Configuring the Modbus/TCP Client

Note
Modbus/TCP configuration is only supported for PLCnext Technology targets with a firmware version 2024.6 or newer. Refer to the PLCnext Info Center regarding Modbus/TCP support for specific controllers.

Note
The Modbus Client TCP service must be enabled on the WBM page 'System Services' of the controller to configure Modbus communication.

Note
Configuring the Modbus/TCP client means describing the properties of the Modbus/TCP remote servers with which the Modbus/TCP client is communicating. Instead, the Modbus/TCP remote server configuration configures the properties of the remote server itself.

Further Info
See the topic "Modbus/TCP Configuration" for general information on Modbus/TCP.

Note
Modbus/TCP client and server devices are provided in a separate library named Modbus. In order to be able to use the Modbus/TCP devices in the project, the 'Modbus' library has to be integrated in the COMPONENTS area in the project (see the topic "Adding libraries" for details).

The configuration of the Modbus/TCP client is done using the editors available for the Modbus TCP Client PLANT node. The Modbus TCP Client node is visible in the PLANT after you have added a Modbus/TCP client device into the PLANT via the COMPONENTS.

The following editors are provided:

'Settings' editor
Provides read-only information on the Modbus/TCP device (information is read from the device description file).
'Modbus Device List' editor
As known from other field bus controllers and field bus devices configured in PLCnext Engineer, use the station editor to add Modbus/TCP devices to your configuration. See the topic "Inserting Devices/Modules in the Station Editor" how to use the editor.
The 'IP address' (IP address of the Modbus/TCP server to read data from) is automatically assigned on insertion. By default, the device gets the first free IP address within the IP range specified in the project settings ('Project' node | 'Settings' editor | 'IP subnet' category). You can edit the IP address here or in the 'Settings' editor of the server.
The 'Unit ID' (Unit ID of the Modbus/TCP server to read data from) is set to 255 by default (valid Unit IDs: 1-255). You can edit the Unit ID here or in the 'Settings' editor of the server. The 'Node ID' (read-only value) is increased by one when you add a new device ('Node ID' remains unchanged when you change the order of devices in the editor).
'Data List' editor
Use the 'Data List' editor to edit the data items of the Modbus/TCP client device. See the topic "Data Lists" how to use the editor.
'GDS Port List' editor
Use the 'GDS Port List' editor to map the IN and OUT ports of the Modbus/TCP client device to each other. See the topic "GDS Port Lists" how to use the editor.