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30219Re: RCA COSMAC Microkit

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  • DougCrawford
    Apr 18, 2013
      Jonathan: That was a very keen observation.
      It'll be cool if you are right!
      I guess that would mean that data transferring to peripheral
      cards for the outside world would have to re-invert before
      shipping the data out... or that would be a mess!

      --- In midatlanticretro@yahoogroups.com, Systems Glitch <systems.glitch@...> wrote:
      > > Inverted BUS? I have not yet started trying to determine the purpose of the code.
      > Some early bus structures were "inverted" in that a logic 0 was represented by what you would normally consider a logic 1 voltage. For TTL, this means that +3 and up is logic 0. The Ohio Scientific uses such a bus for their OSI-48 structure. Tranceivers usually exist with an inverted complement, like the 8T26/8T28.
      > Thanks,
      > Jonathan
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