Commodore C286-LT User manual

rn N
SERVICE MANUAL
C286-LT
OCTOBER, 1990 PN-400400-01
__ 5,
C=z Commodore

Produced
By:
Commodore
International
Spare
Parts
GmbH
Braunschweig,
West
Germany
SERVICE MANUAL
C286-LT
OCTOBER, 1990 PN-400400-01
INTERNATIONAL EDITION
COMMODORE “INTERNATIONAL EDITION?” SERVICE MANUALS CON-
TAIN PART NUMBER INFORMATION WHICH MAY VARY ACCORDING TO
COUNTRY. SOME PARTS MAY NOT BE AVAILABLE IN ALL COUNTTRIES.
Commodore Business Machines, Inc.
1200 Wilson Drive, West Chester, Pennsylvania 19380 U.S.A.
Commodore makes no express or implied warranties with
regard to the information contained herein. The infor-
mation is made available solely on an as is basis, and the
entire risk as to completeness, reliability, and accuracy
is with the user. Commodore shall not be liable for any
damages in connection with the use of the information
contained herein. The listing of any available replacement
part herein does not constitute in any case a recommenda-
tion, warranty or guaranty as to quality or suitability of
such replacement part. Reproduction or use without ex-
press permission, of editorial or pictorial content, in any
matter is prohibited.
This manual contains copyrighted and proprietary information. No part
of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photo-
copying, recording or otherwise, without the prior written permission
of Commodore Electronics Limited.
Copyright © 1990 by Commodore Electronics Limited.
All rights reserved. Printed in U.S.A.

C286-LT SERVICE MANUAL
TABLE OF CONTENTS
SECTION
1
—
SPECIFICATIONS
TECHNICAL
SPECIFICATIONS.
....ueueueesesenenenenennnsnenensnnnnnnnnnenenenenne
sense
nen
1-1
SECTION
2
—
THEORY
OF
OPERATIONS
2.1
MAIN
PCB
BLOCK
DIAGRAM........ccunseneenennunsensnennensnntnnenneeneenteeteereerenn
2-1
2.2
MAIN
SYSTEM
PARTS..........2222enseneensensnnsunennnunnneeennuneenneeneenteeteereeteen
2-2
2.3
SYSTEM
OVERVIEW.
.....ounnnssenseesensensunsunsnnenneneeentennenetneteeteettereeteeeeen
2-4
DD)
19
2
N
Ze
R
2-5
2.5
VGA
SYSTEM
BLOCK
DIAGRAM......uncenseesenennennsuneensenneenseeeeeeeneeereetennenn
2-6
2.6
FLOPPY
DISK
DRIVE
AND
CONTROLLER.
........cuccnneenennsunnnensunseneneneenee
nennen
2-7
2.7
HARD
DISK
DRIVE.
......2eeeneeseneeseesesunsnennunennnnensenenenenneneeneneneeeneneeenen
2-7
2.8
PARALLEL
PRINTER
INTERFACE........ceccecceneeneeneensunsnnennnennneneeneenenee
nenn
2-8
2.9
RS-232C
INTERFACE.........cccceceseeneneeeensnnunsnennenseneuneneeneeneneeneneenneeenen
2-9
2.10
MODEM
UF
SLOT.......22222eseeseseesenseseennenennennenennenneneeneneenennenennenennen
2-10
2.11
C286-LT
MEMORY
MAP.
......uceeesseeeeseesesnenesnnenenneneenenseneeneeseeenseeneeneeen
2-11
2.12
WO
ADDRESS
MAP.
.....cececeeseeeesenenseeensnennensnneesenennensenesnensenenseesenenen
2-12
SECTION
3
—
TROUBLESHOOTING
3.0
TROUBLESHOOTING
SECTION
—
CAUTION.........2ceeeeseeeneeseeeeneeseeeeeeessennenn
3-1
DISASSEMBLY
INSTRUCTIONS
FOR
C286-LT
3.1
KEYBOARD
REMOVAL
INSTRUCTIONS..........2222esseseeseeeeeeeeenseneeneneen
nennen
3-2
3.2
NICAD
BATTERY
PACK
AND
LITHIUM
CELL
REMOVAL
INSTRUCTIONS................
3-3
3.3
HDD
REMOVAL
INSTRUCTIONS........22e@seeseeeeeeseesenenesenneeneenneen
essen
nenn
3-4
3.4
LCD
POWER
UNIT
INVERTER
REMOVAL
INSTRUCTIONS...........22c2sssesseneenenen
3-5
3.5
MAIN
PCB,
POWER
SUPPLY
PCB,
FDD
AND
SPEAKER
REMOVAL
INSTRUCTIONS......
3-6
3.6
MEMORY
PCB
(OPTION)
INSTALLATION.............22cnsenseseeeeeeenesenseensennenenn
3-7
3.7
WIRING
DIAGRAM.......2cneeneeseseneseenesesneeneeseeeensenensensenessensensenennensene
3-8
3.8
TROUBLESHOOTING
ERROR
MESSAGES.
..........2.cessesseeeenseeneeeseneseee
tens
nnne
3-9
3.9
POWER
ON
DIAGNOSTICS.........2.22eeseeeeseeeeeeeeeeneeneneeeeeseneensenneren
nennen
3-10
SECTION
4
—
PARTS
COMMODORE
STOCKED
PARTS.
......ceeesseseeeeeseeeeenennneneeeennssnn
nennen
nnn
seen
4-1
SERVICE
REFERENCE
PARTS
DIAGRAM.
........cecenseeeeeenseeeeeenenesen
sense
nr
nennen
4-2
SECTION
5
—
SCHEMATICS
C286-LT
>.
|||‘ een

SECTION 1
SPECIFICATIONS

C286-LT SERVICE MANUAL
1.1
TECHNICAL
SPECIFICATIONS
C286-LT
MEMORY
RAM on board
VIDEO RAM
ROM
RAM EXPANDABLE
on board
CPU
Type
Clock speed
EXTERNAL STORAGE
Floppy disk drive
Type
Supported disks
Hard disk
Capacity
Type
Access time
Interface
DISPLAY
Dimensions
Type
Video mode
Gray scale
AC ADAPTER
Input
Output power
Input current
Dimensions
Weight
SOFTWARE
Operating System
Language
Utilities
Eagle.com
Switcher.com
Alarm.com
Mdmon.com/mdmoff.com
AT Compatible
1MB:
640
KB
Base
memory,
384
KB
extended/expanded
memory;
con-
figurable
by
user
256
KB
(A000:0000H-13000;FFFH):
32
KB
(frame
buffer
for
LCD)
128
KB
(64
KB
for
system
BIOS,
64
KB
for
VGA
video
BIOS)
Yes; to SM — 2 meg. memory expansion cards optional (maximum of two
cards for a total of 5 meg.)
80C286
12.5 MHz, 8 MHz
3.5-inch double-sided high density
3.5-inch 1.4 MB, 3.5-inch 720 KB
20 MB
2.5-inch, low power consumption type
23 ms mean access time
IDE
197 mm x 149 mm (7%” x 5%") diagonal 247 mm (9% ")
0.27 mm dots size and 0.3 mm dot pitch
1:1 aspect ratio
STN type LCD with CFL backlight lamp
Compatible with VGA
Text: 80 characters x 25 lines or 40 characters x 25 lines
Graphics: 640 x 480
8 shades of gray
Operating voltage — 100 to 240 VAC
Frequency — 50/60 Hz
Adapter mode — 24 W
Charger mode — 45 W
Adapter mode — 0.6 A
Charger mode — 1 A
85Wx205Dx55 Hmm
0.65 Kg
MS-DOS 4.01 with Shell
GW-BASIC
LCD control
LCD control
Indicating low battery
Modem power on/off
1-1

SECTION 2
THEORY OF OPERATIONS
NOTE
PLEASE REFER TO C286-LT OPERATIONS MANUAL
PN-363573-01 FOR ADDITIONAL INFORMATION

2-1
I
OPTION
or
EXT
VO
SNP-100
_-_— _- ..-.,
pn
—-
—-
--_
-.
r---
"-
I
VGA-MONITOR
|
RS-232C
| |
(Analog
I/F)
pn
L-
BOARD ASSY
(LED
PCB)
LITHIUM
(@.6V
x
1900mA)
(for
RTC/CMOS)
SNP-286
(MAIN
PCB)
CPU:
80C286
(12.5MHz/8MHz)
*** MAIN PARTS ***
LCD PANEL (with CFL)
(640 x 480)
E FL12V
BATTERY-PACK
(12V
x
1700mA)
AT
CHIP
SET
(OAK)
OTI-051:
SYSTEM
CONTROL
OTI-052:
/O
CONTROL
OTI-053:
DMA
&
MEMORY
CONTROL
OTI-054:
ADDRESS
BUFF
& RTC
OTI-055:
DATA
BUFF
&
PWR
MANAGE
CFP-24
(INVERTOR
PCB)
2.1
MAIN
PCB
BLOCK
DIAGRAM
SPECIAL CARD SLOT
r-—-—-- - -. .
(TTL
V/F
level)
1 SNP-XXX I
| | (MODEM pcB) | |
I
SR-170
(POWER PCB)
5V/0V/+12V/-12V
—-23V/FL12V
CHARGE/ALMIY/ALM2
ALMCK
ROM: 128KB (16 bit) with VGA-BIOS
SYSRAM: 1MB or 2MB
3.5" FDD X1
(720KB/1.44MB)
FL12V
T
VGA CHIP SET (CIRRUS)
GD-610:
GRAPHIC/ATTRIBUTE
CTRL
GD-620:
SEQUENCER/CRT
CONTROL
AC
Adaptor
VRAM: 256KB/FRAM: 128KB (256Kx4)
INTERNAL CONNECTOR
2.5” HDD X1
(20MB)
K/B Matrix
(Membrane
Type)
2.1
—
MAIN
PCB
BLOCK
DIAGRAM
SPEAKER
EXT MEMORY
| |
t 2MB module |
' 1:
|
2MB module
Total:
max
5MB
(STD:
1MB)
/
4MB
(STD:
2MB)
C286-LT
SERVICE
MANUAL

2.2
MAIN
SYSTEM
PARTS
SYSTEM CONTROL OTI-051
1/0 CONTROL OTI-052
DMA
&
MEMORY
CONTROL
OTI-053
ADDRESS
BUFFER
&
RTC
OTI-054
DATA
BUFFER
&
POWER
MANAGER
OTI-055
SYSTEM CLOCK OTI-051
DMA CHANNEL ASSIGNMENT
Channel 0O- Not used
Channel 1 - Not used
Channel 2- Floppy Disk Controller
Channel 3 - 4 Not used
Channel 5 - 7 Not used
INTERRUPT CONTROL OTI-052
INTERRUPT CONTROLLER CHANNEL ASSIGNMENT
IRQ 0 - Timer Channel 0
IRQ 1- Keyboard Interface Interrupt
IRQ 2 - Not used
IRQ 3 - Com2 Interrupt
IRQ4- Com Interrupt
IRQS5 - Not used
IRQ 6 - Floppy Disk Controller Interrupt
IRQ 7 - Printer Interface Interrupt
IRQ 8 - Real Time Clock
IRQ 9 - Not used
IRQIO - Power Saving Mode
IRQ11 - 13 Not used
IRQ14
-
Hard
Disk
Controller
Interrupt
IRQIS - Not used
BUS
CONTROLLER
OTI
-
051
TIMER/COUNTER
OTI
-
052
TIMER/COUNTER
CHANNEL
ASSIGNMENT
Channel
0
-
System
Timer
for
use
with
MS-DOS
Channel
1
-
Memory
Refresh
Timing
Generator
Channel
2
-
Speaker
Beep
Tone
Generator
KEYBOARD/SENSE
CONTROL
PORT
80C42
OUTLINE
OF
OTI-051
C286-LT SERVICE MANUAL
The
OTI-051
is
a
customized
IC
in
the
Oak
Model
35
chip
set
and
it
is
a
system
control
chip
used
in
IBM
AT
and
Model
30-286
architectures.
Its
main
features
are
described
below.
8 MHz, 10 MHz, 12.5 MHz, 16 MHz and 20 MHz system
speeds supported
8 MHz asynchronous mode, and 8 MHz, 10 MHz and 12
System Control
I/O Channels
MHZ synchronous modes
Programmable wait state
Laptop Power management function
Other Features
Fast reset and time-out counter
2-2

C286-LT SERVICE MANUAL
2.2
MAIN
SYSTEM
PARTS
(Continued)
OUTLINE
OF
OTI-052
The
OTI-052
is
an
/O
peripheral
controller
circuit
which
comes
with
the
following
functions.
e
Two
8259-compatible
interrupt
controllers
e
8254-compatible
timer/counter
e
16450-compatible
serial
communication
controller
e Floppy disk controller, hard disk subsystem, keyboard controller, numerical calculation processor and other chip
select circuits
e Numerical calculation processor interface circuit
OUTLINE OF OTI-053 DMA & MEMORY CONTROLLERS
The OTI-053 is an integrated circuit which has a DMA controller and memory controller, and its main features are
listed below.
© () wait cycle page mode and interleave mode
e DRAMSs with access times ranging from 60ns to 120ns supported
e System speeds up to a maximum 20 MHz
e Programmable wait state for slow-speed DRAMs
e Non-wait state ROM cycle execution enabled with use of shadow RAM
© EMS4.0 supported
e 640KB system memory and total memory space of up to 8MB using extension/expansion memories supported
e 256KB and 1IMB type DRAMSs supported
e Dummy SRAM for laptop models supported
® Cartridge ROMs supported
DMA Control
e Fast and normal DMA modes with built-in 8237 to handle operating speeds up to 10 MHz
Laptop Support
e Power-saving mode
OUTLINE OF OTI-054
The OTI-054 is a customized IC in the Oak Model 35 chip set and it is an address buffer driver for IBM AT, Model
30 and other 286-compatible systems. It features all the TTL address and command driver functions normally re-
quired on a system board. In addition to its address driver functions, it comes with an RTC (real-time clock) function.
Except for the 3 items below, the RTC function is compatible with the MC146818.
®
128-byte
CMOS
RAM
in
total
®
No
CKFS
(clock-out
frequency
select)
input
facility
°
No
SQW
(square
wave)
output
facility
OUTLINE
OF
OTI-055
The OTI-055
features
all the
TTL
data driver
functions
normally
required
on
a system
board
and,
in addition
to its
data
buffer
functions,
it
comes
with
power
manager
functions
for laptop
computers.
It has
16 bidirectional
control/status
signal
lines
which
can
be
used
by system
designers
to
control
power
distribution
to peripheral
units
inside
a
system.
Besides these 16 signal lines, it features an internal timer/counter which enables the user to supply power automatically
to the system.
2-3

2-4
OPTION
(2M)
BMB
SD0-
15
MEMORY
RAS/CAS
OTI-053
Extended/
Expanded
MAI1-10
DMA
and
Memory
n
|
"BASE
MODEL
1
ı
MEMORY
SIZE
1MB
(FUCTORY)
I
OPTION
2M,
2M
|
TOTAL
MEMORY
SIZE
5MB
|
BASE
MODEL
2
|
MEMORY
SIZE
2MB
(FUCTORY)
|
OPTION
2M
| _
TOTAL
MEMORY
SIZE
4MB
0OSC
Controller
SD0-»-15
BIOS
PCAI1-16
SA1»23
80386SX-16
CPU
SA0»23
SD0»15
80386SX-16 |
Co-Processor |
_
(Option)
___1
OTI-051
32/40M
Bus Control
RESET
NMI
VGA
SA0x23
SA0»23
SDO-
15
SD0-15
OTI-054
Address
Buffer
RTC
PCA0-9
WD37C65C
FDC XD0x7
LA1723
PCA0»20
XD0-7
OTI-052
Vo
Personal
Controller
XD0-7
80C42G
Keyboard
Controller
DATA/CLK
XD0»7
LOCAL BUS
OTI-055
Data
Buffer
Power
Mg
PCDO-
15
XD0-7
3.5 inch 2HD
SPEAKER
RS232C
PRINTER
HARD
DISK
(IDE)
80C41
Keyboard
Interface
iss]
16C450
sı0
XD0-7
INTERNAL
1/O
BUS
2.2
—
SYSTEM
OVERVIEW
AT
BUS
GD610/620
VGA/LCD
INTERFACE
VRAM
Size
256Kb
16 Bit Memory
B Bit VO
CPT
LCD
2.3
SYSTEM
OVERVIEW
C286-LT
SERVICE
MANUAL

