15.1 Overview

The Watchdog Timer (WDT) is a system function for monitoring correct program operation. It makes it possible to recover from error situations such as runaway or deadlocked code. The WDT is configured to a predefined time-out period, and is constantly running when enabled. If the WDT is not cleared within the time-out period, it will issue a system Reset. An early-warning interrupt is available to indicate an upcoming Watchdog Time-out condition.

The Window mode makes it possible to define a time slot (or window) inside the total time-out period during which the WDT must be cleared. If the WDT is cleared outside this window, either too early or too late, a system Reset will be issued. Compared to the Normal mode, this can also catch situations where a code error causes the WDT to be cleared frequently.

When enabled, the WDT will run in Active mode and all Sleep modes. It is asynchronous and runs from a CPU-independent clock source. The WDT will continue operation and issue a system Reset or interrupt even if the main clocks fail.