GE 9030 CPU364 & Modbus/TCP

12brich

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• Apr 13, 2005

• #1

Does anyone know if this GE9030 Ethernet CPU is capable of responding to Modbus/TCP messages? I know the CMM321 does but not sure about the CPU. Thanks.

 

RussB

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• Apr 14, 2005

• #2

Yes it does.

 

cjh

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• Apr 29, 2005

• #3

Really? Does the CPU374 also support MODBUS TCP directly? How do you make that work? I can't see anything in the manuals or help on how to do this?

 

RussB

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• Apr 29, 2005

• #4

Sorry, I am wrong.
The current release of the CPU364 and CPU374 can be Modbus TCP/IP Clients through the COMM_REQ (gfk-1541) a future version of the CPU374 will offer the Server side as well, but it will be *new* hardware.
You are right.
The IC693CMM321 is a Modbus TCP/IP Server inherently.

 

12brich

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• Apr 29, 2005

• #5

GE 9030 CPU364 and Modbus/TCP

So let me clarify, does this CPU364 respond to a Modbus TCP request from a client such as Wonderware or Intellution? Yes or No?

The earlier answer from RusB was YES.

 

RussB

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• Apr 29, 2005

• #6

The later answer from RussB was:

The current release of the CPU364 and CPU374 can be Modbus TCP/IP Clients through the COMM_REQ (gfk-1541) a future version of the CPU374 will offer the Server side as well

Click to expand...

I would interpret this as a No, but the CPU374 can initiate communications to the WonderWhere if it can respond to the CPU374 Client as a Server.

 

cjh

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• May 2, 2005

• #7

I did a search in the GFK-1541 and didn't find anything on MODBUS TCP.
Do you have to create your own MODBUS packet to put on top of the TCP/IP and then send out? Or is the PLC supposed to create the packet for you?
Or is this one of those hidden features that I am not figuring out...

 

12brich

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• May 2, 2005

• #8

cjh - The CMM321 will respond to Modbus TCP queries from a client such as SCADA computer. This requires no additional programming at the PLC level. You just need to know the correct mapping (slightly different than the CMM311 Modbus RTU which is almost a 1 to 1 relationship).

If you want to configure the CMM321 to be a TCP client, you need to do COMREQs and a whole bunch of ladders to fabricate Modbus commands very similar to the Modbus RTU Master Mode. This is job security for me hah hah!

 

cjh

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• May 2, 2005

• #9

Actually, I was talking about sending MODBUS TCP queries straight out of the ethernet port on the CPU374 without using a CMM321.

Looks to me you have to actually create the commands, which is pretty easy with MODBUS TCP (no CRC to calculate!).

 

12brich

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• May 2, 2005

• #10

cjh - I haven't worked with any CPU374 to date simply because it's so expensive. I was told that it's quite similar to CPU364. I've used COM_REQs as Modbus RTU master via CPU363 and you are right, CRC calc is done via a selection (very easy). I am almost certain that the COM_REQ calls between CPU363 and CPU374 resemble each other.