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'PIC12CE518 EEPROM'
1999\10\13@150220 by Gary Schroeder

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I am using a pic12ce518 in back-up alarms that go on utility vehicles.
Some vehicles cause the on board EEPROM to be erased. What might be the
cause of and solution to this problem?
Thanks in advance.
Gary

1999\10\13@184349 by Matthew Fries

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It's probably me erasing your EEPROMS. :)

I live next door to a garage where vehicles for the city are repaired.
It's deserted during the day, but at night there are front-end loaders and
garbage trucks abcking up all over the place. All night long during the
week I hear "Beep Beep Beep"... Drives me nuts!

More than once I have had an urge to sneak in there on a weekend and rip
the speaker wires from those alarms, or maybe just stuff a sock in the
horn...



On Wed, 13 Oct 1999, Gary Schroeder wrote:

> I am using a pic12ce518 in back-up alarms that go on utility vehicles.
> Some vehicles cause the on board EEPROM to be erased. What might be the
> cause of and solution to this problem?
> Thanks in advance.
> Gary
>

1999\10\13@191050 by jeff

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A couple things that may be part of your EEPROM corruption problem:

- Do you provide protection against load dumps (24-50V+) and other
 transients?
- Does your circuit run properly over the normal operating range of
 the battery (generally 9-16V). Do you have any built-in detection
 of under/over battery voltage? Does the code enter a safe mode
 when this condition arises?
- Are the lines going to your serial EEPROM short and guard banded?
- Do you keep checksums for both the EEPROM data and the data that
 is to be written?

I've had problems with EEPROM corruption before. It can generally
be traced back to either noise on the serial lines or the MCU
getting "lost", especially during normal EEPROM access.

Jeff

1999\10\14@115838 by Gary Schroeder

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> -----Original Message-----
> From: Jeff Hunsinger [SMTP:spam_OUTjeffTakeThisOuTspamSILICONENGINES-LTD.COM]
> Sent: Wednesday, October 13, 1999 4:10 PM
> Subject:      Re: PIC12CE518 EEPROM
>
>
       [Gary Schroeder] Jeff, Thank-you for your response
> A couple things that may be part of your EEPROM corruption problem:
>
> - Do you provide protection against load dumps (24-50V+) and other
>   transients?
>
       [Gary Schroeder]  I use a very simple voltage regulator that
includes a transient
       voltage suppressor

> - Does your circuit run properly over the normal operating range of
>   the battery (generally 9-16V).
>
       [Gary Schroeder] Yes.

>  Do you have any built-in detection
>   of under/over battery voltage? Does the code enter a safe mode
>   when this condition arises?
>
       [Gary Schroeder]  I am using brown out protection circuitry.
When the alarm
       1st turns on, it reads a value from its EEPROM and uses this
value to control the
       pitch of the alarm. I use no code that reacts to under/over
battery voltage. When the EEPROM
       is erased the alarm has an extremely low pitch. I can not
reproduce this failure with my power
       supply in the lab. It only happens on certain electric vehicles.
If I take a failed alarm to the lab
       and power it up, it continues to fail. I am assuming the code is
behaving O.K., it's just that some
       type of noise erased the EEPROM value.

       Also, I have added code so that if the EEPROM read fails, a
nominal pitch controlling value is used
       in place of the EEPROM value so that the alarm will sound at a
decent pitch.


> - Are the lines going to your serial EEPROM short and guard banded?
>
>
       [Gary Schroeder]   the PIC12CE518 has an on board EEPROM.
       What is guard banded?


> - Do you keep checksums for both the EEPROM data and the data that
>   is to be written?
>
       [Gary Schroeder]  I did not know that you could have checksums
for EEPROM data.
       How do you obtain these checksums and how do you use them?

> I've had problems with EEPROM corruption before. It can generally
> be traced back to either noise on the serial lines or the MCU
> getting "lost", especially during normal EEPROM access.
>
       [Gary Schroeder] Again, I think the code is acting O.K., it's
that some kind of noise erased the
       EEPROM. I suspect the solution will be better protection for the
PIC against spikes. I guess the problem is getting to the EEPROM through
the Vdd pin. Or could other pins be allowing some signal to get to the
EEPROM?
> Jeff

1999\10\14@121928 by jamesp

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Gary,

You say these are in electric vehicles.  Is it possible that
they are in a place and position such that high currents that
operate these vehicles are causing very strong electric
fields, and thereby, erasing the EEPROM?  If you read the
EEPROM, is the data all zeros by chance?  Or is it a mixture
of ones and zeros?  If it's all zeros, you may want to try
either moving the PIC or placing it inside some sort of Faraday
shield to potect it from the electric fields that are no doubt
present.   Just a thought.

                                          Regards,

                                             Jim



>> {Original Message removed}

1999\10\22@103506 by Gary Schroeder

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Date:    Thu, 14 Oct 1999 11:18:53 -600
>From:    Mr and Mrs James Paul <.....jamespKILLspamspam@spam@INTERTEX.NET>
>Subject: Re: PIC12CE518 EEPROM

>Gary,

>You say these are in electric vehicles.  Is it possible that
>they are in a place and position such that high currents that
>operate these vehicles are causing very strong electric
>fields, and thereby, erasing the EEPROM?  If you read the
>EEPROM, is the data all zeros by chance?  Or is it a mixture
>of ones and zeros?  If it's all zeros, you may want to try
>either moving the PIC or placing it inside some sort of Faraday
>shield to potect it from the electric fields that are no doubt
>present.   Just a thought.

                                      >    Regards,
>
>                                             Jim
------------------------------
Jim,

Thank-you for your response. I hadn't thought about electric fields
erasing the EEPROM.

>If you read the EEPROM, is the data all zeros by chance?  Or is it a
mixture
>of ones and zeros?

Are you saying that all zeros is evidence of E field erasure and a mix
of ones and zeros is not?
I feel fairly certain that the EEPROM is erased to contain all zeros or
some value close to that.
I have seen no evidence of randomness appearing in the EEPROM.

I think the EEPROM erasure problem may at least in part be coming from a
situation where the PIC is reset a number of times in rapid successcion
at a very low(brownout) voltage.

Gary


'PIC12CE518 EEPROM'
2000\02\08@160159 by Larry G. Nelson Sr.
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I did a bit of design for systems in vehicles including transit busses and
the power specs are lousy. If you look at what you need to design for it is
a wonder anything cheap works at all. Spikes are all over the place even
directly across the battery when things like breaks are released or air
conditioner compressors cycle. Spikes and surges last a while so there is a
lot of energy to handle. Power is probably your problem and the problems
will vary vehicle to vehicle.


At 10:57 AM 10/14/99 -0500, you wrote:
>> {Original Message removed}

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