| Target Support Package™ FM5 | |
Target Support Package FM5/ MPC555 Driver Library
The Watchdog block lets you set the time-out period for the watchdog timer. The watchdog timer is a safety feature that is used to monitor correct behavior of the application. The timer is loaded with an initial value and counts down from this value. If the timer ever reaches zero, a watchdog time-out occurs, forcing a processor reset.
In normal operation, the is serviced at a regular interval (each model step) by the application code; this occurs at a higher frequency than the Watchdog Timeout parameter period. Therefore the counter never reaches zero and a processor reset is never triggered.
In the event of a software failure that causes the application to lock up, the watchdog timer will not be serviced. Therefore, it will time out when the counter reaches zero. This in turn causes a processor reset, which restarts the application.
You do not need to include a Watchdog block in your model unless you want to change the Watchdog Timeout parameter period to a value other than the default. By default, the watchdog timer is enabled and the time-out period is set to the largest possible value, which is several seconds, depending on system frequency.
Note that the Watchdog block has neither input nor output connections.
The Watchdog Timeout period must be set to a value that is larger than the fastest sample rate in the system, because this is the rate at which the watchdog timer is serviced. To set the Watchdog Timeout period, place a Watchdog block anywhere in the model and open its dialog box.
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