Rockwell Automation Publication 5094-UM001C-EN-P - April 2019 35
Digital I/O Module Operation in a Logix 5000 Control System Chapter 1
Listen Only Mode
Any controller in the system can listen to the data from an I/O module. An
owner-controller, as described in Ownership
on page 22, exchanges data with
digital I/O modules.
Other controllers can use a Listen Only connection with the digital I/O module.
In this case, the ‘listening’ controller can only listen to input data or ‘echoed’
output data. The listening controller does not own the module configuration or
exchange other data with the module.
During the I/O configuration process, you can specify a Listen Only connection.
For more information on Connection options, see
Module Definition on
page 94.
IMPORTANT Remember the following:
• The Listen Only Mode applies only to standard I/O modules.
• If a controller uses a Listen Only connection, the connection must use the
Multicast option. In this case, all other connections to the module, for
example, the connection of the owner-controller, must also use the
Multicast option.
• If a controller attempts to use a Listen Only connection to a module but
the owner-controller connection uses the Unicast option, the attempt at
a Listen Only connection fails.
The ‘Listen Only’ controller receives data from the module as long as a
connection between an owner-controller and module is maintained.
• If the connection between an owner-controller and the module is
broken, the module stops sending data and connections to all ‘listening
controllers’ are also broken.
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