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Re: [midatlanticretro] RCA COSMAC Microkit

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  • B. Degnan
    ... the ROM as inverted so you didn t have to put another buffer chip on the bus. If you re trying to disassemble it, just run it through a program to flip
    Message 1 of 13 , Apr 18, 2013
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      >
      > In this case, if you had an inverted bus, it would make sense to store
      the ROM as inverted so you didn't have to put another buffer chip on the
      bus. If you're trying to disassemble it, just run it through a program to
      flip the bits.
      >
      >
      -Thanks Dave-
    • joshbensadon
      ... I don t think Bill has determined that the bus is inverted. I observed the dump that Bill posted didn t make sense as 1802 machine code until I guessed
      Message 2 of 13 , Apr 18, 2013
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        --- In midatlanticretro@yahoogroups.com, "B. Degnan" <billdeg@...> wrote:
        >
        >
        > >
        > > In this case, if you had an inverted bus, it would make sense to store
        > the ROM as inverted so you didn't have to put another buffer chip on the
        > bus. If you're trying to disassemble it, just run it through a program to
        > flip the bits.
        > >
        > >
        > -Thanks Dave-


        I don't think Bill has determined that the bus is inverted.

        I observed the dump that Bill posted didn't make sense as 1802 machine code until I guessed that the bits might be inverted.

        I am only guessing that the bus is inverted and wish to advise Bill to look out for that.

        I could be totally out to lunch, since it is an 1801 chip set.

        :)J
      • B Degnan
        When I get back from a brief vacation I will look up the commands from their HEX values, and/or convert to an Intel record that would be easier to assemble. I
        Message 3 of 13 , Apr 19, 2013
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          When I get back from a brief vacation I will look up the commands from their
          HEX values, and/or convert to an Intel record that would be easier to
          assemble. I believe I have the instruction set in my
          vintagecomputer.net/RCA/COSMAC directory, or elsewhere. If assembly is
          possible. No way to know about whether inversion is necessary yet.



          -----Original Message-----
          From: midatlanticretro@yahoogroups.com
          [mailto:midatlanticretro@yahoogroups.com] On Behalf Of joshbensadon
          Sent: Thursday, April 18, 2013 1:39 PM
          To: midatlanticretro@yahoogroups.com
          Subject: [midatlanticretro] Re: RCA COSMAC Microkit

          --- In midatlanticretro@yahoogroups.com, "B. Degnan" <billdeg@...> wrote:
          >
          >
          > >
          > > In this case, if you had an inverted bus, it would make sense to
          > > store
          > the ROM as inverted so you didn't have to put another buffer chip on
          > the bus. If you're trying to disassemble it, just run it through a
          > program to flip the bits.
          > >
          > >
          > -Thanks Dave-


          I don't think Bill has determined that the bus is inverted.

          I observed the dump that Bill posted didn't make sense as 1802 machine code
          until I guessed that the bits might be inverted.

          I am only guessing that the bus is inverted and wish to advise Bill to look
          out for that.

          I could be totally out to lunch, since it is an 1801 chip set.

          :)J




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