// Chapter 6 6811 C programs// Jonathan W. Valvano// This software accompanies the book,// Embedded Microcomputer Systems: Real Time Interfacing// published by Brooks Cole, 1999//  Program 6.3. Periodic interrupt using input capture and an external clock.// MC68HC11A8// PA0 input = external signalunsigned int TIME;   // incrementedvoid Init(void){asm(" sei");   // make atomic   TCTL2 = (TCTL2&0xFC)|0x01;   TMSK1 |= 0x01;  // Arm IC3   TFLG1=0x01; // initially clear     TIME=0;  asm(" cli");}#pragma interrupt_handler IC3Hanvoid IC3Han(void){     if((TFLG1&0x01)==0) asm(" swi");    TFLG1=0x01;   // acknowledge    TIME++;}   //  Program 6.6. C language period measurement.// MC68HC11A8// PA2/IC1 input = external signal// rising edge to rising edge// resolution = 500ns // Range = 36 祍 to 32 ms, // no overflow checking// IC1 interrupt each period,unsigned int Period;  // units of 500 nsunsigned int First;   // TCNT first edgeunsigned char Done;   // Set each rising void Ritual(void){    asm(" sei");    // make atomic     TCTL2 = (TCTL2&0xCF)|0x10; // rising    First = TCNT;  // first will be wrong    Done=0;         // set on subsequent    TFLG1 = 0x04;   // Clear IC1F     TMSK1 |= 0x04;  // Arm IC1     asm(" cli");}#pragma interrupt_handler TIC1handler()void TIC1handler(void){    Period=TIC1-First;       First=TIC1;  // Setup for next    TFLG1=0x04;  // ack by clearing IC1F    Done=0xFF;}//  Program 6.10. C language 32-bit period measurement.// MC68HC11A8unsigned int MsPeriod,LsPeriod;    unsigned int First;     unsigned int Count;     unsigned char Mode;#pragma interrupt_handler TOhandler()void TOhandler(void){     TFLG2=0x80;              Count++;     if(Count==65535){ // 35 minutes        MsPeriod=LsPeriod=65535;        TMSK1=0x00;         TMSK2=0x00;  // Disarm        Mode=2;}}#pragma interrupt_handler TIC1handler()void TIC1handler(void){  if(Mode==0){    First = TIC1; Count=0; Mode=1;    if(((TIC1&0x8000)==0)       &&(TFLG2&0x80)) Count--;}    else {      if(((TIC1&0x8000)==0)        &&(TFLG2&0x80))Count++;      MsPeriod=Count; Mode=2;      LsPeriod=TIC1-First;      if (TIC1<First) MsPeriod--;       TMSK1=0x00; TMSK2=0x00;} // Disarm   TFLG1=0x04;}  // ack, clear IC1Fvoid Ritual(void){  asm(" sei");    // make atomic   TFLG1 = 0x04;   // Clear IC1F   TMSK1 |= 0x04;  // Arm  IC1   TCTL2 = (TCTL2&0xCF)|0x10;  // rising   TFLG2 = 0x80;   // Clear TOF   TMSK2 |= 0x80;  // Arm TOF   Mode=0;   asm(" cli"); }//  Program 6.13. C language pulse width measurement.// MC68HC11A8unsigned int Measure(void) { unsigned int Rising; TCTL2=(TCTL2&0xF3)|0x04; // Rising edge TFLG1=0x02;      // clear IC2F  PORTB&=0x7F; PORTB|=0x80;     // rising edge on PB7  while(TFLG1&0x02==0){}; // wait rise    Rising=TIC2;     // TCNT at rising edge  TCTL2=(TCTL2&0xF3)|0x08; // Falling edge TFLG1=0x02;      // clear IC2F while(TFLG1&0x02==0){}; // wait fall     return(TIC2-Rising-1000); }   void Init(void){ TMSK1=0x00;}     // no interrupts  TMSK1=0x00;}     // no interrupts//  Program 6.15. C language pulse width measurement.