted via the serial interfac e. the address register table 20-4. bdm registers address register $ff00 bdm instruction register $ff01 bdm status register $ff02 ? $ff03 bdm shift register $ff04 ? $ff05 bdm address register $ff06 bdm ccr holding register
development support technical data mc68hc912dt128a ? rev 4.0 406 development support motorola is temporary storage for bd m commands.the ccrsav register preserves the content of the cpu12 ccr wh ile bdm is active. the only registers of interest to us ers are the status register and the ccrsav register.the other bdm registers are only used by the bdm firmware to execute commands.the r egisters are accessed by means of the hardware read_bd and write_ bd commands, but should not be written during bdm operation (except the ccrsav register which could be written to modify the ccr value). 20.4.5.1 status the status register is read and writ ten by the bdm hardware as a result of serial data sh ifted in on the bkgd pin. read: all modes. write: bits 3 through 5, and bit 7 are writable in all modes. bit 6, bdmact, can only be writt en if bit 7 h/f in the instruction register is a zero. bit 2, clksw, can only be written if bi t 7 h/f in the instruction register is a one. a user would never write ones to bits 3 through 5 because these bits ar e only used by bdm firmware. enbdm ? enable bdm (permit active background debug mode) 0 = bdm cannot be made active (hardw are commands still allowed). 1 = bdm can be made active to allow firmware commands. bdmact ? background mode active status status? bdm status register (1) $ff01 bit 7654321bit 0 enbdm bdmact entag sdv trace clksw - - reset: 0 (note 1) 1000000 special single chip & periph reset: 0 0000000all other modes 1. enbdm is set to 1 by the firmware in special single chip mode.
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 407 bdmact becomes set as active bdm mode is entered so that the bdm firmware rom is enabled and put into the map. bdmact is cleared by a carefully ti med store instruction in the bdm firmware as part of the exit sequenc e to return to user code and remove the bdm memory from the map. this bit has 4 clock cycles write delay. 0 = bdm is not active. bdm ro m and registers are not in map. 1 = bdm is active and waiting for serial comm ands. bdm rom and registers are in map the user should be careful that the state of the bdmact bit is not unintentionally changed with the writ e_next firmware command. if it is unintentionally changed from 1 to 0, it will cause a system runaway because it would disabl e the bdm firmware ro m while the cpu12 was executing bdm firmwa re. the following tw o commands show how bdmact may unintentionally get changed fr om 1 to 0. write_x with data $fefe write_next with data $c400 the first command writes the data $fefe to the x index register. the second command writes the data $c4 to the $ff00 instruction register and also writ es the data $00 to the $ff01 status register. entag ? tagging enable set by the taggo command and cleared when bdm mode is entered. the serial system is di sabled and the tag function enabled 16 cycles after this bit is written. 0 = tagging not enabled, or bdm active. 1 = tagging active. bdm cannot pr ocess serial commands while tagging is active. sdv ? shifter data valid shows that valid data is in the serial interface shift register. used by the bdm firmware. 0 = no valid data. shift op eration is not complete. 1 = valid data. shift operation is complete. trace ? asserted by the trace1 command clksw ? bdmclk clock switch 0 = bdm system op erates with bclk.
development support technical data mc68hc912dt128a ? rev 4.0 408 development support motorola 1 = bdm system op erates with eclk. the write_bd_byte@ff01 command that changes clksw including 150 cycles after the data portion of the command should be timed at the old speed. beginning with the start of the next bdm command, the new clock c an be used for timing bdm communications. if eclk rate is slower than bd mclk rate, clksw is ignored and bdm system is forced to operate with eclk. 20.4.5.2 instruction - ha rdware instruction decode the instruction register is written by the bdm hardware as a result of serial data shifted in on the bkgd pin. it is readable and writable in special peripheral mode on the parallel bus. it is discussed here for two conditions: when a hardware command is executed and when a firmware command is executed. read and writ e: all modes . the hardware clears t he instruction regist er if 512 bdmclk cycles occur between fall ing edges from the host. the bits in the bdm inst ruction register have the foll owing meanings when a hardware command is executed. h/f ? hardware /firmware flag 0 = firmware command 1 = hardware command instruction? bdm instruction register (hardware command explanation) $ff00 bit 7654321bit 0 h/f data r/w bkgnd w/b bd/u 0 0 reset: 00000000
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 409 data ? data flag - shows that data acco mpanies the command. 0 = no data 1 = data follows the command r/w ? read/write flag 0 = write 1 = read bkgnd ? hardware request to enter active background mode 0 = not a hardware background command 1 = hardware background co mmand (instruction = $90) w/b ? word/byte transfer flag 0 = byte transfer 1 = word transfer bd/u ? bdm map/user map flag indicates whether bdm register s and rom are mapped to addresses $ff00 to $ffff in the standard 64-kb yte address space. used only by hardware read/ write commands. 0 = bdm resources not in map 1 = bdm rom and registers in map the bits in the bdm inst ruction register have the foll owing meanings when a firmware command is executed. h/f ? hardware /firmware flag 0 = firmware command 1 = hardware command data ? data flag ? shows that data a ccompanies the command. 0 = no data 1 = data follows the command instruction ? bdm instruction register (fir mware command bit explanation) $ff00 bit 7654321bit 0 h/f data r/w ttago regn
development support technical data mc68hc912dt128a ? rev 4.0 410 development support motorola r/w ? read/write flag 0 = write 1 = read ttago ? trace, tag, go field regn ? regist er/next field indicates which register is being affe cted by a command. in the case of a read_next or write_next comm and, index register x is pre- incriminated by 2 and the word pointed to by x is then read or written. table 20-5. ttago decoding ttago value instruction 00 ? 01 go 10 trace1 11 taggo table 20-6. regn decoding regn value instruction 000 ? 001 ? 010 read/write next 011 pc 100 d 101 x 110 y 111 sp
development support background debug mode mc68hc912dt128a ? rev 4.0 technical data motorola development support 411 20.4.5.3 shifter this 16-bit shift register contains dat a being received or transmitted via the serial interface. it is also us ed by the bdm firmware for temporary storage. read: all modes (but not normally accessed by users) write: all modes (but not normally accessed by users) 20.4.5.4 address this 16-bit address register is temporary storage for bdm hardware and firmware commands. read: all modes (but not normally accessed by users) write: only by bdm har dware (state machine) shifter ? bdm shift register ? high byte $ff02 bit 15 14 13 12 11 10 9 bit 8 s15 s14 s13 s12 s11 s10 s9 s8 reset: xxxxxxxx shifter ? bdm shift register ? low byte $ff03 bit 7654321bit 0 s7 s6 s5 s4 s3 s2 s1 s0 reset: xxxxxxxx address ? bdm address register ? high byte $ff04 bit 15 14 13 12 11 10 9 bit 8 a15 a14 a13 a12 a11 a10 a9 a8 reset: xxxxxxxx address ? bdm address register ? high byte $ff05 bit 7654321bit 0 a7 a6 a5 a4 a3 a2 a1 a0 reset: xxxxxxxx
development support technical data mc68hc912dt128a ? rev 4.0 412 development support motorola 20.4.5.5 ccrsav the ccrsav register is us ed to save the ccr of the users program when entering bdm. it is also used for tem porary storage in the bdm firmware. read and writ e: all modes 20.5 breakpoints hardware breakpoints are us ed to debug software on the mc68hc912dt128a by co mparing actual addre ss and data values to predetermined data in set up registers. a successf ul comparison will place the cpu in backgr ound debug mode ( bdm) or initiate a software interrupt (swi). breakpoint features designed into the mc68hc912dt128a include: mode selection for bdm or swi generation program fetch tagging for cycl e of execution breakpoint second address compar e in dual address modes range compare by disabl e of low byte address data compare in full featur e mode for non-tagged breakpoint byte masking for high/lo w byte data compares r/w compare for non-tagged compares tag inhibit on bdm trace ccrsav? bdm ccr holding register $ff06 bit 7654321bit 0 ccr7 ccr6 ccr5 ccr4 ccr3 ccr2 ccr1 ccr0 reset: note 1 (1) xxxxxxxx 1. initialized to equal the cpu12 ccr register by the firmware.
development support breakpoints mc68hc912dt128a ? rev 4.0 technical data motorola development support 413 20.5.1 breakpoint modes three modes of oper ation determine the type of breakpoint in effect. dual address-only breakpoints, each of which will cause a software interrupt (swi) single full-feature breakpoint whic h will cause the part to enter background debug mode (bdm) dual address-only break points, each of which will cause the part to enter bdm breakpoints will not occu r when bdm is active. 20.5.1.1 swi d ual address mode in this mode, dual addr ess-only breakpoints can be set, each of which cause a software interr upt. this is the only breakpoint mode which can force the cpu to execute a swi. pr ogram fetch tagging is the default in this mode; data breakpoi nts are not possible. in the dual mode each address breakpoint is affected by the bkpm bit and the bkale bit. the bkxrw and bkxrwe bi ts are ignored. in dual address mode the bkdbe becomes an enable for t he second address breakpoint. the bksz8 bit will have no effect when in a dual address mode. 20.5.1.2 bdm full breakpoint mode a single full feature breakpoint which causes the part to enter background debug mode. bdm mode may be entered by a breakpoint only if an internal si gnal from the bdm indi cates background debug mode is enabled. breakpoints are not allowed if t he bdm mode is already active. active mode means the cpu is executing out of the bdm rom. bdm should not be entered from a breakpoint unless the enable bit is set in the bdm. this is important because even if the enable bit in the bdm is negated the cpu actually does execute the bdm rom code. it checks the e nable and returns if not set. if the bdm is not serviced by the monitor then the breakpoint would be re-asserted when the bdm returns to normal cpu flow.