2.4 DISPLAY
CONTROL
DEVICE
GRAPHIC
RESOLUTION
CHARACTER
DISPLAY
EMULATION MODE
DISPLAY DEVICE
DISPLAY CONTROL
VIDEO RAM
VIDEO RAM ACCESS
CHARACTER GENERATOR
BASE SYSTEM DISPLAY DEVICE
AFFECTIVE DISPLAY AREA
Display Size
Dot Size
Dot Pitch
Aspect Ratio
CFL/LCD Auto OFF
BACKLIGHT
BRIGHTENERS
CFL
BACKLIGHT
LIFE
C286-LT SERVICE MANUAL
Graphics/Attributes CL-GD610; Sequencer CL-GD620
620 x 480 Dots
80
Character
x
25
Line
or
40
Character
x
25
Line
CGA,
EGA,
MDA,
and
Hercules
(register
level)
The
following
devices
can
be
used:
LCD Panel; (8 GRAY SCALES); CRT with external Analog
output; (64 GRAY SCALES at MDA mode); (16 colors 640
x 480); (256 colors 320 x 200)
At the boot-up, LCD Panel is always enable. You can change
LCD Panel, or External CRT by Utility software (Eagle.
com/Switcher .com)
NOTE: VGA BIOS loads the appropriate parameter, after
recognizing which monitor is connected, Color or Mono-
chrome. When power switch is turned to on and no monitor
is connected, VGA BIOS sets its parameter for monochrone
monitor.
VGA mode
256K Bytes + frame buffer 32K Bytes
The Video RAM can be accessed completely in the same way
as accessing normal memory RAM, from CPU. Write and
Read functions are freely executed without checking the status
of the display control device.
Character ROM is stored in the Video Bios and used for the
character display mode (US ASCII ver.).
Consists of STN LCD (blue) panel with CFL back light. In
addition, the display can be switched to the analog CRT (color/
monochrome) output by software.
197mm x 149mm
0.27mm x 0.17mm
0.3mm x 0.3mm
1:1
If
you
close
the
panel
while
power
switch
is
on,
the
CFL
and
LCD
Panel
will
be
automatically
shut
off.
Backlight
brightness
can
be
set
high
(3.2W),
or
LOW
(1.5W)
by
SETUP
MENU.
About
8,000
hours
(condition:
within
the
max.
rating)
2-5

C286-LT SERVICE MANUAL
2.5
VGA
SYSTEM
BLOCK
DIAGRAM
il
2 “ = o
a > E
B
.
u
._—
I
COMMAND | 4 64x4DRAM x2
ADDRESS
1 CLK25/28 MA-DATA Z
| cık Z
DATA x
[pecope} cs ne ]
ADDRESS BUFFER CONT.
oe
|
monitor
|
HCT244 ADDRESS Luonon |
DATA 2
ASEL
2
RAM-DAC
[7
IMS176
==
wa COMMAND
DIR ADDRESS 256x4
AA
TUFFER
DSELL/H
ADDRESS
FRAME-DRAM
DATA
GD620 GD61V
l
1/O CONTROL
2.3 — VGA SYSTEM BLOCK DIAGRAM
CONNECTOR: 15 Pin D-sub (male)
CONNECTOR PIN ASSIGNMENT
PIN NUMBER DESCRIPTION PIN NUMBER DESCRIPTION
1 Red 9 Reserved
2 Green 10 Ground
3 Blue 11 MS0*
4 MS2* 12 MSI*
5 Ground 13 Horizontal sync.
6 R Ground 14 Vertical sync.
7 G Ground 15 Not connected
8 B Ground
*MS0-MS2 are used for sensing a type of monitor.
2-6

C286-LT SERVICE MANUAL
2.6
FLOPPY
DISK
DRIVE
AND
CONTROLLER
FLOPPY
DISK
DRIVE
Type
Data
Capacity
Data
Transfer
Rate
Track
Density
Required
Power
Track
to
Track
Time
Disk
Rotation
Speed
LED
Indicator
Width
Height
Depth
Current and Power Consumption
FLOPPY DISK CONTROLLER
Data Transmission
Transfer Rate
2.7 HARD DISK DRIVE
Type
Data Capacity
Data Transfer Rate (Media)
Data Transfer Rate (Buffer)
Seek Time
Rotation Speed
Total Tracks
Cylinders
Disks
Data Heads
Width
Height
Length
Power Requirement
FD-334HF;
3.5
inch
double
side
drive
1.44M/T20K
Bytes
(formatted)
2M/1M
Bytes
(unformatted)
500K bits/sec/250K bits/sec
135 tpi
+5V Single (4.6 - 5.5V)
3msec
300rpm
Green
101.6mm
19mm
135mm
Typ. current
Standby 10.0mA
Read Operation 0.40A
Write Operation 0.42 A
Motor Start 0.07A
WD37C65B
DMA transmit
High Density — 500K bit/sec.
Normal Density — 250K bit/sec.
CP2024; 2.5 inch 20M Bytes Hard Disk
21.4M Bytes (formatted)
1.25 MB/sec
3.75 MB/sec
Track to Track — 5ms
Average — 23 ms
Maximum — 40ms
3,433rpm
1,306
653
1
2
69.8mm
17.5mm
101.6mm
+5V +5% 600mA (Typ.r/w)
Typ. power
50mW
2.0W
2.1W
3.5W
2-7

C286-LT
SERVICE
MANUAL
2.8
PARALLEL
PRINTER
INTERFACE
CONTROL
OUTPUT
PARALLEL
CONNECTOR
Printer handshaking is controlled by STROBE, and BUSY signals.
Standard TTL input printers can be used, such having TTL input. When
the printer is used, the connector can be plugged in or removed without
destroying the inner circuits of the devices regardless of power ON/OFF.
D shell 25P (female)
PARALLEL
CONNECTOR
PIN
ASSIGNMENT
PIN
NUMBER
DESCRIPTION
CONTENTS
1
OUTPUT
STROBE
STROBE
Signal
2
OUTPUT
PDB
0
Print
data
bit
O0
3
OUTPUT
PDB
1
Print
data
bit
1
4
OUTPUT
PDB
2
Print
data
bit
2
5
OUTPUT
PDB
3
Print
data
bit
3
6
OUTPUT
PDB
4
Print
data
bit
4
7
OUTPUT
PDB
5
Print
data
bit
5
8
OUTPUT
PDB
6
Print
data
bit
6
9
OUTPUT
PDB
7
Print
data
bit
7
10
INPUT
ACK
Printer
acknowledge
11
INPUT
BUSY
Printer
busy
12
INPUT
P.end
Out
of
paper
13
INPUT
SELECT
Printer
select
14
OUTPUT
ATF
Auto
feed
15
INPUT
ERROR
Printer
error
16
OUTPUT
INIPRN
Initialize
Printer
17
OUTPUT
SELINP
Select
input
18
-
25
GND
2-8

2.9
RS-232C
INTERFACE
STANDARD
DEVICE
OUTPUT
SIGNAL
LEVEL
INPUT
SIGNAL
VOLTAGE
BAUD RATE
CONNECTOR
C286-LT SERVICE MANUAL
EIA standard
OTI-052
Output
signals
based
on
+12V
supplied
voltage.
SPACE = +3V, +15V
MARK = -3V, +15V
(50),
(75),
110, 150,
300,
600,
1200,
2400,
4800,
9600
NOTE:
The
valuesin(
)
are
not
supported
by
software
(INT
14h).
They
need
to
be
directly
accessed
by
software.
9 Pin D-sub (male)
SERIAL CONNECTOR PIN ASSIGNMENT
PIN NUMBER SIGNAL DESCRIPTION
l CD Carrier Detect
2 RxD Receive Data
3 TxD Transmit Data
4 DTR Data Terminal Ready
5 GND Signal Ground
6 DSR Data Set Ready
7 RTS Request To Send
8 CTS Clear To Send
9 RI Ring Indicator

