2 pointing device interface operation – Compaq 4000N User Manual
Page 120
Chapter 5 Input/Output Interfaces
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition – September 1997
5-30
5.6.2
POINTING DEVICE INTERFACE OPERATION
The pointing device (typically a mouse) connects to a 6-pin DIN-type connector that is identical
to the keyboard connector both physically and electrically. The operation of the interface (clock
and data signal control) is the same as for the keyboard. The pointing device interface uses the
IRQ12 interrupt.
5.6.3
KEYBOARD/POINTING DEVICE INTERFACE PROGRAMMING
5.6.3.1
8042 Configuration
The keyboard/pointing device interface must be enabled and configured for a particular speed
before it can be used. Enabling and speed parameters of the 8042 logic are affected through the
PnP configuration registers of the 87307 I/O controller. Enabling and speed control are
automatically set by the BIOS during POST but can also be accomplished with the Setup utility
and other software.
The PnP configuration registers are accessed through I/O registers 15Ch (index) and 15Dh
(data). The keyboard and mouse interfaces are initiated by firmware selecting logical device 0 or
1 of the 87307. This is accomplished by the following sequence:
1. Write 07h to I/O register 15Ch.
2. Write 00h or 01h to I/O register 15Dh (for selecting the keyboard or mouse interface).
3. Write 30h to I/O register 15Ch.
4. Write 01h to I/O register 15Dh (this activates the interface).
The parallel interface configuration registers are listed in the following table:
Table 5–17. Keyboard/Mouse Interface Configuration Registers
Table 5-17.
Keyboard/Mouse Interface Configuration Registers
Index
Address
Function
R/W
Reset
Value [2]
30h
Activate
R/W
01h / 00h
31h
I/O Range Check [1]
R/W
00h / na
60h
Base Address MSB [1]
R/W
02h / na
61h
Base Address LSB [1]
R/W
78h / na
62h
Command Base Address MSB [1]
R/W
00h / na
63h
Command Base Address LSB [1]
R/W
00h / na
70h
Interrupt Select
R/W
01h / 0Ch
71h
Interrupt Type
R/W
01h / 01h
74h
DMA Channel Select
R/W
04h / 04h
75h
Report DMA Assignment
RO
04h / 04h
F0h
Configuration Data [1]
R/W
-- / na
NOTES:
[1] Keyboard I/F only.
[2] Keyboard I/F / Mouse I/F