Chronometer with Timer0 and External Interrupt #28

#include <stdio.h>
#include <stdlib.h>
#include <pic18f45k22.h>
#include <htc.h>
#define _XTAL_FREQ 8000000
#pragma config FOSC = HSHP
#pragma config WDTEN = OFF

unsigned char seg_char[10] ={0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F};
unsigned long counter = 0;
unsigned int value = 0;
unsigned char digits[10] = {0, 0, 0, 0};
unsigned char digit_counter = 0;
unsigned char cont = 0;

void main(void) {
ANSELA = 0x00;
TRISA = 0xF0;
PORTA = 0x00;

ANSELD = 0x00;
TRISD = 0x00;
PORTD = 0x00;

ANSELB = 0x00;
TRISB = 0xFF;
PORTB = 0x00;

T0CON = 0xC3;
TMR0L = 6;

RBPU = 0;
TMR0IE = 1;
TMR0IP = 1;
INT1IE = 1;
INT1IP = 1;
GIE = 1;

while (1) {
    value = counter / 50;
    digits[3] = value / 1000;
    digits[2] = (value % 1000) / 100;
    digits[1] = (value % 100) / 10;
    digits[0] = value % 10;
}
return;

}

void __interrupt(high_priority) isr() {
if (TMR0IF) {
TMR0IF = 0;
TMR0L = 6;
PORTA = 0x00;
PORTD = seg_char[digits[digit_counter]];
PORTA = 0x01 << digit_counter;
digit_counter++;
if (digit_counter >= 4) {
digit_counter = 0;
}
if (cont)
counter++;
if (counter > 50 * 10000) {
counter = 0;
}
}
if (INT1IF) {
INT1IF = 0;
cont = 1 - cont;
}
}