Page 218 - Programming Microcontrollers in C

Pulse Width Modulator System 203

period will be 2 microseconds times the total count value. Prior to
starting use of the PWM, the bit flag.ON should be reset and the
value for count, which is the main time base period count, should
be set.
/* bits in flag */

#define ON 0

union both time_cnt;
unsigned long off_count,pwm_number,count;
bits flag;

void __TIMER_OC(void)
{
if( TSR.OCF2==1) /* accesses the TSR */
{
if(flag.ON==0)
{
flag.ON=1;
TCR.OLVL2=0; /* Timer Compare 2 off*/
time_cnt.b.hi=OCHI2;/* get start time */
time_cnt.b.lo=OCLO2; /* reset the OCF */
time_cnt.l +=pwm_number;
OCHI2=time_cnt.b.hi;
OCLO2=time_cnt.b.lo;
return;
}
else
{
flag.ON=0;
TCR.OLVL2=1;/* Timer Compare 2 to on */
time_cnt.b.hi=OCHI2;/* get start time */
time_cnt.b.lo=OCLO2; /* reset the OCF */
time_cnt.l +=off_count;
OCHI2=time_cnt.b.hi;
OCLO2=time_cnt.b.lo;
return;