Use the watchdog timer to set critical outputs to a safe state if software fails, a system crashes, or the application loses communication with the USB-6453.

Enabling the watchdog timer sets the USB-6453 to go to a safe state you define if the USB-6453 does not receive a watchdog reset software command within an amount of time you specify. You can set a watchdog timer for all digital I/O lines.

The USB-6453 will remain in the defined safe state until you disarm it. The signal that indicates an expired watchdog timer continues to assert until you disarm the watchdog timer. After the watchdog timer expires, the USB-6453 ignores any digital writes until you disarm the watchdog timer.

Note When the watchdog timer is enabled and the computer enters a fault condition, ports that are set to tri-state remain tri-stated and do not go to user-defined safe states.

You can set the watchdog timer timeout period to specify the amount of time that must elapse before the watchdog timer expires. You can configure the counter on the watchdog timer up to (232 - 1) × 8 ns (approximately 34 seconds) before it expires.