User`s manual

DIGITAL-LOGIC AG MSLB-P5 Manual V0.3
PRELIMINARY 73
4.9 BIOS Data Area Definitions
The BIOS Data Area is an area within system RAM that contains information about the system
environment. System environment information includes definitions associated with hard disks,
diskette drives, keyboard, video, as well as other BIOS functions. This area is created when the
system is first powered on. It occupies a 256-byte area from 0400h - 04FFh. The following table
lists the contents of the BIOS data area locations in offset order starting from segment address
40:00h.
Location Description
00h - 07h I/O addresses for up to 4 serial ports
08h - 0Dh I/O addresses for up to 3 parallel ports
0Eh - 0Fh Segment address of extended data address
10h - 11h Equipment list
bits 15-14 = Number of parallel printer adapters
00 = Not installed
01 = One
10 = Two
11 = Three
bits 13-12 = Reserved
bits 11-9= Number of serial adapters
00 = Not installed
001 = One
010 = Two
011 = Three
100 = Four
bit 8 = Reserved
bits 7-6 = Number of diskette drives
00 = One drive
01 = Two drives
bits 5-4 = Initial video mode
00 = EGA or PGA
01 = 40 x 25 color
10 = 80 x 25 color
11 = 80 x 25 monochrome
bit 3 = Reserved
bit 2 = (1) Pointing device present
bit 1 = (1) Math coprocessor present
bit 0 = (1) Diskette drive present
12h Reserved for port testing by manufacturer
bits 7-1 = Reserved
bit 0 = (0) Non-test mode
(1) Test mode
13h Memory size in kilobytes - low byte
14h Memory size in kilobytes - high byte
Continued...