What is the Meaning of Watchdog Timer in Microcontroller or Embedded System

August 27th, 2015

Nilesh Chaurasia

What is Watchdog Timer

Watchdog-timer is a timer which, actually reset the embedded system or microcontroller after the timeout specified completes.
To avoid the system from reset, the programmer needs to write some instructions (timer restart command) to prevent the timeout of the Watchdog timer.
In case of faulty operation, the timer restart command will not be executed and finally, the Watchdog resets the system.
Watchdog timer is used to prevent the system from faulty functioning.
Watchdog timer safeguard the system and considered as a corrective measure.

Significance or Use of the Watchdog Timer

Watchdog timer acts like the electronic watchman of the system, if identified something wrong, it will just reset the system.

How the Watchdog Timer Function

When system working properly, the watchdog timer never roll-over or expire because the execution of timer restart instruction again and again.

But if the program is stuck-up or hung somewhere, then the timer restart instruction will not be executed. Hence Watchdog timer reaches its maturity and finally, reset the system.

Warning: It is very important to note that, the programmer has to make sure that the timer must restart before reach to the watchdog delay in normal system functioning.

Figure below shows how the Watchdog timer is used to safeguard the system functioning.

what is meaning of watchdog timer in microcontroller embedded system — Fig.1 – How to implement Watchdog timer based Embedded System

Note:If there is no Watchdog timer, and the system program is trapped or stuck-up somewhere then the system behaves like halted.

Explain in Detail What is a Watchdog Timer

Restarting the watchdog is also known as a ‘KICKING’.

The purpose or role of the watchdog timer is like a watchman, as soon as the timeout signal arrives he will reset the embedded system.

Now it is the responsibility of the programmer to program the system so that before timeout the program should restart the timer again and again.

Note: Watchdog timer says the programmer that, you have to reset me continuously otherwise I will reset the whole system after reaching to my timeout. If the system stuck-up somewhere, the reset instruction execution missed and then the Watchdog timer will reset the system.

For example, 10ms is the execution time of the loop program then the programmer has to program the watchdog timer such that its timeout is higher than the 10ms.

In the computer system, there are drivers for watchdog timer device which are used for kicking it.

Final Words, What Does a Watchdog Timer Do in Any Computing Systems

Note:A watchdog timer (WDT) is a safety measure that brings the system back to life when it hangs in some trap, and not able to come out of some block of code. It is basically a device that keeps track of the program is running continuously and if not just reset the system to start from the beginning again.