development support technical data mc68hc912dt128a ? rev 4.0 414 development support motorola there is no hardware to enforce restriction of breakpoint operation if the bdm is not enabled. 20.5.1.3 bdm dual address mode dual address-only breakpoi nts, each of which ca use the part to enter background debug mode. in the dual mode each addr ess breakpoint is affected, consistent across modes, by the bkpm bit, t he bkale bit, and the bkxrw and bkxrwe bits. in dual address mode the bkdbe becomes an enable for the second address breakpoint . the bksz8 bit will have no effect when in a d ual address mode. bdm mode may be entered by a breakpoint only if an inte rnal signal from the bdm indicates background debug mode is enabled. bkdbe will be used as an enable for the second address only breakpoint. breakpoints are not allowed if t he bdm mode is already active. active mode means the cpu is executing out of the bdm rom. bdm should not be entered from a breakpoint unless the enable bit is set in the bdm. this is important because even if the enable bit in the bdm is negated the cpu actually does execute the bdm rom code. it checks the e nable and returns if not set. if the bdm is not serviced by the monitor then the breakpoint would be re-asserted when the bdm returns to normal cpu flow. there is no hardware to enforce restriction of breakpoint operation if the bdm is not enabled. 20.5.2 breakpoint registers breakpoint operation consists of co mparing data in the breakpoint address registers (br kah/brkal) to the address bus and comparing data in the breakpoint data registers (brkdh/b rkdl) to the data bus. the breakpoint data registers can al so be compared to the address bus. the scope of comparison can be ex panded by ignoring the least significant byte of address or data matches. the scope of comparison can be limited to program data only by setting the bkpm bit in breakpoint control register 0.
development support breakpoints mc68hc912dt128a ? rev 4.0 technical data motorola development support 415 to trace program flow, se tting the bkpm bit caus es address comparison of program data only. control bits ar e also available that allow checking read/write matches. read and write anytime. this register is used to c ontrol the breakpoint logic. bken1, bken0 ? break point mode enable bkpm ? break on program addresses this bit controls whether the breakpoi nt will cause a break on a match (next instruction boundary) or on a match that will be an executable opcode. data and non-executed opcodes cannot cause a break if this bit is set. this bit has no mean ing in swi dual address mode. the swi mode only performs program breakpoints. 0 = on match, br eak at the next instruction boundary 1 = on match, break if the match is an instruction that will be executed. this uses tagging as its breakpoi nt mechanism. bk1ale ? breakpoint 1 range control only valid in dual address mode. 0 = brkdl will not be used to compare to the address bus. 1 = brkdl will be used to co mpare to the address bus. brkct0 ? breakpoint control register 0 $0020 bit 7 6 5 4 3 2 1 bit 0 bken1 bken0 bkpm 0 bk1ale bk0ale 0 0 reset: 0 0 0 0 0 0 0 0 table 20-7. breakpoint mode control bken1 bken0 mode selected brkah/l usage brkdh/l usage r/w range 0 0 breakpoints off ? ? ? ? 0 1 swi ? dual address mode address match address match no yes 1 0 bdm ? full breakpoint mode address match data match yes yes 1 1 bdm ? dual address mode address match address match yes yes
development support technical data mc68hc912dt128a ? rev 4.0 416 development support motorola bk0ale ? breakpoint 0 range control valid in all modes. 0 = brkal will not be used to compare to the address bus. 1 = brkal will be used to co mpare to the address bus. this register is read/ write in all modes. bkdbe ? enable data bus enables comparing of address or dat a bus values using the brkdh/l registers. 0 = the brkdh/l registers are not used in any comparison 1 = the brkdh/l regist ers are used to co mpare address or data (depending upon the mode selections bken1,0) bkmbh ? breakpoint mask high disables the comparing of the high byte of data when in full breakpoint mode. used in conjuncti on with the bkdbe bit (which should be set) 0 = high byte of data bus (bit s 15:8) are compared to brkdh 1 = high byte is not us ed to in comparisons table 20-8. breakpoint address range control bk1ale bk0ale address range selected ? 0 upper 8-bit address only for full mode or dual mode bkp0 ? 1 full 16-bit address for full mode or dual mode bkp0 0 ? upper 8-bit address only for dual mode bkp1 1 ? full 16-bit address for dual mode bkp1 brkct1 ? breakpoint control register 1 $0021 bit 7 6 5 4 3 2 1 bit 0 0 bkdbe bkmbh bkmbl bk1rwe bk1rw bk0rwe bk0rw reset: 0 0 0 0 0 0 0 0
development support breakpoints mc68hc912dt128a ? rev 4.0 technical data motorola development support 417 bkmbl ? breakpoint mask low disables the matching of the low by te of data when in full breakpoint mode. used in conjuncti on with the bkdbe bit (which should be set) 0 = low byte of data bus (bits 7:0) are compared to brkdl 1 = low byte is not us ed to in comparisons. bk1rwe ? r/w compare enable enables the comparison of the r/w signal to further specify what causes a match. this bit is not us eful in program breakpoints or in full breakpoint mode. this bit is used in conjun ction with a second address in dual address mode when bkdbe=1. 0 = r/w is not us ed in comparisons 1 = r/w is used in comparisons bk1rw ? r/w compare value when bk1rwe = 1, this bit determi nes the type of bus cycle to match. 0 = a write cycle w ill be matched 1 = a read cycle w ill be matched bk0rwe ? r/w compare enable enables the comparison of the r/w signal to further specify what causes a match. this bit is not useful in program breakpoints. 0 = r/w is not used in the comparisons 1 = r/w is used in comparisons bk0rw ? r/w compare value when bk0rwe = 1, this bit determines the type of bus cycle to match on. 0 = write cycle will be matched 1 = read cycle w ill be matched
development support technical data mc68hc912dt128a ? rev 4.0 418 development support motorola these bits are used to compare against the most significant byte of the address bus. these bits are used to compare against the least significant byte of the address bus. these bits may be exclud ed from being used in the match if bk0ale = 0. these bits are compared to the most significant byte of the data bus or the most significant by te of the address bus in dual address modes. bken[1:0], bkdbe, and bkmbh control how this byte will be used in the breakpoint comparison. table 20-9. breakpoint read/write control bk1rwe bk1rw bk0rwe bk0rw read/write selected ??0x r/w is don?t care for full mode or dual mode bkp0 ??10r/w is write for full mode or dual mode bkp0 ??11r/w is read for full mode or dual mode bkp0 0x??r/w is don?t care for dual mode bkp1 10??r/w is write for dual mode bkp1 11??r/w is read for dual mode bkp1 brkah ? breakpoint address register, high byte $0022 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 reset: 0 0 0 0 0 0 0 0 brkal ? breakpoint address register, low byte $0023 bit 7 6 5 4 3 2 1 bit 0 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0 brkdh ? breakpoint data register, high byte $0024 bit 7 6 5 4 3 2 1 bit 0 bit 15 14 13 12 11 10 9 bit 8 reset: 0 0 0 0 0 0 0 0
development support technical data mc68hc912dt128a ? rev 4.0 419 development support motorola these bits are compared to the least significant byte of the data bus or the least significant by te of the address bus in dual address modes. bken[1:0], bkdbe, bk1ale , and bkmbl control how this byte will be used in the break point comparison. 20.6 instruction tagging the instruction queue and cycle-by-cycle cpu activity can be reconstructed in real ti me or from trace histor y that was captured by a logic analyzer. howeve r, the reconstructed queue cannot be used to stop the cpu at a specific instruct ion, because exec ution has already begun by the time an op eration is visible outsi de the mcu. a separate instruction tagging me chanism is provided for this purpose. executing the bdm taggo command configures two mcu pins for tagging. the taglo signal shares a pin with the lstrb signal, and the tag h i signal shares a pin with the bkgd signal. tagging information is latched on the falling edge of eclk. table 20-10 shows the functions of t he two tagging pins. the pins operate independently - the st ate of one pin does not affect the function of the other. th e presence of logic le vel zero on either pi n at the fall of eclk performs the indica ted function. tagging is allowed in all modes. tagging is disabled when bdm becom es active and bdm serial commands are not processed while tagging is active. brkdl ? breakpoint data register, low byte $0025 bit 7 6 5 4 3 2 1 bit 0 bit 7 6 5 4 3 2 1 bit 0 reset: 0 0 0 0 0 0 0 0
development support technical data mc68hc912dt128a ? rev 4.0 420 development support motorola the tag follows program information as it advances through the queue. when a tagged instruction reache s the head of t he queue, the cpu enters active background debugging mo de rather than execute the instruction. table 20-10. tag pin function taghi taglo tag 1 1 no tag 1 0 low byte 0 1 high byte 0 0 both bytes
mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 421 technical data ? mc68hc912dt128a section 21. electrical specifications 21.1 contents 21.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 21.3 tables of data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 21.2 introduction the mc68hc912dt128a microcontrolle r unit (mcu) is a16-bit device composed of standard on -chip peripherals including a 16-bit central processing unit (cpu12), 128-kbyte flash eeprom, 8k byte ram, 2k byte eeprom, two asyn chronous serial comm unications interfaces (sci), a serial peripher al interface (spi), an 8-channel, 16-bit timer, two16-bit pulse accumulators and 16-bi t down counter (ect), two 10-bit analog-to-digital converte r (adc), a four-channel pulse-width modulator (pwm), an iic interface module, a nd three mscan mo dules. the chip is the first 16-bit microcontroller to include both byte-erasable eeprom and flash eeprom on the same device. system resource mapping, clock generation, interrupt control and bus interfacing are managed by the lite integration m odule (lim). the mc68hc 912dt128a has full 16- bit data paths throughout, however, the multiple xed external bus can operate in an 8-bit narrow mode so single 8-bit wide memory can be interfaced for lower cost systems.
