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
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