Quote:
Re: UD8 being an 8KB device , with 'Upper' half reading all FF
Could it be that it was actually a 4KB device, with an active-low chip select connected to the 'A12' pin.
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I had my sums mixed up there in any case, the PROMs are 4K devices (not 8K as I said - too many late nights) but UD8 contains only 2K of code. It may well be a 2K device with an active low CS2 on pin 18, rather than A11.
The next time I'm using the programmer I will try reading 'no device' and see whether the data reads in as 00 or FF.
Fortunately UD8 is not the one we need to worry about as it was OK. Hopefully Colin will get some good news re: availability of suitable replacements from that source mentioned earlier.