AVR Freaks

void Timer_Init (void)
{
	//Setup for timer
	ASSR |= (1<<AS2);              //Timer/Counter2 is clocked from a crystal Oscillator connected to the Timer Oscillator1 (TOSC1) pin.
	TCCR2A |= (1<<WGM21);          //CTC mode (1<<CS20)|(1<<CS21)|(1<<CS22); == 1024
	TCCR2B |= (1<<CS21)|(1<<CS22); //Prescaler 256
	OCR2A = 128;                   //128 should be equal to 1 second at prescaler of 256 32.768Khz external crystal.
	while ((ASSR & ((1<<TCN2UB)|(1<<OCR2AUB)|(1<<TCR2AUB))) != 0);.
	TIMSK2 |= (1<<OCIE2A); //Timer/Counter2 Compare Match A interrupt is enabled.
//	TIMSK2 |= (1<<TOIE2);	//Timer/Counter2 Overflow interrupt is enabled.
}

ISR ( TIMER2_COMPA_vect )
{
	Tick = 1;
	Seconds--;
	if(Seconds == -1)
	{
		Minutes--;
		Seconds = 59;

		if(Minutes == -1)
		{
			Hours--;
			Minutes = 59;
		}
	}
}


int main (void)
{
	DDRB = 0b00001000; //Set as output
	Timer_Init();

	sei();		//Enable global interrupts
	for(;;)
	{
		if (Tick == 1)
		{
			PORTB ^= (1<<3);
			Tick = 0;
		}
	}
}