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PLC Ethernet Module Models, Firmware & Settings affecting communications performance with ControlLogix PLCs

I am using the TOP Server Allen-Bradley suite to communicate with a ControlLogix controller. I am seeing multiple device disconnects, extremely slow communications, and all around bad performance.

As with all systems, there are multiple variables that can affect total communications performance besides software configuration:

Please verify that the ControlLogix System Overhead Timeslice is set to 25%-50% depending on how much data is being requested from the controller - the timeslice designates the percentage of processing time that the controller will dedicate to communications.

It has also been found to be vital to set the PLC Ethernet module's port speed to a fixed port speed, and NOT auto-negotiate. These settings must match between the port on the Ethernet module and the port in the switch/router to which the module is connected.  Ideally, these should be set to 100Mbps and Full Duplex on both ends of the connection.

It is also known that different models and firmware versions of 1756 Ethernet modules support different maximum packet rates, ranging from a low of 500 packets per second to a high of 25,000 packets per second when used with a 1756-L7x processor.  Please refer to Rockwell's Logix Ethernet Module Specifications for details for your hardware.

If these do not resolve the issue please contact our support line as soon as possible.