132 Rockwell Automation Publication 1769-UM021I-EN-P - May 2018
Chapter 6 Communicate over Networks
Quality of Service (QoS) and I/O Module Connections
CompactLogix 5370 controllers support Quality of Service (QoS) technology.
QoS lets the controller prioritize EtherNet/IP network traffic. By default, the
CompactLogix 5370 controllers are QoS-enabled. QoS can be disabled by
configuring a message instruction in the Logix Designer application.
Some EtherNet/IP devices do not support QoS technology unless the
firmware of the device is updated to a required minimum firmware revision
level. For example, the ControlLogix® 1756-ENBT communication module
must use firmware revision 4.005 or later to support QoS technology.
To make sure communication between CompactLogix 5370 controllers and
I/O modules are maintained, verify that the EtherNet/IP devices use the
minimum firmware revision level of the product that is required to support
QoS technology.
For more information on the following, see Rockwell Automation
Knowledgebase Tech Note 66325 (the document is available at
http://www.rockwellautomation.com/knowledgebase/
):
• Minimum firmware revision levels of EtherNet IP devices to support
QoS technology
• Enable/disable QoS.
EtherNet/IP Network Connections
CompactLogix 5370 controllers use connections to manage communication
on the EtherNet/IP network. A connection is a point-to-point communication
mechanism that is used to transfer data between a transmitter and a receiver.
Connections can be logical or physical.
You indirectly determine the number of connections the controller uses by
configuring the controller to communicate with other devices in the system.
Connections are allocations of resources that provide more reliable
communication between devices than unconnected messages.
All EtherNet/IP connections are unscheduled. An unscheduled connection is a
message transfer between controllers that the requested packet interval (RPI)
or the program, such as a MSG instruction, triggers. Unscheduled messaging
lets you send and receive data when needed.
Tab le 6
lists information for CompactLogix 5370 controllers.
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