| Electronics > Projects, Designs, and Technical Stuff |
| Science of Cambridge (Sinclair) MK14 restoration |
| << < (3/5) > >> |
| glarsson:
If the trace was without PROM installed then the Z80 is reading the opcode FF, rst 38h, over and over again. |
| mpk:
Here are some more traces. The first two are CS on PROM (yellow) vs D0 (purple) and the same for a RAM chip. The third (just a bit of fun, don't cha know) is chip select on PROM (purple) vs RAM (yellow). |
| mpk:
(by the way - one interesting point is that I have no idea whatsoever if the PROM chips are the right way round as they were completely unmarked. I can easily work around that by swapping them over to check both combinations when debugging..) |
| glarsson:
You can't just turn chips around willy-nilly. The probability of a blown chip is high depending on where the power pins are located. |
| mpk:
--- Quote from: glarsson on October 25, 2018, 05:06:01 pm ---You can't just turn chips around willy-nilly. The probability of a blown chip is high depending on where the power pins are located. --- End quote --- Yes, I know that. What I mean is that there are two 4-bit PROMs - one has the high nibble of the monitor code, the other the low - and they may (or may not) be swapped over. |
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