From: Jack Rubin (jack.rubin_at_ameritech.net)
Date: 2007-12-12 00:17:25
> Hi Jack,
>
> that's actually a nice idea considering the simplicity of the
> interface. The problem is the PET memory map First you can
> simply plug the schematics under the PET CPU, but it needs a
> chip select line.
>
> I see those options:
> 1) decode the I/O are $e800-$e80f (other parts of the I/O area
> have mirrors of the original ICs, so won't work
> 2) use the $9xxx or the $Axxx expansion ROM select line
> would only work if those are asserted even on write, but I
> don't think they are
> 3) add an own address decoder (maybe like 2 74ALS688 comparators)
> to decode an open address space (like $e80x as above,
> behind the video RAM, or in the expansion area)
>
> IMHO the 3rd version is always feasible, but needs an
> extension of the schematics as it is now
I'm not very capable on the software side but if there was interest, I
could probably prototype a PET version of the hardware interface for
more development, either based on Ruud's original or even better on
Jim's PC board.
Jack
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