// Parallel ans serial output Demostration from Arduino digital I/O pins

void setup() {
  // put your setup code here, to run once:
DDRD = 0xFF; // Indiate that digital pins 0 -> 7 will be for an output
pinMode(13, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  int ser; // serial shift register 
  for (int n=0; n<127; n=n+1 ) {
    PORTD = n; // Output Binary number on digital pins 0 -> 7 
    ser = n;   // copy current number to serial shift register
    for (int i=0; i<8; i++ ) {
    digitalWrite(13,ser&1); // Output current bit in "low order" postion 
       ser = ser >> 1;  // shift the byte being output serially 
       delay(200);

    }
  }
}