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Thread: Erasing UV EPROMs

  1. #11
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    Just don't overdo it. I've read reports where a UVEPROM was left in the eraser for far too long and would not take programming.

  2. #12
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    Quote Originally Posted by Chuck(G) View Post
    Just don't overdo it. I've read reports where a UVEPROM was left in the eraser for far too long and would not take programming.
    This is true...

    As someone who's erased 1000's of eproms,
    I can vouch for the fact "over-erasure" can cause damage.

    15-20 minutes in a reliable UV eraser is all you need.
    30 minutes max.

    If your eproms are not blank after that, they are likely bad.

    Steph

  3. #13
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    A good 10-15 minutes is all you need if the lamp is working OK.

    I have cards without the sticker over the glass on ROMs that still function after 20+ years.
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  4. #14

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    Quote Originally Posted by maxtherabbit View Post
    About 15 minutes seems to reliably blank most things
    Well I can confirm this worked just fine for my EPROM (AM27C256). After the toothbrush treatment I read the rom and all blank. I then tried programming it. Strange thing is I still had two issues:

    1. I had to try programming multiple times and then it finally worked.
    2. The default seq. in the G540 programmer is to blank->program->verify when I select the above chip. However, it consistently fails on the blank function. What is the blank function supposed to do?

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  5. #15

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    Seems like you need to adjust the chip type in your programmer software. It should not be trying to blank an EPROM.

  6. #16
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    In the software for the device programmers I use, the Blank function checks whether or not the device is blank before attempting to program it. It would do that by reading the entire device and checking each location for the unprogrammed value. Normally you would not want to attempt to program a device which is not currently blank, and the user would be warned before proceeding.

  7. #17

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    If it's doing a blank check that would be correct, but if it's actually trying to perform an erase ala an EEPROM that would be wrong

  8. #18
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    When I select an EPROM device the default sequence in the software for my programmer is:
    Continuity
    ID Check
    Blank Check
    Program
    Verify Twice

    When I select a FLASH device the default sequence in the software for my programmer is:
    Continuity
    ID Check
    Erase
    Program
    Verify Twice


    Blank Check and Erase are different operations and only one of the two is automatically selected depending on the device type. (Internally there would also be a blank check as part of the erase algorithm to verify that the erase operation was successful).

  9. #19

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    Right, but if you go back and read SLs post he said he manually did a blank check which passed, then the "blank" stage of his programming operation failed. Which seems to me to indicate that it's trying to perform an erase

  10. #20
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    He also said that he tried to program it multiple times before it finally succeeded, but didn't say that he also erased it (with the UV lamp) multiple times. In that case the blank check would pass the first time he tried to program it, and then fail every time after that after it was partially programmed the first time around. But I'm just guessing the most likely sequence of events that makes sense to me.

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