Graham, This is the same kind of thing I'm trying to do. I am measuring the time between two different signals. You say you have CCP1 working? I can not get my CCP1 to work. I only have CCP2 working. Look at my code in the other message and see what you think. Best regards, Fred Bailey -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body