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Build your own PDP 8I, book

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    Hi All;

    I have been chasing a problem, and so tomorrow, I will change the MB back to PC bits 00 thru 04 for paging addressing..
    When I put a very small program in it always shows bit 01 being turned on during the state machine processing and it should not turn on..
    I have checked all wiring and all IC's having even remotely to do with bit 01..
    The program is the following..
    Address 0000 Data 0001
    Address 0001 Data 5000
    Address 0002 Data 0000
    I think this will continuously rotate a bit in the Ac register..

    THANK YOU Marty

    Comment


      Marty,

      Try:
      Address 0000 Data 7010 (RAR)
      Address 0001 Data 5000 (JMP)
      or
      Address 0000 Data 7004 (RAL)
      Address 0001 Data 5000 (JMP)
      or
      Address 0000 Data 7001 (IAC)
      Address 0001 Data 5000 (JMP)
      Member of the Rhode Island Computer Museum
      http://www.ricomputermuseum.org

      Comment


        Hi All;

        M-Thompson, Thank You for the Suggestions, I will try them and report back..
        Now that I am finished with other things, I will try the programs you have listed for me to try, while in MB mode..
        Then I will change it to PC mode and thy my program and Your programs as well and report back..
        No difference, between Your Program with 7001 and mine with 0001, I still get bit 1 still goes on..
        So, I will change it to PC from MB 00 thru 04.. I had also tried changing all of the registers, except for the AC Register, but I did change them around.. No, difference..
        I changed to PC and No difference, I also, monitored the line going to the Memory Board, and it is not the problem..
        I will need to look elsewhere.. Just running out of options..
        I found out what was turning on bit 1, it was a BAD 7404 gate, that was always being held High..
        So, now, it works fine in the rest of the machine, but it is not showing up in the AC Register..
        The IR Register, PC Register, MA Register, MB Register and Memory M are all working fine..
        And so, I need to find out what this is about..

        THANK YOU Marty
        Last edited by Marty; May 28, 2015, 02:36 PM.

        Comment


          Hi All;

          It Looks like I GOT IT GOING !!!!

          I checked and changed the OPG1's back to what they originally were, and tried it and it Works..
          I think since it had two (so far) mistakes, that it would not work as it was originally wired..
          One was the missing wire so the F decoder would not work, and the second was the Bad 7404, which was (at times) holding bit 1 up..
          I will now try Kyle's KITT Program..

          THANK YOU Marty

          Comment


            Woo Hoo!
            Jack
            www.computerarium.org

            Comment


              Hi All;
              Thank You Jack, for Your Immediate Response..
              But, it look like a NO go on Kyle's Program..
              But, I first need to make sure that I copied the program correctly..
              And I have only tried out some of the Instructions, but not all of the ones needed for His program..
              Such as ISZ, I should also check out CLA, CLL and CML along with CMA and SZL..
              JMP works, and RAR and RAL as well..
              CLL, CML, CLA and CMA all work, I just checked them out..
              Now to figure out ISZ and SZL..

              THANK YOU Marty
              Last edited by Marty; May 28, 2015, 07:42 PM.

              Comment


                Try the toggle-in programs. They will show if there are any basic problems with the processor.
                Member of the Rhode Island Computer Museum
                http://www.ricomputermuseum.org

                Comment


                  Hi All;
                  M-Thompson, Thank You for Your response and suggestion..
                  Yes, I can toggle in some of the parts of the program, But, having I/O would be a big Help at present, even though I can't say that even that would work at the present state of things..
                  But, I will look them (the listing) over and see what's there and how its done..

                  THANK YOU Marty

                  Comment


                    Hi All;

                    I am starting a new thread for this project.. This is getting long enough..

                    http://www.vintage-computer.com/vcfo...-PDP-8I-Part-2

                    THANK YOU Marty

                    Comment

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