How micro's fail?

[eem2am]

I am using a SAM3N00B microcontroller in an emergency light PCB.

We have to make provision for when the micro fails.

But when it fails, will the pins be..

1...High impedance
2...'stuck' logic high
3...'stuck' logic low
4...a combination of the above
?


SAM3N00B DATASHEET:
http://www.atmel.com/Images/doc11011.pdf

 

[(*steve*)]

Any or all of the above. And perhaps other states too.

 

[eem2am]

which is the most common/likely?

 

[(*steve*)]

It is almost impossible to say. It depends on what caused the failure.

The most common obvious failure is an output which no longer changes as it should.

However if you had an input that failed to read the correct value, how would you know?

One obvious thing is to connect each output to an input so you can physically read back what the pin is doing. If it fails to do what it should, then assert some signal (if you can).

But that's not really going to help with inputs unless you tie an output to them so you can check them, and then leave it in a high impedance state in normal operation.

What are you actually trying to do?