I would like to have a status LED to make sure my microcontroller software hasn't faulted. From software, I will alternate an output so if it dies, the output will be constant. I want the status LED to blink when there's a fault instead of blinking to show there is not one. So, I need a separate circuit that will blink the LED when its input is stuck high or low.
I can come up with a circuit myself, such as an edge detector that resets a 555. However, I would like to know first, is there a name for such a circuit? Or even better, if it comes in/can be made from a single IC?
EDIT: A completely external circuit is preferred because it'd be isolated and unlikely to be affected by software changes.