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
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CORPORATION PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY
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to the information herein; these changes will be incorporated in new
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and/or changes in the
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and/or the program(s) described in this publication at any time.
It is possible that this publication may contain reference to, or information about, IBM
products (machines and programs), programming,
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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
authorized IBM Personal Computer dealer,
mM Product Center, or your IBM Marketing
Representative. .
The following paragraph applies only to the United States and Puerto Rico: A Reader's
Comment
Foml is provided at the back of this publication. If the form has been removed,
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