ATXMEGA32D4-CU View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATXMEGA32D4-CU

8/16-bit Atmel XMEGA D4 Microcontroller

Atmel Corporation 

XMEGA D4

12. WDT – Watchdog Timer

12.1 Features

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

• Asynchronous operation from dedicated oscillator

• 1kHz output of the 32kHz ultra low power oscillator

• 11 selectable timeout periods, from 8ms to 8s

• Two operation modes:

– Normal mode

– Window mode

• Configuration lock to prevent unwanted changes

12.2 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 sit-

uations 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.

27

8135L–AVR–06/12

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