ATXMEGA8E5 datasheet(33/153 Pages) MICROCHIP

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DS40002059A-page 33

ATxmega32E5/16E5/8E5

14. WDT – Watchdog Timer

14.1 Features



Issues a device reset if the timer is not reset before its timeout period

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Asynchronous operation from dedicated oscillator

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1kHz output of the 32kHz ultra low power oscillator

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11 selectable timeout periods, from 8ms to 8s

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Two operation modes:

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Normal mode

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Window mode

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Configuration lock to prevent unwanted changes

14.2 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 a timer, configured to a predefined timeout period,

and is constantly running when enabled. If the WDT is not reset within the timeout period, it will issue a microcontroller

reset. The WDT is reset by executing the WDR (watchdog timer reset) instruction from the application code.

The window mode makes it possible to define a time slot or window inside the total timeout period during which WDT must

be reset. If the WDT is reset 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 constant WDR execution.

The WDT will run in active mode and all sleep modes, if enabled. It is asynchronous, runs from a CPU-independent clock

source, and will continue to operate to issue a system reset even if the main clocks fail.

The configuration change protection mechanism ensures that the WDT settings cannot be changed by accident. For

increased safety, a fuse for locking the WDT settings is also available.

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