ATtiny2313 Interrupt handler

/*
 * AT2313_InterruptHandler.c
 *
 * Created: 2/7/2012 3:59:47 PM
 *  Author: grist.carrigafoyl
 */


#define F_CPU 8000000UL  //  8Mhz

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

// Digit to pin mapping.
const uint8_t LED_PIN = _BV(PD4);


uint8_t mode = 0; // will be changed on interrupt to set the led on or off

int main(void)
{

    // Set the pin mode for output
    DDRD = LED_PIN;

    // Set Pin 6 (PIND2) as the interrupt pin
    PCMSK |= (1<<PIND2);
    // interrupt on falling edge
    MCUCR = _BV(ISC01) | _BV(ISC00);
    // Turn on interrupts
    GIMSK |= _BV(INT0);
    sei();

    // loop forever
    for(;;)
    {
        // turn the led on or off depending on the current value of mode
        if (mode == 1) {
            PORTD |= LED_PIN; // on
        } else {
            PORTD &= ~LED_PIN; // off
        }

    }

}
//----------------------------------------------------------------------------
// Interrupt Handler
//----------------------------------------------------------------------------
SIGNAL (SIG_INT0) {
 // Flip the mode
 mode = 1 - mode;

}
//----------------------------------------------------------------------------
// Functions
//----------------------------------------------------------------------------