Watchdog Timers

Watchdog timers are a hardware feature that you can use to detect a failure in the software controlling the device. Software failures could include a system crash or a loop rate that is slower than you intend. To use a watchdog timer, you must use a watchdog timer task. When you create a watchdog timer task, you specify the timeout value for the watchdog timer and a set of expiration states for digital output physical channels on the device. The channels go to those expiration states if the watchdog timer expires.

Your application must continuously reset the watchdog timer to prevent it from expiring. For example, if you have a digital I/O application, and you expect a loop in the application to acquire and analyze data 10 times per second, you should set the watchdog timer to expire in 100 ms and reset the timer inside the digital I/O loop. If the loop does not execute once every 100 ms, the watchdog timer expires and the device goes into the expired state. You must then clear the expiration or reset the device.

Also, you can use the Expiration Trigger to cause the watchdog timer to expire. Set the timeout of the watchdog timer task to -1 to disable expiration due to timeout if you want the Expiration Trigger to be the only mechanism to cause expiration.