/* Generate two PWMs with OC1 controlling OC2 & OC3. */ 

#code 0xC0F0

#data 0xC000

#include <startup.c>

#include <68hc11.h> /* to use special registers of the 68HC11 */

#include <stdio.h>

#define REG_BASE 0x1000

int temp; /* used by interrupt service routine since service routine cannot have local variables */

int period;

unsigned int duty1; /* duty cycles */

unsigned int duty2;

int one_percent_per; /* one percent period */

/***************************/

interrupt toc1(){

/* Schedule next compare for OC1, OC2, OC3 */

     temp = peek(REG_BASE + TOC2);

     temp = temp + period;

     poke(REG_BASE + TOC2, temp);

     temp = peek(REG_BASE + TOC3);

     temp = temp + period;

     poke(REG_BASE + TOC3, temp);

     temp = peek(REG_BASE + TOC1);

     temp = temp + period;

     poke(REG_BASE + TOC1, temp);

     bit_set(REG_BASE + TCTL1, 0x80); /* clear OC1 flag */

}

/**************************************************

* Calculate offset to schedule first compare for OC2 & OC3

**************************************************/

cal_offset(duty) int duty;{

     return (duty * one_percent_per); 

}

/***************************/

initialize(){

int offset;

     bit_set(REG_BASE+TCTL1,0xA0); /* OC2 and OC3 for toggle */

     pokeb(REG_BASE+TFLG1,0x80); /* clear OC1 flag */

     pokeb(REG_BASE+TMSK1,0x80); /* enable OC1 int. */

     pokeb(REG_BASE+OC1M, 0x60); /* OCM 6,5 = 1 */

     pokeb(REG_BASE + OC1D, 0x60);  /* drive OC2, OC3 high at OC1 successful compare */

     period = (one_percent_per * 100); /* calculate period */

     poke(REG_BASE+TOC1, period); /* schedule first OC1 compare */

     offset = cal_offset(duty1); 

     poke(REG_BASE+TOC2, offset); /* schedule first OC2 compare */

     offset = cal_offset(duty2); 

     poke(REG_BASE+TOC3, offset); /* schedule first OC3 compare */ 

} 

main(){

     poke(0xE0,toc1); /* store addr of toc1 to pseudo int. vector + 1*/

     one_percent_per = 170;

     duty1 = 50;

     duty2 = 50;

     initialize();

     e_int();

     while(1){

          ;

     }

}