// MC68HC11A8unsigned int PW;     // units of 500 ns unsigned int Rising; // TCNT at risingunsigned char Done;  // Set each falling#define PA2 0x04     // the input signal #pragma interrupt_handler TIC1handler()void TIC1handler(void){  if(PORTA&PA2){    // PA2=1 if rising     Rising=TIC1;}  // Setup for next  else{        PW=TIC1-Rising; // the measurement      Done=0xFF;}  TFLG1=0x04;}       // ack, IC1F=0 void Ritual(void){     asm(" sei");    // make atomic     TCTL2 |= 0x30;   // IC1F set on both rising and falling     Rising = TCNT;  // current TCNT      Done=0;         // set on falling     TFLG1 = 0x04;   // Clear IC1F      TMSK1|= 0x04;   // Arm IC1     asm(" cli");}//  Program 6.17. C language pulse width measurement using two input captures.// MC68HC11A8unsigned int PW;     // units of 500 ns unsigned char Done;  // Set each falling#pragma interrupt_handler TIC1handler()void TIC1handler(void){  PW=TIC1-TIC2; // time from rise to fall   Done=0xFF;  TFLG1=0x04;} // ack by clearing IC1Fvoid Ritual(void){  asm(" sei");     // make atomic   TCTL2=(TCTL2&0xCF)|0x20; // falling edges of IC1, TCNT->TIC1  TCTL2=(TCTL2&0xF3)|0x04; // rising edges of IC2, TCNT->TIC2  Done=0;   // set on the falling edge  TFLG1 = 0x04;     // Clear IC1F   TMSK1|= 0x04;     // Arm IC1, not IC2  asm(" cli");}//   Program 6.21. C language periodic interrupt using output compare.// MC68HC11A8#define Rate 2000#define OC5  0x08unsigned int Time;  // Inc every 1ms #pragma interrupt_handler TOC5handler()void TOC5handler(void){   TFLG1=OC5;      // Ack interrupt    TOC5=TOC5+Rate; // Executed every 1 ms   Time++; }void ritual(void) { asm(" sei");    // make atomic   TMSK1|=OC5;  // Arm output compare 5   Time = 0;   TFLG1=OC5;  // Initially clear OC5F   TOC5=TCNT+Rate; // First one in 1 msasm(" cli"); }//   Program 6.24. C language squarewave using output compare.// MC68HC11A8unsigned int Period;   // Period in usec // Number of Cycles Low and number High  #pragma interrupt_handler TOC3handler()void TOC3handler(void){     TOC3=TOC3+Period;  // calculate Next     TFLG1=0x20;}       // ack,  OC3F=0void ritual(void){     asm(" sei");     // make atomic      TFLG1 = 0x20;    // clear OC3F      TMSK1|= 0x20;    // arm OC3      TCTL1 = (TCTL1&0xCF)|0x10;  // PA5 toggle on each interrupt      TOC3  = TCNT+50; // first right away      asm(" cli"); }//  Program 6.27. C language pulse-width modulated squarewave using output compare.// MC68HC11A8unsigned int High; // Num of Cycles Highunsigned int Low;  // Num of Cycles Low  // Period is High+Low Cycles#pragma interrupt_handler TOC3handler()void TOC3handler(void){   if(TCTL1&0x10){    // PA5 is now high       TOC3=TOC3+High; // 1 for High cyc      TCTL1&=0xEF;}   // clear on next   else {             // PA5 is now low      TOC3=TOC3+Low;  // 0 for Low cycles       TCTL1|=0x10;}   // set on next int     TFLG1=0x20;}     // ack, clear OC3F void ritual(void){    asm(" sei");    // make atomic   TFLG1 = 0x20;   // initially OC3F=0   TMSK1|= 0x20;   // arm OC3    TCTL1|= 0x30;   // PA5 set on next int   TOC3 = TCNT+50; // first right away    asm(" cli"); }void main(void){      High=8000; Low=2000;     ritual();     while(1);}// Program 6.28. C language delayed pulse output using output compare.