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Corrupt Flash Memory Discussion

Discussion in 'Beginner Electronics' started by Eric L., May 25, 2006.

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  1. Eric L.

    Eric L. Guest

    Before I get into the nitty-gritty of the problem, I would like to know the
    consensus on whether Flash Memory can be corrupted by anything other than
    cosmic rays, nuclear detonation, and the occasional ray gun. All kidding
    aside, does anyone have any information on EMI, and/or RFI causing bits to
    flip?

    Best regards,
    elarson
     
  2. I bet if you put a Flash Memory chip in liquid helium some of the bits would
    drop out, and maybe
    -20 F.. I don't know, but it could happen if it gets cold or hot enough.

    I think you can exclude EMI wavelengths longer than 4 times the longest edge
    of
    the device from considiration as having no effect whatsoever.
    That means radio waves below microwaves would have to be extremely powerful
    to effect the device. Put the chip in a microwave, turn it on, then
    test.... and if my guess is right, there will be problems. I think it
    would probably turn out that you have to hit the chip-level electronics with
    ultraviolet light to have any hope of flipping bits.. and gamma radiation
    would be more effective.

    If the memory is inside a metal case, it would be better off for
    reliability.

    If I were on a jury however, I would conclude that bit-flipping is too
    far-fetched a defense.

    the wavelength of the offending EMI has to be shorter than four times the
    length of the structure it interacts with, to interact with it
    substantially.. furthermore it has to result in enough 'kick', the rush of
    phonons from the strike spot to
    cause enough electron excitation to bump the voltage enough to cause
    the bit to change and still the circuit has to be susceptible to register
    this change.. so its an
    unlikely proposition even if you try... but if you try a few billion times
    as in a radioactive minute you might have some luck.

    RFI is EMI limited to the RF bands.

    If you record 1,000,000 flash memories then drop them all, one at a time, 3
    feet onto the pavement, 50 of them will have permanent errors from breakage.

    If you record 1,000,000 flash memories then read them back, one or two will
    have non-repeatable errors... thats just the way it goes (without recourse
    to voodoo or microsoft).
    If that's true it's a one in a million chance for just bad luck with 'bit
    retention'.

    Another thing is ageing. Since the 'decay' of chemistry within the chip is
    a function of time..it would stand to reason that with every passing second
    flash memory is more vulnerable to failure.
    After 100 years there is a slim chance that much data could still be
    intact. 0 will still be zero, but adjusting for
    inflation, 1 will be around 27 (which screws up binary), and gasoline will
    be $421 per milliliter
    (synthetic) - converted from yen since the dollar won't exist, having since
    surpassed
    itself by it's value as heating fuel and toilet paper.

    hope that helps
    elvis
     
  3. Eric L.

    Eric L. Guest

    Thank you for your comments.

    I would like to direct your attention to the center ring:
    http://www.eng-tips.com/viewthread.cfm?qid=155287

    I have been having a discussion with a number of engineers over a special
    little topic. I think you will find this most interesting. I would be
    interested in what you have to say.

    elarson
     
  4. Dan H

    Dan H Guest

    I have seen effects when a system was being tested for EMI/RFI
    immunity.

    At certain frequencies that microproc oscillator was affected, confused
    the micro and cause false data to be written to memory chip.

    Dan
     
  5. Eric L.

    Eric L. Guest

    Thanks for your input. What is the recommended test setup for testing for
    EMI/RFI?

    elarson
     
  6. Dan H

    Dan H Guest

    It depends on the application and what the legal requirements are - for
    example

    If the product is to be sold in the European Union there detailed
    specifications as to how the tests must be done. These require the
    equipment be tested in a special built facility with special test
    equipment to do the tests.

    If you just want a confidence check, you can take a hand help VHF
    transmitter, hold the antenna about 6 inches from your product while it
    is running and key it on and off while tuned to different frequencies
    and observe the product operation for unusual events.

    To do a crude test for immunity to electrical spikes wire the contact
    of a relay in series with the power to the relay so that it acts as a
    buzzer. Connect a wire from one end of the relay coil connected to the
    relay contact thru a capacitor and then connect it one at a time to the
    power leads and the input and output leads of the product. Monitoring
    for abnormal operation of the product.

    Without careful design few products will pass even the above tests the
    first time they are applied.

    And of course once you have a product which is immune to outside
    influence then you need to run test to see if it is emitting unwanted
    RF to the air or on the power lines. More special equipment and
    facilities required.

    Hope this helps

    Dan
     
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