electrical specifications technical data mc68hc912dt128a ? rev 4.0 422 electrical specifications motorola 21.3 tables of data note: four pins (vrl0, vrh0, vrl1, and vrh1) show esd susceptibility below the motorola st andards. care should be exercised in handling these pins. table 21-1. maximum ratings (1) 1. permanent damage can occur if maximum ratings are exceede d. exposures to voltages or currents in excess of recom- mended values affects device reliability. device modules may not operate normally while being exposed to electrical ex- tremes. rating symbol value unit supply voltage v dd , v dda , v ddx ? 0.3 to + 6.5 v input voltage v in ? 0.3 to + 6.5 v operating temperature range t a (2) 2. please refer to table 1-1 to identify part numbers associated with each temperature range. t l to t h ? 40 to + 85 ? 40 to + 105 ? 40 to + 125 c storage temperature range t stg ? 55 to + 150 c current drain per pin (3) excluding v dd and v ss 3. one pin at a time, observing maximum power dissipation limits . internal circuitry protects the inputs against damage caused by high static voltages or electric fields; however, normal prec autions are necessary to avoid application of any voltage high- er than maximum-rated voltages to this high-impedance circuit. extended operation at the maximum ratings can adversely affect device reliability. tying unused inputs to an appropriate logic voltage level (either gnd or v dd ) enhances reliability of operation. i in 25 ma v dd differential voltage v dd ? v ddx 6.5 v
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 423 table 21-2. thermal characteristics characteristic symbol value unit average junction temperature t j t a + (p d ja ) c ambient temperature t a user-determined c package thermal resistance (junction-to-ambient) 112-pin quad flat pack (qfp) ja 40 c/w total power dissipation (1) p d p int + p i/o or w device internal power dissipation p int i dd v dd w i/o pin power dissipation (2) p i/o user-determined w a constant (3) k p d (t a + 273 c) + ja p d 2 w c 1. this is an approximate value, neglecting p i/o . 2. for most applications p i/o ? p int and can be neglected. 3. k is a constant pertaining to the device. solve for k with a known t a and a measured p d (at equilibrium). use this value of k to solve for p d and t j iteratively for any value of t a . k t j 273 c + ------------------------- -
electrical specifications technical data mc68hc912dt128a ? rev 4.0 424 electrical specifications motorola table 21-3. dc elect rical characteristics v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted characteristic symbol min max unit input high voltage, all inputs v ih 0.7 v dd v dd + 0.3 v input low voltage, all inputs v il v ss ? 0.3 0.2 v dd v output high voltage, all i/o and output pins except xtal normal drive strength i oh = ? 10.0 a i oh = ? 0.8 ma reduced drive strength i oh = ? 4.0 a i oh = ? 0.3 ma v oh v dd ? 0.2 v dd ? 0.8 v dd ? 0.2 v dd ? 0.8 ? ? ? ? v v v v output low voltage, all i/o and output pins except xtal normal drive strength i ol = 10.0 a i ol = 1.6 ma reduced drive strength i ol = 3.6 a i ol = 0.6 ma v ol ? ? ? ? v ss + 0.2 v ss + 0.4 v ss + 0.2 v ss + 0.4 v v v v input leakage current (1) v in = v dd or v ss all input only pins except irq , atd (2) and v fp v in = v dd or v ss irq i in ? ? 2.5 10 a a three-state leakage, i/o ports, bkgd, and reset i oz ? 2.5 a input capacitance all input pins and atd pins (non-sampling) atd pins (sampling) all i/o pins c in ? ? ? 10 15 20 pf pf pf output load capacitance all outputs except ps[7:4] ps[7:4] when configured as spi c l ? ? 90 200 pf pf programmable active pull-up/pull-down current irq , xirq , dbe , lstrb , r/w . ports a, b, h, j, k, p, s, t moda, modb active pull down during reset bkgd passive pull up i apu 50 50 50 500 500 500 a a a ram standby voltage, power down v sb 1.5 ? v ram standby current i sb ?50 a 1. specification is for parts in the -40 to +85 c range. higher temperature ranges will result in increased current leakage. 2. see table 21-5 .
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 425 table 21-4. supply current v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted characteristic symbol frequency of operation (e-clock) unit 2 mhz (1) 4 mhz (1) 8 mhz maximum total supply current run: single-chip mode expanded mode i dd 20 30 30 50 55 90 ma ma wait: (all peripheral functions shut down) single-chip mode expanded mode w idd 3 4 5 6.5 10 15 ma ma stop: single-chip mode, no clocks s idd 150 150 150 a 1. devices only tested at 8m hz (worst case conditions) table 21-5. atd dc electrical characteristics v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , atd clock = 2 mhz, unless otherwise noted characteristic symbol min max unit analog supply voltage v dda 4.5 5.5 v analog supply currentnormal operation stop i dda 1.0 10 ma a reference voltage, low v rl v ssa v dda / 2 v reference voltage, high v rh v dda / 2v dda v v ref differential reference voltage (1) v rh ? v rl 4.5 5.5 v input voltage (2) v indc v ssa v dda v input current, off channel (3) i off 100 na reference supply current i ref 250 a input capacitancenot sampling sampling c inn c ins 10 15 pf pf 1. accuracy is guaranteed at v rh ? v rl = 5.0v 10%. 2. to obtain full-scale, full-range results, v ssa v rl v indc v rh v dda . 3. maximum leakage occurs at maximum operating temperatur e. current decreases by approximately one-half for each 10 c decrease from maximum temperature.
electrical specifications technical data mc68hc912dt128a ? rev 4.0 426 electrical specifications motorola table 21-6. analog converte r characteristics (operating) v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , atd clock = 2 mhz , unless otherwise noted characteristic symbol min typical max unit 8-bit resolution (1) 1 count 20 mv 8-bit absolute error ,(2) 2, 4, 8, and 16 atd sample clocks ae ? 1 + 1 count 10-bit resolution (1) 1 count 5 mv 10-bit absolute error (2) 2, 4, 8, and 16 atd sample clocks ae ?2.5 2.5 count 1. at v rh ? v rl = 5.12v, one 8-bit count = 20 mv, and one 10-bit count = 5mv. 2. these values include quantization error which is inherently 1/2 count for any a/d converter. absolute errors only guaranteed when v rl =v ss , v rh =v dd and when external source impedence is close to zero. table 21-7. atd ac characteristics (operating) v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , atd clock = 2 mhz, unless otherwise noted characteristic symbol min max unit atd operating clock frequency f atdclk 0.5 2.0 mhz conversion time per channel 0.5 mhz f atdclk 2 mhz 16 atd clocks 30 atd clocks t conv 8.0 15.0 32.0 60.0 s s stop and atd power up recovery time (1) v dda = 5.0v t sr 10 s 1. from the time adpu is asserted unt il the time an atd conversion can begin.
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 427 table 21-8. atd maximum ratings characteristic symbol value units atd reference voltage v rh v dda v rl v ssa v rh v rl ? 0.3 to + 6.5 ? 0.3 to + 6.5 v v v ss differential voltage | v ss ? v ssa | 0.1 v v dd differential voltage v dd ? v dda v dda ? v dd 6.5 0.3 v v reference to supply differential voltage v dda ? v rh v rh ? v dda v dda ? v rl v rl ? v dda 6.5 0.3 6.5 0.3 v analog input differential voltage v dda ? v indc v indc ? v dda 6.5 0.3 v table 21-9. eeprom characteristics v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted characteristic symbol min max unit minimum programming clock frequency f prog 250k hz programming time t prog 10 ms clock recovery time, following stop, to continue programming t crstop t prog + 1 ms erase time t erase 10 ms write/erase endurance 10,000 cycles data retention 10 (1) years eeprom programming maximum time to ?auto? bit set ? ? 500 s eeprom erasing maximum time to ?auto? bit set ? ? 10 ms 1. based on the average life time operating temperature of 70 c.
electrical specifications technical data mc68hc912dt128a ? rev 4.0 428 electrical specifications motorola table 21-10. flash eeprom characteristics v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted characteristic symbol min max units bytes per row ? 64 64 bytes read bus clock frequency f read 32k 8m hz erase time t eras 8?ms pgm/eras to hven set up time t nvs 10 ? s high-voltage hold time t nvh 5? s high-voltage hold time (erase) t nvhl 100 ? s program hold time t pgs 5? s program time t fpgm 30 40 s return to read time t rcv 1? s cumulative program hv period t hv ?8ms row program/erase endurance ? 100 cycles data retention ? 10 (1) years 1. based on the average life time operating temperature of 70 c. table 21-11. pulse width modulator characteristics v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted characteristic symbol min max unit e-clock frequency f eclk 0.004 8.0 mhz a-clock frequency selectable f aclk f eclk /128 f eclk hz bclk frequency selectable f bclk f eclk /128 f eclk hz left-aligned pwm frequency 8-bit 16-bit f lpwm f eclk /1m f eclk /256m f eclk /2 f eclk /2 hz hz left-aligned pwm resolution r lpwm f eclk /4k f eclk hz center-aligned pwm frequency 8-bit 16-bit f cpwm f eclk /2m f eclk /512m f eclk f eclk hz hz center-aligned pwm resolution r cpwm f eclk /4k f eclk hz
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 429 note: reset is recognized during t he first clock cycle it is held low. internal circuitry then drives the pin low for 16 clock cycles, releases the pin, and samples the pin level 9 cycles late r to determine the source of the interrupt. figure 21-1. timer inputs table 21-12. control timing characteristic symbol 8.0 mhz unit min max frequency of operation f o 0.004 8.0 mhz e-clock period t cyc 0.125 250 s external oscillator frequency f eo 0.5 16.0 (1) mhz processor control setup time t pcsu = t cyc / 2 + 30 t pcsu 92 ? ns reset input pulse width to guarantee external reset vector minimum input time (can be preempted by internal reset) pw rstl 32 2 ? ? t cyc t cyc mode programming setup time t mps 4? t cyc mode programming hold time t mph 20 ? ns interrupt pulse width, irq edge-sensitive mode pw irq = 2t cyc + 20 pw irq 270 ? ns wait recovery startup time t wrs ? 4 cycles timer input capture pulse width pw tim 270 ? ns 1. when using a resonator (quartz or ceramic), see table 21-17 for allowable values. pt7 2 pt7 1 pt[7:0] 2 pt[7:0] 1 notes : 1. rising edge sensitive input 2. falling edge sensitive input pw tim pw pa
electrical specifications technical data mc68hc912dt128a ? rev 4.0 430 electrical specifications motorola figure 21-2. por and exter nal reset timing diagram t pcsu internal moda, modb eclk extal v dd reset 4098 t cyc free fffe fffe 3rd 1st 2nd free fffe fffe fffe t mph pw rstl t mps address pipe pipe pipe 1st exec 3rd pipe 2nd pipe 1st pipe 1st exec note: reset timing is subject to change.
