ATMEGA 2561 losing first page of flash

Hi all,

I am using ATMega 2561 processors in my data loggers. So far, I was happy with the devices. However, in the series of devices, that were delivered last year to me, I have encounterd the problem, that after a power off / power on sequence the data loggers do not start up anymore.

I searched and found, that the first page ( = 256 bytes) of flash memory is overwritten by $FF, i.e. the page is erased. So, the first 256 bytes of the program are missing..

I have absolutely NO idea what the reason for this is. I can reproduce it on one device by switching in off and on again for five to ten times - then all of a sudden the first page is erased.

Any ideas for the reason of this phenomen? Can I do something to prevent it?

Thanks for any help, Michael

Hello Michael,

it would be helpful if you compare these two types of ASM files generated by the
two different Optimiser versions. Maybe this is not a real problem of the Opti but
the operation speed of the two program versions may differ heavily in some parts.

rolf

Hello Michael,

if there is a startup problem maybe SUTx and BODLEVELx can help.

rolf

Hello Rolf,

you were right, it is not an Optimizer error. Finally I solved the problem: I inserted a mDelay(300) before initializing the Ports, the ADC registers, the ACSR and the Soft I2C of the ATMega. It is the second command after a power up now. That seems to solve the problem. Small thing, big issue.

But why the first Flash Page of the µP got erased, that is still a mystery to me. Quite a rough behaviour - and strange, that the little delay keeps the optimized programs from doing it.

Anyway, I am glad, that the problem is gone.

Thank you; Michael