24.
WDT – Watchdog Timer
24.1. 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.
24.2. 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
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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