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<1000000;i++);
    Serial.println(j,DEC);
    j++;
 }

}
void init_port(){
  volatile char *dirf=(volatile char*) 0x30;
  *dirf=0x01;
}
void init_timer(){
  volatile char *Timer3_TCCR3A=0x90;
  volatile char *Timer3_TCCR3B=0x91;
  volatile short *Timer3_TCCNT3=0x94;
  volatile short *Timer3_OCRIA=0x98;
  volatile char *Timer3_TIMSK3=0x71;

  *Timer3_TCCR3A=0;
  *Timer3_TCCR3B=0;
   *Timer3_TCCNT3=0;

   *Timer3_OCRIA=60000;
   *Timer3_TCCR3B=0x0c;
   *Timer3_TIMSK3=0x02;

}
ISR(TIMER3_COMPA_vect){
      volatile char *outf=(volatile char*)0x31;
      *outf= *outf ^ 0x01;
}
void loop() {
  // put your main code here, to run repeatedly:

}