Andyf, Sorry I haven't returned a reply before this but I just got back from a wedding of one of my sisters kids. The wedding was in Traverse city which is about 4 hours away. I left Friday at noon and just got back Sunday at about 5:00pm. You have it right. the expression needs a Boolean operator to work so if you use one of the predefined keywords ie HIGH or LOW or 1 or 0 or a variable that would be set to 1 or 0 that would work. No need for brackets after the equals sign unless you have some kind of equation that requires hierarchal order. If that doesn't work I would check the Tris register for being setup properly.

Dave Purola,
N8NTA