overflow.c

#pragma config FOSC = HS, WDTE = OFF, PWRTE = OFF, MCLRE = ON, CP = OFF,       \
                      CPD = OFF, BOREN = OFF, CLKOUTEN = OFF
#pragma config IESO = OFF, FCMEN = OFF, WRT = OFF, VCAPEN = OFF, PLLEN = OFF,  \
                      STVREN = OFF, LVP = OFF
#define _XTAL_FREQ 8000000

#include <xc.h>

volatile unsigned char id;
void init() { 
  GIE = 1; //Enable global interrupt
  PEIE = 1; //Enable peripheral interrupt
  ADIE = 1; //Enable ADC interrupt 
  ADIF = 0;
  TMR0IF=0;
  TMR0IE=1;
  TMR0CS = 0;
  PSA = 0;
  id = 0;

  OPTION_REGbits.TMR0CS = 0;
  OPTION_REGbits.PSA = 0;
  OPTION_REGbits.PS0 = 1;
  OPTION_REGbits.PS1 = 1;
  OPTION_REGbits.PS2 = 1;
  TMR0 = 0;
  INTCONbits.GIE = 1;
  INTCONbits.TMR0IE = 1;
}

void interrupt handler() {
  if (TMR0IE && TMR0IF) {
    PORTB = ++id;
    __delay_ms(2000);
    TMR0IF = 0;
    id--;
  }
}

void main(void) {
  init();
  for (;;) { }
}