Create Modbus TCP data points

Modbus TCP data points represent the individual Modbus values of a Modbus TCP device. Within logic groups, they are used via the Modbus TCP Value Input and Modbus TCP Value Output logic elements.

A new data point is created by clicking the gray area with the plus sign (+).

New data points are automatically assigned the first available address for the currently selected Unit ID.

In addition, data points can be copied, deleted individually, or selected using multiple selection and deleted together.

General

• Name
  Enter a descriptive name for the data point.

• Description
  This text field can be used to enter a more detailed description or additional information about the data point.

• Data Type
  Select the data type of the Modbus register.

  The following data types are available:

  • Float

  • Integer

  • Unsigned Integer

  • String

  The selected data type determines how received and transmitted values are interpreted.

Register Settings

This section is used to configure the basic parameters for accessing the Modbus register.

• Unit ID
  Specifies the device address of the Modbus participant. The Unit ID is used to address the corresponding participant within Modbus communication.

• Register Type
  Select the register type to be accessed.

  The following register types are available:

  • Holding Register

  • Input Register

  • Coil

  • Discrete Input

  The register type determines, among other things, whether a value can be read and/or written.

  For Coil and Discrete Input, only the Bool data type with a size of 1 bit is permitted.

  For Holding Register and Input Register, numeric data types as well as the String data type are available.

  When using the String data type, a size between 1 and 250 bytes can be specified.

• Address
  Defines the register address accessed by this data point.

  Valid values range from 0 to 65535.

  The combination of Unit ID and register address must be unique within a Modbus TCP device.

  Note

  Depending on the manufacturer, register addressing may be 0-based or 1-based.

  Refer to the documentation of the respective Modbus device.

• Polling Interval in Seconds
  This option determines whether the data point uses the default polling interval of the associated Modbus TCP device or an individual polling interval.

  • If the option is enabled, the data point automatically uses the default polling interval configured for the Modbus TCP device.

  • If the option is disabled, an individual polling interval in seconds can be specified for this data point.

  This allows individual data points to be polled more or less frequently, independently of the default interval.

  Note

  A shorter polling interval allows values to be updated more quickly, but also increases the communication load between the LOGIKEDITOR and the Modbus TCP device.

Editing Data Points in Use

If a Modbus TCP data point is used in an active logic group, certain properties cannot be changed.

The affected fields are disabled in the configuration and marked with a corresponding note.

This may apply, for example, to the following properties:

• Name

• Data Type

• Register Type

To edit these properties, the logic group in which the data point is used must first be deactivated.

Management

Add

Click the gray area with the plus sign (+) to create a new Modbus TCP data point.

Copy

Use the copy icon to duplicate the selected Modbus TCP data point.

The copied data point is created as a new entry and receives the prefix Copy of … in its name.

When copying, all settings of the original data point are retained. This also includes the configured register address.

Because the combination of Unit ID and register address must be unique within a Modbus TCP device, the copied data point is initially marked as invalid.

Delete

Use the trash can icon to remove the selected Modbus TCP data point.

Before deletion, the LOGIKEDITOR checks whether the data point is used within logic groups.

• If the data point is used in an active online logic group, it cannot be deleted.

• If the data point is used only in a working copy, it can be deleted. However, this affects the corresponding logic groups.

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