IBM Personal System/2 65 SX User Manual

Type
2
Serial-Port
Controller
Some
Type
2
serial
controllers
used
on
the
Model
65
SX
system
board
do
not
respond
as
described
in
the
Hardware
Interface
Technical
Reference
serial
controller
information.
After
the
FIFO
mode
is
enabled,
bit
6
of
the
Interrupt
Identification
register
is
erroneously
set
to
0,
indicating
a
Type
1
serial
controller
is
installed.
Any
application
program
or
operating
system
that
uses
bit
6
of
the
Interrupt
Identification
register
as
an
indicator
to
determine
FIFO
support
will
default
to
the
character
mode.
This
indicator
is
ignored
by
the
Model
65
SX
ABIOS.
Therefore,
programs
that
operate
through
ABIOS
can
use
the
FIFO
mode.
The
ABIOS
routines
also
clear
any
error
indications
remaining
after
a
mode
change.
Some
application
programs
reset
the
received-data-ready
indication
by
writing
bit
0
of
the
Line
Status
register
as
a0.
This
method
can
Cause
compatibility
problems
and
is
not
supported
by
Type
1
or
Type
2
serial
controllers.
Compatibility
problems
can
be
avoided
by
resetting
bit
0
of
the
Line
Status
register
to
0.
This
can
be
accomplished
by
reading
the
data
and
discarding
the
data
if
it
is
not
used.
Hardware
Compatibility
The
Model
65
SX
maintains
many
of
the
interfaces
used
by
the
IBM
Personal
Computer
AT.
In
most
cases
command
and
status
organization
of
these
interfaces
is
maintained.
The
functional
interfaces
for
the
Model
65
SX
are
compatible
with
the
following
interfaces:
*
The
Intel”
8259
interrupt
controllers
(without
edge
triggering).
*
The
Intel
8253
timers
driven
from
1.193
MHz
(timer
0
and
2
only).
*
The
Intel
8237
DMA
controller-address/transfer
counters,
page
registers,
and
status
fields
only.
The
Command
and
Request
registers
are
not
supported.
The
rotate
and
mask
functions
are
not
supported.
The
Mode
register
is
partially
supported.
*
Intel
is
a
trademark
of
the
Intel
Corporation.
3-26
Model
65
System
Board
—
October
1990

IBM Personal System/2 65 SX Specifications

General

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