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bertronicom
Joined: 17 Nov 2004
Posts: 26
Location: University of Cantabria -SPAIN
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| use of PROTECT in fuses |
 Posted: Thu Nov 18, 2004 10:25 am |
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Can I program again my PIC once a time I've programmed with PROTECT?
After I've programmed with PROTECT ICDS verification isn't correct. |
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Ttelmah
Guest
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| Re: use of PROTECT in fuses |
| Posted: Thu Nov 18, 2004 10:52 am |
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| bertronicom wrote: | Can I program again my PIC once a time I've programmed with PROTECT?
After I've programmed with PROTECT ICDS verification isn't correct. |
The 'full' answer, depends in part on the chip (most of the larger chips have multiple 'protection' fuses, affecting dfferent parts of the memory, and different operations).
However there are common features:
After read protection is enabled, the area of memory, returns a 'scrambled' version of the contained data, when read. Hence it will allways verify incorrectly. The recommended sequence is to program the chip, verify the code, then enable the protection sequence, and read the contents of the chip. In future, you can verify latter chips, by comparing them with this stored set of values.
Most of the reprogrammable chips, can be _erased_, using a high voltage erase only, once protection is enabled. The erase clears everything, including the protection fuse, allowing the chip to again be used. However a low voltage erase cycle, will not clear the protection fuse.
The whole 'point' of protection, is to prevent other people reading the code. If you could directly verify the code in a programmer, this would bypass what the fuse is trying to do.
Best Wishes |
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bertronicom
Joined: 17 Nov 2004
Posts: 26
Location: University of Cantabria -SPAIN
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| PROTECT |
| Posted: Thu Nov 18, 2004 11:19 am |
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I'm using PIC18lf252 running at 4Mhz at 3.3volts.
I'm trying to erase chip but verification and programming always fail. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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bertronicom
Joined: 17 Nov 2004
Posts: 26
Location: University of Cantabria -SPAIN
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| erase PROTECT fuses |
| Posted: Fri Nov 19, 2004 5:48 am |
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Thanks PCM programmer,
I'm looking myself removing PIC from the board.
I can't erase bulk PIC at 5volts because board is running at 3.3volts and the rest of devices (Bluetooth) will be died.
Big problem because all my boards are with smd PIC's. |
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