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Hi Andre.

The first thing I would check is EEPROM_write code particularly there is =
"magic"
sequence
and interrupts have to be disabled (for sure) during it. And just review =
that
code in common
sense (I was using Microchip example awhile ago but ended up rewriting it=
 don't
remember
details why thought, interrupts?)

2nd place I would verify is EEPROM_read code to make sure you always read=
 the
same
(and return what you are expecting) every time you call it to read EEPROM.
(interrupts?)

Next thing I would check is anybody else calls EEPROM_write and EEPROM_re=
ad
(because some other rarely happening bugs in the code) besides the partie=
s you
expect
the only users of EEPROM_read/write.

Another thing I would verify is anybody else could corrupt RAM data buffe=
r which
you
use to write the data to EEPROM or read from it.

And so on.. :)
=A0

WBR Dmitriy.
=A0
=A0

Andre Abelian wrote:

> Hi to all,
>
> I am working with PIC18F4550 and I store 8 bytes of data in Data EEPROM=
. On
> Startup pic loads those value and the only time data eeprom values may
> change
> Is when user will press and hold 2 buttons combination then it will upd=
ate
> data
> EEPROM. I started having problem loosing data EEPROM values intermitten=
tly I
> decided
> To have a copy of each byte saved some where else in Data EEPROM as a c=
opy
> to compare
> With and later I went to customer " in Texas Dallas" I found that Data
> EEPROM
> First 8 bytes are getting changed all random locations. This is USB dev=
ice
> they only restart the whole
> System using small PC. After reading Data EEPROM values I found that
> Copy of same data is always stable and after I moved the location to wh=
ere
> the copy bytes are
> The system started working well. My question is how is it possible that=
 data
> eeprom
> Being effect no matter what they do externally. I checked the USB power=
 line
> was
> Clean ground was ok no thing else to check it is only USB device.
> Unfortunately we only had one device
> To work with. I use CCS C compiler known to be reliable compiler I use =
it
> very long time.
> Any Idea or experience or feedback about data EEPROM getting change wil=
l
> appreciate.
> I know this kind of question is hard to answer but you guys may see it =
one
> day good to know
> The reason.
>
> Thanks
>
> Andre
>
> --
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