RS logix 500 & 5000 programming for modbus communication

[srv]

Hi,

I have a doubt about configuring PLCs for modbus communication.For that do we need to add any program for mobbus configuration to the main PLC program.Is there any supporting programs like "device net tag generator" for devicenet configuration.I would like to communicate a control logix and a micrologix PLC to a server through modbus.Any body please advice me how i can do configuration program in the both Plcs.

 

[sthompson]

Hi,

I have a doubt about configuring PLCs for modbus communication.For that do we need to add any program for mobbus configuration to the main PLC program.Is there any supporting programs like "device net tag generator" for devicenet configuration.I would like to communicate a control logix and a micrologix PLC to a server through modbus.Any body please advice me how i can do configuration program in the both Plcs.

Most of the Allen Bradley PLCs do not support Modbus natively. That has started to change with the MicroLogix Line, but even there it is not universal.

Exactly which PLC Models do you wish to implement Modbus on?

Do you want to implement Modbus RTU (Serial) or Modbus TCP?

Stu....

 

[srv]

I want to communicate a control logix and a micro logix 1100 to a main server.Control logix should communicate with a TCP/IP to micro logix 1100 and micro logix 1100 with Modbus RTU ( serial) to server.Is it possible.How we can add PLC code to micro logix 1100 for modbus RTU communication

 

[sthompson]

I want to communicate a control logix and a micro logix 1100 to a main server.Control logix should communicate with a TCP/IP to micro logix 1100 and micro logix 1100 with Modbus RTU ( serial) to server.Is it possible.How we can add PLC code to micro logix 1100 for modbus RTU communication

Ok, this is the same subject you Posted before in a different thread. I would suggest you read Ken Roach's Posts there.

There shouldn't be a lot of Programming required. You could write to the ML1100 from the ControlLogix over Ethernet CIP to Data Tables. Then set up your ML1100 as a Modbus Server, and have the Main Server read the Data from the same Data Tables.

Most of the setup would be the Communications Links, and organizing the Data Tables.

I have never tried to write Data to an ML1100 from a ControlLogix, so I have no direct knowledge. However, according to AB/RA it is possible to do so.

You would have to do all your Data gathering at the ControlLogix, then set up a Message Instruction (MSG) to Write to the ML1100 over Ethernet to the Data Tables you have set up for the Data.

In the ML1100, I think all you would have to do is set up the Serial Port as a Modbus Slave. You may have to do some Data Formatting if the Main Server expects the Data in a different Format. i.e. Big Endien vs Little Endien etc.

However, as Ken Roach pointed out in your other Thread, the results may not be up to your expectations.

I still think a Modbus TCP Card in the ControlLogix would yield much better results if your Main Server would support this.

Stu....