Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
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Analog I/O Module Operation in the ControlLogix System
Chapter 1
Output Modules in a Local Chassis
When an output module resides in a local chassis (see
), it receives data almost immediately after the owner-controller sends it.
The analog output module broadcasts data using Multicast as its connection
method in a local chassis.
Output Modules in a Remote Chassis
When an output module resides in a remote chassis (see
), and is connected to the local chassis via an EtherNet/IP network, the
following events occur for the controller to send data to the output module.
1.
The controller broadcasts data to its local chassis at one of the
following events:
•
RPI value
•
A programmed Immediate Output (IOT) instruction is executed.
An IOT sends data immediately and resets the RPI timer.
2.
The 1756 ControlLogix EtherNet/IP communication module in the local
chassis broadcasts the data over the EtherNet/IP network.
3.
After receiving the output data, the 1756 ControlLogix EtherNet/IP
communication in the remote chassis broadcasts the data to its backplane,
that is, the remote chassis.
4.
The output module receives the data almost immediately after it is
broadcast to the remote chassis backplane.
Broadcast Method
The analog output module broadcasts data by using one of the following
connection methods:
•
Multicast - Data is sent to all network devices at once
•
Unicast - Data is sent to a specific controller depending on the module’s
configuration
For more information on guidelines for specifying RPI rates, see the Logix5000
Controllers Design Considerations Reference Manual, publication
