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easy eprom questions

Discussion in 'Electronic Design' started by [email protected], Jan 2, 2005.

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  1. Guest

    Hi Group,

    I am a foolish hobbyist who would like to program 27XX eproms sometime
    within the next year.

    First question: I pulled what I think is an eprom from a board. The
    chip is an OKI M2764Z-N. It has no quartz window which causes
    confusion. I assumed so far that all 2764s were eproms. Can it be an

    Second question: I plan on building a simple eprom burner for 2764s,
    27128s, 27256s. I would like it to use LPT1 under DOS (for simplicity's
    sake). Are there any projects on the web I can study to help me in my

    Third question: which junky old electronics am I likely to find these
    eproms in?

  2. I haven't tried ot find the data sheet, but it is just as likely to be
    an OTP (one time programmable) EPROM. Eliminating the erasure window
    cuts the manufacturing cost way down.
    You start with Google.
    Anything with a old microprocessor (not a PIC or any of the newer
    units that contain the memory inside the processor.

    EPROMs go cheap on ebay.
    If you ask nicely, someone here will probably send you some.
    I have a few of some size in my desk drawer.

    You should look for a small ultraviolet eraser, also.
  3. Guest

    Of course. I forgot to put on my thinking cap before posting.
    I have. I only found one page with two projects: one parallel interface
    and another serial interface. Basically the same project but with
    revisions. Do you know of any others? I am
    not interested in building a willem programmer.
    I will keep that in mind. No real sense in collecting them until I've
    built some kind of programmer.
    I was thinking of building one with a germicidal lamp. If I can find a
    local supplier and they are cheap.

  4. Guest

    Er. Ok I'm finding more. Ignore my gravely insulting use of newsgroups
  5. and another serial interface. Basically the same project but with
    There seem to be a lot of derivatives of my EPROMr 2 floating about on the

    The general design of the EPROMr 2 is actually based on programming
    algorithms used in an ancient, ancient totally hand-operated
    2716/2732A/2732B programmer that I once saw in kit form (but never built
    because I didn't feel the urge to set up 1K of data on DIP switches).

    I've been getting progressively more email over the years about PCs
    with which the design doesn't work. If you build it as a weekend project,
    and it works for you, great - but if not, it could turn into a very
    frustrating debugging exercise, I'm warning you now.

    I built that project solely because I needed to repair and upgrade a few
    coin-op arcade game boards in my collection. I was experimenting with
    various patches to their ROMs, and I needed a quick and dirty burner that
    basically worked. EPROMr 2 was it.

    The EPROMr 3 prototype and sourcecode were lost when I moved to America.
    It's most unlikely I will ever look at that project again, life's too
  6. I suggest you use EEPROMs rather than UVPROMs - no need to worry about
    the UV lamp, or waiting for the chips to erase.

    I've used Microchip 28C64 EEPROMs as replacements for 27C64s during
    program development.

    Peter Bennett, VE7CEI
    peterbb4 (at)
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  7. Mark Zenier

    Mark Zenier Guest

    You're out of luck, unless you can find a friendly high energy
    physics lab that has an accelerator that can produce enough stray
    x-rays to erase them. ;-) These are OTP (One Time Programming) EPROMS.
    The most expensive part of the EPROM is/was the fancy package with
    the quartz glass window.
    Steve Ciarci's old Byte magazine Circuit Cellar project books.
    Or Steve Walz's web/ftp site.
    Older IBM clone keyboards. The ones with a XT/AT switch on the
    bottom. Circa 1985 they were usually a 8031 or 8039 single chip
    microcontroller with an external 2764 EPROM. Some used 8748 EPROM
    based microcontrollers, too.

    If you have to punt and buy some, try Jameco or B&G Micro.

    Mark Zenier Washington State resident
  8. Rich Grise

    Rich Grise Guest

    Where are you at? I'm in Whittier, CA, and I have a fairly big
    eraser, with about a 9" "germicidal" bulb - it's a little longer
    than a shoebox, but only about 2 1/2" tall and 6" wide, that you
    can have if you want to come and get it.

  9. CBarn24050

    CBarn24050 Guest

    Subject: Re: easy eprom questions
    What for? flash is easier, faster, pin compatable and cheaper.
  10. Guest

    I guess it all started when I was found an old atari 800xl. I peeked
    inside and saw that everything was socketed. I wanted to mod it
    immediately. I found some documentation (on the net) from it's heyday.
    It all deals with eproms. I assume eeproms weren't available/or cheap
    at the time.

    I'll look for eeprom (flash) alternatives then.
    Thanks for the wack in the head :)
  11. I agree. EPROMs are obsolete.
  12. Guest

    Ew. I have something similar in an old book. Definately not worth
    Thanks for the warning. I would have tons of old PCs to hook it up to.
    I wasn't planning on trying it on anything above more recent than a 486
    (I'm not that thick).

    I am going to look into eeproms instead...
  13. Guest

    You're right. I should do everything possible to preserve my eyesight.
    Thanks for the tip. I'll look into that.
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