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Functions
9.3 Watchdog (WD)
The temperature error is retained in memory until temperatures have fallen below the
thresholds and are reset by one of the following measures:
● Check whether the ambient temperature limit has been exceeded, or whether the filter is
● Acknowledgment of the error message by the monitoring software
● Restart of the device
9.3
Watchdog (WD)
Function
The watchdog monitors program execution and reports a program crash to the user by
means of various reactions.
After POWER ON of the PC, or after a HW RESET (cold restart), the watchdog is in idle
state, that is, a reaction of the WD is not triggered and the Watchdog LED is switched off.
The Watchdog LED is lit green when the watchdog is enabled (by means of the driver, SOM
program or DiagMonitor software.)
WD reactions
If the WD is not triggered again within the set time (by the driver or SOM program), the
following reactions are initiated:
Reaction
Watchdog LED changeover from green to red
Trigger a PC reset
SIMATIC monitoring software is activated
WD monitoring times (TWD)
The monitoring times can be set in increments of one second within a range from 3 to 255
seconds.
Note
The watchdog is retriggered if the monitoring time is changed at the active watchdog (that is
while the watchdog is running)!
58
soiled.
Option
None
Configurable
None
SIMATIC Rack PC 847B
Operating Instructions, 06/2008, A5E02203168-01
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