IBM Personal System/2 65 SX User Manual

System-Board
POS
Register
2
(Hex
0102)
When
the
system
board
is
in
the
setup
mode,
this
read/write
register
controls
the
diskette-drive
controller,
serial
port,
and
parallel
port.
Reading
this
register
returns
the
current
state
of
the
following
system-board
functions.
Bit Function
7
Disable
Parallel-Port
Extended
Mode
6,5
Parallel-Port
Select
4
Enable
Parallel
Port
3
Serial-Port
Select
2
1
0
Enable Serial Port
Enable Diskette-Drive Interface
Enable System Board
Figure
2-4.
System-Board
POS
Register
2
(Hex
01
02)
Bit7
When
set
to
0,
this
bit
allows
the
parallel
port
to
be
configured
as
an
8-bit,
parallel,
bidirectional
interface.
When
set
to
1,
this
bit
disables
the
bidirectional
mode.
This
bit
is
set
to
0
at
power-on
time,
and
the
power-on
self-test
(POST)
sets
it
to
1.
Bits
6,5
These
bits
select
the
configuration
of
the
system-board
parallel port.
Bits
65
Assignment
Address
(Hex)
Interrupt
Level
00
Parallel
1
O3BC
-
03BE
7
01
Parallel
2
0378
-
037A
7
10
Parallel
3
0278
-
027A
7
11
Reserved
——wnnnnnnwwnnnnns
-
Figure 2-5. Parailel-Port Select Bits
Bit4
When
this
bit
and
bit
0
are
set
to
1,
the
system-board
parallel
port
is
enabled.
Bit
3
When
set
to
1,
this
bit
sets
the
system-board
serial
port
as
Serial
1
(addresses
hex
03F8
through
O3FF),
which
uses
interrupt
level
4.
When
set
to
0,
this
bit
sets
the
serial
port
as
Serial
2
(addresses
hex
02F8
through
02FF),
which
uses
interrupt
level
3.
2-8 Model 65 POS — October 1990

IBM Personal System/2 65 SX Specifications

General

Brand	IBM
Model	Personal System/2 65 SX
Category	Desktop
Language	English