View Full Version : Function Code 4 with Momentum PLC
October 25th, 2004, 02:21 PM
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?
October 26th, 2004, 05:49 AM
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...
October 26th, 2004, 12:29 PM
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?
October 26th, 2004, 01:03 PM
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?
October 26th, 2004, 02:25 PM
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?
October 26th, 2004, 02:31 PM
MODBUS TCP ethernet.
Concept Version 2.6. I can use any of the languages. I'm not particular to any of them.
October 26th, 2004, 04:22 PM
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.
October 26th, 2004, 07:08 PM
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.
October 27th, 2004, 08:45 AM
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?
October 27th, 2004, 02:25 PM
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.