Table Of Content---------,----- PHearrsdownarl eC Roemfepruetnecre
Library
Technical
Reference
Revised Edition (April 1984)
The following paragraph does not apply to the United Kingdom or any country where such
provisions are inconsistent with local law: International Business Machines Corporation
provides this manual "as is," without warranty of any kind, either expressed or implied,
including, but not limited to the particular purpose. IBM may make improvements and/or
changes in the product(s) and/or the program(s) described in this manual at any time.
This product could include technical inaccuracies or typographical errors. Changes are
made periodically to the information herein; these changes will be incorporated in new
editions of the publication.
It is possible that this material may contain reference to, or information about, IBM
products (machines or programs), programming, or services that are not announced in
your country. Such references or information must not be construed to mean that IBM
intends to announce such IBM products, programming, or services in your country.
Products are not stocked at the address below. Requests for copies of this product and for
technical information about the system should be made to your authorized IBM Personal
Computer dealer.
The following paragraph applies only to the United States and Puerto Rico: A Reader's
Comment Form is provided at the back of this publication. If the form has been removed,
address comments to: IBM Corp., Personal Computer, P.O. Box 1328-C, Boca Raton,
Florida 33432. IBM may use or distribute any of the information you supply in any way it
believes appropriate without incurring any obligations whatever.
© Copyright International Business Machines Corporation 1981, 1982, 1983, 1984
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 IBM are used with the
equipment, it is suggested to use shielded grounded cables
with in-line filters if necessary.
CAUTION
The 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.
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Preface
This publication describes the various units of the IBM Personal
Computer XT and IBM Portable Personal Computer; and the
interaction of each.
The information in this publication is for reference, and is
intended for hardware and program designers, programmers,
engineers, and anyone else with a knowledge of electronics
and/ or programming who needs to understand the design and
operation of the IBM Personal Computer XT or IBM Portable
Personal Computer.
This publication consists of two parts: a system manual and an
options and adapters manual.
The system manual is divided into the following sections:
Section 1, "System Board," discusses the component layout,
circuitry, and function of the system board.
Section 2, "Coprocessor," describes the Intel 8087
coprocessor and provides programming and hardware
interface information.
Section 3, "Power Supply," provides electrical input/output
specifications as well as theory of operation for both the IBM
Personal Computer XT power supply and the IBM Portable
Personal Computer power supply.
Section 4, "Keyboard," discusses the hardware make up,
function, and layouts of the IBM Personal Computer XT and
the IBM Portable Personal Computer keyboards.
Section 5, "System BIOS," describes the basic input/ output
system and its use. This section also contains the software
interrupt listing, a BIOS memory map, descriptions of vectors
with special meanings, and a set of low memory maps. In
addition, keyboard encoding and usage is discussed.
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Section 6, "Instruction Set," provides a quick reference for the
8088 assembly instruction set.
Section 7, "Characters, Keystrokes, and Colors," supplies the
decimal and hexadecimal values for characters and text
attributes.
Section 8, "Communications,"describes communications
hardware and discusses communications interface standards
and the sequence of events to establish communications.
A glossary, bibliography, and index are also provided.
The Technical Reference options and adapters manual provides
information, logic diagrams, and specifications pertaining to the
options and adapters available for the IBM Personal Computer
family of products. The manual is modular in format, with each
module providing information about a specific option or adapter.
Modules having a large amount of text contain individual indexes.
The modules are grouped by type of device into the following
categories:
• Expansion Unit
• Displays
• Printers
• Storage Devices
• Memory Expansion
• Adapters
• Miscellaneous
• Cables and Connectors
Full page length hard tabs with the above category descriptions,
sep~rate the groups of modules.
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The term" Technical Reference manual" in the option and adapter
manual, refers to the IBM Personal Computer XT /IBM Portable
Personal Computer Technical Reference system manual.
The term "Guide to Operations manual" in the option and adapter
manual, refers to either the IBM Personal Computer XT Guide to
Operations manual or the IBM Portable Personal Computer Guide
to Operations manual.
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Prerequisite Publications
• IBM Personal Computer XT Guide to Operations
• IBM Portable Personal Computer Guide to Operations
Suggested Reading
• BASIC for the IBM Personal Computer
• Disk Operating System (DOS), Version 2.1
• IBM Personal Computer XT Hardware Maintenance and
Service
• IBM Portable Personal Computer Hardware Maintenance and
Service
• MACRO Assembler for the IBM Personal Computer
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Contents
SECTION 1. SYSTEM BOARD ..................... 1-1
Description .................................. 1-3
Microprocessor ............................... 1-4
Data Flow Diagrams ........................... 1-5
System Memory Map .......................... 1-8
System Timers .............................. 1-10
System Interrupts ............................ 1-10
ROM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-12
RAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1-12
DMA ..................................... 1-12
I/O Channel ................................ 1-13
System Board Diagram ........................ 1-15
I/O Channel Diagram ......... . . . . . . . . . . . . . . .. 1-16
I/O Channel Description ...................... 1-18
I/O Address Map ............................ 1-21
Other Circuits ............................... 1-23
Speaker Circuit .......................... 1-23
8255A I/O Bit Map ...................... 1-25
System-Board Switch Settings .............. 1-27
Specifications ............................... 1-28
Card Specifications ....................... 1-28
Logic Diagrams .............................. 1-30
SECTION 2. COPROCESSOR ..................... 2-1
Description .................................. 2-3
Programming Interface ......................... 2-3
Hardware Interface ............................ 2-4
SECTION 3. POWER SUPPLY ..................... 3-1
IBM Personal Computer XT Power Supply ......... 3-3
Description .............................. 3-3
Input Requirements ....................... 3-3
Outputs ................................. 3-4
Overvoltage/Overcurrent Protection .......... 3-5
Power-Good ............................. 3-5
Connector Specifications and Pin Assignments .. 3-5
IBM Portable Personal Computer Power Supply ..... 3-7
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