Recently I've been idly thinking about how I might keep my CorsairIIs
running in the event of failure of the MCU on the Logic Board. I realise
the preferred approach might well be to replace most of the
functionality with a modern PIC frequency-counter/display module.
However, I was interested to come across a series of articles on the Web
about how to extract data from a "good" 68705P3 and copy it into
another. The technique is a bit time consuming - it involves forcing the
reference MCU into the verification stage of a programming cycle,
offering it all possible Hex values of every byte, and noting by
differences of bus timing which byte verifies successfully. Sounds
involved, but at least one guy has automated the process and produced a
stand-alone 68705P3 copier:
http://matthieu.benoit.free.fr/144.htm
The programmer/copier also allows you to dump the reference contents
from RAM to a PC; it would then be easy and fast to replicate the part.
I wonder if anyone readers have tried something similar? I also wonder
if it's worth asking the author if he would be prepared to use his
copier to provide a dump of the contents of a CorsairII MCU?
73,
Steve G3TXQ
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