Rockwell Automation Logix5000 Controllers Controller Information and Status Programming Manual - Manual (Page 9)

Chapter 1
Connections
A Logix5000 controller uses connections for most, but not all, of its
communication with other devices.
Term Definition
Connection A communication link between two devices, such as between a controller and an I/O
module, PanelView terminal, or another controller.
Connections are allocations of resources that provide more reliable communication
between devices than unconnected messages. The number of connections that a single
controller can have is limited.
You indirectly determine the number of connections the controller uses by configuring the
controller to communicate with other devices in the system. These communication types
use the following connections:
•
I/O modules
• Produced and consumed tags
• Program parameters
• Certain types of Message (MSG) instructions (not all types use a connection)
Requested packet
interval (RPI) The RPI specifies the period 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.
•
Typically, you configure an RPI in milliseconds (ms). The range is 0.2 ms
(200 microseconds)…750 ms.
• If a ControlNet network connects the devices, the RPI reserves a slot in the stream of
data flowing across the ControlNet network. The timing of this slot may not coincide
with the exact value of the RPI, but the control system guarantees that the data
transfers at least as often as the RPI.
Path The path describes the route that a connection takes to get to the destination.
Typically, you automatically define the path for a connection when you add the devices to
the I/O Configuration folder of the controller.
Introduction
Rockwell Automation Publication 1756-PM015F-EN-P – October 2014 9