IBM AT 5170 Use and care manual

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Hardware Reference
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Library
Technical
Reference

First Edition (September, 1985)
The following paragraph does not apply to the United Kingdom or any country where such
provisions are inconsistent
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CORPORATION PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY
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and/or changes in the
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It is possible that this publication may contain reference to, or information about, IBM
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Products are not stocked at the address below. Requests for copies
of this publication and
for technical information about IBM Personal Computer products should be made to your
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The following paragraph applies only to the United States and Puerto Rico: A Reader's
Comment
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address comments to: IBM Corporation, Personal Computer, P.O. Box
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~
© Copyright International Business Machines Corporation 1985

Federal Communications Commission
Radio Frequency Interference Statement
Warning: The equipment described herein has been
certified to comply with the limits for a Class B computing
device, pursuant to Subpart J
of Part 15 of the FCC rules.
Only peripherals (computer
input/output devices, terminals,
printers, etc.) certified
to comply with the Class B limits may
be attached to the computer. Operation with non-certified
peripherals
is likely to result in interference to radio and TV
reception. If peripherals not offered by mM are used with
the equipment, it is suggested to use shielded grounded cables
with in-line filters if necessary.
CAUTION
This product described herein is equipped with a grounded
plug for
the user's safety. It is to be used in conjunction with
a properly grounded receptacle
to avoid electrical shock.
iii

Notes:
iv

Preface
This manual describes the various units of the IBM Personal
Computer AT and how they interact.
It also has information
about the basic
input/output system (BIOS) and about
programming support.
The information in this publication
is for reference, and is
intended for hardware and program designers, programmers,
engineers, and anyone else who needs to understand the design
and operation
of the IBM Personal Computer AT.
This manual consists
of nine sections:
• The first three sections describe the hardware aspects of the
IBM Personal Computer AT including signal charts and
register information.
• Section 4 describes keyboard operation, the commands to
and from the system, and the various keyboard layouts.
• Section 5 contains information about the usage of BIOS and
a system BIOS listing.
• Section 6 contains instruction sets for the 80286
microprocessor and the 80287 math coprocessor.
• Section 7 provides information about characters, keystrokes,
and colors.
• Section 8 has general communications information.
• Section 9 contains information about the compatibility of the
IBM Personal Computer AT and the rest of the IBM
Personal Computer family.
A glossary of terms and a bibliography of related publications are
included.
v

Prerequisite Publications
Guide to Operations for the IBM Personal Computer AT
Suggested Reading
• BASIC for the IBM Personal Computer
• Disk Operating System (DOS)
•
MA CR 0 Assembler for the IBM Personal Computer
vi

Contents
SECTION 1. SYSTEM BOARD .....•..•............ 1-1
Memory .................................... 1-4
Microprocessor ............................... 1-4
System Performance
........................... 1-7
Direct Memory Access ......................... 1-9
System Interrupts ............................ 1-12
Hardware Interrupt Listing
................. 1-13
Interrupt Sharing ......................... 1-14
System Timers
.............................. 1-22
System Clock
............................... 1-23
ROM Subsystem ............................. 1-23
RAM Subsystem
............................. 1-24
I/OChannel ................................ 1-24
Connectors ............................. 1-25
I/O Channel Signal Description ............. 1-31
NMI and Coprocessor Controls
............. 1-38
Other Circuits ............................... 1-40
Speaker
................................ 1-40
RAM Jumpers
........................... 1-40
Display Switch .......................... 1-41
Variable Capacitor ....................... 1-41
Keyboard Controller
...................... 1-42
Real-Time Clock/CMOS RAM Information ... 1-56
Specifications ............................... 1-69
System Unit
............................ 1-69
Connectors
............................. 1-71
Logic Diagrams -Type 1 .................. 1-76
Logic Diagrams -Type 2
.................. 1-98
SECTION 2. COPROCESSOR ...................... 2-1
Description
.................................. 2-3
Programming Interface
......................... 2-3
Hardware Interface
............................ 2-4
SECTION 3.
POWER SUPPLY ..•....•.........•.... 3-1
Inputs ...................................... 3-3
vii

