HP Vectra Technical Reference Manual page 189

On Entry: AH
=
F_'O_CONTROL
(04H)
AL
=
SF_CLLCRTSW (18H)
On Exit: AH
=
Return Status Code
Registers Altered: AX, BP, DS
This function outputs the byte in BL to the 8041 using the pass thru command to prevent the
8041 from interpreting the data as a scancode or a command.
On Entry: AH
=
F_IO_CONTROL (04H)
AL
=
SF_PASS_THRU (1AH)
BL
=
data byte to pass thru the 8041
On Exit: AH
=
Return Status Code
Registers Altered: AX, BP, DS
5.4 8041 Keyboard Controller
5.4.1 Overview
The primary function of the 8041 Keyboard controller is to emulate the industry standard 8042
keyboard interface. (Directly accessing this hardware interface may affect program portability
and is not recommended). The 8042 interface, in turn, emulates the keyboard interface of the
IBM-PC. The 8041 keyboard controller acts as a command buffer from the STD-BIOS keyboard
driver to the Input System while it acts as a loopback buffer for the Input System to the STD-BIOS
keyboard driver. The 8041 is implemented in such a way as to maintain standard AT
compatibility, while at the same time supporting all of the features of the Input System.
~
The 8041 keyboard controller accepts commands from the STD-BIOS drivers that control the
operation of the controller and the keyboard itself. These commands are detailed in the next
subsections of this manual. Some of these commands are executed by the 8041 keyboard
controller, but most are passed on the V_8041 interface driver for execution.
180 Keyboard