On Fri, 17 Dec 2004, Michael Rigby-Jones wrote:
> 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.

I thought I understood the refresh requirement, but I guess I was
unclear about the cycle limit.  The way I read the datasheet was that if
I refreshed the EEPROM before the cycle limit, it would basically reset
the cycle count to zero.

However, it would appear that this is mistaken.  The cycle limit is a
"hard" limit.  Is this correct?  For example, if the data sheet says
that the cycle limit before refresh is 1M cycles, then the EEPROM can
_only_ handle 1M cycles before it starts to fail.

So, in my application where the EEPROM value is updated once every two
seconds, I would see a failure rate after approx. 23 days.

  1M cycles / ((30 cycles/min) * 60min/hour * 24hour/day) =~ 23 days

Is my understanding of how the EEPROM work correct now?  There is no way
for an EEPROM to work "forever"?

Thank you for your time.
	-- Robert

-- 
Robert James Kaes
WormBytes Consulting and Contracting
http://www.wormbytes.ca/
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