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 No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.17.0/1180 - Release Date: 12/10/2007 2:51 PM Message was sent through the cbm-hackers mailing list
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