52 Rockwell Automation Publication 5069-UM004A-EN-P - April 2019
Chapter 1 Digital Module Operation in a Control System
Local Compact 5000 I/O Digital Output Modules
Local Compact 5000 I/O digital output modules receive output data from a
controller and send data to the controller. The data exchange occurs over the
system backplane.
Controller to Local Output Module Data Transmission
The controller broadcasts data to its local backplane at one of the following:
•RPI
• An IOT instruction is executed.
Based on the RPI rate and the length of the controller program scan, the
output module can receive and echo data multiple times during one program
scan.
When the RPI is less than the program scan length, the output channels can
change values multiple times during a program scan. The owner-controller
does not depend on the program scan to complete to send data.
The following events occur when the controller sends data to a local
Compact 5000 I/O output module.
1. The controller sends data to system backplane at the RPI or when an
IOT instruction is executed.
2. The local output module receives the data from the system backplane
and behaves as dictated by its configuration.
IMPORTANT An IOT instruction sends data to the output module immediately,
and resets the RPI timer.
Compact GuardLogix 5380 controllers cannot send data when
an IOT instruction is executed. You cannot use IOT instructions in
safety programs.
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