Siemens PC 670 - Manual (Page 140)

Hardware Information Release 04/02
7-8 Panel PC 670 Computing Unit, Equipment Manual
7.4.4 Watchdog (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!