Strange EEPROM related issue

the values in the EEPROM sometimes seem to be messed up. We suspect that this is happening after powering on & powering off the system a few times repeatedly but have been unable to reproduce the issue so far. Does anyone have a clue what this might be? Would it be safer to store the data in Flash instead of in EEPROM? Any hints or pointers would be appreciated!

I have some distrust of on-chip BOR circuits.. but anyhow, have you set the BOR trip point to a voltage where operation at your clock frequency is _guaranteed_ with worst-case trip? Is it in a relatively high power mode?

How are you using the EEPROM? Is there a single structure or data set that you are writing or are you using multiple locations?

Without knowing any of the details, try using alternating storage blocks in the EEPROM and including a CRC with each block. If the system dies in the middle of an update then fall back to the other block.

Also, I seem to recall that some micros (the early AVRs maybe?) could initiate an inadvertent write to an internal EEPPROM under an unlikely but possible set of circumstances, with a recommendation that the EEPROM address register always be left pointing to an unused location. Or perhaps it was that the spurious write would be to EEPROM location

If you haven't read the errata sheets for your processor, that may be a place to start.

What kind of EEPROM? If I2C, a classic problem is violation of "bus free time" and/or "write cycle time", which are typically timed in software.

Not really, flash just opens up a different set of problems.

Leo Havmøller.

that the values in the EEPROM sometimes seem to be messed up. We suspect th= at this is happening after powering on & powering off the system a few time= s repeatedly but have been unable to reproduce the issue so far. Does anyon= e have a clue what this might be? Would it be safer to store the data in Fl= ash instead of in EEPROM? Any hints or pointers would be appreciated!

You need to make sure that you are not changing the EEPROM address while a write is in progress. What would happen if you were writing the EEPROM when the system powered down?

the values in the EEPROM sometimes seem to be messed up. We suspect that this is happening after powering on & powering off the system a few times repeatedly but have been unable to reproduce the issue so far. Does anyone have a clue what this might be? Would it be safer to store the data in Flash instead of in EEPROM? Any hints or pointers would be appreciated!

It can be a good idea to organize all the data items you want to store in EEPROM into a structure and when you write to the EEPROM always write two copies of the whole structure in succession. Each structure should include a CRC-16 computed across the structure contents. When the system wakes up read in the EEPROM data structure to local RAM for run-time usage. Check the CRC-16 if the first image and if good then use the first read copy. If the CRC-16 fails then proceed to use the 2nd copy of the stored data structure. If the CRC fails in the second access then set all your parameters to default values and wait for the user to readjust the parameter settings and result in re-write if the two data structures.

Any EEPROM usage scenaro requires the MCU to have a precise voltage monitor that asserts the hardware reset line whenever the VDD level droops down any where near or below the speced minimum operating voltage of the MCU and its associated components.