On Fri, 23 Jul 2010 00:44:31 +0930 "Roger Weichert" wrote: [ Long ago ] I built myself a bus emulator using a cheap Micro board from NewMicros ( 68HC11 based ) that had an onboard FORTH language. This makes it really easy to set and reset digital lines. I would remove the Z80 ( If you cut the leads to remove the Z80, you can solder the Z80 chip to a 40 pin machine pin socket and re-use it. ) and then exercise the bus lines that the Z80 drives. I even made the bus read and write to connected chips ( very slowly ). Gus -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist