Keyboard Interface; Keyboard Controller - HP Vectra Reference Manual

SECTION 4.
KEYBOARD
INTERFACE
The HP Vectra interface to its keyboard is through an HP-Human
Interface Link (HP-HIL). HP-HIL is the Hewlett-Packard proprietary
standard for interfacing one or more input devices to the system.
HP-HIL provides an asynchronous serial communication protocol
that enables the user to select a set of input devices (up to seven),
and connect them to the HP Vectra without purchasing additional
I/O cards or using additional I/O slots. Cable management is
simplified because the various input devices are "daisy-chained"
from the HP Vectra. The term daisy-chained refers to process of
plugging the first input device into the HP Vectra, plugging the
second input device into the first, and so on.
The keyboard interface consists of two blocks: the keyboard
controller, and the HP-HIL interface. This section will describe
these two blocks. Also included, is a cursory description of the
data flow necessary to receive a keycode from the keyboard and
to send a command to the keyboard. For a detailed description of
the keyboard interface refer to the
HP Vectra Technical Reference
Manual Volume
2:
System BIOS.
Keyboard Controller
The keyboard controller is an 8041 microcomputer (U87) which
has been programmed to provide a communication path between
the BIOS and/or application programs and the HP-HIL subsystem.
It also provides three output lines and one input line for various
hardware system purposes. The 8041 provides two logical paths
for communicating with the 80286: the application path and the
keyboard path.
Keyboard Interface 55