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PICList Thread
'[PIC]: eeprom loses data on high ambient temeratur'
2005\06\24@015917 by Buehler, Martin

picon face
i have a pic based device in my car (16f872) which is always on.

this device has it's configuration stored in the internal eeprom of the
pic.

when it's cold out there, everything works fine, but as soon as it gets
really hot in summer, the eeprom loses some bytes of it's configuration
(usually addresses 0 and 1).
the code, running, never writes to any address of the eeprom. only a
read access then and now.

has anyone seen this before?

tino

2005\06\24@044753 by Francois Robbertze

flavicon
face
What is really hot?

Measure the temperature and if it is more than the spec for the PIC try to
move the PIC somewhere cooler or add cooling...


> when it's cold out there, everything works fine, but as soon as it gets
> really hot in summer, the eeprom loses some bytes of it's configuration

regards

Francois

2005\06\24@063037 by Buehler, Martin

picon face
temp is expected to go up to 50'C, but problems start at about 40'C

tino

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>{Original Message removed}

2005\06\24@080715 by Michael Rigby-Jones

picon face


>-----Original Message-----
>From: spam_OUTpiclist-bouncesTakeThisOuTspammit.edu [.....piclist-bouncesKILLspamspam@spam@mit.edu]
>Sent: 24 June 2005 06:59
>To: Microcontroller discussion list - Public.
>Subject: [PIC]: eeprom loses data on high ambient temerature
>
>
>i have a pic based device in my car (16f872) which is always on.
>
>this device has it's configuration stored in the internal
>eeprom of the pic.
>
>when it's cold out there, everything works fine, but as soon
>as it gets really hot in summer, the eeprom loses some bytes
>of it's configuration (usually addresses 0 and 1). the code,
>running, never writes to any address of the eeprom. only a
>read access then and now.
>
>has anyone seen this before?

Yes, I had a nightmare with a whole batch of 18F devices that would read 0x00 from any location above a certain temperature.  Correct operation was restored at lower temperatures unless a write was attempted at the higher temperature where the EEPROM would be corrupted.

Check the erratas for the part.

Regards

Mike

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2005\06\24@085144 by Buehler, Martin

picon face
in the silicon errata of this device, the eeprom is mentioned nowhere.

tino

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>{Original Message removed}

2005\06\24@175021 by Richard Prosser

picon face
Voltage, Temperature & time are the killers.
A combination of all three is worst.
Do you have brown-out protection and have significant protection
against voltage spikes & induced transients? Automotive power supplies
are notoriously noisy.

Can you periodically refresh the eeprom - i.e. just read a value &
write it back. Shouldn't exceed the endurance spec if you only do it
once a week or month.
If it's a temperature problem it may help.

And at worst it will tell you if it makes things better or worse.

Richard P



On 24/06/05, Buehler, Martin <Martin.BuehlerspamKILLspamkeymile.com> wrote:
> in the silicon errata of this device, the eeprom is mentioned nowhere.
>
> tino
>
> ************************************************************************
> ******************************
>
>
> >{Original Message removed}

2005\06\27@024213 by Buehler, Martin

picon face
i'm not sure if this will help...

on the first release of the software, eeprom data was read about once a
second. the result was, that eeprom data got lost several times a week
during summertime.

so i modified the code in a way, that eeprom data is only read on
startup, and data is transferred to ram. then, during program execution,
only data in ram is accessed.
like that, eeprom data is only accessed when the pic has to restart
after a brownout or disconnection.
this keeps the whole thing alive for usually a few weeks.

what puzzles me a bit is, that only the value, stored in eeprom address
0/1 is affected, while the other configuration data seems to be firmly
stored.

tino

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>{Original Message removed}

2005\06\27@075954 by olin piclist

face picon face
Buehler, Martin wrote:
> on the first release of the software, eeprom data was read about once a
> second. the result was, that eeprom data got lost several times a week
> during summertime.

Reading EEPROM is not supposed to effect its retention life.

{Quote hidden}

I think you have a bug where ERPROM is actually being written to when you
don't think it is.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\06\27@121110 by Andre Abelian

flavicon
face

Buehler,

is your pic extended temperature rated? does it have E letter end of 16f872?
if not that is the problem if yes how high does your temperature go?
is it over 125c?

Andre





Buehler, Martin wrote:

{Quote hidden}

>>--

2005\06\27@154813 by Andre Abelian

flavicon
face
Olin,

also based on my passed experience any pic part possible to run up to 125c
and under high temperature range it can loose some of it's data. it is
very important to know
what temperature range are we talking about and what part without
knowing all
this we are just shooting in the air.  I even applied 150c heat to pic
micro no thing
happened microchip parts are bullet proof extremely reliable.

Andre





Olin Lathrop wrote:

{Quote hidden}

2005\06\28@023006 by Buehler, Martin

picon face
andre
the pic is commercial temp range, but 'high temperature' is extremely
relative. i don't think that it goes above 50'C, as it's mounted under
the seat of my car.
tino

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>{Original Message removed}

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