Maybe some clarification.

Section 10.3.1 in the 16F88x data sheet says:

10.3.1       USING THE DATA EEPROM
The   data   EEPROM   is   a   high-endurance,   byte
addressable  array  that  has  been  optimized  for  the
storage   of   frequently   changing   information   (e.g.,
program variables or other data that are updated often).
When variables in one section change frequently, while
variables in another section do not change, it is possible
to  exceed  the  total  number  of  write  cycles  to  the
EEPROM  (specification  D124)  without  exceeding  the
total   number   of   write   cycles   to   a   single   byte
(specifications  D120  and  D120A).  If  this  is  the  case,
then a refresh of the array must be performed. For this
reason,  variables  that  change  infrequently  (such  as
constants,  IDs,  calibration,  etc.)  should  be  stored  in
Flash program memory.

with 17.5 saying (sorry about the format):
Data EEPROM Memory
D120      ED Byte Endurance 100K 1M -          E/W   -40=B0C ? TA ? +85=B0C
D120A    ED Byte Endurance 10K 100K          -          E/W   +85=B0C ? TA ?
+125=B0C
D121      VDRW         VDD for Read/Write VMIN - 5.5 V      Using EECON1 to
read/write
VMIN =3D Minimum operating
voltage
D122      TDEW         Erase/Write Cycle Time - 5 6 ms
D123      TRETD        Characteristic Retention 40 - -          Year
Provided no other specifications
are violated
D124      TREF Number of Total Erase/Write
Cycles before Refresh(4)
1M 10M          -          E/W   -40=B0C ? TA ? +85=B0

The way that I read this was that each byte in EEPROM would last typically
1M writes (D120) and that the eeprom could have typically 10M writes (D124)
before the whole thing would need to be refreshed.

Have I got it right?

Gordon Williams



----- Original Message ----- =

From: "Gordon Williams" <gwilliams@ncf.ca>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Thursday, October 29, 2009 3:07 PM
Subject: Re: [PIC] eeprom redundant-values routines


>
> > So far as I know, reading the eeprom does NOT cause the
> > problems,  Instead, the problem is caused by many writes to one part
> > of the eeprom array.
>
> Thanks for the clarification.  By "many writes" are you talking about
> hundreds, tens of thousand.  The eeprom endurance is spec'ed at 1M writes.
>
> Gordon Williams
>
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