main()
{
	/* Timer clock = I/O clock / 1024 */
	TCCR0B = (1<<CS02)|(1<<CS00);
	/* Clear overflow flag */
	TIFR0  = 1<<TOV0;
	/* Enable Overflow Interrupt */
	TIMSK0 = 1<<TOIE0;

	/*turn on all maskable interrupts)
	sei();

	while(1);
}

ISR (TIMER0_OVF_vect)
{
	/* Toggle a pin on timer overflow */
	PORTB  ^= (1 << USER_LED);
}