Modbus Client Read

Read data from Modbus server

Since R2024b

• 

Libraries:
Industrial Communication Toolbox / Modbus

Description

The Modbus Client Read block reads data from one or more registers on a Modbus^® TCP/IP or serial server.

Each output port returns data from a corresponding register specified in the Registers parameter of the block. The data at the output ports is of size 1-by-N, where N corresponds to the number of consecutive registers to read specified in the Registers table.

Note

You need a license for Industrial Communication Toolbox™ and Simulink^® to use this block.

Note

You must connect the Modbus Client Read block to a Modbus TCP/IP or serial server. You can create the client to connect to the Modbus TCP/IP or serial server using the Modbus pane in the Configuration Parameters dialog box of the model. You must add at least one Modbus Client Read or Modbus Client Write block in the model to enable this pane. For more information, see Configure Modbus Client in Simulink.

Other Supported Features

The Modbus Client Read block supports the use of Simulink accelerator and rapid accelerator modes. You can speed up the execution of Simulink models by using these modes. For more information on these simulation modes, see Acceleration (Simulink).

Examples

Control Water pH Remotely Using Modbus Client Blocks in Simulink

Use the Modbus Client Read and Modbus Client Write blocks in Simulink® to read and write sensor data from a Modbus server to regulate the pH level in a water treatment plant.

• Since R2024b
• Open Live Script

Ports

Output

Reg_x — Current values of registers

vector

Values read from Modbus TCP/IP or serial server. The number of output ports (x) corresponds to the number of rows you add in the Registers parameter. The data at each port is of size 1-by-N, where N corresponds to the number of consecutive registers to read. The value of N is specified in the Count field of the Registers parameter. The block reads the values from N consecutive registers starting with the register address specified in the Address field of the Registers parameter.

Dependencies

To enable this port, specify one or more registers in the Registers parameter.

Data Types: double

Parameters

Client — Select Modbus client

drop-down list

Select the Modbus client to associate with the block. The block updates the Connection endpoint parameter once you select a client.

• To add the clients using the Modbus pane, click Configure clients. For more information, see Configure Modbus Client in Simulink.

• To update the client list and to show the latest Modbus clients, click Refresh.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

To get the block parameter value programmatically, use the get_param (Simulink) function.

Parameter:	ClientList
Values:	Modbus client name
Data Types:	character vector | string

Server ID — Address of the server

1 (default) | nonnegative integer in the range [0, 255]

Server address to read from, specified as a nonnegative integer in the range [0, 255]. The default value is 1. The server address refers to the unit identifier for the Modbus TCP/IP server.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

To get the block parameter value programmatically, use the get_param (Simulink) function.

Parameter:	ServerId
Values:	1 (default) | nonnegative integer in the range [0, 255]
Data Types:	double

Registers — List of Modbus registers

table

Add registers to read from the specified client.

• To add a register, click Add. This action adds a row in the Registers table with Name, Register Type, Precision and Count set to the default values of Reg_1, Holding Register, uint16 and 1, respectively. You must specify an address for the register to read from in the Address column. Each time you click Add, the block adds a new row in the Registers table and increments the name by 1.

  • Sl. no. : This field is noneditable and specifies the serial number of the register. The serial number determines the order in which the block outputs the signals at the output ports.

  • Name: This is an editable text field that specifies a name for the register. This field also defines the names for the output ports.

  • Address: This is an editable text field that specifies a starting address for the Modbus read operation.

  • Register Type: This is a drop-down list that specifies the target area to read. You can perform a Modbus read operation on four types of targets: coils, inputs, input registers, and holding registers.

  • Precision: This is a drop-down list that specifies the data format of the read register. Note that the Precision field does not refer to the data type of the block output. The data type of the output is always double. Precision specifies how the block interprets the register data.

    • For coils and inputs, set this field to bit.

    • For holding registers and input registers, set this field to int16, uint16, int32, uint32, single, double, int64 or uint64.

  • Count: This is an editable text field that specifies the number of registers to read starting from the address specified in the corresponding Address field.

• To delete registers, select the registers and click Delete.

• To import a register table saved as a MAT file, click Import. This action opens the Load register table dialog box for the current workspace. Using this browser, you can select the MAT file with the register information. The MAT file that you select must have a table named ModbusRegisterTable.

  Note

  The Modbus Explorer app exports the contents of the register table as a MAT file. You can import this MAT file into the Modbus Client Simulink blocks to reuse the register table. For more information, see Use the Modbus Explorer App.

• To save the register table as a MAT file, click Export. This action opens the Save register table dialog box for the current workspace. Using this browser, you can save the register table as a MAT file in the location of your choice. The default filename is ModbusRegisterTable.mat.

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

To get the block parameter value programmatically, use the get_param (Simulink) function.

Parameter:	RegisterTable
Values:	register name and information
Data Types:	character vector | string

Block sample time — Sample time for read operation

-1 (default) | nonnegative scalar

Define the sample time of the block in seconds. The block reads the data from the server synchronously at the specified sample time. For more information, see Specify Sample Time (Simulink).

Programmatic Use

To set the block parameter value programmatically, use the set_param (Simulink) function.

To get the block parameter value programmatically, use the get_param (Simulink) function.

Parameter:	SampleTime
Values:	-1 (default) | nonnegative scalar
Data Types:	double

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using Simulink® Coder™.

Limitations:

• This block generates platform-specific code for the host machine's platform only (Windows^®, macOS, Linux^®).

• You cannot have more than one Modbus Client block (Read or Write) in a model connected to the same serial port of a Modbus serial server.

Version History

Introduced in R2024b