CPLD designing in progress...

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By RetroTechie

Paragon (1563)

RetroTechie's picture

16-08-2010, 00:18

Got a chance to do some tests @ the MVM meeting yesterday, unfortunately I didn't have a spare 512K SRAM at the moment (more to be ordered soon). So I tested with a 128Kx8 SRAM, and results should be meaningful since logic function & timing requirements are very similar between 128Kx8 and 512Kx8 SRAMs. Results:

  • On Philips NMS8255 (or was it a 8250? I forgot): perfect operation, and read-back okay for all 5 mapper bits and values/page combinations. Just another, 100% working mapper in the machine.
  • On Turbo-R in both primary slots, also worked fine (TestMap v4.2). Somehow with MMC or CF i/f connected, we didn't manage to boot into DOS1 Question to run some more tests.
  • On Turbo-R, in Gouda's slot-expander (= good/reliable device AFAIK): fail. Not sure what exactly didn't work (SRAM access, writing mapper registers, or reading them back). Perhaps this works fine with MSX2 or 2+ machines, maybe it's just a signal integrity issue (fast switching CPLD outputs + long cable between machine & slot-expander). No way to know for sure until closer investigation, which could be a while since I don't have a slot-expander (thx OeiOei, for letting me use yours Smile).

Probably I'll publish the design as is - plenty useful now, and few people have/use slot-expanders anyway. Subslot or primary slot isn't the problem I think, but that's something I can (and will) check.

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