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Great Watchdog Timers For Embedded Systems (2016)
Watchdog timers can be surprisingly hard to get right. This page shows the right ways to design the hardware and firmware.
This makes a lot of sense, since any software failure that causes the stack pointer to go odd will crash the code, and a further exception-handling interrupt of any sort would drive the part into a "double bus fault". A bit of research showed that their system's watchdog properly drove the CPU's reset signal, and the code then recognized a warm boot, going directly to the application with no indication to the users that the time-out had occurred. A pair of design rules leads to decent WDTs: kick the dog only after your code has done several unrelated good things, and make sure that erratic execution streams that wander into your watchdog routine won't issue incorrect tickles.
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