No Operation O and F produce pulses on there pins. A empty program memory (or holes in the program) defaults to either 0x00 or 0xFF depending the technology used and therefore to NOPO or NOPF commands. If the program counter runs over a not programmed program memory section then NOPO or NOPF instructions are executed.

Some designs use the corresponding pins to reset the program counter.

Linurs Servernest startpage