..... will, indeed tell you that things are going awry.

However, what guarantee do you have that the uC will not emit any signals when 'going dead' ?

Nobody will have any trouble to stop writing on an early power fail interrupt, but, as far as I can see, the REAL problem is "what comes out of the micro when it goes into reset".

I'd even suggest that instead of read after write, you connect the 'early' supervisor for the BBRAM to an interrupt, then you will not need read after write. That way you have a fully protected BBRAM AND an "early power fail interrupt". Yes, you can have your cake and eat it too.

This is slowly coming back from the dusty archives in my DNA computer.

Erik