atxmega128d4-mh ATMEL Corporation, atxmega128d4-mh Datasheet - Page 23

• Manufacturer Part Number: atxmega128d4-mh
• Description: 8/16-bit Xmega D4 Microcontroller
• Manufacturer: ATMEL Corporation

11.3.5
11.3.6
12. WDT - Watchdog Timer
12.1
12.2
8135F–AVR–02/10
Features
Overview
PDI reset
Software reset
The MCU can be reset through the Program and Debug Interface (PDI).
The MCU can be reset by the CPU writing to a special I/O register through a timed sequence.
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The XMEGA D4 has a Watchdog Timer (WDT). The WDT will run continuously when turned on
and if the Watchdog Timer is not reset within a software configurable time-out period, the micro-
controller will be reset. The Watchdog Reset (WDR) instruction must be run by software to reset
the WDT, and prevent microcontroller reset.
The WDT has a Window mode. In this mode the WDR instruction must be run within a specified
period called a window. Application software can set the minimum and maximum limits for this
window. If the WDR instruction is not executed inside the window limits, the microcontroller will
be reset.
A protection mechanism using a timed write sequence is implemented in order to prevent
unwanted enabling, disabling or change of WDT settings.
For maximum safety, the WDT also has an Always-on mode. This mode is enabled by program-
ming a fuse. In Always-on mode, application software can not disable the WDT.
11 selectable timeout periods, from 8 ms to 8s.
Two operation modes
Runs from the 1 kHz output of the 32 kHz Ultra Low Power oscillator
Configuration lock to prevent unwanted changes
– Standard mode
– Window mode
XMEGA D4
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