Outputs ..................................... 3-4
DC Output Protection ......................... 3-4
Output Voltage Sequencing
..................... 3-4
No-Load Operation
........................... 3-5
Power-Good Signal
............................ 3-5
Connectors
.................................. 3-7
SECTION 4. KEYBOARD
.......................... 4-1
Description .................................. 4-3
Power-On Routine ............................ 4-4
Commands from the System
..................... 4-5
Commands to the System
....................... 4-9
Keyboard Scan-Code Outputs
.................. 4-11
Clock and
Data Signals ........................ 4-12
Keyboard Layouts
........................... 4-15
Specifications ............................... 4-22
Logic Diagram
.............................. 4-23
SECTION 5. SYSTEM BIOS
..•.................•... 5-1
System BIOS Usage ........................... 5-3
Keyboard Encoding and Usage
.................. 5-13
Quick Reference
............................. 5-24
SECTION 6. INSTRUCTION SET
................... 6-1
80286 Instruction Set
.......................... 6-3
Data Transfer
............................ 6-3
Arithmetic
............................... 6-6
Logic
................................... 6-9
String Manipulation
...................... 6-11
Control Transfer
......................... 6-13
Processor Control
........................ 6-17
Protection Control
....................... 6-18
80287 Coprocessor Instruction Set
............... 6-22
Data Transfer ........................... 6-22
Comparison
............................ 6-23
Constants
.............................. 6-24
Arithmetic .............................. 6-25
Transcendental
.......................... 6-26
SECTION 7. CHARACTERS, KEYSTROKES, AND
COLORS •..............••.....•••..•......•... 7-1
Character Codes .............................. 7-3
Quick Reference
............................. 7-14
viii

SECTION 8. COMMUNICATIONS .•.••.....•..••.•• 8-1
Hardware
................................... 8-3
Establishing a Communications Link
.............. 8-5
SECTION 9. IBM PERSONAL COMPUTER
COMPATIBILITY
..........•.••..••.......••.••• 9-1
Hardware Considerations
....................... 9-3
System Board
............................ 9-3
Fixed Disk Drive
.......................... 9-5
Diskette Drive Compatibility
................ 9-5
Copy Protection
.......................... 9-5
Application Guidelines
......................... 9-7
High-Level Language Considerations
.......... 9-7
Assembler Language Programming Considerations 9-8
Multitasking Provisions
.................... 9-16
Machine-Sensitive Code
................... 9-19
Glossary ••.••.•..•..••••.•••..•..••••.••.•• Glossary-l
Bibliograpby ..•••••••••.••.•••••••••••...• Bibliograpby-l
Index ........................................ Index-l
ix

Notes:
x

INDEX TAB LISTING
Section 1: System Board ............................... .
Section 2: Coprocessor
................................ .
Section 3: Power Supply
............................... .
Section 4: Keyboard
.................................. .
Section 5: System BIOS
............................... .
Section 6: Instruction Set
.............................. .
xi

Notes:
xii

Section 7: Characters, Keystrokes, and Colors .............. .
Section
8: Communications ............................ .
Section 9: Compatibility
............................... .
Glossary
........................................... .
Bibliography
........................................ .
Index
.............................................. .
xiii

SystemBlockDiagram
System Unit
System Board
80286 80287 Osci
llator
Power Supply
Microprocessor
Coprocessor
115/230
16 Interrupt
ROM
Speaker Speaker
Levels
Connector
7 Channel
RAM Keyboard Keyboard
DMA
Controller
CMOS Real-Time
Battery
Battery
Clock Connector
Fixed
Diskette
Disk
Drives
Drives
I/O
Channel Fixed Disk and
00000000
Diskette Adapter
DDDDD D
xiv

SECTION 1. SYSTEMBOARD
Contents
Memory .................•...•............•.•..•• 1-4
Microprocessor ................•.................. 1-4
Real Address Mode .......................... 1-4'
Protected (Virtual Address) Mode .............. 1-5
System Performance
..•............•••.•....••..... 1-7
DirectMemory Access .................•...•..•...• 1-9
System Interrupts ................................ 1-12
Hardware Interrupt Listing ...................... 1-13
Interrupt Sharing
.............................. 1-14
Design Overview
........................... 1-14
Program Support
........................... 1-15
Precautions
............................... 1-17
Examples
................................. 1-18
System Tinters
.........•.........•.........••...• 1-22
System Clock .......................••........... 1-23
ROM Subsystem 1-23
RAM Subsystem
1-24
110 Channel .................................... 1-24
Connectors .................................. 1-25
110 Channel Signal Description .................. 1-31
NMI and Coprocessor Controls
.................. 1-38
Other Circuits
.............•.•...........•...••.. 1-40
Speaker ..................................... 1-40
RAM Jumpers ................................ 1-40
System Board 1-1

