Timer1; 3.3ms

Timer1.c

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

void initTimer1()
{
	TIMSK |= (1<<TOIE1);		// 4; 0x04; (1<<2); 0b00000100; _bv(2);
	sei();						// gloable Interrupts aktivieren
	TCCR1B |= (1<<CS10);		// Prescaler = 1
}

ISR(TIMER1_OVF_vect)
{
	TCNT1 = 0xFFFF-3299;		// (Maximalwert->Timer schaltet ím nächsten Takt)-3299
}

void main()
{
	initTimer1();
	while(1){};
}