void init_port();
void init_timer();
volatile char *f_data = 0x31; 
 volatile char *_TCCR1A = 0x80;
 volatile char *_TCCR1B = 0x81;
 volatile short *_TCNT1 = 0x84;
 volatile short *_OCR1A = 0x88;
 volatile char *_TIMSK1 = 0x6F;

void setup() {
  init_port();
  init_timer();
  volatile char *k_dir  = 0x107, *k_data=0x108;
  *k_dir = 0xff; *k_data=0x01;
  //delayMicroseconds(5000);
  *_TCCR1B = 0x0D;   //CTC mode & 1024 prescaler 

}

void init_timer(){
  *_TCCR1A = 0;
  *_TCCR1B = 0;
  *_TCNT1  = 0;

  *_OCR1A  = 60000;  
  *_TIMSK1 = 0x02;   //enable timer compare interrupt
}

void init_port()
{

  volatile char *f_dir  = 0x30;
  *f_dir = 0x01;
}

ISR(TIMER1_COMPA_vect)          
{
  
  *f_data  = 0x01;
  for (volatile long i = 0; i < 1000000; i++);
  *f_data  = 0x00;
  *_TCCR1B = 0x00;
}


void loop(){}