PIC16F628A code protection

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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


Re: PIC16F628A code protection



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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



Re: PIC16F628A code protection


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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.



Re: PIC16F628A code protection


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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


Re: PIC16F628A code protection



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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?



Re: PIC16F628A code protection



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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



Re: PIC16F628A code protection



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

Octavio



Re: PIC16F628A code protection


Sounds like this problem:

http://support2.microchip.com/KBSearch/KB_StdProb.aspx?ID=SQ6UJ9A003LD0

but it depends on what config fuses and what programmer you're using


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