Category : Tutorials + Patches
Archive   : WFX4.ZIP
Filename : 6068.TXT

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===========================================================================
T E C H N I C A L N O T E S
Product: WinFax PRO 4.0
Document No.: 6068
Document Date: December 8, 1994
===========================================================================
Subject: Hardware Setup: Configuring COM Ports Properly

Situation
=========
many communications problems in Windows can be attributed to incorrectly
configured communication ports. Windows will use the port addresses that
are set up in the BIOS regardless of how they are set up in the Windows
Control Panel. This Technical Note explains how to use the Microsoft
Diagnostics tool (MSD) included with Windows 3.1 to determine which COM
port your fax/modem is on and to ensure that your COM ports are properly
configured.

Typical symptoms include:

- you receive the message "WinFax Cannot Communicate With Fax Modem".
- you receive the message "Error Locating Hardware".

Note: This type of problem occurs most often, but not exclusively, with
modems configured for the COM 4 port.

Proper Settings
---------------
Each COM port has a corresponding port address. When you select a COM port
to be used by a piece of hardware, you are actually selecting the port
address for that device. Most computer systems assign the following
addresses to the COM ports:

COM1 = 03F8
COM2 = 02F8
COM3 = 03E8
COM4 = 02E8

Note: Computer systems rarely use addresses other than those shown above.
If you have a system which uses different addresses, please consult
your hardware manual or dealer for the correct address.

Checking COM Port Addresses Using MSD
-------------------------------------
The Microsoft Diagnostics program (MSD.EXE) tests your computer's COM
ports. Type MSD at the DOS prompt and choose the COM PORTS option to check
the current settings for each COM port. If the COM port settings do not
match the port addresses, then a phenomenon called "COM port packing" has
likely taken place.

Identifying Your Fax/Modem In MSD
---------------------------------
A fax/modem can usually be identified in the COM ports list in MSD by the
fact that the Data Set Ready (DSR) and Clear To Send (CTS) values show YES
when a modem is connected. Serial printers also give the same response to
DSR and CTS.

Com Port Address Packing
------------------------
COM port packing takes place when your installed COM ports are not
installed sequentially (i.e. 1, 2, 3). If you skip one of the COM ports
(e.g. 1, 2, 4), your computer's BIOS will mismatch the COM addresses with
the sequence of your installed COM ports<197>for example, COM 4 will
display the COM 3 address.

COM port packing can produce the following error messages in WinFax:

ERROR LOCATING HARDWARE
WINFAX CANNOT COMMUNICATE WITH THE FAX\MODEM...

Solving COM Port Packing
------------------------
If the COM ports do not match the port addresses in "Checking COM Port
Addresses", you can solve the problem through one of two methods. The
first solution involves changing the settings in your hardware, as
outlined in "1. Preventing COM Port Packing." The second solution
involves fixing the problem by 'patching' the proper port addresses into
your computer's memory, as outlined in "2. Fixing COM Port Packing."

1. Preventing COM Port Packing
---------------------------

To prevent COM port packing, set your hardware (COM ports, fax/modems)
to use consecutive COM ports (i.e. 1, 2, 3). To do this, please consult
your hardware dealer, fax/modem manual or your fax/modem manufacturer.

2. Fixing COM Port Packing
-----------------------
You can fix the problem caused by COM port packing by correcting the
port addresses assigned for each COM port in your computer's memory. To
do this, you must write a Debug Script to patch port addresses.

To write a Debug Script (Patching the BIOS setting for COM 3/COM 4):

1. Open any standard text editor, such as Windows notepad.
2. Type the following three lines ...

E40:0
F8 03 F8 02 E8 03 E8 02
q

... and press Enter.

Notes: You must press [Enter] after the last line or else your system
will remain in the Debug mode.

If your hardware requires non-standard addresses, you can
specify these addresses in the Debug Script.

3. Save the file as C:\FIXCOM.DEB, or any filename with the .DEB
extension.

4. Add the following line to the end of your AUTOEXEC.BAT file.

DEBUG NUL

Notes: This command must be executed prior to any TSR being loaded and
immediately after the path statement.

Do not place this entry after a program execution line, such as
WIN. If you do, the Debug Script will not execute.

The >> NUL ending keeps the Debug Script from echoing to the
screen.

5. Save the AUTOEXEC.BAT file and reboot your PC. The port address
setting on your physical serial device must match what you
specify in the Debug Script.

Check it Again
--------------
After fixing the problem using either method, be sure to run MSD again to
confirm that all port addresses correctly correspond to their respective
COM Port Numbers.

Ghost COM Ports
---------------
After using the Debug Script in "Fixing COM Port Packing," any COM port
that was skipped and does not physically exist will report 'strange' values
in the COM Ports list in MSD. This occurs because MSD attempts to test the
COM port at that location, when in fact one does not exist.