Re: EEPROM/Flash data loss: probability & patterns?

On 23 Nov 2003 01:46:02 -0800, [EMAIL PROTECTED] (jtp) wrote:

>[EMAIL PROTECTED] (Mark Piffer) wrote in message news:<[EMAIL PROTECTED]>...
>> Hi group,
>> I am asked to rewrite a stable-storage scheme on a Motorola HC12 (in
>> its' 4K EEPROM). The module momentarily in use does an array of  small
>> (16 byte) records, each with a checksum and a 1-bit correction code.
>> The fixed sized records are ok (to avoid fragmentation) but I highly
>> doubt that a 1-bit correction will win anything with respect to faulty
>> data in an electrical r/w memory. Which are the most common cases of
>> corrupted data in the presence of the following 3 error sources?
>> - data loss due to wear stress: at the end of the lifetime, errors due
>> to this will increase, but will they come bit by bit? How reliable
>> will a cell be after it showed its' first error? Better to avoid it
>> after that?
>> - data loss due to power down while erasing/writing: I think that
>> whole words of memory will come out wrong in that case, hardly ever a
>> single bit alone.
>> - wrong data due to spikes on data/address lines: this sounds like the
>> most probable source of 1-bit errors but will be less of a problem for
>> single-chippers like the HC12. Any hints on that?
>> 
>> I am under the impression that for errors of the kind that will show
>> up in an EEPROM you will have to invest a considerable amount of error
>> correcting bits if you want to catch a significant percentage of them.
>> I will duly stand corrected in case someone has the expertise...
>> 
>> regards,
>> Mark
>> 
>> PS: the persistent memory will of course not rely on the correction
>> code but rather on the right storage strategy; the correction should
>> only offer a higher access probability for the "youngest" data.
>
>Check out this article
>
>http://www.embedded.com/showArticle.jhtml?articleID=13100883

Also check my ESP articles "Forget Me Not" and "A Version Therapy",
which cover a double buffering technique and some tips on ensuring
that your eeprom remains valid when the s/w is upgraded. 

The articles are available online atat
http://www.panelsoft.com/murphyslaw

===========================
See the User Interfaces for Embedded Systems Page 
at http://www.panelsoft.com