Watchdog Timeout

The WDOGTO (System Watchdog Timeout) is a timer run internally within each I/O module from start-up. The following syntax is used for the Watchdog Timeout:

If the TMR Processor does not pet the module’s watchdog within the programmed time, the module adopts the shutdown mode. However this parameter adjusts the system watchdog timeout interval. It is not normally required to adjust this parameter unless the system is very large or to allow certain tests to be performed. The timeout value is entered in milliseconds, and a value of zero disables the timeout.

For the Watchdog timeout, it is recommended to poll the module at least four times at the normal scan time within the timeout, taking scheduled polling into account. For example, if the current scan time is 200 milliseconds and the module is set for scheduled polling at every 5th scan, then the timeout needs to be set to 200 x 5 x 4 = 4000ms minimum. Ensure that the timeout is still safe. For example, the timeout is less than half the process safety time.