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 431 figure 21-3. stop r ecovery timing diagram pw irq t stopdelay 3 irq 1 irq or xirq eclk 1st address 4 sp-9 free free vector free free resume program with instruction wh ich follows the stop instruction. internal address 5 clocks notes: 1. edge sensitive irq pin (irqe bit = 1) 2. level sensitive irq pin (irqe bit = 0) 3. t stopdelay = 4098 t cyc if dly bit = 1 or 2 t cyc if dly = 0. 4. xirq with x bit in ccr = 1. 5. irq or (xirq with x bit in ccr = 0). opt 1st 2nd 3rd 1st exec pipe pipe exec sp-8 sp-6 fetch pipe sp-6 sp-8 sp-9
electrical specifications technical data mc68hc912dt128a ? rev 4.0 432 electrical specifications motorola figure 21-4. wait recovery timing diagram t pcsu pc, iy, ix, b:a, , ccr stack registers eclk r/w address irq , xirq , or internal interrupts sp ? 2 sp ? 4 sp ? 6 . . . sp ? 9 sp ? 9 sp ? 9 . . . sp ? 9 sp ? 9 vector free 1st 2nd 3rd pipe t wrs note: reset also causes recovery from wait. address pipe pipe 1st exec
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 433 figure 21-5. interr upt timing diagram eclk pw irq 1st 3rd address irq 1 sp ? 9 t pcsu irq 2 , xirq , or internal interrupt vector sp ? 2 1st sp ? 4 sp ? 6 2nd sp ? 8 data vect pc iy ix b:a ccr prog r/w notes: 1. edge sensitive irq pin (irqe bit = 1) 2. level sensitive irq pin (irqe bit = 0) fetch addr exec pipe pipe pipe prog fetch prog fetch
electrical specifications technical data mc68hc912dt128a ? rev 4.0 434 electrical specifications motorola figure 21-6. port read timing diagram figure 21-7. port write timing diagram table 21-13. peripheral port timing characteristic symbol 8.0 mhz unit min max frequency of operation (e-clock frequency) f o 0.004 8.0 mhz e-clock period t cyc 0.125 250 s peripheral data setup time mcu read of ports t pdsu 81 ? ns peripheral data hold time mcu read of ports t pdh 0?ns delay time, peripheral data write mcu write to ports except port can t pwd ?40ns delay time, peripheral data write mcu write to port can t pwd ?71ns port rd tim eclk mcu read of port ports t pdsu t pdh port wr tim eclk mcu write to port previous port data new data valid port a t pwd
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 435 table 21-14. multiplex ed expansion bus timing v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted num characteristic (1), (2), (3), (4) 1. all timings are calculated for normal port drives. 2. crystal input is required to be within 45% to 55% duty. 3. reduced drive must be off to meet these timings. 4. unequalled loading of pins will affect relative timing numbers. delay symbol 8 mhz unit min max frequency of operation (e-clock frequency) f o 0.004 8.0 mhz 1 cycle timet cyc = 1 / f o ? t cyc 0.125 250 s 2 pulse width, e lowpw el = t cyc / 2 + delay ? 2 pw el 60 ns 3 pulse width, e high (5) pw eh = t cyc / 2 + delay 5. this characteristic is affected by clock stretch. add n t cyc where n = 0, 1, 2, or 3, depending on the number of clock stretches. ? 2 pw eh 60 ns 5 address delay timet ad = t cyc / 4 + delay 14 t ad 45 ns 7 address valid time to eclk riset av = pw el ? t ad ? t av 15 ns 8 multiplexed address hold timet mah = t cyc / 4 + delay ? 16 t mah 15 ns 9 address hold to data valid ? t ahds 5ns 10 data hold to high zt dhz = t ad ? 20 ? t dhz 20 ns 11 read data setup time ? t dsr 38 ns 12 read data hold time ? t dhr 0ns 13 write data delay timet ddw = t cyc / 4 + delay 14 t ddw 45 ns 14 write data hold timet dhw = t cyc / 4 + delay ? 11 t dhw 20 ns 15 write data setup time (5) t dsw = pw eh ? t ddw ? t dsw 15 ns 16 read/write delay timet rwd = t cyc / 4 + delay 19 t rwd 50 ns 17 read/write valid time to e riset rwv = pw el ? t rwd ? t rwv 10 ns 18 read/write hold timet rwh = t cyc / 4 + delay ?2 6 t rwh 5ns 19 low strobe (6) delay timet lsd = t cyc / 4 + delay 6. without tag enabled. 26 t lsd 57 ns 20 low strobe (6) valid time to e riset lsv = pw el ? t lsd ? t lsv 3ns 21 low strobe (6) hold timet lsh = t cyc / 4 + delay ?2 6 t lsh 5ns 22 address access time (5) t acca = t cyc ? t ad ? t dsr ? t acca 26 ns 23 access time from e rise (5) t acce = pw eh ? t dsr ? t acce 22 ns 24 dbe delay from eclk rise (5) t dbed = t cyc / 4 + delay 20 t dbed 51 ns 25 dbe valid timet dbe = pw eh ? t dbed ? t dbe 9ns 26 dbe hold time from eclk fall t dbeh 010ns
electrical specifications technical data mc68hc912dt128a ? rev 4.0 436 electrical specifications motorola figure 21-8. multiplexed expansion bus timing diagram dbe 24 25 eclk r/w 1 2 3 18 11 12 14 note: measurement points shown are 20% and 70% of v dd 13 16 17 read write 23 lstrb 21 19 20 (w/o tag enabled) 5 7 22 8 15 address/data multiplexed address address data data 10 9 26
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 437 table 21-15. spi timing (v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , 200 pf load on all spi pins) (1) num function symbol min max unit operating frequency master slave f op 1/256 1/256 1 / 2 1 / 2 f eclk sck period master slave t sck 2 2 256 ? t cyc t cyc enable lead time master slave t lead 1 / 2 1 ? ? t sck t cyc enable lag time master slave t lag 1 / 2 1 ? ? t sck t cyc clock (sck) high or low time master slave t wsck t cyc ? 30 t cyc ? 30 128 t cyc ? ns ns sequential transfer delay master slave t td 1 / 2 1 ? ? t sck t cyc data setup time (inputs) master slave t su 30 30 ? ? ns ns data hold time (inputs) master slave t hi 0 30 ? ? ns ns slave access time t a ?1 t cyc slave miso disable time t dis ?1 t cyc data valid (after sck edge) master slave t v ? ? 50 50 ns ns data hold time (outputs) master slave t ho 0 0 ? ? ns ns rise time input output t ri t ro ? ? t cyc ? 30 30 ns ns fall time input output t fi t fo ? ? t cyc ? 30 30 ns ns 1. all ac timing is shown with respect to 20% v dd and 70% v dd levels unless otherwise noted.
electrical specifications technical data mc68hc912dt128a ? rev 4.0 438 electrical specifications motorola a) spi master ti ming (cpha = 0) b) spi master ti ming (cpha = 1) figure 21-9. spi timing diagram (1 of 2) sck (output) sck (output) miso (input) mosi (output) ss 1 (output) 1 10 6 7 msb in 2 bit 6 . . . 1 lsb in msb out 2 lsb out bit 6 . . . 1 11 4 4 2 10 (cpol = 0) (cpol = 1) 5 3 12 13 1. ss output mode (dds7 = 1, ssoe = 1). 2. lsbf = 0. for lsbf = 1, bit order is lsb, bit 1, ..., bit 6, msb. sck (output) sck (output) miso (input) mosi (output) 1 6 7 msb in 2 bit 6 . . . 1 lsb in master msb out 2 master lsb out bit 6 . . . 1 4 4 10 12 13 11 port data (cpol = 0) (cpol = 1) port data ss 1 (output) 5 2 13 12 3 1. ss output mode (dds7 = 1, ssoe = 1). 2. lsbf = 0. for lsbf = 1, bit order is lsb, bit 1, ..., bit 6, msb.
electrical specifications tables of data mc68hc912dt128a ? rev 4.0 technical data motorola electrical specifications 439 a) spi slave timing (cpha = 0) b) spi slave timing (cpha = 1) figure 21-10. spi timi ng diagram (2 of 2) sck (input) sck (input) mosi (input) miso (output) ss (input) 1 10 6 7 msb in bit 6 . . . 1 lsb in msb out slave lsb out bit 6 . . . 1 11 4 4 2 8 (cpol = 0) (cpol = 1) 5 3 13 note: not defined but normally msb of character just received. slave 13 12 11 see 12 note 9 spi slave cpha1 sck (input) sck (input) mosi (input) miso (output) 1 6 7 msb in bit 6 . . . 1 lsb in msb out slave lsb out bit 6 . . . 1 4 4 10 12 13 11 see (cpol = 0) (cpol = 1) ss (input) 5 2 13 12 3 note: not defined but normally lsb of character just received. slave note 8 9
electrical specifications technical data mc68hc912dt128a ? rev 4.0 440 electrical specifications motorola table 21-16. cgm characteristics 5.0 volts +/- 10% characteristic symbol min. max. unit pll reference frequency f ref 0.5 8 mhz bus frequency f bus 0.004 8 mhz vco range f vco 2.5 8 mhz vco limp-home frequency f vcomin 0.5 2.5 mhz lock detector transition from acquisition to tracking mode ? trk 3% 4% ? lock detection ? lock 0% 1.5% ? un-lock detection ? unl 0.5% 2.5% ? lock detector transition from tracking to acquisition mode ? unt 6% 8% ? pllon stabilization delay (1) pllon total stabilization delay (2) t stab 3ms pllon acquisition mo de stabilization delay (3) t acq 1ms pllon tracking mode stabilization delay (3) t al 2ms 1. pll stabilization delay is highly dependent on operational re quirement and external component values (e.e. crystal, xfc filter component values). note (2) shows typical delay values for a typical co nfiguration. appropriate xfc filter values should be chosen based on oper ational requirement of system. 2. f ref = 4mhz, f sys = 8mhz (refdv = #$00, synr = #$01), xf c: cs = 33nf, cp - 3.3nf, rs = 2.7k ? . table 21-17. oscillator characteristics mc68hc912dt128a mc68hc912dx 128c mc68hc912dx128p unit input buffer hysteresis (1) min max 0 50 75 350 75 350 mv resonator frequency (2) (vddpll=vdd) min max 0.5 8 0.5 8 0.5 8 mhz resonator frequency (2) (vddpll=0v) min max 4 10 4 10 0.5 16 mhz 1. these values are dervied from design simulation and are not tested 2. specifications apply to quartz or ceramic resonators only table 21-18. stop key wake-up filter characteristic symbol min. max. unit stop key wake-up filter time t kwstp 210 s stop key wake-up filter pulse interval t kwsp 20 - s
mc68hc912dt128a ? rev 4.0 technical data motorola appendix: changes from mc68hc912dg128 441 technical data ? mc68hc912dt128a section 22. appendix: cha nges from mc68hc912dg128 22.1 contents 22.2 significant changes from the mc68hc912dg128 (non-suffix device) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441 22.2.1 flash. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441 22.2.2 eeprom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .442 22.2.3 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 22.2.4 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 22.2.5 kwu filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .444 22.2.6 port adx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 22.2.7 atd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 22.2 significant changes from th e mc68hc912dg128 (non-suffix device) 22.2.1 flash 22.2.1.1 flash architecture the flash arrays are made from a new non-volatile memory (nvm) technology. an external vfp is no longer used. programming is now carried out on a whole row (64 bytes) at a time. erasing is still a bulk erase of the entire array. 22.2.1.2 flash control register the flash control register (feectl) is in the sa me location. however, the individual bit functi ons have changed significant ly to support the new technology.
