Modbus ASCII

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Product Overview

The Modbus ASCII driver works in conjunction with KEPServerEX to provide an easy and reliable way to connect to Modbus ASCII compliant PLCs and other devices to your OPC client applications, including HMI, SCADA, Historian, MES, ERP, and countless custom applications.



  • Ethernet Encapsulation
  • Modbus ASCII Multi-drop Supported
  • Full Address Range Support (0 - 65535)
  • User Definable Read Block Sizes
  • Adjustable Address Base (0 or 1)
  • Word Order Swapping for Floating Point and Longs
  • RTU Functions used: 01, 02, 03, 04, 05, 06, 16
  • Direct Support of Flow Automation flow computers
  • All memory types and data types supported
  • Modem Support
    • Automatic Dial Configuration
    • Multiple Phone Number Management
  • Communication Serialization


  • Modbus ASCII

Supported Devices

  • Any Device Supporting Modbus ASCII
  • Any Modbus ASCII Compliant PLC
  • Flow Computers

Available Languages

  • English
  • German
  • Japanese
  • Simplified Chinese

Application Support

  • DDE Format CF_Text and AdvancedDDE
  • NIO Interface for iFIX
  • OPC .NET Service (OPC .NET) Version 1.00
  • OPC Alarms and Events (OPC AE) Version 1.10
  • OPC Data Access (OPC DA) Versions 1.0a, 2.0, 2.05a, and 3.0
  • OPC Unified Architecture (OPC UA) Clients
  • SuiteLink and FastDDE for Wonderware

Release Notes



  • Fixed an issue where the driver would not retry a request after receiving a response from the wrong station ID.



  • Resolved an issue where the driver could incorrectly respond to transactions that did not match the station ID.



  • Fixed an issue where Device ID was ignored so the driver would process data from a slave other than the intended one.



  • Added Chinese language support.



  • Added German language support.
  • Added Japanese language support.



  • Fixed an issue where write-only strings failed to write when "Perform block read on strings" was enabled.



Updated the driver with the new Connection Sharing feature.



  • Increased the character limit of the tag Description field from 64 to 255.
  • Added a new option for handling illegal address exceptions that allows users to deactivate tags when an illegal address is detected.


Added support for Channel Serialization.


  • Added string data type support for Internal Registers.

What Is a Driver?

KEPServerEX is more than an OPC server—it's a connectivity platform for industrial automation and IoT. Simply download KEPServerEX, and then select from Kepware's library of more than 150 device drivers, client drivers, and advanced plug-ins to fit the communication requirements unique to your industrial control system.

A driver is a software component that enables KEPServerEX to meet the connectivity requirements of a specific device, system, or other data source. The driver handles all proprietary communications to the data source for KEPServerEX; the client interfaces handle all supported OPC, proprietary, and open standards connectivity to applications that monitor or control the devices.

Drivers may be licensed individually or in suites. Additional drivers can be licensed on demand as connectivity needs evolve.