Re: Flash retention in uC at higher temps, experience?

Joerg wrote:

> One could add some code so it re-flashes itself once in a while, that's 
> another option here. However, the device cannot lose power during that 
> brief period or it'll be really toast. So that would require large 
> enough electrolytics and some pre-regulator voltage monitoring. The 
> latter would require a relayout, bigger ECO and all that. Not a VP of 
> Engineering's favorite path, usually.

If the flash is big enough, you could copy the program to an unused memory
area and back again the next cycle. Then the only critial moment is
writing
the switchover. But should be no problem, if you can monitor the supply
voltage and if you can guarantee, that it remains over the flash limit for
the time needed to write the switchover bytes.

What do you think of MRAM for critial applications? It's a bit expensive,
but they claim data retention of minimum 20 years and unlimited number of
writes. It is even used in a satellite:

http://www.eetimes.com/showArticle.jhtml?articleID=206900226
http://www.freescale.com/files/microcontrollers/doc/data_sheet/MR2A16A.pdf

-- 
Frank Buss, fb@[EMAIL PROTECTED]
 http://www.it4-systems.de