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Thread: Poly 88 case

  1. #291


    Quote Originally Posted by falter View Post
    Question.. do you know of any documentation for the 0.75 'disk' EPROM I have? I've tried putting it in my now-working setup and it just gives me a screen full of garbage. I'm wondering if you have to change the memory address select or jumper something on the card for it to work.
    That is the first PROM of a two PROM set, that along with the 4.0 Poly monitor PROM, provided the “BIOS” for System-88. Your PROM goes in the middle PROM socket (0400h), with the 4.0 PROM in the right socket (0000h), and the missing version 7.5 PROM in the far left socket (0800h).

    Source code for the Poly 4.0 monitor and disassembly of the version 7.5 PROMs (both PROMs in a single source file) can be found here:

    A newer version (8.2) of the PROMs can be found there as well.


  2. #292


    Hi Mike
    I only had a few minutes to look at stuff you had. It is a great collection of the Poly stuff.
    I wasn't sure about the other EPROM, since it was just the single EPROM and I knew it needed all three for the System 88. I think he will have enough with the cassette setup but if he ever comes across a disk controller, making it a System 88 can be done with the information you've collected.
    I was reading through the file that I'd had on how to use the TPERR. Even I'd have a hard time figuring it out. It was a most useful program when repairing tape images of BASIC programs. The typical error was to have a bit or few dropped, such that all the bits would be shifted, across the bytes. I'd write a simple bit shift program and shift the bits until the remainder would look like basic again. Then I'd analyse the program to figure out the missing part. Once corrected, I'd write the tape images back to the tape. I was able to restore several tapes that had folded sections of tape. Most I was able to recover by tightly winding the tapes but some required the bit level repair.
    The TPERR was also used to edit records headers and such. I wanted StarTrek to auto start as well as use the SAVE extension I'd made to TinyBasic( it also had PEEK and POKE ). I was able to patch together a tape with all the parts using TPERR. The hardest part was keeping track of all the offsets. TPERR keeps all the headers. It took a lot of side notes on a piece of paper as not all the tape records were maximal length. There were some long and some short. So indexing through the record was a pain. I should have written a record step program but never got around to it.
    Still, I hope that someday someone will have a tape that they want to recover the image from and they'll find TPERR useful.
    Last edited by Dwight Elvey; June 28th, 2018 at 07:51 AM.

  3. #293


    Here is what I'd do to make a program to make the PC a keyboard for the Poly88.
    First some information:
    IBM PC connector
    1 STROBE
    2 D0
    3 D1
    4 D2
    5 D3
    6 D4
    7 D5
    8 D6
    9 D9
    10 ACK
    11 BUSY
    13 SEL
    14 AUTO FEED
    15 ERROR
    17 SELIN
    18 TO 25 GROUND

    Depending on how may ports you have:
    LPT1 3BC
    LPT2 378
    LPT3 278
    LPT1 378
    LPT2 278
    LPT1 278

    The base address + 2 is the control port Bit 0 is the inverse of STROBE.

    In Forth Code it might look like:

       1000 0 DO 5555 4444 / DROP LOOP ;
    : POLY-KB ( - )
        KEY DUP
       ( DUP EMIT ) \ if I wanted to see it on the PC.
        1B -  \ break out on an escape key
       WHILE  \ while not the escape key
        LPT1 PC!  \ send to the Poly88 keyboard input
        1  LPT1 2 + PC!  \ strobe it
        DELAY \ allow the Poly 88 enough time to see the input
        0 LPT1 2 + PC!  \ clear the strobe, ready for the next key
       DROP ;  \ always keep a clean stack in Forth
    Depending on what Forth I was running it might change the PC! to some other word. Maybe someone else could help with some C or BASIC.
    Last edited by Dwight Elvey; June 28th, 2018 at 02:36 PM.

  4. #294


    Here is my attempt at GW BASIC. It may not work but it should be close.

    10 A$ = INKEY
    20 IF LEN(A$)=0 THEN 10
    30 A% = ASC(A$)
    50 OUT &H278,A%
    60 OUT &H27A,1
    70 B=TIMER+0.1
    80 C=TIMER
    90 IF C<B THEN 80
    100 OUT &H27A,0
    110 GOTO 10
    The TIMER function might not work at midnight or right on the hour when the time is reset or synchronized.
    This shouldn't be an issue. The port number may be different, see my previous post. The strobe port is always the port number plus 2. I don't like BASIC much but it is a simple program.
    Last edited by Dwight Elvey; June 29th, 2018 at 11:22 AM.

  5. #295
    Join Date
    Jan 2011
    Vancouver, BC
    Blog Entries


    Okay so I have my GRI 756 keyboard. Pretty nice. Interesting how closely the keys match the layout of my Netronics keyboard, even the font looks the same.

    So I was reading the manual trying to figure out how to hook it up to my Poly 88 and now i have a slight problem - the keyboard requires -12V. No problem, the Poly VTI board will supply a neg voltage - you just need to install the correct caps, resistors and diode into the marked spots on the board. My VTI does not have these installed so I presume it's not supplying any negative voltage to the pin.

    I'm a bit stuck in understanding what I need in the way of values for the zener, resistor, etc. The manual tries to explain it here on page 22 but it just sort of goes over my head. Anyone feel like giving me a primer?

  6. #296


    I don't know what your keyboard requires but if we assume a bias current of 5 to 10 ma someplace. It may be more or less. Lets say the zener is going to use about 10 ma. The total current for the resistor is the about 20 ma.
    It will likely take the raw input voltage of around 18 volts. That leave 6 volts to drop across the resistor. 6/.020=300 ohms. 6*.02 = .12 or little less then 1/8 watt. A 1/4W 300 ohm or 330 ohm resistor should be fine. The capacitor can likely be a .1uf and be fine.
    The zener could be a 1N5242 as 12V rated at 0.5W. If there was no load from the keyboard the zener has to eat all 20 ma. 12*.02= .24 watts or about half the rated value.
    What more do you need?

  7. #297
    Join Date
    Jan 2011
    Vancouver, BC
    Blog Entries


    Thanks muchly Dwight. I am rereading it severally to try and understand the concept.

    I think the three parts are the basics required. I do need to locate a pinout for the 25pin keyboard connector that plugs into the one on the vti so you can connect keyboard on the back of the machine. But for the negative voltage I think those are the only components we need.


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