Siemens SIMATIC Box PC 820, Manual

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Box PC 820 / PC FI45 V2, Manual
A5E00051531-03
2.11.4 Watchdog (WD)
Function
The watchdog monitors the program execution. The watchdog has the task of
informing the user about different reactions to a program crash.
When you switch on your PC, or when you execute a cold restart (HW RESET) the
watchdog remains in its quiet state, that means that it does not trigger any reaction
and the RUN LEDs remain dark. If the watchdog is actve, this is indicated by the green
RUN LED (via driver or SOM program).
Watchdog Reactions
If the watchdog is not triggered within a preset time interval (by driver or SOM
program), the following reactions occur:
Reaction Option
RUN LED changes from GREEN to RED always
Canceling WD always
Initiating of PC reset can be set
Transmitting IRQ to PC can be set
Reactions can be configured with the driver or SOM program.
Watchdog Monitoring Times TWD
Monitoring times are set in steps (from 3 to 255) in the configuration register.
Note
If you modify the WD time after the Watchdog has been activated (that is, during
Watchdog execution), the Watchdog is retriggered!
2.11.5 SW Interfaces
Overview
The monitoring function can be called up by driver or SOM program. The included
driver and the functions of the SOM program are described in the documentation.
You can find this documentation on the included CD Documentation and Drivers.
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