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What Is a Windowed Watchdog Timer (WWDT)?


A Windowed Watchdog Timer (WWDT) acts as a system supervisor that ensures normal operation of the software. If the software execution takes longer or shorter than expected, the WWDT issues a reset of the microcontroller (MCU). A WWDT offers an upper and lower time threshold whereas a Watchdog Timer (WDT) offers only single threshold.

Why Is WWDT a Used?


Even after extensive tests and careful validation, an MCU can still get locked up while executing its program code. There are many reasons that can trigger this unexpected event including something as simple as a temperature change or noise spike from the power supply. A proper implementation of the WDT can save the system from failure in these unfortunate cases, acting as a last line of defense by simply issuing a reset of the MCU.

How Does the WWDT Work in PIC® and AVR® MCUs?


The WWDT is a built-in hardware module for most modern PIC and AVR MCUs. The WWDT uses the internal oscillator as clock source and offers a variable time-out period and window sizes. When the application starts, the WWDT starts counting to its pre-programmed time. User-written code clears the WWDT within the pre-defined time window, and the process starts over again. If the timer is not cleared during the pre-defined time window, then the WWDT issues a reset of the MCU.

8-bit Microcontrollers with a Windowed Watch Dog Timer

View All Parametrics
Product Status Windowed Watch Dog Timer (WWDT) Watch Dog Timers (WDT)
ATMEGA1608 In Production Yes
ATMEGA1609 In Production Yes
ATmega164PA In Production Yes
ATmega168PB In Production Yes
ATmega169PA In Production Yes
ATmega16A In Production Yes
ATmega16U2 In Production Yes
ATmega16U4 In Production Yes
ATmega2561 In Production Yes
ATMEGA3208 In Production Yes
ATMEGA3209 In Production Yes
ATmega324PA In Production Yes
ATmega324PB In Production Yes
ATmega328P In Production Yes
ATmega328PB In Production Yes
ATmega32A In Production Yes
ATmega32U2 In Production Yes
ATmega32U4 In Production Yes
ATMEGA4808 In Production Yes
ATMEGA4809 In Production Yes Yes
ATmega48A In Production Yes
ATmega48PA In Production Yes
ATmega48PB In Production Yes
ATmega644PA In Production Yes
ATmega64A In Production Yes
ATMEGA808 In Production Yes
ATMEGA809 In Production Yes
ATtiny102 In Production Yes
ATtiny104 In Production Yes
ATtiny13A In Production Yes
ATTINY1604 In Production Yes Yes
ATTINY1606 In Production Yes Yes
ATTINY1607 In Production Yes Yes
ATTINY1614 In Production Yes Yes
ATTINY1616 In Production Yes Yes
ATTINY1617 In Production Yes Yes
ATTINY1624 In Production Yes Yes
ATTINY1626 In Production Yes Yes
ATTINY1627 In Production Yes Yes
ATTINY202 In Production Yes
ATTINY204 In Production Yes
ATTINY212 In Production Yes
ATTINY214 In Production Yes
ATTINY3216 In Production Yes
ATTINY3217 In Production Yes
ATTINY402 In Production Yes
ATTINY404 In Production Yes
ATTINY406 In Production Yes
ATTINY412 In Production Yes
ATTINY414 In Production Yes Yes
ATTINY416 In Production Yes Yes
ATTINY417 In Production Yes Yes
ATtiny44A In Production Yes
ATtiny48 In Production Yes
ATTINY804 In Production Yes
ATTINY806 In Production Yes
ATTINY807 In Production Yes Yes
ATTINY814 In Production Yes Yes
ATTINY816 In Production Yes Yes
ATTINY817 In Production Yes Yes
AVR128DA28 In Production Yes Yes
AVR128DA32 In Production Yes Yes
AVR128DA48 In Production Yes Yes
AVR128DA64 In Production Yes Yes
AVR128DB28 In Production Yes Yes
AVR128DB32 In Production Yes Yes
AVR128DB48 In Production Yes Yes
AVR128DB64 In Production Yes Yes
AVR32DA28 In Production Yes Yes
AVR32DA32 In Production Yes Yes
AVR32DA48 In Production Yes Yes
AVR64DA28 In Production Yes Yes
AVR64DA32 In Production Yes Yes
AVR64DA48 In Production Yes Yes
AVR64DA64 In Production Yes Yes
PIC12F1571 In Production Yes
