20.1 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 too frequently.

When enabled, the WDT will run in active mode and any sleep modes, except Hibernate, Backup and OFF sleep mode. It is asynchronous and runs from a CPU-independent clock source (OSCULP32K). The WDT will continue operation and issue a system reset or interrupt even if the main clocks fail.