Application Path; Keyboard Path; Output Lines - HP Vectra Reference Manual

Application Path
The application path consists of two read/write registers and an
interrupt line. The register at port 60H is used for keyboard
commands and data, and controller data. The register at port 64H
is used to write commands to the controller and to read the 8041
status. The interrupt line (OBFIND is set to interrupt when the
8041 places data in the read register at port 60H.
Keyboard Path
The keyboard path provides a way for the 80286 to receive
commands to be sent to the HP-HIL keyboard, and to return data
from the HP-HIL keyboard, through the keyboard controller. The
keyboard path consists of a read register at port 69H, a write
register at port 68H, and an interrupt line.
The read register is a buffered version of the 8041 Port 1 (P10-
P17). The 8041 places data on its port, then signals the 80286
that new information is available by pulsing -INTHP (P23) low.
This causes HPINT to go active, generating an interrupt. When the
80286 has completed processing the interrupt, it clears HPINT by
doing a write to port 6AH. This write informs the 8041 (through
its T1 input) that the 80286 has completed processing the data.
Output Lines
The keyboard controller also provides three output lines for uses
in other parts of the system. These output lines are: the AP line,
the RC line, and the A20_GATE.
The output line AP provides a 60 Hz signal to the HP-HIL controller
for use in polling the HP-HIL.
56 Keyboard Interface