f_13_15b_tmr1sqwave_good.c

* Use 10 MHz crystal frequency. * Use Timer0 for ten millisecond looptime. * Blink "Alive" LED e

#include "config.h"
#include "serial.c"
#include "serio.c"


#define HPERIOD 0x0100

unsigned int match;
// uses Timer1, compare & toggle mode to generate sq wave
#if defined(HI_TECH_C)
void interrupt timer_isr(void)
#endif
#if defined(__18CXX)
#pragma interrupt timer_isr
void timer_isr(void)
#endif
{
  if (CCP1IF) {
    // don't clear timer1, change compare register
    match = match + HPERIOD;
    CCPR1H = match >> 8;
    CCPR1L = match & 0xFF;
    CCP1IF = 0;
  }
}

void main(void){
  // 19200 in HSPLL mode, crystal = 7.3728 MHz 
  serial_init(95,1); 
  // initialize timer 1
  T1CKPS1 = 0; T1CKPS0 = 0;// prescale by 1
  // use internal clock
  T1OSCEN = 0;  TMR1CS = 0;  T1SYNC = 0; 
  T1RD16 = 1;    // 16 bit r/w to timer1
  bitclr(TRISC,2);// set RC2/CCP1 as output
  // initialize CCPR1 for compare
  match = HPERIOD;
  CCPR1H = (HPERIOD >> 8); 
  CCPR1L = (0xFF & HPERIOD);
  CCP1CON = 0x02; // toggle mode
  // interrupt enable
  CCP1IF = 0;   CCP1IE = 1; 
  TMR1ON = 1;   // enable timer 1
  IPEN = 0;   PEIE = 1;  GIE = 1;  
  printf("Configured!");pcrlf();
  while(1);  // interrupt does all work 
    // of generating sqwave
}

//for MCC18, place the interrupt vector goto
#if defined(__18CXX)
#if defined(HIGH_INTERRUPT)
#pragma code HighVector=HIGH_INTERRUPT
#else
#pragma code HighVector=0x0008  
#endif
void HighVector (void)
{
    _asm goto timer_isr _endasm
}
#pragma code
#endif