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Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
Chapter 1
Analog I/O Module Operation in the ControlLogix System
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.
During the I/O configuration process, you can specify a Listen-Only connection.
For more information on Connection options when configuring your system, see
.
When you choose a Listen-Only connection, the controller and module establish
communication without the configuration data being sent by the controller. In
this instance, another controller owns the I/O module.
IMPORTANT
The Listen-Only controller receives data from the I/O module as long as an
owning connection between a controller and I/O module is maintained.
If the connection between all owner-controllers and the module is broken,
the module stops sending data and connections to all `Listening
controllers’ are also broken.
In addition, multicast Listen Only connections require at least one multicast
owning connection to be active.