3 ms·
One must love Drake R8A receiver! I would say, that having no internal ROM is an advantage in this situation.
by lnsru 2y ago
One must love Drake R8A receiver! I would say, that having no internal ROM is an advantage in this situation.
- jandrese 2y ago"No internal ROM" might mean that it relies on a bunch of custom PLA chips which would not be an improvement. With a ROM there is at least a chance you can dump it and run a disassembler on the contents to figure out what it is trying to do.
- lnsru 2y agoLooks like there is regular EPROM in this case. Nothing too ugly. Except very old microprocessor.
- mikewarot 2y agoNope, I've got complete schematics, and a dump of the EPROM. It's going to take a while to figure out how the heck why it's hallucinating a power failure (the signals going into the CPU are appropriate).
- jandrese 2y agoOh, it has a ROM, just on an external chip. I misunderstood your original post. I thought they had somehow programmed the device without using ROM at all, which made it either very old school or very custom.
- evoke4908 2y agoDoesn't a PLA just boil down to a truth table that you can dump the same way? Or am I thinking of the other kind of programmable logic chip used for this purpose? GAL, I think?
- jandrese 2y agoIt is a truth table, but normally there isn't a way to dump them.
- anyfoo 2y agoIf it’s only combinatorial logic, without any flip-flops or anything else you can consider “state”, it depends on how many inputs it has. 16 inputs is 65536 combinations. Even at a very low clock it takes you no time to just try all of them. 32 inputs is 4 billion. Now you’re getting somewhere, but even then, at somewhat reasonable clock speeds it should take you a day at the very most…