blink-5b.c

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

ISR (TIMER0_COMPB_vect)
{
  PORTD ^= 0x40;
}

int main (void)
{
  DDRD = 0xfd;   /* binär: 1111 1101 */
  PORTD = 0x00;  /* binär: 0000 0000 */
  while (1);
  return 0;
}