Main Content

Modbus RS485 Server Write

Server device writes data to server device register over RS485 network

Since R2021b

expand all in page
  • MODBUS RS485 Server Write

Libraries:
Embedded Coder Support Package for STMicroelectronics STM32 Processors / STM32F746G-Discovery
Embedded Coder Support Package for STMicroelectronics STM32 Processors / STM32F769I-Discovery
Embedded Coder Support Package for STMicroelectronics STM32 Processors / STM32L475VG-Discovery (B-L475E-IOT01A)
Simulink Coder Support Package for STMicroelectronics Nucleo Boards / Common

Description

In the Modbus RS485 Server Write block, the server device writes data to its registers. The server can write data only to one register per write operation.

Simulink® Coder™ Support Package for STMicroelectronics® Nucleo Boards and Embedded Coder® Support Package for STMicroelectronics Discovery Boards supports the Modbus® communication protocol over the RS485 network. Each device on the RS485 network is referenced by a unique 8-bit address or identifier.

This table categories the server registers referenced by the Modbus server device.

Register TypeRegister Size
Coil1-bit
Discrete Input1-bit
Holding Register16-bit
Input Register16-bit

Examples

MODBUS RS485 Communication Between Client and Server Devices Using STMicroelectronics Discovery Board

MODBUS RS485 Communication Between Client and Server Devices Using STMicroelectronics Discovery Board

Use the Embedded Coder® Support Package for STMicroelectronics® STM32 Processors to implement a MODBUS® RS485 asynchronous, serial communication between MODBUS client and server devices. The example also shows the four modes of operation: Client Read, Client Write, Server Read, and Server Write.

Ports

Input

expand all

The input to the block is the data to be written to its registers by the server as a 1-bit scalar.

  • If you select the Coil or Discrete Input write operations, the server writes data to its registers as a 1-bit write operation having the Boolean data type.

  • If you select the Holding Register or Input Register write operations, the server writes data to its registers as a 16-bit write operation having the uint16 data type.

Data Types: Boolean | uint16

Output

expand all

The block outputs the status of the server write operation on the server device register.

  • 1: Indicates an unsuccessful write operation to the server registers.

  • 0: Indicates a successful write operation to the server registers.

Dependencies

To enable this port, select the Output status parameter.

Data Types: uint8

Parameters

expand all

Select the type of write operation you want to perform on the server register. Specify any one of the following:

  • Write Coil: Write data to the coil register address specified in the Coil Address parameter

  • Write Discrete input: Write data to the discrete input register address specified in the Discrete Input Address parameter

  • Write Holding register: Write data to the holding register address specified in the Holding Register Address parameter

  • Write Input register: Write data to the input register address specified in the Input Register Address parameter

To notify the server to write data to a specific coil register, specify the coil register address in this parameter. For example, for the server to write data to the coil register with the address 10, enter 10.

Dependencies

To enable this parameter, set Function to Write Coil.

To notify the server to write data to a specific discrete input register, specify the discrete input register address in this parameter. For example, for the server to write data to the discrete input register with the address 80, enter 80.

Dependencies

To enable this parameter, set Function to Write Discrete input.

To notify the server to write data to a specific holding register, specify the holding register address in this parameter. For example, for the server to write data to the holding register with the address 37, enter 37.

Dependencies

To enable this parameter, set Function to Write Holding register.

To notify the server to write data to a specific input register, specify the input register address in this parameter. For example, for the server to write data to the input register with the address 25, enter 25.

Dependencies

To enable this parameter, set Function to Write Input register.

When you select the Output Status parameter, the block configures an output port, Status. The port outputs the status message.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2021b

See Also

| |