the BBS Xchange
the BBS Xchange

  • Electronics project help

    From tfurrows@VERT/KK4QBN to All on Fri Sep 15 18:57:27 2017
    I'm trying to build a breadboard z80 computer, schematics by Grant Searle:

    http://searle.hostei.com/grant/cpm/

    I put it all together, and it was a thing of beauty, but it didn't work at all. So now I need to test/troubleshoot, and maybe start again (which is fine, it was fun to put together the first time.)

    I figured I would start by testing a few of the logic gate ICs that I have; some 74HCT00Ns and 74LS32Ns. Keep in mind, I'm new at all this. So I read online on how to test them, and watched a few YouTube videos, then put together a test setup on a breadboard... but my results were not what I expected, for either of the IC types (multiples per type.) My LED output just doesn't match the logic tables.

    I'm looking for any help I can get. First, I believe I should be able to quickly and easily test these logic gates. If I can't guarantee that is working, then I certainly don't want to consider the entire z80 computer design yet. Any advice/help would be greatly appreciated.

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    * Synchronet * KK4QBN - kk4qbn.synchro.net - 7064229538 - Chatsworth GA USA
  • From tfurrows@VERT/KK4QBN to All on Fri Sep 15 22:14:41 2017
    Re: Electronics project help
    By: tfurrows to All on Fri Sep 15 2017 18:57:27

    I figured I would start by testing a few of the logic gate ICs that I have;

    Answering my own question. I rewired the test setup after dinner and a drive. My problem was that I was leaving pins floating instead of grounding them, and that was giving me random results. I tested each of the 4 gates on a 74HCT00N and 74LS32 and they functioned properly. Now on to testing the z80 breadboard build more, or rebuilding it.

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    * Synchronet * KK4QBN - kk4qbn.synchro.net - 7064229538 - Chatsworth GA USA
  • From Ennev@VERT/MTLGEEK to tfurrows on Wed Oct 4 17:31:25 2017
    I'm looking for any help I can get. First, I believe I should be able to quickly and easily test these logic gates. If I can't guarantee that is working, then I certainly don't want to consider the entire z80 computer design yet. Any advice/help would be greatly appreciated.

    Oh, back then I had a logic probe and a injector. Could inject a signal and with the probe see the state at the other end. I guess as scope could be
    useful too.

    I know know your setup but I guess you'll need tool like that if you don't
    have already :-/

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    ■ Synchronet ■ MtlGeek - Geeks in Montreal - http://mtlgeek.com/ -