Rockwell Automation 1756-XXXX ControlLogix Analog I/O Modules - Manual (Page 33)

Publication 1756-UM009C-EN-P - December 2010 33
Analog I/O Operation in the ControlLogix System Chapter 2
Multiple Owners
of Input Modules Because ‘Listening controllers’ lose their connections to modules when
communication with the owner stops, the ControlLogix system lets you define
more than one owner for input modules.
In the example below, Controller A and Controller B have both been
configured to be the owner of the input module.
When multiple controllers are configured to own the same input module, the
following events occur:
• When the controllers begin downloading configuration data, both try to
establish a connection with the input module.
• Whichever controller’s data arrives first establishes a connection.
• When the second controller’s data arrives, the module compares it to its
current configuration data (the data received and accepted from the first
controller).
– If the configuration data sent by the second controller matches the
configuration data sent by the first controller the connection is also
accepted.
– If any parameter of the second configuration data is different from
the first, the module rejects the connection; RSLogix 5000 software
alerts you to the rejected connection through an error message.
The advantage of multiple owners over a ‘Listen-only’ connection is that now
either of the controllers can lose the connection to the module and the module
will continue to operate and multicast data to the system because of the
connection maintained by the other owner-controller.
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
41056
Initial Configuration Initial Configuration
Controller A Controller B Input Module
A B