This chapter describes programming the PC/AT devices of the V5C. The basic
peripherals such as the serial ports, the parallel port, and the keyboard port are
covered generally, as are the more advanced controllers for the video, floppy
disk, and hard disk interfaces. Devices not usually found on a standard desktop
PC/AT, such as onboard Ethernet are covered in more detail.
Note that it is beyond the scope of this manual to provide the programming
details associated with the IBM PC/AT compatible hardware, MS-DOS software,
and the ROM BIOS. Rather, it is suggested that one of the many good programming
reference books for the PC/AT architecture be consulted. We highly recommend
that you obtain a copy of
Advanced MS-DOS
which is published by Microsoft
Press. It presents the details of the software environment of MS-DOS and the
associated calls to the ROM BIOS. If you are planning to program in 80x86
assembler or a high-level language such as ‘C’ and need to access system
resources directly, you will find this book absolutely essential.
The ROM BIOS is a firmware (installed in ROM) resident set of routines which
is used to interface the particular system hardware to the MS-DOS operating
system, and subsequently to MS-DOS applications. The use of a ROM BIOS in
the original IBM PC/AT design has allowed programs to be developed specifically
for the operating system environment without concern for the underlying hard-
ware. Programs developed using the AT BIOS can be run on a variety of PC/AT
compatible computers without modification. The BIOS provides a very rigid
interface between the operating system and applications, and the hardware
devices of the system. MS-DOS accesses devices through BIOS calls. These
routines must perform their functions and return to the operating system after
completion, without disturbing other system functions.
PC/AT Devices Programming
6-1
Chapter Scope
PC/AT Compatible
ROM BIOS
C H A P T E R 6
PC/AT Devices
Programming
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