Digital Clock using pic18f8680, counters, external clocks

#include <pic18f8680.h>

#include <timers.h>

void int0_ISR (void);

static unsigned char count;

    
    #pragma code high_vector = 0x08
    void high_interrupt (void)
    {
              _asm
              goto int0_ISR
              _endasm
    }
    
    #pragma interrupt int0_ISR
    void int0_ISR (void)
    {
          if (INTCONbits.INT0IF)  // verify interrupt caused by
                                  // INT0
          {
                INTCONbits.INT0IF = 0; // clear INT0 flag
                count++;
                PORTD = ~count; // display INT0 interrupt count
                                // on LEDs
          }
    }
    
    #pragma code
    
    void main (void)
    {
           count          = 0; // initialize count       TRISD          = 0; // configure PORTD for output       PORTD          = 0xFF; // turn off all LEDs       RCON           = 0x80; // enable priority interrupts       INTCON         = 0xD0; //