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COSMAC Microkit ROM Monitor (1801)

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  • billdeg
    I have uploaded a copy of what I believe is the ROM monitor from the COSMAC Microkit to the files section. The two-chip processor chips are marked TC 1084 and
    Message 1 of 7 , Apr 17, 2013
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      I have uploaded a copy of what I believe is the ROM monitor from the COSMAC Microkit to the files section. The two-chip processor chips are marked TC 1084 and TC 1085. I did not actually boot the Microkit, instead I have the Martin Eberhard 1702/A ePROM burner which I used to read the ROMs only. Related to the project I just completed the mods to read 1702's (not 1702-A) so I could read the COSMAC ROMs.

      Most of the Microkit chips are from 1974. I almost had a heart attack trying to extract the ePROMs and re-insert them into the ROM card. sheesh. Hard to find 1702s, don't want to have to reburn new ones because I broke a pin.

      Next I plan to assemble the machine listing, by hand I guess, to see what a 1801 instruction set monitor would do. I also today got the RS232 card for this system, the seller found and sent to me. Up to this point I only had a TTY card. I have uploaded a pic to my site of the serial card along with everything else.

      I don't have this group set to send emails when there are posts, if you have questions, please contact me through vintagecomputer.net contact form. The page I am maintaining for this project is:

      http://vintagecomputer.net/browse_thread.cfm?id=511
    • joshbensadon
      ... Hi Bill, I don t have an account on Vintagecomputers, it s too late at night right now to make one. I looked at the ROM dumps, and at first I thought it
      Message 2 of 7 , Apr 17, 2013
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        --- In cosmacelf@yahoogroups.com, "billdeg" <billdeg@...> wrote:
        >
        > I have uploaded a copy of what I believe is the ROM monitor from the COSMAC Microkit to the files section. The two-chip processor

        Hi Bill,

        I don't have an account on Vintagecomputers, it's too late at night right now to make one.

        I looked at the ROM dumps, and at first I thought it looked nothing like the 1802 machine code. Then I inverted all the bits in my head and it started making sense.

        Could this system be using an inverted bus?

        :)J
      • thinkpast
        ... Bill is a friend and colleage of mine, so I m pleased he is sharing this find and information with cosmacelf. Josh posted later, that he believes the code
        Message 3 of 7 , Apr 18, 2013
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          --- In cosmacelf@yahoogroups.com, "billdeg" <billdeg@...> wrote:
          >
          > I have uploaded a copy of what I believe is the ROM monitor from the COSMAC Microkit to the files section.
          > Most of the Microkit chips are from 1974. I almost had a heart attack trying to extract the [1702R] ePROMs and re-insert them into the ROM card.

          Bill is a friend and colleage of mine, so I'm pleased he is sharing this find and information with cosmacelf. Josh posted later, that he believes the code as dumped from the PROMS is "inverted". So anyone interested in disassembly will have to invert the bits to generate runnable code. It's something I'd do if time permits, but if someone else does it sooner that's great and would compliment Bill's ROM dump.

          I'd be glad to tinker with one of the 1802 cross-assemblers to make an 1801 cross-assembler - if I'm told that there are unique features to Bill's 1801 chip set. I think, to a first order, the 1802 is a superset of the 1801 and so any 1802 assembler would work. But I don't know that and hopefully others who DO can comment.

          I told Bill privately, he'd get some insight about his "1801" chipset by looking at the RCA document MPM-101, "Microprocessor Products - User manual for the COSMAC Microprocessor" which seems to be an early COSMAC processor document from April 1975. The processor was in discussion and possibly small production, before it was called the "1801", as far as I can see. Bitsavers.org and mirrors, have a PDF of this document, under manuals....RCA...cosmac.

          I don't have an "1801 data sheet", or know if one was actually produced. I have the ICAN-6416 document on the "COSMAC microprocessor". If someone can direct me (and Bill Degnan) to additional 1801 and MicroKIT information, please do so. I could not find the ICAN document readily online: if someone knows of a link let me know; otherwise I'll provide the PDF myself on my site and/or to Dave Ruske for his site.

          From some previous discussion about when the 1801 and 1802 were produced, I created this document on the M/S card site. It includes images of the MPM-101 and the ICAN-6416 documents.

          http://www.retrotechnology.com/memship/1802_dates.html

          A side issue, is a question about 1702-R eproms, if they are different from the 1702 and 1702A. I'd like to know, so would Bill.

