4 PLC configuration
4.4 Task monitoring by watchdog
80 Modular PLCs XControl: XC-104-…, XC-204-…, XC-303-… 01/23 MN050005EN Eaton.com
If the processing time of the task exceeds the interval time, the end of the
second interval time is awaited until the task is restarted.
￫
Watchdog inactive.
The watchdog interrupts the program processing if the processing time of
the task exceeds the watchdog time.
Furthermore, the frequency (sensitivity) can be set, which the number of
exceeds allows. In this case the outputs of the PLC are switched off and the
user program is set to the “Halt” state. Afterwards, the user program must
be reset with RESET.
Configuring a watchdog
You can select the following settings in the task configuration:
• Watchdog on/off
• Watchdog time
• Watchdog sensitivity.
These settings apply for time controlled and event controlled tasks.
Watchdog active
The watchdog is started at the commencement of every processing cycle
and reset again at the end of the task.
If the processing time is longer than the watchdog time (sensitivity = 1) –
e.g. with a continuous loop in a program – the watchdog becomes active. If
the processing cycle is shorter than the watchdog time, the watchdog is not
activated.
￫
If the watchdog is deactivated, there will be no task moni-
toring!
CAUTION
If you want to parameterize a task without a Watchdog or want
to deactivate the Watchdog at a later time, all the outputs which
have been accessed up to this time can continue to remain
active. This is the case for example, when the task can't be
ended due to a continuous loop (programming error) and/or
missing end condition (stepping condition). The outputs con-
tinue to retain their “High potential” until the operating mode is
changed from RUN to STOP or until the control voltage for the
outputs is switched off.
￫
The following rule applies for definition of the watchdog
time with several tasks: each watchdog time must be lon-
ger than the sum of task interval times.
To Next Page
Loading...
