Function Code 4 with Momentum PLC

cjh

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• Oct 25, 2004

• #1

How do you do Function Code 4 (3x registers) with the MSTR instructions in the Momentum PLC? Or is there another instruction that will do this?

 

guest

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• Oct 26, 2004

• #2

Wow, I don't see any way to do this? I'm looking in Concept right now and I see no option for 3x registers. Seems crazy to me, there's got to be some way to do this...

 

Jim Dungar

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• Oct 26, 2004

• #3

The 984LL command MSTR can only be used with 4x registers. Peer Cop can be used to share I/O information over Modbus Plus and E-net. Concept has additional commands which are not as restrictive as MSTR.

What are you trying to accomplish?

 

Last edited: Oct 26, 2004

cjh

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• Oct 26, 2004

• #4

I'm trying to read 30000 registers from a third party device.

Is Peer Cop a function block that can be used or another mapping method?

 

Jim Dungar

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• Oct 26, 2004

• #5

Peer Cop is a mapping method that can only be used with other Schneider Electric devices.

What network are you using, Modbus Plus? What programming software/language are you using?

 

cjh

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• Oct 26, 2004

• #6

MODBUS TCP ethernet.
Concept Version 2.6. I can use any of the languages. I'm not particular to any of them.

 

Jim Dungar

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• Oct 26, 2004

• #7

I would not use MSTR nor MBP_MSTR. Look at the function blocks CREAD_REG and READ_REG.
But it still doesn't look like Schneider can access anything over Modbus TCP/IP except 4x registers.

 

cjh

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• Oct 26, 2004

• #8

Yea, I looked at those as well and I don't see any provision in those function blocks either.

That absolutely blows my mind... The makers of MODBUS only let you access 1 data type over ethernet...

Thanks for your help Jim.

 

cjh

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• Oct 27, 2004

• #9

As a follow up question:
When using the CWRITE and CREAD function blocks in the Momentum PLC, there is one parameter called "Address Field". It specifies an array of 5 elements. The first element is asking for a MBP on MET mapping table and a slot ID for the NOE module. What would you put in the word, if you are talking to a 3rd party device?

 

cjh

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• Oct 27, 2004

• #10

Never mind, figured it out.

As a FYI for those who care:
There is definitely no way to read ANY data type directly other than a 4x holding register from a third party device on MODBUS TCP when using a Momentum or Quantum PLC as the master. This means no 3x input registers, no 1x input bits and no 0x coils. Of course, if your device has logic/mapping capabilities you can map over these other data types into 4x holding registers.
I verified this with Schneider Electric.