TECHNICAL BULLETIN #114 - Rev 1.00 (7/30/96)

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TITLE   : Replacement Comm Drivers
PRODUCT : PROCOMM PLUS for Windows, All Versions
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There are two drivers that can affect the functionality of PROCOMM PLUS for
Windows.  The first is the comm driver and the other is the virtual
communications device.  This document will help in troubleshooting problems
caused when these Windows drivers have been replaced.

WHAT ARE COMM DRIVERS?
A "driver" is a program that controls a hardware device in your computer, such
as a printer port, serial port, video card, etc.  A "comm driver" is a program
loaded by Windows upon startup which manages access to your serial ports.

The default comm driver included with and used by Microsoft Windows is a
program called comm.drv and is located in your \WINDOWS\SYSTEM directory.  It
controls the flow of data to and from your serial ports and handles port I/O
requests from Windows communications programs.  If you are running Windows in
386 enhanced mode, Windows also loads a set of functions into memory to
"virtualize" your serial ports, allowing multiple applications to use your
serial ports at the same time.

WHY REPLACE THE DEFAULT COMM DRIVERS?
Developers of communication applications sometimes wish to add functionality
not available in the default comm driver.  By simply replacing the default
drivers with their own proprietary comm drivers, developers can be sure their
application will work as expected.

Replacement comm and virtual comm drivers are not always hazardous to PROCOMM
PLUS for Windows.  However, when building and testing PROCOMM PLUS for
Windows, the DATASTORM programmers used the standard Microsoft Windows
versions of these two drivers.  With this in mind, there are times when
replacement drivers interfere with PROCOMM PLUS for Windows operations.
Problems that can result from replacement comm drivers include General
Protection Faults, computer lockups, initial connection problems, lost
connections, and file transfer problems (such as CRC errors).

DRIVERS ARE LOADED FROM SYSTEM.INI
If a device manufacturer has provided replacement files for comm.drv and *vcd,
they will be located in the \WINDOWS\SYSTEM directory.   When you installed
the device, the device's setup program will have modified the comm.drv= line
under the [Boot] section of your system.ini file.  The default setting will
look like,

   comm.drv=comm.drv

The virtual comm driver is called from the system.ini, [386Enh] section.  Its
default setting will look like the following:

   device=*vcd

RESTORE THE DEFAULT DRIVERS
If you encounter problems with PROCOMM PLUS for Windows, examine your
system.ini file to see if Windows is loading replacement comm drivers.  If
this is the case, you may need to restore the original settings.  Before
attempting to edit the system.ini file, it is a good idea to make a backup
copy.  This can easily be done using Window's File Manager (for further
information about making backup files, please refer to your Microsoft Windows
User Guide).

1. After making a backup of system.ini, open it in a text editor, such as
   Notepad.exe.

2. Once open, locate the lines indicated above to confirm that replacement
   drivers are being loaded.  Usually, when a communications package has
   changed the original drivers, the originals will be commented out
   (disabled) with the use of a semicolon.  The replacement often follows the
   original and looks something like this:

     ;comm.drv=comm.drv
     comm.drv=xyz.drv

3. In order to restore the default driver, remove the semicolon from the
   comm.drv=comm.drv line and add a semicolon in front of comm.drv=xyz.drv.
   Repeat the process to restore the virtual comm driver. The original must be
   restored to device=*vcd and the replacement must be commented out with a
   semicolon.  If there is no line that reads comm.drv=comm.drv, create this
   line and comment the replacement driver with a semicolon.

4. After the changes have been made, save and exit the system.ini file and
   reboot Windows for the changes to take effect.  If you have any problems
   returning to Windows, you can edit system.ini from DOS and return the lines
   to normal or use your backup copy.

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         Copyright (c) 1996 Quarterdeck  All rights reserved.
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