Hi

I have a board I made up using HC logic and an 80C31. This works fine. However that was just an interim arrangement - I really want it to go with an 80C320. However nothing happens.

Symptoms:
All pins seem to go Hi and Lo, _except_ RD and WR. This is obviously a problem, as no IO is written to. However I think the problem is not that, but the fact that it is not getting the instructions from the ROM (I am definitely running it slow enough for the ROM!)

Has anybody else had this problem? I think the answer might lie in TTL/CMOS logic levels and I have heard of people getting around it by using pull-ups. Does anybody have more info or experience on this. Apparently people have had it with some other processors like the 501, as well.

Thanks

Anton