Modbus Advanced Outstations

[bwill1177]

Is there a way to create multiple Modbus TCP Advanced Outstations with the same Modbus slave address but different IP addresses?  My setup is a single Modbus TCP Channel and a single Mdobus Outstation Set.  When I try to add devices with Modbus address 1 and different IP addresses I get an error that I cannot have duplicate Modbus addresses. It seems to me that the check for duplicate addresses should be IP + Modbus address, not just Modbus address.  Is there any way around this?

Any help would be greatly appreciated.

[Khaled_Hamed]

Hello Bwill,

On same serial link you definitely cannot have duplicate slave modbus IDs.

When you say different IP addresses I can assume you have gateway for each slave device, and that shall work. Please let me know more details of the system, that controlled and the devices you are using to be able to help you more.

[bwill1177]

Hi Khaled,

I'm attempting to configure multiple Modbus devices using the Modbus TCP protocol, not serial.  These devices are all uniquely addressed via IP address, however, most of them have a default Modbus address of 1.  When I attempt to configure them in GeoSCADA, I get an error that they cannot have the same Modbus address, even though they have unique IP addresses. 

These devices are a mix of power quality meters, pump protection relays, and others. They are currently communicating to an existing SCADA system (not GeoSCADA).  We are migrating to GeoSCADA and thus need to figure out how to configure them to work with the Modbus - Advanced driver.  Thanks for your help!

[kjwageto]

Here's a few settings to check/try:

1. On the Modbus - Advanced Direct Outstation Set, 'Modbus' tab:
   • Set Address: Make sure it's a unique address and NOT set to '1'
2. On the Modbus - Advanced Direct Channel, 'Connection' tab:
   • Connection Type: Network
   • TCP/IP Type: TCP
   • Merge Connections: Checked
   • Independent Connections: Checked

[Rich-C]

Hello Support,

I am trying to configure a device though modbus outstation, modbus set and modbus channel. My outstation is showing Healthy Multidrop but my channel is showing disconnected. I have tried different configurations on the channel and no luck getting the channel to connect. My current setting for channel are:

Connection Tab:                                             

Network

TCP

Merge Connections unchecked

Independent connections checked.

Modbus Tab:

Protocal type: RTU

Scan Parameters:

Line speed: 19200

Thanks. 

[geoffpatton]

@Rich-CI would start a new post with your question and give some more detail. There are a few types of outstations and channels you can select so it might be that one or both of that you selected aren't really the ones you want. Right click on them and select View to see the type.

[Rich-C]

Ok I will start a new post thanks. Will update question with more detail. 

[TAS1]

BWills question was never answered, and I have exactly the same question. 

To clarify, it is the Advanced Modbus "Direct Outstation" Modbus tab, Address Field. 

If the same address is used in more than one "Direct Outstation", even if the IP address is different, the outstation will go to error and not work.

Modbus TCP devices generally use address 1 or 255, and changing is usually not possible. You cannot have a unique address for every outstation.

Schneider have broken the simple Modbus driver (performance is extremely bad) and recommend everyone use the advanced modbus driver, but with this address limitation, it is unusable for multiple modbus outstations.

Is this maybe a problem with just this version (2021). 

Please can somebody clear up this issue? I must be missing something.

[AndrewScott · Accepted solution]

When using the Modbus TCP protocol the "Unique Modbus Addressing" setting on the outstation set defines whether or not the Modbus addresses of the outstations within the set must be unique, see Specify Whether a Set Uses Unique Modbus Addressing.

When this setting is disabled, the address must still be unique for each IP address.