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Help to copy PAL16 / GAL16 / GAL20 ICs

Discussion in 'General Electronics' started by Henry, Aug 1, 2005.

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  1. Henry

    Henry Guest

    I'm currently working on a project to "clone" some old computer boards I
    have. The companies are long since out of business. These boards are from
    around 1983 to 1985.

    Please be a little patient with me as I'm not that familiar PAL/GAL ICs and
    can use all the advice I can get.

    I'm researching in to copying a few of the PAL16 / GAL16 / GAL20 ICs on
    these boards. I've been reading that it is possible to "read protect"
    (aka - registered) these chips and fear I may run in to this issue.

    I'm going to be purchasing an EPROM/PAL/GAL programmer in the near future
    and could use some advice on what models and software may be appropriate for
    my work. My needs are pretty basic and most of the technology I'll be
    working with is from the 1980s. I've been look at an Advin Pilot-MVP, but
    fear it may be more programmer then I might need. Any recommendations?

    If the PAL16 / GAL16 / GAL20 ICs are "read protected" (aka - registered)
    what options do I have to try and reverse engineer these chips? What
    options do I have to try and
    figure out how these chips are programmed? I have some basic electronics
    knowledge, enough to be dangerous, but nothing advanced enough to guide me
    with PAL/GAL ICs. Any and all advice will be appreciated.

    I'm also looking for someone to help or "tutor" me with these PAL/GAL ICs
    and I'd be willing to pay for this service.

    You can email me directly at "apl2research -at-" or post a
    here. Thanks in advance for your help.

  2. Ben Jackson

    Ben Jackson Guest

    Do you know what they're supposed to do? If they do something
    straightforward it might be easier to just work it out from the
    schematic. For example, if it has some address lines coming in
    and chip selects going out, and you know the memory map, you can
    just recreate the equivalent logic.

    If you can't read them out, find a datasheet for the PAL you have
    and observe how the product terms can be wired. That would tell
    you what combinations of inputs and outputs you'd have to test to
    map out the device. You could probably do the testing with a
    simple parallel port jig.
  3. Henry

    Henry Guest

    Just a brief update if anyone cares. There is hope, if anyone in the future
    has found these threads and was in the same boat as I. Seems there are a
    few options available to people with PAL's (not sure if this will work with
    GAL's, but I'm also going to try) that may be "protected" and need to copy

    I first found a service that used a Brute Force Analyzer to try to recover
    and create a JEDEC file from my PAL's. After they had some issues with the
    analyzer, due to the age of the machine, I then found a buddy who had a few
    good ideas on working with HAL's from the early Mac's. His idea was to
    expose the silicon "chip" so it could be examined by a microscope. Once
    exposed pictures could then be taken of the "fuse field" that is inside a
    HAL/PAL (see data sheet of PAL if you never seen the "fuse field") and it
    could then be possible to recreate a JEDEC file, manually of course. I'm a
    basic idiot (due to frequent parental droppings and lack of experience) and
    probably would have never occurred to me to try such a thing.

    He tried a few different ideas to expose the chip, but most were
    unsuccessful. His Website chronicles different ideas and stages of things
    he has tried. The address is to see some failed
    attempts. The real good stuff is here: Take a
    look around the whole site. He's really quite smart.

    Anyway. he found a service that will "decap" the IC, called They
    do failure analysis, so really we just use "part" of the services they
    offer. If you visit their Website you'll see that they offer a LIB service.
    Basically they can "jumper" the security fuse and then you will be able to
    "read" the JEDEC file from the PAL. Right now I have a HAL I sent to be
    decapped ($175 with return shipping, pics are more if you need them, about
    $350 total). There are issues with HAL's that I go in to in a moment that
    the LIB process won't work. The idea with the HAL is simple - I found a
    version of a HAL (from an Apple IIe) that was in PAL form. Luckily I was
    able to read the PAL with my programmer, convert the PAL code to GAL form
    and burn a working GAL. Sounds like quite an accomplishment? Naaa. If any
    unschooled idiot like me can do it, trust me - you could too. Anyway,
    converting the PAL to a GAL is just kids play - the real luck with this is
    that I found a PAL which I could read. Since I know the HAL is identically
    the same, programmed and logic (fuse field), then I can use the JEDEC as
    sort of a "Rosetta Stone" to read HAL. I could have purchased some old PAL's
    (and YES they are still for sale in some places!) and burned a few and had
    then decapped, but knowing the JEDEC file AND having a piece of equipment to
    test the PAL with is really quite a find!

    Now for some HAL info. These things are VERY rare. I'm not too sure if
    anyone outside of Apple even used them. Basically they are the same as a
    PAL, but they lack the "programming" circuitry that a PAL has. A PAL can be
    programmed "in the field" where as a HAL could only be programmed in the
    factory. HAL's were made by request only. They were a way to "mass
    produce" a PAL, which is just a custom piece of logic. The HAL was
    programmed, or burned, while in the manufacturing process. Since the
    manufacture had access to the bare chip they didn't need any of the
    programming circuitry and that helped keep the cost of the finished IC down
    since it was a "simpler" IC to produce. Since a HAL lacks any programming
    circuitry it also can't be read, so it acts as a copy protection like the
    security fuse does in a PAL. Oh sure, you can read a HAL if you want to
    try, but all you'll get is a "block" of un-blown fuses somewhere in a JEDEC
    file. Nothing useable that will let you recreate the IC. So since HAL's
    don't have a security fuse the LIB process offered by won't help

    Hopefully I won't need to manually decode my PAL's. I'm hoping to just have "jumper" the security fuse back and be able to read it. Feel free
    to contact me if I can be of any help in the future. I can be reached via
    email on any of these two sites: and My email is listed on both sites.

    Thanks again for everyone's input. My next project involves recreating some
    of the PAL logic in CPLD's. If anyone is familiar with CPLD's and their
    programming, please get in touch with me. I could use some help!


    My email is listed on the site if you wish to contact me directly.
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