Hi Rob There is an older Microchip App note AN531 "Intelligent remote = positioner" that I have tried. It is a PID type control and it's implemented on an old 16C54, so an '84 = should be fine. Cheers Mark ------------------------------------------------------------------- Mark Hull Engineering/Technical EMS (Africa) (Pty) Ltd PO Box 1026, Melville, 2109, South Africa Ph +27 11 482 4470 Fax +27 11 726 2552 -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu