Configuration Changes In An Input Module With Multiple Owners - Allen-Bradley 1756-IA8D User Manual

Configuration Changes in an
Input Module with Multiple
Owners
Initial Configuration
Input Module
Configuration
Data
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Zzzzz
Xxxxx
As soon as a controller receives its user program, it will try to establish a
connection with the input module. A connection is established with the
controller whose configuration data arrives first. When the second controller's
configuration data arrives, the module compares it to its current configuration
data, which was received and accepted from the first controller.
If the configuration data sent by the second controller matches the data sent by
the first controller, that connection is also accepted. If any parameter of the
second configuration data is different from the first, the module rejects the
connection and the user is informed by an error in the software or via program
logic.
The advantage of multiple owners over a Listen-only connection is that either of
the controllers can break the connection to the module, and the module will
continue to operate and multicast data to the system through the connection
maintained by the other controller.
You must be careful when changing an input module's configuration data in a
multiple owner scenario. If the configuration data is changed in owner A and sent
to the module, that configuration data is accepted as the new configuration for
the module. Owner B will continue to listen unaware that any changes have been
made in the module's behavior, as illustrated below.
Figure 7 - Module Configuration Changes with Multiple Owners
A message in RSLogix 5000 software alerts you to the possibility of a multiple
IMPORTANT
owner-controller situation and lets you inhibit the connection before changing
the module's configuration. When changing the configuration for a module
with multiple owners, we recommend the connection be inhibited.
Rockwell Automation Publication 1756-UM058G-EN-P - November 2012
Digital I/O Operation in the ControlLogix System
A Input B
A B
Chapter 2
Initial Configuration
Input Module
Configuration
Data
Xxxxx
Xxxxx
Xxxxx
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