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Haplo



Joined: 06 Sep 2003
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Flash...
PostPosted: Thu Dec 18, 2003 6:46 pm     Reply with quote

A simple but interesting question...how many times can I rewrite a cell in the flash of PIC16F87x before it fails? The datasheet says 10000 times, but what is the value for a good practice?
Steve H.
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PostPosted: Fri Dec 19, 2003 9:22 am     Reply with quote

Good practice for a commercial product is not to go over the minimum endurance during the life of the product. If it's a project for you - then go for the max, you can always burn another chip, right?
Haplo



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PostPosted: Fri Dec 19, 2003 4:34 pm     Reply with quote

Thanks. What is the minimum endurance for writing to the flash? Anyone knows the figure?
Mark



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PostPosted: Fri Dec 19, 2003 9:36 pm     Reply with quote

I know that I could probably find it in the datasheet if I were to look Very Happy
Haplo



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PostPosted: Sat Dec 20, 2003 12:54 am     Reply with quote

I never post any questions here before I make sure the answer is not in the datasheet Very Happy

Take PIC16F876 for example. Nowhere in the datasheet it mentions the maximum number of writes to the flash. However, in the datasheet of PIC16F876A it says that value is 10,000 for PIC16f876 (and 100,000 for PIC16F876A). Unfortunately it doesn't mention any 'recommended' values anywhere. Anyone out there wo may know about this? Thanks.
Gerd



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PostPosted: Sat Dec 20, 2003 9:11 am     Reply with quote

Hi Haplo,

I could never find a minmum or recommended values for PIC's. It is a normally difficult to get valus for most Flash memorys.
In the last years I always used 10% of maximum rating, this is maybe a little overcautious, but it worked for me.
Mark



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PostPosted: Sat Dec 20, 2003 9:28 am     Reply with quote

From the datasheet:

Quote:

The PIC16F87X devices do not automatically verify the
value written during a write operation. Depending on
the application, good programming practice may dictate
that the value written to memory be verified against
the original value. This should be used in applications
where excessive writes can stress bits near the specified
endurance limits.
only a full erase of the entire device will disable code
protection.


Take a look at page 158 of this pdf:
http://www.microchip.com/download/lit/pline/picmicro/families/16f87x/30292c.pdf

Look under the minimum column for Program Flash Memory
[/quote]
Haplo



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PostPosted: Sat Dec 20, 2003 4:05 pm     Reply with quote

Thanks. That value (1000) is the minimum, not the recommended. But I think I'll stick to that.
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