appendix: changes from mc68hc912dg128 technical data mc68hc912dt128a ? rev 4.0 442 appendix: changes from mc68hc912dg128 motorola 22.2.1.3 flash programming procedure programming of the flash is greatly simplified ov er previous hc12s. the read / verify / re-pulse programming algorithm is replaced by a much simpler method. 22.2.1.4 flash programming time the most significant change resulting from the new flash technology is that the bulk erase and pr ogram times are now fix ed. the erase time is at least twice as fast while the word programming time is at least 20% faster. 22.2.1.5 flash extern al programming voltage the new flash does not require an ex ternal high volt age supply. all voltages required for programmi ng and erase are now generated internally. pin 97 that was the vfp pin on the 68hc912dg128 is now a factory test pin. on ealy producti on devices it is recommended that this pin is not connected within t he application, but it may be connected to vss or 5.5v max without issue. 22.2.2 eeprom 22.2.2.1 eeprom architecture like the flash, the eeprom is also made from this new nvm technology. the architecture and basic programming and erase operations are unchanged. howeve r, there is a new optional programming method that allows faster progr amming of the eeprom. 22.2.2.2 eeprom clock source and pre-scaler the first major difference on the ne w eeprom is that it requires a constant time base source to ensure secure programming and erase operations. the clock source that is going to driv e the clock divider input is the external clock i nput, extali. the divide rati o from this source has
appendix: changes from mc68hc912dg128 significant changes from the mc68hc912dg128 (non-suffix device) mc68hc912dt128a ? rev 4.0 technical data motorola appendix: changes from mc68hc912dg128 443 to be set by programming an 10-bit time base pre-sca lar into bits spread over two new register s, eedivh and eedivl. the eedivh and eedivl regi sters are volatile. however, they are loaded upon reset by the contents of the non-volatile shadow word much in the same wa y as the eeprom modul e control register (eemcr) bits interact wi th the shadow word fo r configuration control on the existing revision. 22.2.2.3 eeprom auto programming & erasing the second major change to the eepr om is the inclusion in the eeprom control register (eeprog) of an aut o function using the previously unused bit 5 of this register. the auto function enables the logic of the mcu to automatically use the optimum programming or erasing time for the eeprom. if using auto, the user does not need to wa it for the normal minimum specified programming or erasing time. after se tting the eepgm bi t as normal the user just has to poll that bit agai n, waiting for the mcu to clear it indicating that programming or erasing is complete. 22.2.2.4 eeprom sele ctive write more zeros for some applications it may be adv antageous to track more than 10k events with a single byte of eeprom by programmi ng one bit at a time. for that purpose, a special sele ctive bit programmi ng technique is available. when this technique is ut ilized, a program / er ase cycle is defined as multiple writes (up to eight) to a unique locati on followed by a single erase sequence. 22.2.3 stop mode this new version will correctly ex it stop mode wi thout having to synchronize the start of stop with the rti clock.
appendix: changes from mc68hc912dg128 technical data mc68hc912dt128a ? rev 4.0 444 appendix: changes from mc68hc912dg128 motorola 22.2.4 wait mode this new version will correctly exit wait mode using s hort xirq or irq inputs. 22.2.5 kwu filter the kwu filter will now ignore pulses shorte r than 2 microseconds. 22.2.6 port adx power must be applied to vdda at all times even if the adc is not being used. this is necessary for port ad0 and port ad1 to function correctly as digital inputs. 22.2.7 atd 22.2.7.1 channel selection any channel can be selected for the first conversion of a multiple channel conversion. bits ca, cb & cc in at dxctl5 do not get masked but are used to select which channel is us ed to start the s equential conversion sequence. for compatibilty, ensure that the appropriate bits are cleared in the software. see table 19-8 . bit cc of atdxctl5 is not masked when bit s8cm = 1. 22.2.7.2 cd bit bit cd in atdxctl5 is renamed sc to differentiate it from extended functionality of bits ca, cb & cc. functionality is unchanged as it still selects conversion from th e internal reference sources but when doing a multiple channel scan, bi ts ca, cb & cc must be cleared as appropriate for compatible reference selection.
appendix: changes from mc68hc912dg128 significant changes from the mc68hc912dg128 (non-suffix device) mc68hc912dt128a ? rev 4.0 technical data motorola appendix: changes from mc68hc912dg128 445 22.2.7.3 additional features atd flexibility has been increased with additional si gned result, data justification, single conversion selection and results location fifo features. djm & dsgn bits hav e been added to atdxctl2 register. default values are compatible with mc68hc912dg128 functionality. fifo & s1c bits have been added to at dxctl3 register. default values are compatible with mc68h c912dg128 functionality. 22.2.7.4 s8cm bit bit s8cm in atdxctl5 is renamed s8c. functionality is compatible with s8cm but can now be modified by the new s1c bit in atdxctl3. the default is compatible with mc68hc912dg128 functionality. 22.2.7.5 writi ng to atdxctl4 writing to atdxctl4 aborts any ongoing conversion sequence and initiates a new conversion sequence. previously it onl y aborted ongoing sequences leaving the atd in idle mode ( no conversion sequences being processed). writing to atdx ctl2 or adtxctl3 also does not abort an ongoing conversion sequence. previously writing these registers also aborted an y ongoing sequence leav ing the atd in idle mode . this is unlikely to be a compatibility issue as appl ications mostly write these registers to conf igure the atd, closely followed by a write to atdxctl5 to initiate a new conver sion sequence which does abort any ongoing conversion sequence and rese ts the appropriate flags. to ensure compatibility, the applic ation should not rely on ongoing conversions being aborted. also any interrupts from the completion of an ongoing sequence should be masked and/or handled correctly.
appendix: changes from mc68hc912dg128 technical data mc68hc912dt128a ? rev 4.0 446 appendix: changes from mc68hc912dg128 motorola 22.2.7.6 scf bit in scan mode (sc an bit = 1 in atdxctl5) the sequence complete flag (scf bit in atdstatx) is se t after completion of each conversion sequence. previously it was only set at the end of the first conversion sequence. to ensure compatibility the application should not rely on this flag being set only once per scan mode. 22.2.7.7 atdtestx reading the atdtestx register in nor nal modes returns the value of the successive approximation register (sar). previous ly it always read as zero. the rst bit in the atdtestx regist er can be written in normal modes (in order to reset the atd). previously it was read only. to ensure compatibility this register should not be r ead or written to.
mc68hc912dt128a ? rev 4.0 technical data motorola appendix: cgm practical aspects 447 technical data ? mc68hc912dt128a section 23. appendix: cgm practical aspects 23.1 contents 23.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 23.3 practical aspects for the pll usage . . . . . . . . . . . . . . . . . .447 23.4 printed circuit board gui delines. . . . . . . . . . . . . . . . . . . . . . .453 23.2 introduction this sections provides useful and practical pieces of information concerning the implement ation of the cgm module. 23.3 practical aspects for the pll usage 23.3.1 synthesized bus frequency starting from a cera mic resonator or quartz crystal frequency f xtal , if ?refdv? and ?synr? are the decima l content of the refdv and synr registers respectively , then the mcu bus freque ncy will simply be: note: it is not allowed to synthesize a bus frequency that is lower than the crystal frequency, as the correc t functioning of some internal f bus f vco f xtal synr 1 + () ? refdv 1 + () -------------------------- --------------------- - == synr 0,1,2,3...63} { refdv 0,1,2,3...7} {
appendix: cgm practical aspects technical data mc68hc912dt128a ? rev 4.0 448 appendix: cgm practical aspects motorola synchronizers would be jeopardiz ed (e.g. the mclk and xclk clock generators). 23.3.2 operation under adver se environmental conditions the normal operation for t he pll is the so-called ?automatic bandwidth selection mode? wh ich is obtained by having t he auto bit set in the pllcr register. when this mode is selected and as the vco frequency approaches its target, the charge pump current level will automatically switch from a relative ly high value of around 40 a to a lower value of about 3 a. it can happen that this low level of c harge pump current is not enough to overcome leakages present at the xfc pin due to adverse environmental conditions . these conditions ar e frequently encountered for uncoated pcbs in automotive applications . the main symptom for this failure is an unstable characterist ic of the pll which in fact ?hunts? between acquisition and tracking m odes. it is then advised for the running software to place the pll in manual, forced acquisition mode by clearing both the auto and the acq bits in the pll cr register. doing so will maintain the hi gh current level in the c harge pump constantly and will permit to sustain higher levels of leakages at the xfc pin. this latest revision of the clock generator module mainta ins the lock detection feature even in manual bandwidth control, offering then to the application software the same flexibi lity for the clocking control as the automatic mode. 23.3.3 filter compon ents selection guide 23.3.3.1 equations set these equations can be used to select a set of filter components. two cases are considered: 1. the ?tracking? mode. this situation is reac hed normally when the pll operates in automatic bandwidth selection mode (auto=1 in the pllcr register). 2. the ?acquisition? mode. this sit uation is reached when the pll operates in manual bandwidth selection mode and forced
appendix: cgm practical aspects practical aspects for the pll usage mc68hc912dt128a ? rev 4.0 technical data motorola appendix: cgm practical aspects 449 acquisition (auto=0, acq =0 in the pllcr register). in both equations, the power supply should be 5v. st art with the target loop bandwidth as a function of t he other parameters, but obviously, nothing prevents the user from starting with t he capacitor value for example. also, remember that the smoothing capacitor is always assumed to be one tenth of t he series capacitance value. so with: m: the multiplying factor for the reference frequency (i.e. (synr+1)) r: the series resistance of the low pass filter in ? c: the series capacitance of the low pass filter in nf f bus : the target bus freque ncy expressed in mhz : the desired damping factor f c : the desired loop bandwidth expressed in hz for the ?tracking? mode: and for the ?acquisition? mode: 23.3.3.2 particular ca se of an 8mhz synthesis assume that a desired value for the damping factor of the second order system is close to 0.9 as this leads to a satisfactory transient response. then, derived from t he equations above, table 23-1 and table 23-2 suggest sets of values corres ponding to several loop bandwidth possibilities in the case of an 8mhz synthesis for the two cases mentioned above. f c 210 9 2 ?? rc ?? ------------------------- 37.78 e 1.675 f bus ? 10.795 ----------------------------- ?? ?? r ?? 2 m ?? ----------------------------------------------------- - == f c 210 9 2 ?? rc ?? ------------------------- 415.61 e 1.675 f bus ? 10.795 ----------------------------- ?? ?? r ?? 2 m ?? -------------------------------------------------------- - ==
appendix: cgm practical aspects technical data mc68hc912dt128a ? rev 4.0 450 appendix: cgm practical aspects motorola the filter components values are chos en from standard series (e.g. e12 for resistors). the operating voltage is assumed to be 5v (although there is only a minor difference between 3v and 5v operati on). the smoothing capacitor cp in parallel with r and c is set to be 1/10 of the value of c. the reference frequencies mentioned in this table correspond to the output of the fine granularity divider controll ed by the refdv register. this means that the calculations are irrespective of the way the reference frequency is gene rated (directly for the crystal oscillator or after division). the target frequency va lue also has an influence on the calculations of the filter compo nents because the vco gain is not constant over its operating range. the bandwidth limit corresponds to the so-called gardner? s criteria. it corresponds to the maximum value that can be chosen before the continuous time approximation ceases to be justified. it is of course advisable to stay far away from this limit.
