#include <inttypes.h>
#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>
#include <avr/eeprom.h>

volatile char flag;
char temp;
volatile uint8_t clk;
volatile uint8_t dummy;
 
int
main (void)
{
    clk = TCNT0 = 0;
  
    /* Enable the Timer0 overflow interrupt. */
    TIMSK = _BV (TOIE0);

    /* Start the timer/counter running at the CPU clock rate. */
    TCCR0 = _BV (CS00);
    
    sei ();
  
    while (1)
    {
        /* Chew up some MCU cycles. */
        clk += TCNT0;
        //dummy -= TCNT0;
    }

    return 0;
}
 
 
SIGNAL(SIG_OVERFLOW0)
{
  	flag = ~flag;
}