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MODBUS™ Protocol Driver

The ACS MODBUS Protocol Driver is a utility that allows you to create PC programs that communicate with devices that understand the Gould MODBUS protocol. It supports a limited subset of the MODBUS RTU protocol.

The MODBUS Driver is designed to let you communicate with your MODBUS devices using your programming language's ordinary variables and function calls. For example, the following Visual Basic program segment reads 3 Output registers from Node 2 starting at register 40108:

Dim outregs(4) As Integer, Status As Integer
Status = mbdrv(mROR, 2, &O40108, 3, outregs(0))

The Driver provides the following MODBUS commands:

Command Number Description
1 Read Output Status
2 Read Input Status
3 Read Output Registers
4 Read Input Registers
5 Write Single Coil
6 Write Single Register
7 Read Exception Status*
8 Loopback Test
11 Fetch Event Counter*
12 Fetch Event Log*
15 Write Multiple Coils
16 Write Multiple Registers
17 Report Slave ID*
20 Read General Reference*
21 Write General Reference*

* Commands marked with an asterisk are supported only by the MODBUS Driver ActiveX control.

You can also access other commands with the built-in User function, which will format and pass a user-constructed command string and return the result.

Driver ActiveX control

The MODBUS Driver is now available as an ActiveX control. This control will let you communicate with your MODBUS devices using simple properties, events, and methods. Compatible with any 32-bit Windows language that supports ActiveX controls, including the Microsoft CLR languages (C#, etc.), Microsoft Access, Visual Basic, Delphi, Microsoft C++, and many more.

To see if the Driver ActiveX control is right for your application, you can examine the online help file supplied with the control.

View the MODBUS Driver ActiveX control help file (76K)
Modbus ActiveX Users Guide View the MODBUS Driver ActiveX User's Guide (342KB)

Platform Support

The driver is available for DOS, 16-bit Windows (3.x), and 32-bit Windows (95/NT).

The Windows versions of the Driver will work with any language or development environment that supports calling out to external dynamic-link libraries (DLLs).

DOS versions of the Driver are tailored for specific languages. Currently supported are Quick Basic, Turbo Pascal, Interpreted Basic, Microsoft/Borland C/C++ (Small and Large memory models), and several others. Depending upon the specific language, the Driver may be supplied as a linkable object module or a terminate-and-stay-resident (TSR) program. Send us e-mail for details.

Modbus DOS Users Guide View the MODBUS Driver for DOS User's Guide (167KB)
MODBUS for Win16 Users Guide View the MODBUS Driver DLL for 16-bit Windows User's Guide (72KB)
MODBUS for Windows 32 Users Guide View the MODBUS Driver DLL for 32-bit Windows User's Guide (77KB)
Get Acrobat Reader To obtain a free viewer for PDF files visit Adobe's Web Site

Pricing and Availability

The Driver comes in two versions, single-user and OEM. The standard single-user Driver package comes with one language (DOS) or platform (Windows) interface, cable, demonstration program, and documentation for a list price of $450.

The OEM Version of the Driver is designed for customers who want to add MODBUS communications to their commercial software. For a one-time fee of $1450, you can sell or distribute any number of standalone executable programs that use the complete driver library. This product is mainly intended for OEMs and multi-station installations.

For specific technical details, to order, or if you have any questions, please feel free to contact us via e-mail.

Copyright © 1997 – 2012 Automation Consulting Services Inc. All rights reserved. Subject to change without notice. MODBUS is a trademark of Gould Corp. AutoMate is a trademark of Reliance Electric.