This article is from the Programming VCOMM FAQ, by firstname.lastname@example.org (Taed Nelson) with numerous contributions by others.
[Contributed by John Loram (email@example.com).]
A DOS application running under Windows 95 or Windows for Workgroups 3.11
cannot access VCOMM port driver supported devices such as a host-based modems.
This is because the DOS app interacts with a serial communications channel by
way of the Windows COMBUFF module. COMBUFF is UART-based virtual device driver
(VxD) that engages in direct UART manipulation.
COMBUFF must be completely rewritten to serve as a translation layer between a
DOS app's UART based I/O activity and the VCOMM's API. Doing so provides DOS
apps access to the full range of VCOMM port drivers and the standard or
non-standard devices these port drivers serve.
Specifically, COMBUFF must be expanded to include full, 8250, 16450, and 16550
UART register-level emulation complete with appropriate interrupt-generation
In addition, the initialization and contention-handling mechanisms of VCD must
be revised significantly. Separate versions of COMBUFF and VCD must be
created for Windows 95 and WFW 3.11, since there are major differences in the
code base for these environments.
TurboCom ViP (Pacific CommWare) is a finished product that accomplishes these
objectives. For further information, contact John Loram at
firstname.lastname@example.org, call him at 541-482-2744 (Ashland, Oregon), or check their
web site at http://www.turbocom.com/.