#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
void TimerInit();

int hitungan = 0;

ISR (TIMER1_OVF_vect)
{
  if(hitungan < 59)
  {
    hitungan += 1;
  }
  else
  {
    hitungan = 0;
  }
  PORTA = ~(hitungan); //output nilai hitungan ke PORTA
  TCNT1 = -15625;; //reset counter
}

int main(void) {
  DDRA = 0xFF; //Port A sebagai Output
  PORTA = ~(hitungan); //Output nilai awal hitungan ke PORTA
  TimerInit(); // inisialisasi timer
  sei(); //enable global interupt
  while(1)
  {
    sleep_mode(); //sleep
  }
}

void TimerInit(void) {
  TCCR1B |= (1 << CS12) | (1 << CS10); //Seting prescaler 1024
  TIMSK1 |= (1 << TOIE1); //Enable overflow interrupt
  TCNT1 = -15625; //setting counter agar 1 detik (15625 hitungan sebelum overflow)
}