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PIC16F628A code protection

Discussion in 'Electronic Design' started by joseph, Mar 4, 2007.

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  1. joseph

    joseph Guest

    Hi,

    I programmed the code protect fuses on a PIC16F628A. I have tried
    erase the chip thus restting the fuses back to normal using ICProg or
    WinPic but to no avail. When i read the PIC i either get 3FFF or 0000
    and when i try to program it, programming fails altogather. The
    hardware is OK as i have sucessfully programmed andother PIC16F628A.

    Any ideas on how to revice the IC back or shall i conisgn it to the
    dustbin.

    Any help would be greatly appreciated

    Regards

    Joseph
     
  2. Question is which programming voltage the programmers you have tried use?.
    Once the protection fuses are set, a full erase, using a programmer that
    support the high voltage programming algorithm, is needed to once again
    access the chip.

    Best Wishes
     
  3. Hmm, you should be able to erase it. You're not using low voltage
    programming (LVP) are you? I believe you have to use a programmer that
    supports traditional (HVP) to erase it.
     
  4. joseph

    joseph Guest

    Hi,

    Thanks for the information.

    I am using High voltage programming (12V) and the supply voltage is
    4.85V. Does the PIC tolerate such deviation from the supply during
    programming?

    Joseph
     
  5. I'm not sure what you mean. 4.85V is close enough on the 5V supply, but Vpp
    should be close to 13V IIRC. Is your programmer applying that much voltage
    to the /MCLR pin when you program it?
     
  6. You need a HV programmer that can supply the required high voltage. If
    memory serves it is 13.5V for the PIC16F628A. You can find the programming
    specifications at Microchip. Code protection fuses need more power and time
    to be erased then the others. Which is deliberately done by design to make
    sure all others are erased before the code protection fuse is. Make sure to
    select the right component on your programmer. The programming algorithm of
    the PIC16F628A differs from the one of the PIC16F628.

    petrus bitbyter
     
  7. Octavio

    Octavio Guest

    Did you pulldown the PGM pin?
    Just in case the famous and unpredictable conflict between LVP and HVP is
    not the culprit.

    Octavio
     
  8. Guest

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