Hi David and Peter, Thanks for your responses to my silly question. >> MOVF CHECK ; Store masked version of GPIO > > Do you mean MOVWF for the last instruction? If so, then yes. Yes. I did, sorry. > For better readability I'd probably do the IORWF last though. OK, Thanks. > The MOVWF doesn't actually 'move' the byte - just copies it > to the specified register. W reg still contains the byte as well. Yes, I had assumed as much, but could not actually find it in black and white. Thought it best to check with the list gurus rather than assume. Still waiting for "PIC Programming for Dummies" to be published. :-) Thanks again, Sean -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics