// ----------------------------------------------------------------------------
// timer.c											
// ----------------------------------------------------------------------------
#include <avr/io.h>
#include <avr/interrupt.h>	

// ----------------------------------------------------------------------------
#define OUT_PORT			PORTB
#define OUT_PIN				0

#define F_CPU				8000000L		// 8 MHz clock	
#define PIN(x) 				(*(&x - 2))		// input register of port x         
#define DDR(x) 				(*(&x - 1))  	// data direction register of port x 				

// ----------------------------------------------------------------------------
int main(void)
{
	DDR(OUT_PORT) |= _BV(OUT_PIN);			// set out-port
	TIMSK |= _BV(TOIE0);					// enable TIMER0_OVERFLOW		
	TCCR0 |= (_BV(CS00) | _BV(CS02));		// start timer, prescale 1024			
	sei();									// enable global interrupt
	for(;;);								// loop
}

// ----------------------------------------------------------------------------
// ISR(TIMER0_OVF_vect)
//	Interrupt handler for TC0 overflow.
// ----------------------------------------------------------------------------
ISR(TIMER0_OVF_vect)
{
	OUT_PORT ^= 0x01;						// toggle
}

// ----------------------------------------------------------------------------