appendix: cgm practical aspects practical aspects for the pll usage mc68hc912dt128a ? rev 4.0 technical data motorola appendix: cgm practical aspects 451 table 23-1. suggested 8mhz synthesis pll filter elements (tracking mode) reference [mhz] synr fbus [mhz] c [nf] r [k ? ] loop bandwidth [khz] bandwidth limit [khz] 0.614 $0c 7.98 100 4.3 1.1 157 0.614 $0c 7.98 4.7 20 5.3 157 0.614 $0c 7.98 1 43 11.5 157 0.614 $0c 7.98 0.33 75 20 157 0.8 $09 8.00 220 2.7 0.9 201 0.8 $09 8.00 10 12 4.2 201 0.8 $09 8.00 2.2 27 8.6 201 0.8 $09 8.00 0.47 56 19.2 201 1 $07 8.00 220 2.4 1 251 1 $07 8.00 10 11 4.7 251 1 $07 8.00 2.2 24 9.9 251 1 $07 8.00 0.47 51 21.4 251 1.6 $05 8.00 330 1.5 1 402 1.6 $05 8.00 10 9.1 5.9 402 1.6 $05 8.00 3.3 15 10.2 402 1.6 $05 8.00 1 27 18.6 402 2 $03 8.00 470 1.1 0.96 502 2 $03 8.00 22 5.1 4.4 502 2 $03 8.00 4.7 11 9.6 502 2 $03 8.00 1 24 20.8 502 2.66 $02 8.00 220 1.5 1.6 668 2.66 $02 8.00 22 4.7 5.1 668 2.66 $02 8.00 4.7 10 11 668 2.66 $02 8.00 1 22 24 668 4 $01 8.00 220 1.2 1.98 1005 4 $01 8.00 33 3 5.1 1005 4 $01 8.00 10 5.6 9.3 1005 4 $01 8.00 2.2 12 19.8 1005
appendix: cgm practical aspects technical data mc68hc912dt128a ? rev 4.0 452 appendix: cgm practical aspects motorola table 23-2. suggested 8mhz synthesis pll filter elements (acquisition mode) reference [mhz] synr fbus [mhz] c [nf] r [k ? ] loop bandwidth [khz] bandwidth limit [khz] 0.614 $0c 7.98 1000 0.43 1.2 157 0.614 $0c 7.98 47 2 5.5 157 0.614 $0c 7.98 10 4.3 12 157 0.614 $0c 7.98 3.3 7.5 21 157 0.8 $09 8.00 2200 0.27 0.9 201 0.8 $09 8.00 100 1.2 4.4 201 0.8 $09 8.00 22 2.4 9.3 201 0.8 $09 8.00 4.7 5.6 20.1 201 1 $07 8.00 2200 0.22 1 251 1 $07 8.00 100 1 4.8 251 1 $07 8.00 2. 2.2 10.4 251 1 $07 8.00 4.7 4.7 22.5 251 1.6 $05 8.00 3300 0.15 1.1 402 1.6 $05 8.00 100 0.82 6.2 402 1.6 $05 8.00 33 1.5 10.7 402 1.6 $05 8.00 10 2.7 19.5 402 2 $03 8.00 4700 0.1 1 502 2 $03 8.00 220 0.51 4.6 502 2 $03 8.00 47 1 10 502 2 $03 8.00 10 2.4 21.8 502 2.66 $02 8.00 2200 0.12 1.7 668 2.66 $02 8.00 220 0.43 5.3 668 2.66 $02 8.00 47 1 11.6 668 2.66 $02 8.00 10 2 25.1 668 4 $01 8.00 2200 0.1 2.1 1005 4 $01 8.00 330 0.27 5.4 1005 4 $01 8.00 100 0.51 9.7 1005 4 $01 8.00 22 1 20.8 1005
appendix: cgm practical aspects printed circuit board guidelines mc68hc912dt128a ? rev 4.0 technical data motorola appendix: cgm practical aspects 453 23.4 printed circuit board guidelines printed circuit boards (pcbs) ar e the board of choice for volume applications. if designed correctly, a very low noise system can be built on a pcb with consequently good em i/emc performanc es. if designed incorrectly, pcbs can be extremel y noisy and sensitive modules, and the cgm could be disrupted. some common sense rules can be used to prevent such problems. use a ?star? style power routing plan as opposed to a ?daisy chain?. route power and ground from a c entral location to each chip individually, and use the widest trac e practical (the more the chip draws current, the wider the trace). never pl ace the mcu at the end of a long string of se rially connected chips. when using pcb layout software, fi rst direct the routing of the power supply lines as we ll as the cgm wires (c rystal oscillator and pll). layout constraints must be then reported on the other signals and not on these ?hot? nodes. optimizing the ?hot? nodes at the end of the rout ing process usually gives bad results. avoid notches in power trac es. these notches not only add resistance (and are not usually a ccounted for in simulations), but they can also add unnecessa ry transmission line effects. avoid ground and power loops. this has been one of the most violated guidelines of pcb layout. loops are excellent noise transmitters and can be easily avoid ed. when using multiple layer pcbs, the power and ground plane concept wo rks well but only when strictly adhered to (do not compromise the ground plane by cutting a hole in it and running si gnals on the ground plane layer). keep the spacing around via holes to a minimum (but not so small as to add capacitive effects). be aware of the three dimensio nal capacitive effects of multi- layered pcbs. bypass (decouple) the power suppli es of all chips as close to the chip as possible. use one dec oupling capacitor per power supply pair (vdd/vss, vddx/ vssx...). two capacitor s with a ratio of about 100 sometimes offer better performances over a broader
appendix: cgm practical aspects technical data mc68hc912dt128a ? rev 4.0 454 appendix: cgm practical aspects motorola spectrum. this is especially the case for the power supply pins close to the e port, when the e clock and/or the calibration clock are used. on the general vdd power supply input, a ?t? low pass filter lcl can be used (e.g. 10 h-47 f-10 h). the ?t? is pref erable to the ? ? version as the ex hibited impedance is more constant with respect to the vdd curr ent. like many modular micro controllers, hc12 devices have a power consum ption which not only varies with clock edges but also with the functioning modes. keep high speed clock and bus trace length to a minimum. the higher the clock spe ed, the shorter the tr ace length. if noisy signals are sent over long tra cks, impedance adjustments should be considered at both ends of the line (generally, simple resistors suffice). bus drivers like the can physica l interface should be installed close to their connector, with dedi cated filtering on their power supply. mount components as close to t he board as possible. snip excess lead length as close to the board as poss ible. preferably use surface mount devices (smds). mount discrete components as close to the chip that uses them as possible. do not cross sensitive signals on any layer. if a sensitive signal must be cross ed by another signal, do it as many layers away as possible a nd at right angles. always keep pcbs clea n. solder flux, oils from fingerprints, humidity and general dirt can conduct electricity. sensitive circuits can easily be disrupted by small amounts of leakage. choose pcb coatings with care. certain epoxies, paints, gelatins, plastics and waxes can conduct electr icity. if the manufacturer cannot provide the electr ical characteristics of the substance, do not use it.
appendix: cgm practical aspects printed circuit board guidelines mc68hc912dt128a ? rev 4.0 technical data motorola appendix: cgm practical aspects 455 in addition to the a bove general pieces of advice, the following guidelines should be followed for the cgm pins (but also more generally for any sensitive analog circuitry): parasitic capacitance on extal is absolutely critical ? probably the most critical layo ut consideration. the xtal pin is not as sensitive. all routi ng from the extal pin through the resonator and the blocking cap to the actual connecti on to vss must be considered. for minimum capacitance there should ideally be no ground / power plane around the extal pin and associated routing. however, practical emc considerat ions obviously should be taken into consideration for each application. the clock input circuitry is sensit ive to noise so excellent supply routing and decoupling is mandato ry. connect the ground point of the oscillator circuit dire ctly to the vsspll pin. good isolation of p ll / oscillator power supply is critical. use 1nf+ 100nf and keep tracks as low impedance as possible load capacitors should be lo w leakage and stable across temperature ? use npo or c0g types. the load capacitors may ?pull? th e target frequency by a few ppm. crystal manufacturer specs show symmetrical values but the series device capacitance on extal and xtal are not symmetrical. it may be possible to adjust this by changing the values of the load capacitors ? start-up conditions should be evaluated. keep the adjacent port h / po rt e and reset si gnals noise free. don?t connect these to external si gnals and / or add series filtering ? a series resistor is probably adequate. any dc-blocking capacitor should be as low esr as possible ? for the range of crystals we are lookin g at anything over 1 ohm is too much. mount oscillator components on m cu side of board ? avoid using vias in the oscillator circuitry.
appendix: cgm practical aspects technical data mc68hc912dt128a ? rev 4.0 456 appendix: cgm practical aspects motorola mount the pll filter and oscill ator components as close to the mcu as possible. do not allow the extal and xtal signals to interfere with the xfc node. keep these tra cks as short as possible. do not cross the cgm signals with any other signal on any level. remember that the reference vo ltage for the xfc filter is vddpll. as the return path for the oscillat or circuitry is vsspll, it is extremely important to connect vsspll to v ss even if the pll is not to be powered. surf ace mount components reduce the susceptibility of si gnal contamination.