          Gotta run!

          herb johnson
          retrotechnology.com
        • William Donnelly
          After a quick look, it doesn t look inverted to me. I don t think the code starts at address 00. I would have to look at it closer to be absolutely sure. He
          Message 4 of 7 , Apr 18, 2013
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            After a quick look, it doesn't look inverted to me.
            I don't think the code starts at address 00.
            I would have to look at it closer to be absolutely sure.
            He doesn't say what address the code starts at. (hardwired)
            I don't think they can both be address 00.
            The bytes at "00" look like data to me.
            So there is probably some jump into a location to
            wherever the ROM's are addressed.
            Maybe you had to load a long jump and execute it
            to get to the monitor.

            – Bill
             
            On 4/17/2013 8:56 PM, joshbensadon wrote:
             

            --- In cosmacelf@yahoogroups.com, "billdeg" <billdeg@...> wrote:
            >
            > I have uploaded a copy of what I believe is the ROM monitor from the COSMAC Microkit to the files section. The two-chip processor

            Hi Bill,

            I don't have an account on Vintagecomputers, it's too late at night right now to make one.

            I looked at the ROM dumps, and at first I thought it looked nothing like the 1802 machine code. Then I inverted all the bits in my head and it started making sense.

            Could this system be using an inverted bus?

            :)J


          • sbirdasn
            Comments inline... ... Yes, there was an official data sheet with timing, instruction tables, pinouts, etc. I saw a copy of the COSMOS data book
            Message 5 of 7 , Apr 18, 2013
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              Comments inline...

              <snip>
              --- In cosmacelf@yahoogroups.com, "thinkpast" <hjohnson@...> wrote:
              >
              >
              > I told Bill privately, he'd get some insight about his "1801" chipset by looking at the RCA document MPM-101, "Microprocessor Products - User manual for the COSMAC Microprocessor" which seems to be an early COSMAC processor document from April 1975. The processor was in discussion and possibly small production, before it was called the "1801", as far as I can see. Bitsavers.org and mirrors, have a PDF of this document, under manuals....RCA...cosmac.
              >
              > I don't have an "1801 data sheet", or know if one was actually produced.
              </snip>

              Yes, there was an official data sheet with timing, instruction tables, pinouts, etc. I saw a copy of the COSMOS data book that had it, and I think it was copyrighted/released around 1976, with the format something like 8 1/2 x 11" and about 3/4 to 1" thick. It had a white cover with diagonal stripes of both black, and other colors.

              I've seen a copy or two come up on ebay a time or two, but they're not real common.

              It should be noted that as soon as the 1802 was released, the 1801 was dropped from the data book, and was never seen again.

              The 1801 was a dog. It barely ran like 2 MHz (about 1/2 of the 1802 performance), and the instruction set was seriously crippled- the ALU could only shift in one direction, no flag lines... Oh, I seem to remember that it didn't even have the Q F/F with it's associated conditional branch/skip instructions.

              Sbirdasn.
            • William Donnelly
              Here is the 1801 chip set datasheet and RCA manual: http://bitsavers.informatik.uni-stuttgart.de/pdf/rca/cosmac/TA6889_TA6890_Data_Sheet_Feb75.pdf
              Message 6 of 7 , Apr 19, 2013
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                Here is the 1801 chip set datasheet and RCA manual:

                http://bitsavers.informatik.uni-stuttgart.de/pdf/rca/cosmac/TA6889_TA6890_Data_Sheet_Feb75.pdf

                http://bitsavers.informatik.uni-stuttgart.de/pdf/rca/cosmac/Users_Manual_For_The_COSMAC_Microprocessor_May75.pdf

                – Bill
                 
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                On 4/18/2013 10:49 AM, thinkpast wrote:
                 

              • thinkpast
                Thanks to Sbirdasn and William Donnelly for the posted references. I ve updated my Web document (see my previous post) accordingly. Herb Johnson
                Message 7 of 7 , Apr 21, 2013
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                  Thanks to Sbirdasn and William Donnelly for the posted references. I've updated my Web document (see my previous post) accordingly.

                  Herb Johnson
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