Schneider M580 Modbus TCP with slave ID

Hi all,

Sorry to seek help here as I am run out of idea.

recently i need to use my PLC(Schneider M580-Unitypro) as Modbus TCP Master to read slave devices using read_var block, this is due to the IO scanning feature does not support modbus FC4(Read input register 3x).

However, in M580 PLC, i cannot figure out a way to put slave ID on the ADDMX block. And the PLC is sending out command with slave ID 0.
The slave devices does not support modbus broadcast station and will not response to request that slave ID is 0, hence the communication cannot establish.

Just wonder anyone has experience to use READ_VAR and ADDMX with a slave ID and IP address instead of just IP address?

Any other suggestion is also appreciate. Thanks in advance!

Welcome to forum


ADDM '0.0.3{192.168.0.2}TCP.MBS' is for TCP modbus.
ADDM '0.0.3{192.168.0.2}11' is Modbus serial over TCP (slave 11).


ADDM block can be used for local rack (M340 and M580 CPU)
(0.0.3 is rack / slot address for M340 / M580 CPU's own Ethernet port.

ADDX block is for local or Remote (CRA) rack if M580 CPU is used.

Lare said:

ADDM '0.0.3{192.168.0.2}11' is Modbus serial over TCP (slave 11).

Click to expand...

This is not Modbus RTU over TCP, right? But rather simple Modbus TCP with UnitID = 11.

Is it possible to configure Modbus RTU over TCP? Not Modbus TCP, but Modbus RTU over TCP.

Differences are explained by Schneider here:




I have a simple Ethernet - RS-485 converter connected to M580 and would like to read data from Modbus RTU devices connected to this converter.