inter2.c

Minimal PIC16F877 application that handles two time intervals via interrupts and uses watchdog.

//This sample program shows how to use interrupts.
//If there is a LED connected to B7 it will blink
//with a period of 65 ms
//If there is a LED connected to B6 it will blink
//with a period of 1 second (approx.)

// Author : Joan Ilari - e-mail: c2c@ilari.org

#pragma CLOCK_FREQ 4000000

char sscounter=15;

//------------------------------------------------
void interrupt( void )
{
  PORTB ^= 10000000b;     // complement PORTB:7
  if (--sscounter == 0)
  {
    PORTB ^= 01000000b;   // complement PORTB:6
    sscounter = 15;
  }
  clear_bit(INTCON,T0IF); // clear TMR0 interrupt flag
}
//------------------------------------------------

main()
{
  OPTION_REG = 7;       // set prescaler to 1:256
  clear_bit(TRISB,7);   // set PORTB:7 as OUTPUT
  clear_bit(TRISB,6);   // set PORTB:6 as OUTPUT

  enable_interrupt( GIE );  // enable interrupts
  enable_interrupt( T0IE ); // enable TMR0 overflow bit

  while(1)
  {
    clear_wdt();
  }
}