Hello all, I had a poke around on the Microchip site a few weeks ago and found some useful source code, I think it was something to do with a training course. The file is ADVDEMO2.ZIP; I can't remember where it was though. I've just been playing with the ADVUART.ASM program which is included. With a couple of minor changes it worked fine with a 4 MHz 16C84 at 9600 baud, interfaced to the PC via a MAX232. It's a lot simpler and easier to understand than the code in AN555. If anyone has a problem locating it, I can email a copy. Leon -- Leon Heller Amateur radio callsign: G1HSM Email: leon@lfheller.demon.co.uk http://www.lfheller.demon.co.uk Tel: +44 (0) 118 947 1424 (home) +44 (0) 1344 385556 (work)