// Arduino uno default clock freqency 16Mhz

#include <avr/io.h>



int main() {
  // Set pinmode 
  DDRB=_BV(DD)|_BV(4)||_BV(3)|_BV(2);

  // setting clock source
  TCCR2B = _BV(CS20) ; // no prescaling

  // enabling timer2 interrupts interrupt
  TIMSK2 = _BV(TOIE2);
  
  // enabling interrupts
  sei();

  while(1); // empty loop
}