B&B Electronics ESCLP-100 - Manual - Manual (Page 16)

3 Using The Driver
The drivers can service up to 32 serial ports. The names of these ports range from
"COM1" to "COM32".
3.1 OS/2 Application Software
An OS/2 application can access any installed serial port from COM1 through COM32 by
specifying the "COMxx" name.
3.2 WIN-OS/2 Application Software
The Windows environment must be informed of the serial port configuration via the
"Ports" icon in the Windows Control Panel. Use the "/L" port listing option or check in
Hardware Manager (see page 16) to find the base address and IRQ of each installed serial port,
then plug those values into Control Panel. Due to limitations in the Windows environment itself,
Win-OS/2 sessions are limited to the use of COM1 through COM4. COM5 through COM32
cannot be used by a Windows application.
3.3 DOS Application Software
A DOS application can access any installed serial port, COM1 through COM32. DOS
applications normally need to be configured with the base address and IRQ level for the
particular serial port because DOS applications typically do direct access to the hardware. Even
when a DOS application indicates that it is using "COM1", for example, the application is
actually making an assumption as to the hardware configuration. Use the "/L" port listing option
or check in Hardware Manager (see page 16) to find the base address and IRQ of each installed
serial port, then plug those values into the DOS application.
QVCOM.SYS provides the DOS session with an emulation, or virtualization, of a 16550
UART. All of the virtual 16550's registers are available for read or write accesses by DOS
applications. This 16550 emulation holds true even if the actual port in use is equipped with a
16450 UART.
3.3.1 DOS INT14H support
QVCOM.SYS provides full support for the Interrupt 14 hex serial port BIOS interface.
In fact, this interface has been extended to support up to 32 serial ports. To access a serial port
using BIOS Interrupt 14 hex, the port number is placed in the DX register. Normally, this
interface is limited to four serial ports, COM1, COM2, COM3, and COM4, represented by 0, 1,
2, and 3, respectively, in the DX register.
QVCOM.SYS intercepts Interrupt 14 hex accesses and allows any installed port to be
used. Serial ports beyond COM4 are accessed simply by extending the number sequence above.
For example, use DX=4 to access COM5, or DX=31 (decimal) to access COM32.
3.3.2 DOS Properties
Quatech Asynchronous Serial Device Driver for OS/2 13