Datasheet

Table Of Contents

20. WDT – Watchdog Timer

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 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. The WDT will

continue operation and issue a system reset or interrupt even if the main clocks fail.

20.2 Features

• Issues a system reset if the Watchdog Timer is not cleared before its time-out period

• Early Warning interrupt generation

• Asynchronous operation from dedicated oscillator

• Two types of operation

– Normal

– Window mode

• Selectable time-out periods

– From 8 cycles to 16,384 cycles in Normal mode

– From 16 cycles to 32,768 cycles in Window mode

• Always-On capability

SAM D5x/E5x Family Data Sheet

WDT – Watchdog Timer

Datasheet

DS60001507E-page 265