IBM Personal System/2 65 SX User Manual

RT/CMOS RAM
The
real-time
ciock/complementary
metal-oxide
semiconductor
RAM
(RT/CMOS
RAM)
chip
contains
the
real-time
clock
and
64
bytes
of
CMOS
RAM.
The
clock
circuitry
uses
14
bytes
of
this
memory,
and
the
rest
is
allocated
to
configuration
and
system-status
information.
In
addition
to
the
64
bytes
of
CMOS
RAM,
a
2KB
CMOS
RAM
extension
is
provided
for
configuration
and
other
system
information.
A
battery
is
built
into
each
chip
to
keep
the
RT/CMOS
RAM
and
the
2KB
CMOS
RAM
extension
active
when
the
power
supply
is
not
in
operation.
The
following
table
shows
the
RT/CMOS
RAM
bytes
and
their
addresses.
Address
(Hex)
RT/CMOS
RAM
Bytes
000
-
00D
Real-Time-Clock
Bytes
O00E
Diagnostic-Status
Byte
OOF
Shutdown-Status
Byte
010
Diskette-Drive-Type
Byte
011 - 013 Reserved
014 Equipment Byte
015,
016
Low-
and
High-Base
Memory
Bytes
017,
018
Low-
and
High-Expansion
Memory
Bytes
019 - 031 Reserved
032,
033
Configuration
CRC
Bytes
034 - 036 Reserved
037
Date-Century
Byte
038 - O3F Reserved
Figure
3-7.
RT/CMOS
RAM
Address
Map
RT/CMOS
Address
and
NM!
Mask
Register
(Hex
0070)
This
register
is
used
in
conjunction
with
the
RT/CMOS
Data
register
(hex
0071)
to
read
from
and
write
to
the
RT/CMOS
RAM
bytes.
Bit Function
7 NMI Mask
6 Reserved
5-0
RT/CMOS
RAM
Address
Figure
3-8.
RT/CMOS
Address
and
NMI
Mask
Register
(Hex
0070)
3-12
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