#include <mega16.h>
#include <delay.h>

#pragma savereg-
interrupt [2] void switch_(void)    
{
        PORTA=0x01;
        delay_ms(1);
        PORTA=0x00;
}

void main(void)
{              
        DDRA=0xFF;
        PORTA=0x00;
        DDRD=0x00;
        PORTD=0xFF;

        GICR=0b01000000;   // INT0: On
        MCUCR=0b00000011;  // INT0 Mode: Rising Edge 
        
        #asm("sei")   // Global enable interrupts
        
        while (1);
}