Reliable MS-DOS Serial Communication
Under Windows
You can extend the life of your MSDOS serial
communication (RS232 / RS485 /RS422) application with
minimal investment in time or engineering. It is not difficult but may
require minimal changes to your application.
When running an MSDOS serial communication application
under Windows, the serial port (UART) is emulated. In other words, every
byte written or read to/from the UART with the generic OUT/IN
instructions generates a page fault and generates hundreds of CPU
instructions. Given that reading and writing bytes to the UART may
require several additional reads and writes to other control registers
on the UART, this generally means that serial communication becomes
erratic, non-deterministic, slow, and outright unreliable as thousand of
CPU instructions must be executed for simple data access.
Ultimately the solution to the problem is to have a
kernel driver that will handle all communication to the UART in the Windows
kernel domain. Additionally a method to connect to the kernel driver must be
established. WCSC tools are designed to solve this problem in a simple,
efficient, programmer friendly way. The solution to the problem is
dependent on the type of MSDOS application that you have.
Many MSDOS serial communication applications can be
made to work reliably under Windows XP, Windows 2003, Windows 2000, and Windows NT
with our high speed kernel driver/DLL COMM-DRV/NT with minor
modifications to the application. In fact we have tested applications
that ran effectively at 460 KBaud successfully on COM1 - COM4 or our
PCI multiport cards in combination with
our
COMM-DRV/NT product.
Modifying a 16 bit MSDOS application to effect
COMM-DRV/NT usage is rather simple. The
basic steps for a C/C++ MSDOS application are:
- Isolate all serial communication calls. These
could be calls to some other third party library or your own.
- Map isolated calls to
COMM-DRV/NT calls. Our API supports
a myriad of calls that will easily map to the previous calls.
- Recompile and re-link the application.
Modifying a DOS extended 16 or 32 bit application
requires, COMM-DRV/Dos in addition to
COMM-DRV/NT. After installation of the drivers, the same steps listed
for 16 bit MSDOS applications apply.
Note that these tools can also integrate with your
QuickBasic 4.x, Professional Basic, and Visual Basic for DOS
applications as well as all of your Windows applications.
Send email to
support@wcscnet.com if you need additional information on leveraging
your products by integrating them with our offerings.
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