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


void (*reply_gen)(void);


void rep1(void)
{
   PORTB |= 2;
}

void rep2(void)
{
   PORTB &= ~2;
}

SIGNAL(SIG_OUTPUT_COMPARE0A)
{
    reply_gen();
}


/*------------------------------------------------*/
/* Main routine                                   */
/*------------------------------------------------*/
int main (void)
{
   // Initialize ports
   PORTB = 0;
   DDRB = 2;

   // initialize timer 1
   TCCR0A = 0;
   TCCR0B = (1<<CS00); 	
   OCR0A = 1;


   // Initialize variables
   reply_gen = rep1;

   asm("sei");

   for (;;)
   {
      if (PINB & 0x01)
	 reply_gen = rep1;
      else
	 reply_gen = rep2;
	
   }

   // make compiler happy
   return (0);
}