mc68hc912dt128a ? rev 4.0 technical data motorola appendix: information on mc68hc912dt128a mask set changes 457 technical data ? mc68hc912dt128a section 24. appendix: information on mc68hc912dt128a mask set changes 24.1 contents 24.2 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 24.3 oscillator ? major changes . . . . . . . . . . . . . . . . . . . . . . . . . .457 24.4 flash protection feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 24.5 clock circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458 24.6 pseudo stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 24.7 oscillator ? minor changes . . . . . . . . . . . . . . . . . . . . . . . . . .459 24.8 pll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 24.2 introduction the following improvements were made to create t he 1l05h mask set (mc68hc912dx128c) and the 2l05h mask set (mc68hc912dx128p). previous mc68hc912dt128a mask se ts 3k91d (tsmc wafer fab.) and 0l05h (motorola tsc6 wafer fa b.) are equivalent with the only change being the wafe r fab location. 24.3 oscillator ? major changes the following are the primary differenc es between the previous colpitts ("a") and the new colpitts ("c" ) oscillator configurations. 1. optimisation of the bias curren t to the amplifie r for less process variation. 2. addition of hysteresis to the clo ck input buffer to reduce sensitivity to noise.
appendix: information on mc68hc912dt128a technical data mc68hc912dt128a ? rev 4.0 458 appendix: information on mc68hc912dt128a mask set changes motorola 3. change to the input esd resistor from extal to the gate of the oscillator amplifier to provide a parallel path, reducing parasitic phase shift in the oscillator. additionally a new pierce ("p") osci llator configurat ions has been added. see section 13. oscillator for full details. 24.4 flash prot ection feature a flash protection bit has been added to the eemcr register to protect the flash memory from accidental progr am or erasure. this bit is loaded from the eeprom s hadow word at reset, so that the flash can be protected before any software is executed. see eeprom and flash sectio ns for more details. 24.5 clock circuitry the crystal oscillator output is now frozen when limp home (lh) mode is entered to prevent rapid switching between crystal and lh clocks. improvements have been made to the bus clock switching circuitry to eliminate the potential fo r glitches to appear on the internal clock line. the duration of the clo ck monitor pulses was increased to reduce sensitivity of the cl ock monitor circuit to short clock pulses. 24.6 pseudo stop mode oscillator amplifier drive is now not reduced in pseudo stop mode. when exiting pseudo stop mode, the device will now not go into limp home mode since the cryst al is already running.
appendix: information on mc68hc912dt128a mask set changes oscillator ? minor changes mc68hc912dt128a ? rev 4.0 technical data motorola appendix: information on mc68hc912dt128a mask set changes 459 24.7 oscillator ? minor changes the automatic level control (alc) capacitor reference was changed from vdd to vss in the crystal oscillator circuit to improve noise immunity. parasitic capacitance on internal si gnal lines has been decreased, thus decreasing sensitivity to ex ternal capacitance changes. note: for best oscillator performance, it is recommended that the load capacitor selection is verifi ed on changing to the new mask. a reduction was made to the gain of the operat ional transconductance amplifier (ota) to reduce the amplif ication of any noise on the extal pin. 24.8 pll the limp home clock fre quency has been re-alligned to the specification values to reduce sensitivity to system noise and hence reduce pll jitter. note: it is advisable to verify the xfc filter co mponents and pll lock time due to the above changes. vco start-up will now be at the minimum frequen cy whilst the power up sequence of the curr ent controlled oscillator has been improved. the xfc pin is now preconditioned to vddpll when pll is deselected so xfc doesn?t float. this ensures th e pll starts up at low frequency and ramps up to th e desired frequency.
appendix: information on mc68hc912dt128a technical data mc68hc912dt128a ? rev 4.0 460 appendix: information on mc68hc912dt128a mask set changes motorola
mc68hc912dt128a ? rev 4.0 technical data motorola glossary 461 technical data ? mc68hc912dt128a glossary a ? see ?accumulators (a and b or d).? accumulators (a and b or d) ? two 8-bit (a and b) or one 16-bit (d) gener al-purpose registers in the cpu. the cpu uses the accumulators to hold operands and results of arithmetic and logic operations. acquisition mode ? a mode of pll operati on with large loop bandwidth . also see ?tracking mode?. address bus ? the set of wires that the cpu or dma uses to r ead and write memory locations. addressing mode ? the way that the c pu determines the operand address for an instruction. the m68hc12 cpu has 15 addressing modes. alu ? see ?arithmetic logic unit (alu).? analogue-to-digital converter (atd) ? the atd module is an 8- channel, multip lexed-input successive-approximation anal og-to-digital converter. arithmetic logic unit (alu) ? the portion of the cpu that contains the logic circuitry to perform arithmetic, logic, and mani pulation operat ions on operands. asynchronous ? refers to logic circuits and operati ons that are not synch ronized by a common reference signal. atd ? see ?analogue-to-d igital converter?. b ? see ?accumulators (a and b or d).? baud rate ? the total number of bits tr ansmitted per unit of time. bcd ? see ?binary-co ded decimal (bcd).?
glossary technical data mc68hc912dt128a ? rev 4.0 462 glossary motorola binary ? relating to the base 2 number system. binary number system ? the base 2 number system, havin g two digits, 0 and 1. binary arithmetic is convenient in digital circ uit design because digital circuits have two permissible voltage levels, lo w and high. the binary digits 0 and 1 can be interpreted to correspond to the two di gital voltage levels. binary-coded decimal (bcd) ? a notation that uses 4-bit bi nary numbers to represent the 10 decimal digits and that reta ins the same positional struct ure of a decimal number. for example, 234 (decimal) = 0010 0011 0100 (bcd) bit ? a binary digit. a bit has a valu e 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 ? 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 th e 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 in terrupt 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 br eak address registers. bus ? a set of wires that transfers logic signals. bus clock ? see "cpu clock". byte ? a set of eight bits. can ? see "motorola scalable can." ccr ? see ?condition code register.? central processor unit (cpu) ? the primary functi oning unit of any computer system. the cpu controls the execution of instructions.
glossary mc68hc912dt128a ? rev 4.0 technical data motorola glossary 463 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) ? the cgm module generates a base clock signal from which the system clocks are derived. the cgm may include a crystal o scillator circuit and/or phase-locked loop (pll) circuit. comparator ? a device that compares t he magnitude of two inputs. a digital co mparator defines the equality or relati ve differences between two binary numbers. computer operating prop erly module (cop) ? a counter module th at resets the mcu if allowed to overflow. condition code register (ccr) ? an 8-bit register in the cpu that contai ns the interrupt mask bit and five bits that i ndicate the results of the instruction just executed. control bit ? one bit of a register m anipulated by software to c ontrol the operation of the module. control unit ? one of two major units of the cpu. the control unit c ontains 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 ex ecution unit, which contains the arithmetic logic unit (alu), c pu registers, and bus interface. cop ? see "computer operati ng properly module (cop)." cpu ? see ?central proc essor unit (cpu).? cpu12 ? the cpu of t he mc68hc12 family. cpu clock ? bus clock select bits bcsp and bcss in the clock se lect register (clksel) determine which clock drives sysclk for the main syste m, including the cpu and buses. when extali drives the sysclk, th e cpu or bus clock frequency (f o ) is equal to the extali frequency divided by 2.
glossary technical data mc68hc912dt128a ? rev 4.0 464 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 time s will be equal. the length of time required to execute an in struction is measured in cpu clock cycles. cpu registers ? memory locations that ar e wired directly into the cpu logic inst ead of being part of the addressabl e memory map. the cpu always has dire ct access to the information in these registers. th e cpu registers in an m68hc12 are: a (8-bit accumulator) b (8-bit accumulator) ? d (16-bit accumulator formed by co ncatenation of accumulators a and b) ix (16-bit index register) iy (16-bit index register) sp (16-bit stack pointer) pc (16-bit program counter) ccr (8-bit condit ion code register) cycle time ? the period of the op erating frequency: t cyc =1/f op . d ? see ?accumulators (a and b or d).? decimal number system ? base 10 numbering system that us es the digits zero through nine. duty cycle ? a ratio of the amount of time the signal is on versus t he time it is off. duty cycle is usually represented by a percentage. ect ? see ?enhanced capture timer.? eeprom ? electrically erasable, programmable, read-only me mory. a nonvolatile type of memory that can be electrica lly erased and reprogrammed. eprom ? erasable, programmable, read-only memory. a nonvolatile type of memory that can be erased by exposure to an ultraviolet light source a nd then reprogrammed. enhanced capture timer (ect) ? the hc12 enhanced capture time r module has the features of the hc12 standard timer modul e enhanced by additional featur es in order to enlarge the field of applications. exception ? an event such as an inte rrupt or a reset that stops th e sequential execution of the instructions in the main program.
glossary mc68hc912dt128a ? rev 4.0 technical data motorola glossary 465 fetch ? to copy data from a memory location into the accumulator. firmware ? instructions and data program med into nonvolatile memory. free-running counter ? a device that counts from zero to a predeter mined 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. 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. index registers (ix and iy) ? two 16-bit registers in th e cpu. in the indexed addressing modes, the cpu uses the content s of ix or iy to determine the effective address of the operand. ix and iy can also serve as a temporary data storage locations. 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 ar e expressed by programmers as assembly language mnemon ics. a cpu interprets an opcode and its associated operand(s) and instruction. inter-ic bus (i 2 c) ? a two-wire, bidirectional serial bus that provides a simple, efficient method of data exchange bet ween devices. interrupt ? a temporary break in the sequential execution of a pr ogram 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).? jitter ? short-term signal instability.
glossary technical data mc68hc912dt128a ? rev 4.0 466 glossary motorola latch ? a circuit that retain s 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 instruct ion completion and data movement. least significant bit (lsb) ? the rightmost digit of a binary number. logic 1 ? a voltage level approx imately equal to the input power voltage (v dd ). logic 0 ? a voltage level approximately equal to the gr ound voltage (v ss ). low byte ? the least significant eight bits of a word. m68hc12 ? a motorola family of 16-bit mcus. mark/space ? the logic 1/logic 0 conv ention used in formatting dat a in serial communication. mask ? 1. a logic circuit t hat forces a bit or gro up of bits to a desired st ate. 2. a photomask used in integrated circuit fabricati on to transfer an image onto silicon. mcu ? microcontroller unit. see ?microcontroller.? memory location ? each m68hc12 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 dat a bus, and asserts the write signal. to read informat ion from a memory lo cation, the cpu places the address of the location on the address bus and asserts the read signal. in respons e to the read signal, the selected memory location plac es its data onto the data bus. memory map ? a pictorial representati on of all memory locations in a computer system. mi-bus ? see "motorola interconnect bus". microcontroller ? microcontroller unit (mcu). a comp lete computer system, including a cpu, memory, a clock oscillato r, 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. most significant bit (msb) ? the leftmost digi t of a binary number.
