IBM PC Technical Reference Manual for the original IBM PC Personal Computer from 1981. It contains technical information about every component of this computer, and a listing of the ROM BIOS.

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IBM PC Technical Reference Manual
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CONTENTS
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	1-1 SECTION 1. HARDWARE OVERVIEW
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	1-4  System Block Diagram
	
	
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	2-1 SECTION 2. HADRWARE
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	2-3  System Board
	2-6  System Data Flow
	2-8  I/O Channel
	2-9  I/O Channel Diagram
	2-10 System Board I/O Channel Diagram
	2-13 System Board Component Diagram
	2-14 Keyboard
	2-15 Keyboard Interface Block Diagram
	2-16 Keyboard Diagram
	2-17 Keyboard Scan Codes
	2-18 Keyboard Interface Connector Specifications
	2-19 Cassette User Interface
	2-19	Cassette Jumpers
	2-19	Cassette Block Diagram
	2-21 Cassette Interface Connector Specifications
	2-22 Speaker Interface
	2-22	Speaker Drive System Block Diagram
	2-23 I/O Address Map
	2-25 System Memory Map
	2-28 System Board And Memory Expansion Switch Settings
	2-29 5 1/4" Diskette Drives Switch Settings
	2-29 Monitor Type Switch Settings
	2-30 System Board Memory Swith Settings
	2-31 32/64 KB Memory Expansion Option Switch Settings
	
	2-33 Power Supply
	2-34 Power Supply Location
	2-34 Input Requirements
	2-34 DC Output
	2-34 AC Output
	2-35 Power Supply Connectors And Pin Assignments
	2-36 Important Operating Characteristics
	2-36	Over Voltage/Current Protection
	2-36	Signal Requirements
	
	2-37 IBM Monochrome Display and Parallel Printer Adapter
	2-37 Parallel Interface Description
	2-38 IBM Monochrome Display Adapter Block Diagram
	2-39 System Channel Interface
	2-39	Lines Used
	2-39	Loads
	2-39	Special Timming
	2-39	Data Rates
	2-39	Interrupt and DMA Response Requirements
	2-40 Modes of Operation
	2-41 Programming Considerations
	2-41	Programming the 6845 CRT Controller
	2-41	Sequence of Events
	2-41	Memory Requirements
	2-42 DMA Channel
	2-42	Interrupt Levels
	2-42	I/O Address and Bit Map
	2-43 IBM Monochrome Display
	2-43	Operating Characteristics
	2-44 IBM Monochrome Display Drive Interface and Pin Assignment
	
	2-45 Color/Graphics Monitor Adapter
	2-47 Color/Graphics Monitor Adapter Block Diagram
	2-48 Major Components Definitions
	2-48	Motorola 6845 CRT Controller
	2-48	Mode Set and Status Registers
	2-48	Display Buffer
	2-48	Character Generator
	2-48	Timming Generator
	2-48	Composite Color Generator
	2-49 Modes of Operation
	2-49	Alphanumeric Mode
	2-49	Color TV
	2-50	Color Monitor
	2-51 IBM Monochrome Display Adapter Vs. Color/Graphics Adapter Attribute Relationship
	2-51 Color/Graphics Modes
	2-52	Graphics Storage Map
	2-54	Description of Basic Operations
	2-55	Summary of Available Colors
	2-55 Programming Considerations
	2-55	Programming The 6845 Controller
	2-56	6845 Register Description
	2-57	Programming the Mode Control and Status Register
	2-57	Color Select Register
	2-58	Mode Select Register
	2-58	Mode Register Summary
	2-59	Status Register
	2-59	Sequence of Events
	2-60	Memory Requirements
	2-60	Interrupt Level
	2-61	I/O Address and Bit Map
	2-62 Color/Graphics Monitor Adapter Direct Drive, and Composite Interface Pin Assignment
	2-63 Color/Graphics Monitor Adapter Auxiliary Video Conectors
	
	2-65 Parallel Printer Adapter
	2-66 Parallel Printer Block Diagramm
	2-67 Programming Considerations
	2-69 Parallel Printer Adapter Interface Connector Specifications
	2-70 IBM 80 CPS Matrix Printer
	2-71 Printer Specifications
	2-72 Setting the DIP Switches
	2-72	Functions and Conditions of DIP Switch 1
	2-73	Functions and Conditions of DIP Switch 2
	2-73 Parallel Interface Description
	2-74 	Connector Pin Assignment and Description of Interface Signals
	2-77	Parallel Interface Timming Diagrams
	2-78 ASCII Coding Table
	2-79 Control Codes
	
	2-89 5 1/4" Diskette Drive Adapter
	2-90 5 1/4" Diskette Drive Adapter Block Diagram
	2-91 Functional Description
	2-91	Digital Output Register
	2-91	Floppy Disk Controller
	2-94 Programming Considerations
	2-94	Symbol Descriptions
	2-96	Command Summary
	2-100	Command Status Registers
	2-103 Programming Summary
	2-103	DPC Registers
	2-104	Drive Constants
	2-104	Comments
	2-104 System I/O Channel Interface
	2-106 Drive A and B Interface
	2-106	Adapter Outputs
	2-107	Adapter Inputs
	2-108 5 1/4" Diskette Drive Adapter Internal Interface Specifications
	2-109 5 1/4" Diskette Drive Adapter External Interface Specifications
	2-110 5 1/4" Diskette Drive
	2-111 Diskettes
	2-112 Mechanical and Electrical Specifications
	
	2-113 Memory Expansion Options
	2-113 Operating Characteristics
	2-114 Memory Module Description
	2-114 Memory Module Pin Configuration
	2-115 Switch Configurable Start Address
	
	2-117 Game Control Adapter
	2-117 Game Control Adapter Block Diagram
	2-118 Functional Description
	2-118	Address Decode
	2-118	Data Bus Buffer/Driver
	2-118	Trigger Buttons
	2-118	Joystick Positions
	2-119 I/O Channel Description
	2-119 Interface Description
	2-121 Joystick Schematic
	2-122 Game Control Adapter (Analog Input) Connector Specifications
	
	2-123 Asynchronous Communications Adapter
	2-124 Asynchronous Communications Adapter Block Diagram
	2-125 Modes of Operation
	2-125	I/O Decode for Comunications Adapter
	2-126	Interrupts
	2-126 Interface Description
	2-127	Curent Loop Interface
	2-128	Voltage Interchange Information
	2-129 INS 8250 Functional Pin Description
	2-129	Input Signals
	2-132	Output Signals
	2-133	Input/Output Signals
	2-133 Programming Considerations
	2-133	Asynchronous Communications Reset Functions
	2-134	INS 8250 Accessable Registers
	2-134	INS 8250 Line Control Register
	2-135	INS 8250 Programmable Baud Rate Generator
	2-137	Line Status Register
	2-139	Interrupt Identification Register
	2-140	Interrupt Enable Register
	2-142	Modem Control Register
	2-143	Modem Status Register
	2-144	Receive Buffer Register
	2-145	Transmitter Holding Register
	2-146 Selecting The Interface Format
	2-147 Asynchronous Communications Adapter Connector Interface Specifications
	
	
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	3-1  SECTION 3. ROM and SYSTEM USAGE
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	3-2  ROM BIOS
	3-2  Use of BIOS
	3-2  Parameter Passing
	3-3  Interrupt Vector Listing
	3-5  Vectors With Special Meaning
	3-5 	Interrupt ICH - Timer Tick
	3-5 	Interrupt 1DH - Video Parameters
	3-5 	Interrupt 1EH - Diskette Parameters
	3-6 	Interrupt 1FH - Graphics Character Extensions
	3-6 	Other Read/Write Memory Usage
	3-6  BIOS Programming Tip
	3-7  BIOS Memory Map
	
	3-8  BIOS Cassette Logic
	3-8  Interrupt 15
	3-8  Cassette Write
	3-9  Cassette Read
	3-10 Data Record Architecture
	3-10 Error Recovery
	
