M H Stein wrote: > Jim > -------- > Well, I can't even figure out how to print your schematic, so I'm probably > not the one to ask ;-). I kinda thought it'd be just another two rows of pads > beside the 24 pin pads, without any additional logic or pullups, but I > hadn't really thought it through. > You need at least 2 select pins, as you've noted the PET uses multiple CS lines. As well, the layout is markedly different from either the 2364 or the 27XX pinout, As well, I consider PHI2 to be another CS line, as I believe the ROM is only active on PHI2 high. > I thought that if one accepted replacing both the upper and lower 2KB > with a 2732 or greater (except for the E ROM which could be a 2716) > and used the lower socket of each pair, then all you'd need is pin 3 to > /CS and jumpers for pin 4 to A11 and /OE to Vss or /CE. > For the E ROM connect pin 4 to /OE instead (The upper half of E is > memory-mapped I/O). > If you're willing to string wires and such, yes, that's workable, but I dislike making such assumptions on a design like this. Even with the concession, you'd need to deal with PHI2 and a couple select lines, so dealing with all of them took no more effort. > But it probably isn't that simple, and no doubt someone will point out > the flaw(s). Maybe there isn't really enough demand anyway to make it > worth while, especially seeing there's one permanently on eBay... > Well, I'm happy to make a run of the design I have, and I am pretty sure I can offer the board sans EPROM for $10-$15, if that's of interest to enough folks. I'd be willing to offer them even less if folks wanted them in lots of 5 or 10. (individual packaging is what mandates the price points) or, the PCB design is GPL, so anyone can pick it up and run a batch. Powell Electronics offers the 24 pin header, and the rest are easy to source from digikey, farnell, mouser, etc. Jim Message was sent through the cbm-hackers mailing listReceived on 2009-05-07 02:55:09
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