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Flash and EEprom

Discussion in 'Electronic Design' started by terry, Oct 31, 2004.

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  1. terry

    terry Guest


    What is the difference between flash memory and eeprom? Which one is more reliable?

  2. Al Borowski

    Al Borowski Guest

    As far as I know, with EEPROM you can erase/reprogramme individual
    bytes. You can only erase/reprogramme Flash in banks of many bytes. Use
    google for more details.

    Which one is more reliable?

    No idea - look at some datasheets.


  3. John Smith

    John Smith Guest

    Also, if what I've been using is typical, flash has a write-life. That is,
    after so many erase/write cycles (50,000) it may begin to fail.

  4. Tim Wescott

    Tim Wescott Guest

    Both flash and EEPROM have write lives (in cycles) and data retention
    lives (in years). The basic cell AFAIK is the same, so for recent
    technology devices they will have comparable lives. The difference is
    that the flash part saves a lot of real estate with it's block erase, so
    in general if the chip has a lot of memory it'll be flash and if it has
    only a little it'll be EEPROM.

    In fact, for "big" chunks of memory I don't know of anything _but_ flash
    being currently available, and the little 256-byte 8-pin parts are all
    EEPROM for convenience in parameter storage. There are older EEPROM
    chips, but that's only because EEPROM came along several years before
    flash did.
  5. John Smith

    John Smith Guest

    Thanks, Tim. I didn't know that.

  6. Terry Given

    Terry Given Guest

    I once peer-reviewed a design which periodically "refreshed" a couple of
    EEPROM locations. Turns out the idea used up the entire life of the chip
    in about 3 weeks. oops. They re-designed the firmware, scrapping the
    not-so-brilliant idea.

    AFAIK the failure method is increased write cycle time.

  7. Rich Grise

    Rich Grise Guest

    So, you're saying, you could use them for the program store for embedded
    Linux, which gets an update about once a year, but not Windows, because
    the updates would wear them out in a few weeks? ;-)

  8. Terry Given

    Terry Given Guest

    unless you update your windows system as infrequently as I do :)

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