>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 16 December 2004 19:23
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC] EEPROM Limits on a PIC18LF248
>
>
>You will get several ideas on how to do this, so I will tell you mine. 
>It works.
>
>There is no reason to refresh, since you are overwriting every 
>1-2 seconds, why refresh at all? Refreshing is just reducing 
>the cell's lifetime.
>
>So, what I do is to write the variable in 3 places. When I 
>read it next 
>time, I
>read all three and see if they compare, taking the best two out of 
>three, but
>in any case, I have to write all three anyway.  This assures accuracy, 
>as the
>chance that more than one will exhibit failure is unlikely in 
>1-2 seconds.

This was covered in a recent thread.  You DO need to perform a refresh
of the entire EEPROM if one or more cells are written to more than the
number specified in the data sheet.  I don't know the mechanism behind
this, but writing to one cell essentialy removes some charge from the
others so data will be lost unless all cells are refreshed.  This is
explained in the datasheets.

Regards

Mike

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