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Thread: Intel P8021H 2173 / Mac M0110A Keyboard

  1. #1

    Default Intel P8021H 2173 / Mac M0110A Keyboard

    I need to replace the logic IC in an original Mac keyboard. It uses the Intel P8021H 2173. I've seen other numbers at the end of that (like 2175). Does anyone know what 2173 means? The cheapest I could find (on Ali Baba) was $14 for a chip; so I'd rather go cheaper if possible. I've found a number of non-2173 variants, but I'm uncomfortable replacing/testing it with another without knowing anything about what the 2173 means.

  2. #2
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    The 8021 is a member of the 8048 microcontroller family that has a mask ROM program. These were heavily used in keyboards by many manufacturers. I have here an 8021, which I need to dump the ROM from, with a '2059' after the part number. It is from a TRS-80 Model II keyboard.

    While all 8021's are pin-compatible they are not ROM program-compatible and thus you will need one from the exact same model keyboard for a replacement. I think those four numbers could be the mask number, meaning the actual program contents. These are not field-programmable nor are they reprogrammable.
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  3. #3

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    Thanks for the tip. Don't have them in the Model I, DT-1, MC-10, or PC-6300 Keyboard 302. (I don't have a Model II and I don't want to cannibalize my Models III and 4).
    Last edited by raoulduke; October 19th, 2016 at 08:27 PM.

  4. #4

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    Okay... what's the cheapest setup I can get to use these: https://github.com/MisterTea/MAMEHub...chine/mackbd.c

    I know absolutely nothing about programming EPROMs, but will this work? https://www.amazon.com/Velleman-K804...dp/B007YLUJTK/

  5. #5

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    Quote Originally Posted by raoulduke View Post
    I'm afraid not. That programmer only programs a limited subset of Microchip PIC microprocessors.

    If others are correct and your original chip is a mask-programmed 8048 (is it a 40-pin device?) then a logical drop-in replacement would be the 8748, which is the version with a windowed EPROM built in.

    Even if that is so you would need:
    -A blank 8048 or a used one and a UV eprom eraser to empty it before programming it
    -The code to program into it
    -A device programmer which can program ancient microprocessor ICs, and a computer to run its support software (usually DOS) and hardware interface (usually a parallel port).

    Historically there were any number of device programmers which could program eproms of various sorts but only the high end (expensive) ones could program a large range of microprocessors as well. Two examples which I personally know can program the 8748 would be the EMP20 (Needhams Electronics) and the ALL07A (Hi-Lo Systems), both long out of production.

    Obtaining all of these things amounts to a lot of trouble and expense - I would explore every other possible avenue before assuming that the keyboard microprocessor is dud, unless it has a gaping hole in it, glows orange, or is cracked in half of course. For example, are you certain that none of the keyboard key contacts are stuck in the closed state? If there are PCB tracks on one or both sides of the keyboard PCB, check for signs of old liquid spills which are a classic reason for keyboard failure. Any fluid which has been spilled or dripped onto the keyboard at any time may have rotted away a small portion of copper track or a link wire somewhere.

    What are your symptoms? No keys working? A row or column of keys not working?
    Last edited by SiriusHardware; October 24th, 2016 at 10:42 AM.

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    One of the modern 8051 MCUs (e.g. Atmel) might also do the trick with a minimum of twiddling--and be SPI flash-programmable. Pinout is a different matter, of course.

  7. #7

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    Well so this kit - which is serial and thus not ideal but still workable - comes with (I think) a 28-pin EPROM. That can't be used OOB? (Again very limited knowledge at this point). Moreover, I'm not sure what the issue with the original IC is; so it is theoretically possible I can just reflash that one - although it probably isn't flashable so maybe that theory exists mostly in my head...

  8. #8

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    Quote Originally Posted by Chuck(G) View Post
    One of the modern 8051 MCUs (e.g. Atmel) might also do the trick with a minimum of twiddling--and be SPI flash-programmable. Pinout is a different matter, of course.
    You'd need to write the code for it as well. The 8048 code was quite different.
    The 8049 series was similar but had port usage differences. The 4048 was a general
    purpose with normal ports. The 8049 had one port that had an off chip strobe to
    capture 8 bits.
    If all the ports are not needed and you get a dump of the onboard ROM, you may be
    able to use a 8035 with external ROM. There are ways to get all the ports back
    with external latches as well. There are lots of 8035s from junked equipment.
    Dwight

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    I was trying to think of a modern similar flash-programmed device. The 8051 was the closest I could come up with. The github code is C, after all.

    Of course, you could just take your pick of any modern MCU with enough pins and translate the functionality.

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    Quote Originally Posted by raoulduke View Post
    I need to replace the logic IC in an original Mac keyboard.
    Throw it out and get a replacement. All the screwing around isn't worth the $35 for another one.

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