29.3.3.5 WDT Clock Monitor

A clock from an oscillator independent of CLK_WDT is used to detect a failure of CLK_WDT. The WDT is an important safety mechanism in a Functional Safety system, and a failure of CLK_WDT would render the WDT unable to fulfill its function. If the CLK_WDT monitor detects that CLK_WDT has failed, the monitor will immediately request entry to a safe state, implemented by a Machine Check Reset request.

The WDTMON bit field in the CTRLB register controls the behavior of the WDT clock monitor feature in sleep. This read-only bit field is initialized from a fuse value during system initialization.