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All of the Do-more controllers
contain a hardware watchdog timer that is used to put the controller into
a safe mode if the operating system ever stops running for more than 2
seconds. Configuring the desired mode of operation for the hardware watchdog
time is done through the following two system-defined BIT locations:
$HwWatchdogMode (ST24) - Hardware Watchdog Time Mode
If this BIT location is OFF
the controller will execute a warm-reboot in an attempt to return to an
operational state. Each time this process happens the controller will
add an entry to the System Log detailing the time the reboot occurred.
$WatchdogReboot (ST13) will
also be set ON to programmatically indicate that a watchdog-induced reboot
of the controller has occurred.
If this BIT location is ON
the controller will NOT execute a warm-reboot, it will remain in the shutdown
state with all eight of the LEDs glowing red.
$DisableHwWdog (ST25)
- Enable/Disable Hardware Watchdog Timer
If this bit location is OFF,
the hardware watchdog timer is enabled, and will operate according to
the state of $HwWatchdogMode (ST24)
If this BIT location is ON,
the hardware watchdog timer is disabled, meaning that the hardware will
not do anything if the operating system stops operating.
Note: if the hardware watchdog
timer is disabled, and the operating system stops responding, the reset
line on the backplane will be asserted, which will cause the I/O modules
in the base to revert to their reset state, which typically is OFF for
discrete outputs, a value of 0 for analog outputs, the CTRIO/2 modules
will transition out of RUN mode, and ERM/100 modules will write their
remote outputs to OFF or 0 as appropriate.
Note:
DIP switch #2 is also used to disable the hardware watchdog timer. Follow this link for details on the DIP
switches on the Do-more Controller.
Note:
Do-more controllers also have a Software Watchdog Timer
that is used to put the controller into STOP mode if the controller scan
time exceeds a preset time limit. Follow
this link for details on Configuring the Software Watchdog Timer.
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