PRB: VCD_Virtualize_Port Works in 3.1 but Fails in Windows 95
PSS ID Number: 141232
Article Last Modified on 3/4/1999
The information in this article applies to:
- Microsoft Win32 Device Driver Kit (DDK) Windows 95
This article was previously published under Q141232
SYMPTOMS
To claim a COM port in Windows 3.1, VCD services were sometimes employed.
VCD is the virtualizer for the serial ports. In particular, the
VCD_Virtualize_Port call was used. However, programmers find that this call
fails in Windows 95 as if the port has already been virtualized.
CAUSE
Under Windows 95, the port has indeed been virtualized. COMBUFF, which
buffers all MS-DOS VM serial port data, virtualizes all serial ports during
initialization. VCOMM is the new VxD controlling COMM ports for Windows-
based applications. As such, VCOMM is the intended VxD through which COMM
ports are acquired through VCOMM_Acquire_Port. This would be called from a
dynamic port driver. See Vcomm.doc in the DDK for a complete description.
STATUS
This behavior is by design.
REFERENCES
MSDN Library Compact Disc October 95
Windows 95 DDK
Additional query words: 4.00 VCD
Keywords: KB141232
Technology: kbAudDeveloper kbWin32DDK95 kbWin32DDKSearch kbWin32sSearch kbWin95search kbWinDDKSearch