Modbus TCP Channel Tag

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The Modbus TCP Channel Tag Channel Tag Icon provides a TCP/IP SCADA communication channel to Modbus Devices.

Configuration Properties

The Modbus TCP Channel Tag supports the properties of the Active Channel Tag plus these properties:

Host WSTRING 1.0 The network address of the Modbus Device. This can be any of the following:
  • An IP Address. For example:
  • A node name. For example: MODBUSDEVICE
  • A fully qualified domain name. For example:
Port WSTRING 1.0 The port number used for communications. The default port number for Modbus is 502.
Protocol USINT 1.0 The variant of Modbus TCP to use:
  1. Modbus TCP
  2. Modbus RTU over TCP
For most applications use the default: Modbus TCP.
TransactionIdMin UINT 3.89 The minimum value to use for the Modbus TCP Transaction Id.
TransactionIdMax UINT 3.89 The maximum value to use for the Modbus TCP Transaction Id.

TransactionIdMin and TransactionIdMax Properties

Each Modbus TCP message sent by Fernhill SCADA includes a 16-bit Transaction Id. Fernhill SCADA uses the Transaction Id to match responses with requests. By default, Fernhill SCADA uses the full range of Transaction Id values 0 - 65535.

If you want to restrict Fernhill SCADA to use a limited range of Transaction Id values, enter the range in the TransactionIdMin and TransactionIdMax Properties.

Tag Commands

The Modbus TCP/IP Channel Tag supports the tag commands of the Modbus Channel Tag.

Example Configuration

This is an example of a channel configured to support Modbus TCP protocol to host :

ProtocolModbus TCP

Relationships to Other Tag Types

The Modbus TCP/IP Channel Tag builds on the features of these tag types:

Further Information

Modbus Protocol

To learn more about the Modbus Protocol.

Active Channel Tag

To learn about the properties common to all active channels.

Modbus serial channel

To learn about Modbus Serial Channels.

Modbus Device Tag

To learn about Modbus Device Tags that can be associated with Modbus TCP Channel Tags.

Alarm Conditions

To learn about abnormal conditions in SCADA applications.


For the meaning of terms used in Fernhill SCADA.