Tracy will have the final say, as he wrote the code, but most likely:
NOP = No Operation. or Non Operational. Uh for the life of me I can not recall when I started using that notation, but if you flag part of a schematic, or assembly code, with NOP it is pretty universal comment among geeks (EE's).
At least it isn't flashing "Fubar". :) Once I "inherited" some assembly code on a project which had never been commented (debug/maintenance nightmare). Thankfully the previous engineer had a hard copy with his hand written Chinese notation along side the code. Excited as I started to recognize a pattern of hand written characters by the sections of code I couldn't figure out. Thankfully another engineer explained what "fubar" looked like in Chinese.
Tom
Boardwalk for $500? In 2007? Ha!
Play Monopoly Here and Now
(it's updated for today's economy) at Yahoo! Games.