	3-11 Keyboard Encoding and Usage
	3-11 Encoding
	3-11 Character Codes
	3-13 Extended Codes
	3-13	Extended Functions
	3-14	Shift States
	3-15	Shift Key Priorities
	3-15 Special Handling
	3-15	System Reset
	3-16	Break
	3-16	Pause
	3-16	Print Screen
	3-17 Keyboard Usage
	3-19 BASIC Screen Editor Special Functions
	3-19 DOS Special Functions
	
	3-21 Low Memory Maps
	3-21 0-7F Interrupt Vectors
	3-22 BASIC and DOS Reserved Interrupts (80-3FF)
	3-22 Reserved Memory Locations (400-5FF)
	3-23 BASIC Workspace Variables
	
	
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	A-0  APPENDICES
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	A-1  Appendix A: ROM BIOS Listing
	B-1  Appendix B: Assembly Instructions Set Reference
	C-1  Appendix C: Of Characters Keystrokes and Color
	D-1  Appendix D: Logic Diagrams
	E-1  Appendix E: Unit Specifications
	G-1  Glossary
	Bib-1  Bibliography
	I-1  Index
	
	
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FIGURE LISTING
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	1	System Block Diagram							1-4
	2	System Board Data Flow							2-6, 2-7
	3	I/O Channel Diagram								2-9
	4	System Board Component Diagram					2-13
	5	Keyboard Interface Block Diagram				2-15
	6	Keyboard Diagram								2-16
	7	Cassette Interface Read Hardware				2-19
	8	Cassette Interface Write Hardware				2-20
	9	Cassette Motor Control							2-20
	10	Speaker Drive System Block Diagram				2-22
	11	System Memory Map								2-25
	12	System Memory Map (Increments of 16 KB)			2-26
	13	Power Suply and Connectors						2-35
	14	IBM Monochrome Display Adapter Block Diagram	2-38
	15	Color/Graphics Monitor Adapter Block Diagram	2-47
	16	Parallel Printer Adapter Block Diagram			2-66
	17	Location of (Printer) DIP Switches				2-72
	18	Parallel Interface Timing						2-77
	19	5 1/4" Diskette Driver Adapter Block Diagram	2-90
	20	Game Control Adapter Block Diagram				2-117
	21	Joystick Schematic								2-121
	22	Asynchronous Communications Adapter Block Diagram	2-124
	23	Current Loop Interface							2-127
	24	Selecting The Interface Format					2-146
	25 BIOS Memory Map									3-7
	
	
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TABLE LISTING
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	1	Keyboard Scan Codes							2-17
	2	6845 Initialization Parameters				2-41
	3	Monochrome Vs. Color/Graphics Attributes	2-51
	4	Color/Graphics Modes						2-51
	5	Summary of Available Colors					2-55
	6	6845 Register Description					2-56
	7	Printer Specifications						2-71
	8	Functions and Conditions of DIP Swich 1		2-72
	9	Functions and Conditions of DIP Swich 2		2-73
	10	Connector Pin Assignment and Description of Interface Signls	2-74
	11	ASCII Coding Table							2-78
	12	DC1/DC3 and Data Entry						2-82
	13	Symbol Description							2-94
	14	Status Register 0							2-100
	15	Status Register 1							2-101
	16	Status Register 2							2-102
	17	Status Register 3							2-103
	18	Mechanical and Electrical Specifications	2-112
	19	Memory Module Pin Configuration				2-114
	20	DIP Module Star Address						2-115
	21	I/O Decodes (3F8-3FF)						2-125
	22	Asynchronous Communications Reset Functions	2-133
	23	BAUD Rate at 1.843 Mhz						2-137
	24	Interrupt Control Functions (Asynchronous)	2-140
	25	Character Codes								3-11
	26	Keyboard Extended Functions					3-14
	27	Keyboard - Commonly Used Functions			3-17
	28	Basic Screen Editor Special Functions		3-19
	29	DOS Special Functions						3-19
	30	0-7F Interrupt Vectors						3-21
	31	Basic & DOS Reserved Interrupts (80-3FF)	3-22
	32	Reserved Memory Locations (400-5FF)			3-22