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unstable eeprom data on microcontrollers

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Amin Khorsandi

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hello everybody
I always have problem by eeprom data storage on avr microcontrollers. I saved a data on eeprom of a microcontroller but after a few days the data had changed spontaneously.
there was no reason for that change. it's sound like a noise effect on micro. is it possible?:-?
what shoud I do with that?
I'll appreciate if you help me. ;-)
 

I think,there could be an internal wiring fault within the IC that is causing the contents of the EEPROM to get changed..Could you please give some more details on how exactly is it happening.? Is it like...you are saving some value on EEPROM and after some time,when you check it,its value has changed?Can you share an instance of this phenomenon..?
PS:Can you share the details of the AVR microcontroller you are using?
 
I used an Atmega32. that project was created for an LED writer. I put text data on eeprom. and writer began to work. after a few days a character failed. I checked eeprom, a byte or eeprom had changed. a few days later this happened to another byte. programing the eeprom solved the problem temporarily. but eeprom data changed with no pattern or reasom.
I'm sure about not changing data by program. microcontroller was not allowed to change it's data.
probably it is related to noise effect. but I'm not sure.
 

Although I don't know about the Atmega32, I have experienced the same problem on PIC chips. The problem of the eeprom data changing was due to the power supply rise and fall times, in my case due to switch bounce on the on off switch. The fix in my case was to add a large capacitor across the 5V supply.
 
thanks for your help. I'm still waiting for other experiences if anybody has.
 

I found this on avr datasheets:
EEPROM data corrupt ion can easi ly be avoided by following this design
recommendation:
Keep the AVR RESET active (low) during periods of insufficient power supply voltage.
This can be done by enabling the internal Brown-out Detector (BOD). If the
detection level of the internal BOD does not match the needed detection level, an
external low VCC Reset Protection circuit can be used. If a reset occurs while a write
operation is in progress, the write operation will be completed provided that the
power supply voltage is sufficient.
 
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