Display Switch ................................ 1-41
Variable Capacitor
............................ 1-41
Keyboard Controller
........................... 1-42
Keyboard Controller Initialization
.............. 1-42
Receiving
Data from the Keyboard ............. 1-43
Scan
Code Translation ....................... 1-43
Sending
Data to the Keyboard ................. 1-48
Inhibit
................................... 1-48
Keyboard Controller System Interface
.......... 1-48
Status Register
............................. 1-49
Status-Register Bit Definition
................. 1-49
Output Buffer ............................. 1-50
Input Buffer ............................... 1-51
Commands
(I/O Address Hex 64) ............. 1-51
I/O Ports ................................. 1-54
Real-Time
Clock/CMOS RAM Information ........ 1-56
Real-Time Clock Information
................. 1-57
CMOS
RAM Configuration Information ......... 1-59
1/0 Operations ............................. 1-68
Specifications
•.......•.•........•....•........•. 1-69
System Unit .................................. 1-69
Size
..................................... 1-69
Weight
................................... 1-69
Power Cables
.............................. 1-69
Environment
.............................. 1-69
Heat Output ............................... 1-70
Noise Level
............................... 1-70
Electrical
................................. 1-70
Connectors
.................................. 1- 71
Logic Diagrams -Type 1 ........................ 1-76
Logic Diagrams -Type 2 ........................ 1-98
1-2 System Board

The type 1 system board is approximately 30.5 by 35 centimeters
(12 by 13.8 inches). The type 2 system board
is approximately
23.8 by 35 centimeters (9.3 by 13.8 inches). Both types
of
system boards use very large scale integration (VLSI) technology
and have the following components:
• Intel 80286 Microprocessor
• System support function:
Seven-Channel Direct Memory Access (DMA)
Sixteen-level interrupt
Three programmable timers
System clock
• 64K read-only memory (ROM) subsystem, expandable to
128K
• A 512K random-access memory (RAM) Subsystem
.~
• Eight
input/output (I/O) slots:
Six with a 36-pin and a 62-pin card-edge socket
Two with only the 62-pin card-edge socket
• Speaker attachment
• Keyboard attachment
• Complementary metal oxide semiconductor (CMOS)
memory
RAM to maintain system configuration
• Real-Time Clock
• Battery backup for CMOS configuration table and
~
Real-Time Clock
System Board 1-3

Memory
The type 1 system board has four banks of memory sockets, each
supporting 9 128K-by-1-bit modules for a total memory size of
512K, with parity checking.
~
The type 2 system board has two banks of memory sockets, each
supporting 9 256K-by-1-bit modules for a total memory size of
512K, with parity checking.
Microprocessor
The Intel 80286 microprocessor has a 24-bit address, 16-bit
memory interface1,
an extensive instruction set, DMA and
interrupt support capabilities, a hardware fixed-point mUltiply and
divide, integrated memory management, four-level memory
protection,
1G (1,073,741,824 bytes) of virtual address space for
each task,
and two operating modes: the 8086-compatible real ~
address mode and the protected or virtual address mode. More
detailed descriptions of the microprocessor may be found in the
publications listed in the Bibliography
of this manual.
Real Address Mode
In the real address mode, the microprocessor's physical memory is
acontiguous array of up to one megabyte. The microprocessor
addresses memory
by generating 20-bit physical addresses.
The selector portion
of the pointer is interpreted as the upper 16
bits
of a 20-bit segment address. The lower 4 bits of the 20-bit
segment address are always zero. Therefore, segment addresses
begin
on multiples of 16 bytes.
In this manual, the tenn interface refers to a device that carries signals between
functional units.
1-4 System Board