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Copying EEPROM with Checksum

Discussion in 'Electronic Design' started by [email protected], May 7, 2008.

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  1. Guest

    Hello to all
    I had Copied (For future Backup Purpose)One EPROM (In one of the
    Industrial Electronic Module )with Checksum using the EPROM Reader .
    After reading the EPROM I put it back in the Module. It is not
    working.I later note that the EPROM (27C512)had first 128 Lines
    reserved for Application Program + Checksum for Configuring the Module
    Operation) balance up to 8 K for Firmware of the Module )Anybody
    explain why it happen . How I can recover it and make the module
    Function again . Please reply Thank you

  2. James Beck

    James Beck Guest

    Just READING an EPROM, by definition, can not change the contents.
    Did you do anything else to it, that you have have forgotten to mention?
    Have you tried burning another copy from the image you stored?

  3. mpm

    mpm Guest

    On May 7, 2:37�pm, wrote:
    How I can recover it and make the module
    I'm not sure I understand, because if you copied an EPROM, regardless
    of what the actual bytes were to be used for, the copy should be
    identical to the source.

    IF however you copied the contents without regard to any required
    offset start address (or similar, etc..), and then copied the file to
    some other starting address, then I can see where that would cause a
    problem. However, in that case, the checksum should fail because it
    is generated in part using the address.

    Perhaps the checksum did not fail because you are on a page boundary,
    or ??

    To fix it, I guess you could try loading the file to a new (separate)
    EPROM using 128x8 as the offset start address and see if that does
    it. You'll have to check the documentation on your programmer on how
    to do this. Many can correct the checksums on the fly.

    If the original read was wrong (offset problem, etc..) you should
    still have all the data, but the start addresses and checksums will
    all be incorrect. You'll have to strip these, insert the correct
    start addresses, and then calculate the new checksums.

    There are utlilties available for this. Avocet had a real nice one,
    and if you truly get stuck, maybe I can get you a copy. (It's from
    the mid '80's so I doubt they'd complain too much?)

    Finally, I should mention that it is possible on some hardware to
    "read" correctly, but not "write" the same part. (For parts where the
    EPROM read and write voltages differ.) If that is the case, your
    original read is probably fine, but you clobbered the device when you
    re-wrote the file back to the device. Double check the EPROM Manuf &
    part# and make sure your EPROM programmer is actually set to the job
    at hand. Most good device programmers would give you a write error,
    but some won't.

    Good luck.
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