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

ISR(TIMER3_COMPA_vect)
{
  
    PORTF = 0x01;
}

ISR(TIMER3_COMPB_vect)
{
  
    PORTF = 0x03;
}


int main (void)
{
    unsigned char sreg;

    DDRF = 0xff;
    PORTF = 0x00;

    OCR3AH=0x05;
    OCR3AL=0x03;
    
    TCCR3A=0xA0;
    TCCR3B=0x02;
    
    // Timer(s)/Counter(s) Interrupt(s) initialization
    TIMSK=0x18;
    ETIMSK=0x00;

    sei();
    
    while (1)
    {
    }

    return 0;
}