User`s manual

DIGITAL-LOGIC AG MSLB-P5 Manual V0.3
PRELIMINARY 207
16.7.1 Extended BIOS Data Area
The Extended BIOS Data Area (EBDA), located in the top 1k of system RAM, contains information
about the pointing device (PS/2 mouse).
INT 15h AH = C1h returns the segment starting address of this table.
Extended BIOS Data Area
Offset Size Description
00h 1 Size of EBDA in kbytes
01h 33 Reserved
21h 4 Pointer to device routine
25h 1 First byte of pointer information:
Bit .... Definition
4....... Pointer error
5....... Pointer acknowledge
6....... Resend request
7....... Command in progress
26h 1 Second byte of pointer information
Bit .... Definition
6....... Enable pointer device
7....... Pointer external device
27h 2 Pointer data package
16.8 Interrupt Vectors
The following table describes the AT system interrupt vectors. Status indicates whether the BIOS sup-
ports the interrupt.
INT Description Status
00 Divide by zero Not Supported
01 Single step Not Supported
02 Non-Maskable interrupt Supported
03 Breakpoint Not Supported
04 Overflow Not Supported
05 Print Screen Interrupt Supported
06 286 LoadAll Handler Supported
07 Reserved Not Supported
08 IRQ0 - System Timer Interrupt Supported
09 IRQ1 - Keyboard Interrupt Supported
0A IRQ2 - Reserved Not Supported
0B IRQ3 - COM2: Interrupt Supported
0C IRQ4 - COM1: Interrupt Supported
0D IRQ5 - LPT2: Interrupt Supported
0E IRQ6 - Floppy Disk Interrupt Supported
0F IRQ7 - LPT1: Interrupt Supported
10 BIOS Video Interface Supported
11 BIOS Equipment Check Supported
12 BIOS Memory Request Supported
13 BIOS Fixed Disk/Diskette Interface Supported
14 BIOS Serial Interface Supported
15 BIOS System Functions Interface Supported
16 BIOS Keyboard Interface Supported
17 BIOS Parallel Printer Interface Supported
18 BIOS Secondary Boot Request Supported
19 BIOS Primary Boot Request Supported
1A BIOS System Timer Interface Supported
1B BIOS Control Break Interrupt Supported
1C BIOS User System Timer Interrupt Supported
1D BIOS Video Init Parameters Supported
1E BIOS Diskette Parameters Supported
1F BIOS Video Graphic Characters Supported
40 BIOS Diskette (when fixed disk present) Supported
41 BIOS Fixed disk 0 parameters Supported
46 BIOS Fixed disk 1 parameters Supported
70 IRQ8 - Real time clock interrupt Supported
71 IRQ9 - IRQ2 redirection Supported
72 IRQ10 - Reserved Not Supported
73 IRQ11 - Reserved Not Supported
74 IRQ12 - Available/PS/2 Mouse Supported
75 IRQ13 - Math coprocessor Supported
76 IRQ14 - Primary IDE HDD Supported
77 IRQ15 - Available/Secondary IDE HDD Supported