#include <avr/io.h>
#define XTAL 16000000L //Crystal Freq.
#define TIMER_CLOCK 2 // Toggling Freq.
int main(void)
{
DDRD = _BV(PD5); // set OC1A pin as output, required for output
TCCR1A = _BV(COM1A0); // enable toggle OC1A output on compare
TCCR1B = _BV(CS10) | _BV(CS11) | _BV(WGM12); // prescaler=64, clear timer/counter on compareA match
OCR1A = ((XTAL/64)/(2*TIMER_CLOCK)) - 1; // preset timer1 high/low byte
/*
* Initialisation done, LED will now flash without executing any code !
*/
for(;;){} // loop forever
}