Re: [avr-chat] Bootloader stops working

[Bjarne Laursen]

The brownout should ideed be used as Ian Caddy says.
We had the exactly same problem, only we could not turn on the brownout 
detection, because the device should be operated on battery at a lower 
voltage than the brownout will allow, but was allowed for the device (I 
think it was a Mega163)

It seems that the processor could make abitrary jump when the voltage 
was to low.

There is a 4 cycle window after writing SPMCR, where the write 
instructions can be used. This window should be used to verify that a 
programming really is allowed, by testing some global variable set far 
away in the program. This will make it more unlikely that a random jump 
into the code will change the flash.
I think that will have to be in asembler.

At least that cured our problem.

-Bjarne Laursen, RoseTechnology A/S