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MODBUS Communications Driver

Introduction

The MBDRV Communications Driver is a Windows Dynamic Link Library (DLL) that enables Windows programs to communicate with devices that understand the Gould MODBUS™ Process Control Protocol.

The driver provides an easy way for the user to develop programs that access a MODBUS device’s points and registers. Information is passed using standard variables in the user’s host language. The MODBUS driver handles all protocol formatting and variable conversion in both directions. MBDRV always operates in “RTU” (Binary) mode.

The MODBUS driver can be used with any language that supports calls to external DLLs, including Microsoft Access, Microsoft Visual Basic, Microsoft Visual C/C++, and Borland Delphi.

“Include” files

Many languages (such function definitions. programming easier.

as C) have Wherever

facilities for “include” or “unit” possible, ACS has supplied

files that can establish constants and appropriate include files to make

Sample Files

Each version of the Driver is supplied with one or more demonstration programs. Please take the time to examine and run these demonstrators; a few minutes with the samples can save you a lot of frustration. Since the sample programs are known to run, you can use them to test your hardware setup. If the demonstration programs won’t run, your own code probably won’t either. Also, since we wrote the samples, it will be easy for us to diagnose problems encountered while working with them.

The sample programs can give you a head start on your own application by showing you proven ways to construct an application program. In fact, you may wish to simply “cannibalize” the Demonstrator programs to fit your own application.

Help!

If you have trouble, have any questions about how the driver works, or want advice about special applications, please be sure to contact us... a two minute phone call could save you hours of frustration. We are more than willing to help you use any unmodified software provided by ACS. We will also answer questions about your programs (and help you debug programs that use MBDRV) as time permits.

If you find a bug in MBDRV, be sure to let us know. To help us fix the bug, document it as completely as possible. If you are not sure whether the bug is in your program or the driver, please ship us your program on an IBM compatible disk with documentation of the problem. If the problem is in the driver, we will locate and repair it and return your disk as quickly as we can.

Revision 2.210

June 6, 1998

Page 1

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