How does the DDC Suite treat the watchdog?
The FBox "Initialisation 2.0" from the DDC Suite FBox library has a "WD" input. When activated, this will close the onboard watchdog relay of the PCD (and open it if an error on the PCD occurs or if the user program takes more than 250 ms to be executed).
If the input WD (see below in the screenshot) is activated, the onboard WatchDog relay stays switched on (closed) until an internal error is detected. The WD relay is turned off and stays deactivated until the error has been reset via FBox parameter "diagnostic history" and if no error occurs immediately again.
An error detected once will stay active after power down/up. This means that the WD relay stays open until a "reset" will be done.
This mechanism can e.g. be used for switching on an alarm signal (horn, lamp) or to indicate to another PCD to take over some functionality in case of error (a kind of redundancy).
- If the WatchDog relay should only be opened in case the CPU cycle time exceeds 250 ms (as it has been the common when not working with the DDC Suite), the FBox "Hardware WatchDog" from the standard FBox family "Special functions" has to be used.
In that case the "WD" input of DDC Suite FBox "Init" will be overwritten by the feature of this FBox.
- The description of this mechanism has not been present in the help of the DDC Suite until version 2.5.101 (for PG5 1.4) and 2.6.101 (for PG5 2.0).
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PG5 2.0 / DDC Suite
Last update: 25.05.2015 01:14
First release: 26.03.2010 16:01