Siemens PC 670 manual Watchdog WD, WD-Reaktionen, WD monitoring times TWD

Hardware Information Release 04/02

7.4.4Watchdog (WD)

Function

The watchdog monitors the execution of a program. The purpose of the WD is to report a program crashing to the user by means of different reactions.

After switching on the computing unit or after a HW-RESET (cold start) the watchdog remains in standby, i.e. no WD reaction is activated and the RUN-LED remains switched off. If the watchdog is activated (by driver or SOM program) the Run LED is green.

WD-Reaktionen

If the WD is not retriggered within the set time (by driver or SOM program), the following reactions are triggered:

Reaction	Options
RUN LED switches from green to red	Always
Acknowledge WD	Always
Initiate reset on the computing unit	Adjustable
IRQ an die Rechnereinheit absetzen	Adjustable
SOM application is displayed	Adjustable

The reactions you want to have triggered can be set by drivers or the SOM program.

WD monitoring times TWD

The monitoring times can be adjusted in increments of one second over the range from 3 to 255 seconds.

Note

If the watchdog time is modified after the watchdog has been activated – in other words, while the watchdog is running – the watchdog will be retriggered as a result!

7-8 Panel PC 670 Computing Unit, Equipment Manual