void init_port();
void init_timer();

void setup() {
  // put your setup code here, to run once:
  volatile long i;
  int j = 0;
  init_port;
  init_timer();
  Serial.begin(9600);
  while(1)
  {
    for(i=0; i<500000; i++);
    Serial.println(j, DEC);
    j++;
  }
}

void init_timer()
{
  volatile char *Timer1_TCCR1A = 0x80;
  volatile char *Timer1_TCCR1B = 0x81;
  volatile short *Timer1_TCNT1 = 0x84;
  volatile short *Timer1_OCR1A = 0x88;
  volatile char *Timer1_T1MSK1 = 0x6F;

  *Timer1_TCCR1A = 0;
  *Timer1_TCCR1B = 0;
  *Timer1_TCNT1 = 0;

  *Timer1_OCR1A = 60000;
  *Timer1_TCCR1B = 0x0C;
  *Timer1_T1MSK1 = 0x02;
}

void init_port()
{
  volatile char *dirf = (volatile char *)(0x30);
  *dirf = 0x01;
}

ISR(TIMER1_COMPA_vect)
{
  volatile char *outf = (volatile char *)(0x31);
  *outf = *outf ^ 0x01;
}

void loop() {
  // put your main code here, to run repeatedly:

}