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Modbus / TCP with Modicon's Quantum PLC
Can someone explain to me what does "peer copy" mean and can it be used with Modbus / TCP

Our VFD can be a Modbus RTU, ModbusPlus or Modbus/TCP slave. One customer wants to use Quantum's Peer copy function with Modbus/TCP. Is that possible?

I have thought that the peer copy has something to do with the global data of ModbusPlus and Modbus/TCP does not have global data. Am I wrong?

Thanks for any advise


By Fernando Capelari - Schneider Electric Brasil on 28 March, 2002 - 9:29 am

No, you are right. Actually there is no global data over Modbus TCP. It will be available on may, at the next release of the Quantum TCP/IP module, which will be reference 140NOE77101/11.

In fact, Peer Cop is a Modbus Plus function that allows global data to all nodes of the network and specific data to any specific node of the network. The advantage is that you do not need to use communication blocks inside the program, it is only a table to fill in with the bits/words that you want to allocate to each node.

Nowadays you can use over Modbus TCP the function "Ethernet I/O Scanner", which is similar to the specific data function of the MB+ Peer Cop service. It is what we use with the Schneider Altivar 58 VFD over Modbus TCP/IP.

I think your customer is referring to PEER COP where I/O is mapped into memory of a PLC much like the TRAFFIC COP does on the I/O channel. I believe that PEER COP does work with Quantum PLC using Modbus/TCP over ethernet but perhaps someone from Schneider or Square D can confirm. I know that it originally was designed for MODBUS PLUS but it is a separate thing from Global Data.

Thanks for the replies.

Does anyone know which Modbus function codes are sent to the network when the PEER COP is used with Modbus/TCP?

By Robert Willis on 29 March, 2002 - 10:05 am

What is the part number of the TSX Quantum Ethernet module that you have installed??

There are currently two versions:

140NOE77100 ---- I/O Scanner Capability
140NOE77110 ---- Customized WebPage Capability

If you have the 140NOE77100 module you can configure the I/O scanner to read and write the data to your VFD. Who is the manufacture of the VFD? If it is a Tele Altivar 58 the the manual that comes with the ethernet interface has the
details of how to accomplish this.

You can download the 140NOE771xx manual from "": that will provide the specific details of how to configure the card.

The 140NOE77100 module's design provides you the ability to configure it's Modbus I/O Scanner as either a Peer Cop or Enhanced Modbus Scanner. The
determination as to which scanner is used depends on the programming package that is installed on your system. If you are presently using Modsoft, then you must configure the I/O scanner for Peer Cop operation. If you are using Concept 2.2 or ProWORX NxT 2.1 (Or higher revisions), then you can configure the I/O scanner for either Peer Cop or enhanced Modbus/TCP operation.::

Robert Willis
Square D Company
Houston, Texas

Peer cop is a global and specific data exchange tool with Modbus Plus. For Modbus TCP, the easiest way is to use either the Ethernet IO scanner or the Modbus TCP read/write register commands depending on Ethernet card being used.
I can email procedure if you provide details of Ethernet card/processor and email address.


By Stan Brown on 29 March, 2002 - 11:05 am


The modicon data table is set up as follows

Oxxxxx = digital outputs
1xxxxx = digital inputs
3xxxxx = analog input registers
4xxxxx = analog outputs,timers/counters, store words.

The peer cop command is under the configuration subcategory. When connecting devices to the
modbus or modbus plus network, the developer can use peer cop to talk directly to the data table
of the drive, given the drive has the capabilities to connect to the network.This ends the need for hardwire starts/stops, status, speed control, speed references, etc.

Think of it as a network that transfers control data rather than email.

If you need more help write me back I'll be glad to help.

Stan Brown or

Have a nice day.

It is not yet clear to me what this peer cop exactly means. I know the different Modbus protocols and communication part well, but I'm
novice in the PLC programming, so I have little bit difficulties finding the answer from all of the replies. I have basic understanding of
the Modicon PLCs, because I have used old 984 for testing our Modbus and ModbusPlus interfaces, but I have always done it using the MSTR

Our VFD's Modbus/TCP interface supports Modbus function codes 1,2,3,4,5,6,7,15,16,22 and 23. One customer wants to use the Peer Cop instead
of the MSTR block, because Peer Cop is faster. So I need to know if the Peer Cop uses one of these functions or do I have to tell them, that
they have to use the MSTR block?

Thanks for all who replied!
Sari Vallinmaki
ABB Inc., Drives & Power Products