If you want to turn on ports together on a '328P:
PORTB = 0x00; // or 0xff D8-9-10-11-12-13
PORTC = 0x00; // or 0xff D14-15-16-17-18-19
PORTD = 0x00; // or 0xff D0-1-2-3-4-5-6-7
If you want to turn on ports together on a '328P:
PORTB = 0x00; // or 0xff D8-9-10-11-12-13
PORTC = 0x00; // or 0xff D14-15-16-17-18-19
PORTD = 0x00; // or 0xff D0-1-2-3-4-5-6-7