C286-LT SERVICE MANUAL
2.10 MODEM I/F SLOT
CONNECTOR
20-Pin
Connector
Edge
Socket
STANDARD
AND
SIGNAL
LEVEL
Based
on
RS-232C,
TTL
Level
MODEM CONNECTOR PIN ASSIGNMENT
PIN NUMBER SIGNAL NAME
Al CONTROLLED 5 Volt
A2 CONTROLLED 5 Volt
A3 RTS
A4 DTR
A5 TXD
A6 DSR
A7 RI
AB DCD
A9
CTS
A1O
RXD
Bl
-12V
B2
GND
B3
GND
B4
GND
BS5
GND
B6 GND
B7
GND
B8 GND
B9 GND
BIO
GND
2-10

C286-LT SERVICE MANUAL
2.11
C286-LT
MEMORY
MAP
The
C286-LT
has
available
1
MB
of
RAM.
Base
memory
is
640
KB
(kilobytes)
and
384
KB
is
allocated
for
extended
memory.
By
adding
Commodore
2
MB
RAM
modules,
memory
may
be
augmented
to
a
total
of
5
MB.
By
using
MS-DOS
4.01
features,
a
portion
or
all
extended
memory
can
be
used
to
emulate
expanded
memory
confor-
ming
to
the
LIM
4.0
specification.
Extended memory can be utilized by many applications and operating systems functioning in protected and standard
modes.
FFFFFFhRroöoöo
een
rennen
IPL,MAIN
BIOS
ROM
Area
FF0000h
RR:
500000h
4AFFFFFh
Extended
Memory
100000h
OFFFFFh
OF0000h
IPL,
MAIN
BIOS
ROM
area
Video
BIOS
ROM
area
0E0000h
Expanded
(EMS)
Memory
0C0000h
Video
RAM
area
0A0000h
Main
Memory
000000h
2.4 — MEMORY MAP

C286-LT SERVICE MANUAL
2.12
W/O
ADDRESS
MAP
1/0 ADDRESS R/W STATUS
0000h-000Fh
R/W
DMA
controller
1,
8237
A
0010h-0018h
R/W
EMS
register
001Eh-001Fh R/W OAK special register
0020h-003Fh R/W Interrupt controller 1, 8259A, Master
0040h-005Fh R/W Timer, 8254
0060h-006Fh R/W 80C42 (Keyboard), System control register
0070h-007Fh R/W Real-time clock, NMI (non-maskable interrupt) mask
0080h-008Fh R/W DMA page register
0094h R/W System board setup enable register
00A0h-00BFh R/W Interrupt controller 2, 8237 A
00C0h-00DFh R/W DMA controller 2, 8237 A
0102h R/W POS register 2
O1F0h-01F7h R/W Fixed Disk 0
0278h-027Fh R/W Parallel port 3
02F8h-02FFh R/W Serial port 2
0378h-037Fh R/W Parallel port 2
03BOh-03BFh R/W Video Graphics Adapter I and Parallel port 1
03C0h-03CFh R/W Video Graphics Adapter 1
03D0h-03DFh R/W Video Graphics Adapter 1
03F0h-03F7h R/W Floppy Disk A
03F8h-03FFh
R/W
Serial
port
1

SECTION 3
TROUBLESHOOTING

C286-LT SERVICE MANUAL
3.0
TROUBLESHOOTING
SECTION
1)
DISASSEMBLY
INSTRUCTIONS
FOR
FIELD
REPLACEMENT
UNITS
2)
POWER
ON
DIAGNOSTIC
TESTS
A CAUTION
USE ANTI-STATIC PRECAUTIONS
2)
Ä L N WHEN SERVICING THIS PRODUCT
3-1