ard at p850ug1.demon.co.uk
Sun Feb 10 12:51:49 CST 2008
> Basically I'm trying to reverse-engineer the firmware of a couple of
> late-80s Alesis HR-16 and HR-16B drum machines. They use a 32kx8 EPROM
> for the firmware, a pair of 512kx8 ROMs for the sampled sounds, a big
> custom ASIC for the sample playback and an 80C31 for the clever stuff.
I assume the ROM address latch is hidden in that ASIC, and isn't a
seprate '373 or '572 chip If it was, it would be trivial to trace out the
address bit order, of course. Do the ROM data pins connect straight to
the 8031 (without going through the ASIC). At least you could make sure
the data bits are in the expected order.
What aobut using a logic analyser, connected to the EPROM? You could
capture the first few instructions and the addresses _at the ROM pins_.
You can spot jumps, etc and thus work out what the addresses _should_ be
and thus work out which bit ends up on which EPROM pin.
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