Communication Port Data Loss in Enhanced-Mode Windows 3.0
ID: Q63793
|
The information in this article applies to:
-
Microsoft Windows versions 3.0, 3.0a
SUMMARY
This article contains information about why MS-DOS applications lose
communication-port data when running from enhanced mode in Microsoft
Windows version 3.0, and the steps to eliminate this problem.
MORE INFORMATIONData Loss at 2400 Bits Per Second (BPS) or Slower
Communication-port data loss should not occur when using MS-DOS
applications operating at bit rates of 2400 BPS or less. However, data
loss may occur at higher bit rates. If you are experiencing problems
at 2400 BPS or slower, check for a hardware communication-port I/O
base or interrupt assignment conflicts.
Data Loss at Rates Higher than 9600 BPS
MS-DOS applications cannot use bit rates greater than 9600 BPS when running
under enhanced-mode Windows 3.00. To use higher rates, such as 19,200
BPS, use a Windows-based communications application, such as
FutureSoft's DynaComm Asynchronous, or DCA's CrossTalk for Windows.
19.2 kilobits per second (Kbps) is the maximum possible data rate for a
Windows-based application.
Data Loss at 9600 BPS
On many hardware platforms it is not possible to use 9600 BPS in an
MS-DOS application under enhanced mode. This depends on the speed of the
processor and the type of communication-port hardware being used. If
you are experiencing problems at 9600 BPS, take the appropriate steps as
explained below. The steps are different for text only or text/binary data.
- Text data only
If you are transferring text data ONLY, and your MS-DOS application
supports XON/XOFF software flow control, you can configure
enhanced-mode Windows to process the XON/XOFF signals internally.
This may assist in preventing data loss at 9600 BPS. To enable
this feature, insert the following line in the [386Enh] section of
the SYSTEM.INI file:
COMxProtocol=XOFF
where x is the communication port in question. For example, if you
are using COM1, use COM1Protocol=XOFF. It is important to note that
this switch does NOT work if you are performing ANY binary data
transfers, and actually prevents such data from being transferred
correctly. In addition to adding this switch, you should increase
the enhanced-mode virtual communication-port buffer size, as detailed
below (in Step 2).
- Binary data, or text and binary data combination
If you are transferring any type of binary data, such as
downloading from a computer bulletin board by modem, you may want
to increase the enhanced-mode virtual communication-port buffer
size. This may be done by adding a switch to the [386Enh] section
of the SYSTEM.INI file, as follows
COMxBuffer=yyy
where x is the communication port in question, and yyy is the
buffer size in characters (default 128). For example, if you are
using COM1, and want to increase the buffer size to 256, use
COM1Buffer=256. Since the buffer default is 128, start with 256 and
work upward in 128-character increments until the data loss is
eliminated. Note that data loss cannot be eliminated in all cases;
in such situations, a Windows communications application should be
used.
Additional query words:
3.00 3.0 3.0a 3.00a wincomm win30
Keywords :
Version : WINDOWS:3.0,3.0a
Platform : WINDOWS
Issue type :
|