// MC68HC11A8void Pulse(unsigned int Delay,     unsigned int Width){  asm(" sei");  // make atomic  TOC1=TCNT+Delay;  TOC3=TOC1+Width;  OC1M=0x20;    // connect OC1 to PA5/OC3  OC1D=0x20;    // PA5=1 when TOC1=TCNT    TCTL1=(TCTL1&0xCF)|0x20; // PA5=0 when TOC3=TCNT  TFLG1 = 0x20;     // Clear OC3F   TMSK1|= 0x20;     // Arm OC3F  asm(" cli");}#pragma interrupt_handler TOC3handler()void TOC3handler(void){  OC1M=0;  // disconnect OC1 from PA5  OC1D=0;   TCTL1&=0xCF;  // disable OC3  TMSK1&=0xDF;} // disarm OC3F  //  Program 6.30. C language frequency measurement.// MC68HC11A8#define IC1F 0x04   // connected here#pragma interrupt_handler TIC1handler()void TIC1handler(void){  Count++;      // number of rising edges   TFLG1=IC1F;}  // ack, clear IC1F#define Rate 20000  //  10 ms #define OC5F 0x08#pragma interrupt_handler TOC5handler()void TOC5handler(void){    TFLG1= OC5F;      // Acknowledge     TOC5 = TOC5+Rate; // every 10 ms     Freq = Count;     // 100 Hz units    Done = 0xff;    Count = 0; }      // Setup for next void ritual(void) { asm(" sei");          // make atomic     TMSK1|=OC5F+IC1F; // Arm OC5 and IC1    TOC5=TCNT+Rate;   // First in 10 ms     TCTL2 = (TCTL2&0xCF)|0x10; /* IC1F set on rising edges */    Count = 0;        // Set up for first     Done=0;          /* Set on the subsequent measurements */     TFLG1=OC5F+IC1F;  // clear OC5F, IC1F asm(" cli"); }//  Program 6.33. C language implementation of period measurement.// MC68HC11A8#define resolution 2000#pragma interrupt_handler TOC3handler()void TOC3handler(void){     TOC3=TOC3+resolution;  // every 1 ms      TFLG1=0x20;     // ack, clear OC3F     Cnt++;     if(Cnt==0) OverFlow=0xFF;}#pragma interrupt_handler TIC1handler()void TIC1handler(void){     TFLG1=0x04;   // ack, clear IC1F     if(OverFlow){         Period=65535;         OverFlow=0;}     else         Period=Cnt;     Cnt=0;     Done=0xFF;}void Ritual(void){     asm(" sei");  // make atomic      TFLG1 = 0x24;    // Clear OC3F,IC1F      TMSK1 = 0x24;    // Arm OC3 and IC1      TCTL2 = 0x10;    // rising edges      while((TFLG1&0x04)==0); // wait for first rising     TFLG1 = 0x04;    // Clear IC1F      TOC3=TCNT+resolution;     Cnt=0; OverFlow=0; Done=0;     asm(" cli"); } //  Program 6.36. C language implementation of frequency measurement.// MC68HC11A8#define IC1F 0x04    // connected here#pragma interrupt_handler TIC1handler()void TIC1handler(void){  Count++;      // number of rising edges  TFLG1=IC1F;}  // ack, clear IC1F#define Rate 50000  //  25 ms #define OC5F 0x08#pragma interrupt_handler TOC5handler()void TOC5handler(void){    TFLG1= OC5F;      // Acknowledge    TOC5 = TOC5+Rate; // every 25 ms    if (++FourHundred==400){       Freq = Count;   //  0.1 Hz units        FourHundred=0;       Done = 0xff;       Count = 0; }}  // Setup for nextvoid ritual(void) { asm(" sei");    // make atomic     TMSK1|=OC5F+IC1F; // Arm OC5 and IC1     TOC5=TCNT+Rate;  // First in 25 ms     TCTL2 = (TCTL2&0xCF)|0x10; /* IC1F set on rising edges */    Count = 0;       // Set up for first    Done=0;  // Set on subsequent meas    FourHundred=0;    TFLG1 = OC5F+IC1F; // Clear OC5F IC1Fasm(" cli"); }