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Incorporating Recovery Procedures in a Real-Time VI

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    Last Modified: January 12, 2018

    Some real-time controllers contain a built-in hardware timer known as a watchdog timer or a dead man's switch that interfaces with the embedded software application. If your real-time controller contains a watchdog timer, you can incorporate recovery procedures in your real-time VI to detect software failures and to ensure that the software process continues to execute in a defined state in case of software failures.

    What to Use

    Real-Time Watchdog Timer Nodes

    What to Do

    Create the following diagram to incorporate recovery procedures in your real-time VI.

    Customize the gray sections for your unique programming goals.

    Configure a watchdog timer object using the Watchdog Timer Configure node. The watchdog timer starts counting down as soon as the Watchdog Timer Configure node executes.

    You can define the recovery procedure in the expiration actions input of the node. In this example, the node restarts the current application on the controller when the watchdog timer expires. You also can configure the node to perform other actions in case of expiration, such as restarting the real-time controller.

    Use the Watchdog Timer Restart node to periodically reset the watchdog timer to prevent the timer from expiring and triggering the recovery procedure. If a software failure prevents the application from resetting the watchdog timer, the timer eventually expires and triggers the recovery procedure.

    Use the Watchdog Timer Clear node to reset and close the watchdog timer object. You must close the current object before using another one.

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