PIC12F1572 In Production Yes
PIC12F1612 In Production Yes
PIC16F15213 In Production No Yes
PIC16F15214 In Production No Yes
PIC16F15223 In Production No Yes
PIC16F15224 In Production No Yes
PIC16F15225 In Production No Yes
PIC16F15243 In Production No Yes
PIC16F15244 In Production No Yes
PIC16F15245 In Production No Yes
PIC16F15256 In Production No Yes
PIC16F15274 In Production No Yes
PIC16F15275 In Production No Yes
PIC16F15276 In Production No Yes
PIC16F15313 In Production Yes Yes
PIC16F15323 In Production Yes Yes
PIC16F15324 In Production Yes Yes
PIC16F15325 In Production Yes Yes
PIC16F15344 In Production Yes Yes
PIC16F15345 In Production Yes Yes
PIC16F15354 In Production Yes Yes
PIC16F15355 In Production Yes Yes
PIC16F15356 In Production Yes Yes
PIC16F15375 In Production Yes
PIC16F15376 In Production Yes Yes
PIC16F15385 In Production Yes Yes
PIC16F15386 In Production Yes Yes
PIC16F18313 In Production Yes
PIC16F18323 In Production Yes
PIC16F18324 In Production Yes
PIC16F18325 In Production Yes
PIC16F18326 In Production Yes
PIC16F18344 In Production Yes
PIC16F18345 In Production Yes
PIC16F18346 In Production Yes No
PIC16F18424 In Production Yes No
PIC16F18425 In Production Yes No
PIC16F18426 In Production Yes No
PIC16F18444 In Production Yes No
PIC16F18445 In Production Yes No
PIC16F18446 In Production Yes No
PIC16F18455 In Production Yes No
PIC16F18456 In Production Yes No
PIC16F18854 In Production Yes Yes
PIC16F18855 In Production Yes Yes
PIC16F18856 In Production Yes Yes
PIC16F18857 In Production Yes Yes
PIC16F18875 In Production Yes Yes
PIC16F18876 In Production Yes Yes
PIC16F18877 In Production Yes Yes
PIC16F19155 In Production Yes No
PIC16F19156 In Production Yes Yes
PIC16F19175 In Production Yes Yes
PIC16F19176 In Production Yes Yes
PIC16F19185 In Production Yes Yes
PIC16F19186 In Production Yes Yes
PIC16F19195 In Production Yes Yes
PIC16F19196 In Production Yes Yes
PIC16F19197 In Production Yes Yes
PIC18F04Q40 In Production Yes No
PIC18F04Q41 In Production Yes No
PIC18F05Q40 In Production Yes No
PIC18F05Q41 In Production Yes No
PIC18F06Q40 In Production Yes No
PIC18F06Q41 In Production Yes No
PIC18F14Q40 In Production Yes No
PIC18F14Q41 In Production Yes No
PIC18F15Q40 In Production Yes No
PIC18F15Q41 In Production Yes No
PIC18F16Q40 In Production Yes No
PIC18F16Q41 In Production Yes No
PIC18F24K40 In Production Yes Yes
PIC18F24K42 In Production Yes Yes
PIC18F24Q10 In Production Yes Yes
PIC18F25K40 In Production Yes Yes
PIC18F25K42 In Production Yes No
PIC18F25K83 In Production Yes Yes
PIC18F25Q10 In Production Yes Yes
PIC18F25Q43 In Production Yes No
PIC18F26K40 In Production Yes Yes
PIC18F26K42 In Production Yes Yes
PIC18F26K83 In Production Yes Yes
PIC18F26Q10 In Production Yes Yes
PIC18F26Q43 In Production Yes No
PIC18F26Q83 In Production Yes Yes
PIC18F26Q84 In Production Yes Yes
PIC18F27K40 In Production Yes Yes
PIC18F27K42 In Production Yes Yes
PIC18F27Q10 In Production Yes Yes
PIC18F27Q43 In Production Yes No
PIC18F27Q83 In Production Yes Yes
PIC18F27Q84 In Production Yes Yes
PIC18F45K40 In Production Yes Yes
PIC18F45K42 In Production Yes Yes
PIC18F45Q10 In Production Yes
PIC18F45Q43 In Production Yes No
PIC18F46K40 In Production Yes Yes
PIC18F46K42 In Production Yes Yes
PIC18F46Q10 In Production Yes Yes
PIC18F46Q43 In Production Yes No
PIC18F46Q83 In Production Yes Yes
PIC18F46Q84 In Production Yes Yes
PIC18F47K40 In Production Yes Yes
PIC18F47K42 In Production Yes Yes
PIC18F47Q10 In Production Yes Yes
PIC18F47Q43 In Production Yes No
PIC18F47Q83 In Production Yes Yes
PIC18F47Q84 In Production Yes Yes
PIC18F55K42 In Production Yes Yes
PIC18F55Q43 In Production Yes No
PIC18F56Q43 In Production Yes No
PIC18F56Q83 In Production Yes Yes
PIC18F56Q84 In Production Yes Yes
PIC18F57Q43 In Production Yes No
PIC18F57Q83 In Production Yes Yes
PIC18F57Q84 In Production Yes Yes

Documentation


Application Notes