Compaq 850 Pointing Device Interface Operation, KEYBOARD/POINTING Device Interface Programming

Chapter 5 Input/Output Interfaces

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

Programming the keyboard interface consists of configuration, which occurs during POST, and control, which occurs during runtime.

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 LPC47B357 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 keyboard interface configuration registers are listed in the following table:

Table 5–14. Keyboard Interface Configuration Registers

Table 5-14.

Keyboard Interface Configuration Registers

Index
Address	Function	R/W
30h	Activate	R/W
70h	Primary Interrupt Select	R/W
72h	Secondary Interrupt Select	R/W
F0h	Reset and A20 Select	R/W

5-18Compaq Deskpro EXS and Workstation 300 Personal Computers

Featuring the Intel Pentium 4 Processor

First Edition – December 2000