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13.
8.
1
Joystick
l/F
The
controller
1
and
controller
2
universal
input/output port
devices are
equipped with
four
input
bits,
two
input/
output
bits,
and one output
bit in
addition
to
5V
and
GND
for joystick
and
tablet
connections.
The
controller
1
and
2
ports
formed
by
using
PSG IOA
and
IOB
are
used
in
the
following ways.
(1)
IOA
are
used
as
"input only".
Pins 1 thru
4 of
controllers
1
and
2
are
connected
to pins
IOAO
thru
IOA3
via
the data
selector
IC
74LS157
(IC30). Likewise, pins
6 and
7 of
controllers 1
and 2
are
connected
to pins
I0A4
and
IOA5
via
the data
selector
IC
74LS157
(IC31).
The
IOA7
pin
is
also
used
as
a
CMT
serial
input
port,
while the
IOA6
input
is
not used
in this
case,
and
is
left
at
H
level.
(2)
IOB
are
used
as
"output
only".
The IOBO
thru
IOB3
pins are
connected
by
open
collector via
respective buffers
74LS04
(IC39)
and
74LS05
(IC41),
IOBO
and
IOB1
being
connected
to
pins
6 and
7 of
controller 1
and
IOB2
and
IOB3
being
connected
to pins
6 and
7 of
controller
2.
IOB6
is
used
as
a
selector signal in
controller
1
and
2 switching
(L: controller
X,
H:
controller
2).
IOB4
and
IOB5
are
connected
to pin
8
of
controllers 1
and
2
respectively,
and
the
IOB7
output
is
not
used.
(3)
When
a
joystick
is
used, pins 1
thru
4
are
used
as
forward /back
and
left/right
key
inputs,
pins
6 and
7
are
used
as
trigger
button
inputs,
and
pin
8
is
used
as
a scan pulse output.
That
is,
IOBO
thru
IOB3
are at
H
level
and IC41
is
open.
CONTROLLER
I
CONTROLLER
2
INPUT/OUTPUT
INPUT/OUTPUT
OUTPUT
Fig.
13-37
Joystick
interface circuit
97
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