Siemens Simatic PC Panel PC 870, Equipment Manual

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Hardware Information Release 11/02
7-6
SIMATIC Panel PC 870 Computing Unit, Equipment Manual
7.4.3 Fan control
The fan control is performed by the SOM program (see above). It can be
deactivated in the BIOS SETUP (Main menu, Hardware Options submenu, Fan
Control parameter, see Chapter 5). If this is done, the fans run at maximum speed
when the temperature limit is exceeded (refer to Section 7.4.2).
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.
The watchdog is idle when you turn on the computer unit or following a HW
RESET(cold restart) – in other words, no reaction by the WD is initiated.
WD reactions
If the WD is not retriggered within the set time (by driver or SOM program), the
following reactions are triggered:
Reaction Option
Acknowledge WD –
Initiate reset on the computer unit adjustable
Send IRQ on computer unit 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!