The watchdog

A common feature in many microcontrollers is the presence of a watchdog timer. A watchdog ensures that the system is not stuck within an endless loop or any other blocking situation within the code. This is particularly useful in bare-metal applications that rely on an event-driven loop, where calls are required not to block, and to return to the main event loop within the allowed amount of time.

The watchdog must be seen as the very last resort to recover an unresponsive system, by triggering a forced reboot regardless of the current state of execution in the CPU.

The reference platform provides one independent watchdog timer, with a counter similar to those of the generic timers, with a 12-bit granularity and a prescaler factor. The prescaler of the watchdog, however, is expressed in multiples of 2 and has a range between 4 (represented by the value 0) and 256 (value 6).

The clock source is connected to a lower-speed oscillator, through an independent branch...