Omron WS02-9094G - V1.0 Operation Manual page 99

Configuring the Master
Unit Behaviour upon PLC
Mode Changes
Note
Auto-CLEAR behaviour
84
• The behaviour of the Master Unit in case an error occurs in one of the
slave devices allocated to the Master Unit.
• The method of I/O data mapping.
The figure below shows the Master Setup tab.
The user can select the way the Unit will behave if the PLC mode is changed.
The default settings are:
• Set the Unit's operational mode to CLEAR (i.e. set all outputs to a safe
state), when switching the PLC CPU to PROGRAM mode.
• Set the Unit's operational mode to OPERATE (i.e. start I/O data
exchange with the slave devices), when switching the PLC CPU to RUN /
MONITOR mode.
1. The advantage of this setting is that the user does not have program the
starting of the network. The disadvantage is that the moment at which the
network is started is out of direct control of the PLC user program. I/O data
exchange is started, while the program may still be initializing its memory.
Depending on the application this may have unexpected effects.
2. To avoid potential problems at startup, it is recommended to set the net-
work operational mode to 'keep current mode' in case the PLC mode in
case the PLC mode changes to RUN / MONITOR and to set the operation-
al mode to CLEAR in case the PLC mode changes to PROGRAM. This re-
quires the PLC user program to switch the network to OPERATE, after
startup. Refer to section 3-6-2 Changing PROFIBUS Mode of the Master
Unit for a programming example.
3. A side effect of the default settings can be that the network is started right
after downloading the parameters to the CS1/CJ1W-PRM21 PROFIBUS
Master Unit. After downloading the parameters, the CS1/CJ1W-PRM21
Master DTM will restart the Unit and switch the PLC mode back from PRO-
GRAM mode to the mode it had before downloading. This can be RUN /
MONITOR mode.
The Auto-CLEAR behaviour defines how the CS1/CJ1W-PRM21 PROFIBUS
Master Unit will behave in case one of its allocated slave devices fails during
I/O data exchange. This option can be enabled if the application in which the
Master Unit is used warrants safety precautions to be taken to prevent unex-
pected behaviour of the application.
If Auto-CLEAR has been enabled, the Master Unit will automatically transition
to the CLEAR state and set the allocated slave device outputs to the safe
Section 3-4