glossary mc68hc912dt128a ? rev 4.0 technical data motorola glossary 467 motorola interconnect bus (mi-bus) ? the motorola in terconnect bus (mi bus) is a serial communications protocol which supports distributed real-time control efficiently and with a high degree of noise immunity. motorola scalable can (mscan) ? the motorola scalable controll er area network is a serial communications protocol that ef ficiently supports distributed real-time control with a very high level of data integrity. mscan ? see "motorola scalable can". msi ? see "multiple serial interface". multiple seri al interface ? a module consisting of multiple independent serial i/o sub-systems, e.g. two sci and one spi. multiplexer ? a device that can select one of a number of inputs and pass the logic level of that input on to the output. nibble ? a set of four bi ts (half of a byte). object code ? the output from an assembler or compil er 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 transisto r. an external pu llup device can be connected to the power supply to provide the logic 1 output voltage. operand ? data on which an operati on is performed. usually a statement consists of an operator and an operand. for exam ple, the operator may be an add instruction, and the operand may be the qu antity to be added. oscillator ? a circuit that produces a constant frequency square wa ve that is used by the computer as a timing and sequencing reference. otprom ? one-time programmable read-only memo ry. a nonvolatile ty pe 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).
glossary technical data mc68hc912dt128a ? rev 4.0 468 glossary motorola parity ? an error-checking scheme that counts the nu mber of logic 1s in each byte transmitted. in a system that uses odd parity, every byte is expec ted to have an odd number of logic 1s. in an even parit y system, every byte should have an even number of logic 1s. in the transmitter, a parity generator appends an extra bit to each by te 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 clock generator circ uit in which a voltage controlled oscillator produces an oscillation which is syn chronized 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 calcul ation of the address of an oper and, and theref ore points to the operand. polarity ? the two opposite logi c levels, logic 1 and logic 0, wh ich correspond to two different voltage levels, v dd and v ss . polling ? periodically reading a st atus bit to monitor the c ondition of a peripheral device. port ? a set of wires for communica ting 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 instruct ions that cause a computer to perform a desi red operation or operations. program counter (pc) ? a 16-bit register in the cpu. the pc r egister holds the address of the next instruction or operand that the cpu will use. pull ? an instruction that copies into the accu mulator the contents of a stack ram location. the stack ram address is in the stack pointer.
glossary mc68hc912dt128a ? rev 4.0 technical data motorola glossary 469 pullup ? a transistor in the output of a logic gate th at connects the output to the logic 1 voltage of the power supply. pulse-width ? the amount of ti me a signal is on as opposed to being in its off state. pulse-width modulation (pwm) ? controlled variation (modulati on) 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 comp lete 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 vali d until the cpu writes a different value or until power is turned off. rc circuit ? a circuit consisting of capacitors and resistors having a de fined time constant. read ? to copy the contents of a memo ry location to the accumulator. register ? a circuit that st ores a group of bits. reserved memory location ? a memory location that is used only in special fa ctory test modes. writing to a reserved loca tion has no effect. reading a reserved location returns an unpredictable value. reset ? to force a device to a known condition. sci ? see "serial communicati on interface module (sci)." serial ? pertaining to s equential transmission over a single line. serial communications inte rface module (sci) ? a module that supp orts asynchronous communication. serial peripheral inte rface module (spi) ? a module that su pports synchronous communication. set ? to change a bit from logic 0 to logic 1; opposite of clear. shift register ? a chain of circuits that c an retain the logic levels (log ic 1 or logic 0) written to them and that can shift the logic levels to the right or left th rough adjacent ci rcuits in the chain.
glossary technical data mc68hc912dt128a ? rev 4.0 470 glossary motorola signed ? a binary number notation that accommodates both po sitive and negative numbers. the most significant bit is us ed to indicate whet her the number is po sitive 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 operati on of a microcontroller. software interrupt (swi) ? an instruction that causes an interrupt and its associated vector fetch. spi ? see "serial pe ripheral interfac e module (spi)." stack ? a portion of ram reserved fo r storage of cpu regi ster contents and subroutine return addresses. stack pointer (sp) ? a 16-bit register in the cpu containing the address of the next available storage location on the stack. start bit ? a bit that signals t he beginning of an asynchronous serial transmission. status bit ? a register bit t hat indicates the condition of a device. stop bit ? a bit that signals th e end of an asynchron ous serial transmission. subroutine ? a sequence of instructions to be used more than once in the course of a program. the last instruction in a subrout ine is a return from subrouti ne (rts) instruct ion. at each place in the main program where the subrouti ne instructions are needed, a jump or branch to subroutine (jsr or bsr) in struction 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, t he cpu returns to the main program where it left off. synchronous ? refers to logic circuits and operati ons that are synchr onized by a common reference signal. 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 ? a mode of pll operation with narro w loop bandwidth. also see ?acquisition mode.? two?s complement ? a means of performing bi nary subtraction using addi tion techniques. the most significant bit of a tw o?s complement number indicate s the sign of the number (1 indicates negative). the two?s complement negative of a num ber is obtained by inverting each bit in the number and then adding 1 to the result.
glossary mc68hc912dt128a ? rev 4.0 technical data motorola glossary 471 unbuffered ? utilizes only one regist er for data; new data ov erwrites current data. unimplemented memory location ? a memory location that is not used. writing to an unimplemented location has no effect. reading an unimple mented location returns an unpredictable value. variable ? a value that changes during t he course of program execution. vco ? see "voltage-controlled oscillator." vector ? a memory location that co ntains the address of the beginni ng of a subroutine written to service an interrupt or reset. voltage-controlled oscillator (vco) ? a circuit that pr oduces an oscillating output signal of a frequency that is c ontrolled by a dc voltage ap plied to a control input. waveform ? a graphical representation in which the amplitude of a wa ve is plotted against time. wired-or ? connection of circuit outputs so that if an y output is high, t he 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.
glossary technical data mc68hc912dt128a ? rev 4.0 472 glossary motorola
mc68hc912dt128a ? rev 4.0 technical data motorola revision history 473 technical data ? mc68hc912dt128a revision history this section lists the revi sion history of the do cument since the first release. data for previous in ternal drafts is unavailable. 24.9 changes in rev. 4.0 24.10 changes from rev 2.0 to rev 3.0 section page (in rev 3 .0) description of change electrical specifications 437 clock (sck) high or low time, master, t wsck changed from t cyc ? 60 to t cyc ? 30. section page (in rev 3.0) description of change pinout and signal descriptions 42 , 43 note about test pin updated 46 pll loop filter connections diagram ( figure 3-4 ) updated 48 note added about consideration of crystal selection due to emc emissions 54 description of test pin added as new section and to table 3-2 55 , 60 text added in table 3-2 and port can pin descriptions about non- connection of rxcan pins when mscan modules are not used. registers 68 fpopen bit added to eemcr register flash memory 116 new paragraph added to overview about flash protection via fpopen bit 117 last part of feemcr opening paragraph changed to ?if hven or pgm or eras in the feec tl register is set? 120 changes made to the flash programming description for clarification of aligned words 122 new section 7.11 flash protection bit fpopen added
revision history technical data mc68hc912dt128a ? rev 4.0 474 revision history motorola eeprom memory 128 , 129 fpopen bit added to eemcr register 132 paragraph added to the eepgm description to clarify block protection clock functions 159 note added about consideration of crystal selection due to emc emissions 159 opening paragraphs of pll description changed for clarification 163 in the section on clock loss during normal operation, description of operation in limp home mode has been expanded for clarification 182 in figure 12-6 , mscan clock source selection via clksrc bit corrected mscan controller 339 first two bullets of sleep mode description updated 352 slprq = 1 description updated analog-to-digital converter major rewrite of entire section for clarification development support clock for the bdm has been renamed as bdmclk, to differentiaite it from another internal signal, bclk electrical specifications 425 units for i off corrected to na 427 reference to supply differential voltage values updated. v ref differential voltage row removed analog input differential voltage row added 429 f xtal removed 429 footnote added restricting extern al oscillator oper ating frequency to 8mhz when using a quartz crystal 440 table footnote removed from table 21-16 regarding v ddpll appendix: changes from mc68hc912dg128 444 additional paragraphs added describing atd differences from the non a suffix device appendix: cgm practical aspects 447 section 23.3 a few hints fo r the cgm crystal oscillator application removed. all po ints are covered in new oscillator section 455 extra bullets added appendix: information on mc68hc912dt128a mask set changes new section section page (in rev 3.0) description of change
revision history changes from rev 1.0 to rev 2.0 mc68hc912dt128a ? rev 4.0 technical data motorola revision history 475 24.11 changes from rev 1.0 to rev 2.0 24.12 changes from first version (int ernal release, no revision number) to rev 1.0 section page (in rev 2.0) description of change pinout and signal descriptions 30, 31 figures 4 and 5, pin 97 changed to test and note added. 33 note added about connection of power supplies. 35 note about non-standard oscillator circuit expanded. 35 additional paragraphs added covering dc bias. registers 55 cd bit name corrected in atd0ctl5. eeprom 104 new section added ?eeprom selective write more zeros? clock functions 143 to 153 major rewrite of limp home and fast stop recovery section. 160 system clock frequency formulae updated for clarification. 161 figure 18 modified for clarification. 164 figure 21 modified for clarification. ect 194 figure 28 modified for clarification. atd 321 shading removed from cc bit in table 52. cd bit name corrected. electrical characteristics 353, 354 preliminary notes removed. 361 eeprom programming maximum time to ?auto? bit set and eeprom erasing maximum time to ?auto? bit set added to table 71. 369 several values in table 76 updated. appendix a 377 new section added ?2d. eeprom selective write more zeros?. new section added ?6. port adx?. new section added ?7. atd?. appendix b 380 new section added ?dc bias?. section page (in rev 1.0) description of change general description 21 ordering information updated. eeprom 109 addition of caution regarding attempts to erase or program protected locations.
revision history technical data mc68hc912dt128a ? rev 4.0 476 revision history motorola msi 236 clarification of sp0dr register state on reset. section page (in rev 1.0) description of change

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