In article <4.1.19990812100611.009a6100@pop.fast.net>, Andy Kunz writes >>Thanks for that. Do you use an emulator of any sort? I am coming around >>to thinking it must be a bug in the bondout, or possibly my emulator, >>although I can't see how the emulator could influence things when it's >>running at full speed. > >Well, since the bondout uses the same die... > >We use the Tech Tools Mathias emulator. Andy, I don't know much about the emulation side of things, but it has been explained to me by my supplier as follows; My emulator contains a 16C02-ME/L (the "bondout") and a 16C77-ME. The code actually runs in the 16C02. I guess you are correct in saying that comes from the same die as the 16C77, but it has parts of the die, which were never intended to see the outside world, brought out to pins. That alone may cause subtle differences in operation. (Apparently it also makes the bondouts especially sensitive to static in handling). The 16C77 in the emulator is also "special" - a normal one won't work here. It provided the interface to the real world, presumably using the special connections into the 16C02. But the main point was that the world demand for bondouts is not very high, so the first batch tends to last a long time! Thus they tend to be rather old silicon, with all the finest bugs known to man. Well I don't know if all that is true, but it has been suggested that replacing my 16C02 with the later 16C03 will fix my problem (and let me emulate at 20MHz). I'll let you know. Do you know which part/date code is in your Tech Tools? Regards, -- Alan Hall, Ipswich, UK