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Polar Instruments DDT Disk drive tester - Firmware needed !
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pedrocelli:
The existing Eprom always shows a CRC error. In some cases, pressing OK will allow to continue, but most of the time it stuck.
Using the corrected binary and burn it into an Eprom will not show a CRC error (as it has been compensated in the binary) but it always stuck, even earlier in the boot-up sequence compared the original Eprom. So in both cases, some bits have changed.
I also suspect, that reading at processor speed also gives different data compared to reading with a much slower Programmer. Still hope someone else owns this DDT Tester.

pedrocelli:
Finally I was able to fix the ROM code.
Using Ghidra, a software reverse engineering tool, helped a lot to find the flipped bits in the ROM binary (Ghidra V 11.1.2 was used).
Attached the exported XML project including source code listing and corrected binary image file.

Ghidra provides a powerfull disassembler that highlights strange calls or data refrences.
The best feature is the simply click and jump to calls or data elemnts and the code previwe window feature.
Within a few hours checking calls and strings, the suspiecous fipped bit was found (probaly 50% by luck).

If you want to dissassemble any code from old 8bit up to modern ARM CPU's, Ghidra is my recommendation.  :-+
tv84:

--- Quote from: pedrocelli on August 06, 2024, 10:50:11 am ---Finally I was able to fix the ROM code.

--- End quote ---

Well done.  :-+
coromonadalix:
 :popcorn:


send it to Polar ...
tv84:

--- Quote from: coromonadalix on August 06, 2024, 11:08:55 am --- :popcorn:


send it to Polar ...

--- End quote ---

I don't think they have an active support contract with him...   :-DD
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