Allen-Bradley 1756 ControlLogix - Chapter 4 Set up the Hardware.....................................................................................; Communication Format; Requested Packet Interval (RPI)

Chapter 4
Control I/O
60 Rockwell Automation Publication CNET-UM001F-EN-P - February 2018
In this example, the Logix 5000 controller uses a ControlNet communication
module in the local chassis to connect to the ControlNet network. The
distributed (remote) I/O has a ControlNet adapter to connect it to the
ControlNet network.
Figure 10 - Overview of ControlNet I/O Distribution
Make sure of the following:
• All wiring and cabling are properly connected.
• The communication driver is configured for the programming
workstation.
When you configure an I/O module, you define the RPI for the module. The
RPI specifies the interval at which data updates over a connection. For
example, an input module sends data to a controller at the RPI that you
assign to the module. Configure the RPI in milliseconds.
RPI is used only for a module that produces or consumes data. For example,
a local ControlNet communication module does not require an RPI because it
is not a data-producing member of the system, but only a bridge.
In Logix 5000 controllers, I/O values update at an interval that you configure
via the I/O configuration folder of the project. The values update
asynchronously to the execution of logic. At the specified interval, the
controller updates a value independently from the execution of logic.
When you configure a remote ControlNet communication module or an I/O
module, you choose a communication format. The chosen communication
format determines the data structure for tags associated with the module.
Many I/O modules support different formats. Each format uses a different
data structure.
The chosen communication format also determines the following:
• Direct or rack-optimized connection
• Ownership of outputs
Set Up the
Hardware
Requested Packet
Interval (RPI)
Communication
Format