#include "avr/io.h"
  #include "avr/interrupt.h"
  
  int main ()
  {
    ddrb |= 0x20;    
  
    tcnt0 = -32;    
    tccr0 = 0x01;    
  
    timsk = (1<<toie0);
    sei ();      
  
    ddrc = 0x00;  
    ddrd = 0xff;  
  
    while (1)      
      portd = pinc;  
  }
  
  isr (timer0_ovf_vect)  
  {
    tcnt0 = -32;
    portb ^= 0x20;    
  }