Listen-only mode, Multiple owners of input modules, Listen-only mode multiple owners of input modules – Rockwell Automation 1756-OF8H ControlLogix HART Analog I/O Modules User Manual
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Rockwell Automation Publication 1756-UM533C-EN-P - February 2011
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ControlLogix Module Operation Chapter 3
Listen-only Mode
Any controller in the system can listen to the data from any I/O module (that is,
input data or ‘echoed’ output data) even if the controller does not own the
module. In other words, the controller does not have to own a module’s
configuration data to listen to it.
During the I/O configuration process, you can specify a ‘Listen-Only’ mode in
the Connection box of the Module Definition section on the Module Properties
dialog box. See
for more details.
Choosing a ‘Listen-Only’ mode option lets the controller and module establish
communication without the controller sending any configuration data. In this
instance, another controller owns the module being listened to.
Multiple Owners of Input
Modules
Because listening controllers lose their connections to modules when
communication with the owner stop, the ControlLogix system lets you define
more than one owner for input modules.
In the example, Controller A and Controller B have both been configured to be
the owner of the input module.
Figure 3 - Multiple Owners with Identical Configuration Data
IMPORTANT
If a ‘Listen-Only’ connection is being used by any controller to the
module, any connections over the Ethernet network cannot use the
Unicast option. See the Unicast box on
.
The ‘Listen-Only’ controller continues to receive multicast data
from the I/O module as long as a connection between an
owner-controller and I/O module is maintained.
If the connection between all owner-controllers and the module is
broken, the module stops multicasting data and connections to all
Listening controllers are also broken.
IMPORTANT
Only input modules can have multiple owners. If multiple owners
are connected to the same input module, they must maintain
identical configuration for that module.
Input Module
Configuration
Data
Xxxxx
Xxxxx
Xxxxx
Input Module
Configuration
Data
Xxxxx
Xxxxx
Xxxxx
Initial Configuration
Initial Configuration
Controller A
Controller B
Input Module
CTR A
CTR B
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