#define F_CPU 16000000UL

 

#include <avr/io.h>              // Most basic include files

#include <util/delay.h>

#include <avr/interrupt.h>       // Add the necessary ones

#include <avr/signal.h>          // here

 

volatile unsigned char state = 0;

 

// ***********************************************************

// Main program

//

int main(void) {

// variable initialize

EIMSK |= 1<<INT0;

EICRA = 0x02;

PORTD |= 1<<INT0;

DDRA |= 1<<PA0;

sei();

 

   while(1) {             // Infinite loop; define here the

    // user Define Here

 

    // end

   }

 

}

 

ISR(INT0_vect)

{

if(state == 0)

state = 1;

else if(state > 0)

state = 0;

PORTA = ~state;

}