CompactLogix to Modbus RTU slaves via PLC2 unprotected read MSG

I am attempting to use a ControlLogix processor and a Digi One IAP, to read from several Modbus RTU slaves(GE Multilin motor protection relays). Apparently I need to use a PLC2 unprotected read MSG instead of a SLC typed read, due to the location of the 4x registers in the GE Multilins. I have mapped an array with the mapping tool in RS5K (or so I believe). My problem thus far is configuring the MSG as a PLC2 unprotected read. I keep on getting an error that the source file type is not correct. Has anyone ever set up a MSG this way?

Thks
Adam

Welcome to the forum !

What is the precise syntax you used for the PLC-2 data address ?

Post screenshots or descriptions of exactly how you have configured the MSG instruction in RSLogix 5000.

The mapping tool is unrelated to the MSG instruction. It is only used when the controller needs to respond to a PLC/SLC message that it has received (usually over DH+, but sometimes also over DF1, Ethernet, or ControlNet).

Hi thanks!
I think that is part/all of the issue. I am not sure what the addressing structure of the PLC-2 source should look like. A] because its not actually a PLC-2 that I am trying to read from (it's a DOIAP) and B] any and all of the help files and google searches so far have not really shown me how to properly configure the MSG PLC-2 Unprotected Read instruction over ethernet.

I don't actually have the DOIAP yet, its being shipped. I am just trying to set up the code first. It may be a moot issue until I actually get the unit from Digi.

Thks Adam.

I think that the PLC-2 memory is just "offsets", instead of having data files with File Numbers and Data Types (B,N,F, etc).

Say you need to read Modbus addresses 420001 through 420101. You'd put the value "20000" in the Source Element field of the ControlLogix MSG instruction.

The Destination Element should be an INT[x] array tag. Call it "Multilin_Data".

The Destination Element does not have to be part of the PLC-2/3/5 Mapping feature in this case. In fact, I'd keep the tag out of there to avoid confusing future users. The PLC-2/3/5 mapping feature is only used by the ControlLogix when it receives a command request with one of those legacy addresses in it.

I found a doc on the PLC-2 addressing. The PLC-2 data table addressing structure is set up xxxx/xx, word/bit, 0000-17777 octal/0-17 octal.
As an offset of 0, if I try to enter 000000 to allow me to access 4x00001 it will not allow it.
It will not accept an entry of 20000...hmmmm
It WILL accept a values of 010000, 010001, 010002, 010003, 010004, 010005, 010006, 010007, 010010...
however...
not 000000

Will experiment some more...thks

Issue Solved?

Did you find a solution to this issue. I've run into the same issue where I'm try to read holding register (4x) 30001 through my DigiOne IAP in compact logix using a MSG block. Since register 30001 is N310:0 in a SLC type read, it's over the limit of N255 for a SLC Type Read according to Digi Document 90000643_A. According to this document I need to use either PLC2 or CIF Unprotected Read but I don't know what the format of the "Source Element" should be for this type of read. If I'm trying to read holding register (4X) 30001 what do I put into the source element field in my message block for a PLC2 Unprotected Read?

same issue

anyone have an answer for this?