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43 Chapter 4
Figure 4.14: Display Properties dialog
4.4.5 Watchdog timer
It is important in industrial applications that control systems rarely crash,
or are capable of self-recovery if they are halted somehow. The watchdog
function is provided to reset the TREK-725 if the software crashes. There
is a countdown timer inside the watchdog function. The user’s application
program enables the watchdog timer, then regularly reloads this count-
down timer. If the user’s application program crashes, it fails to reload the
countdown timer and when the countdown timer reaches zero, the TREK-
725 is reset. The watchdog function in the TREK-725 provides eight dif-
ferent time intervals: 2 seconds, 5 seconds, 10 seconds, 30 seconds, 60
seconds, 2 minutes, 5 minutes, and 10 minutes. The “Test” button is used
to start the watchdog countdown function, and the “Enable Trigger” but-
ton is used to trigger the watchdog periodically.