IBM 5150

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SECTION

ROM and SYSTEM

r",

USAGE

Contents:

ROM

BIOS.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

BIOS Cassette Logic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Keyboard Encoding and Usage . . . . . . . . . . . . . . . . . . .

3-11

Low Memory

Maps.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-21

3-1

Main Page

Table of Contents8
Hardware Overview16
System Block Diagram19
Section 2. Hardware20
System Board22
System Board Data Flow25
I/O Channel27
I/O Channel Diagram28
System Board I/O Channel Description29
System Board Component Diagram32
Keyboard33
Keyboard Interface Block Diagram34
Keyboard Scan Codes36
Keyboard Interface Connector Specifications37
Cassette User Interface38
Cassette Jumpers38
Circuit Block Diagrams38
Cassette Interface Read Hardware38
Cassette Interface Write Hardware39
Cassette Motor Control39
Cassette Interface Connector Specifications40
Speaker Interface41
Speaker Drive System Block Diagram41
I/O Address Map42
System Memory Map44
System Memory Map (Increments of I6KB)44
System Board and Memory Expansion Switch Settings47
1/4" Diskette Drives Switch Settings48
Monitor Type Switch Settings48
System Board Memory Switch Settings49
32/64KB Memory Expansion Option Switch Settings50
Power Supply52
Power Supply Location53
Input Requirements53
DC Output53
AC Output53
Important Operating Characteristics55
Over Voltage/Current Protection55
Signal Requirements55
IBM Monochrome Display and Parallel Printer Adapter56
Parallel Interface Description56
IBM Monochrome Display Adapter Block Diagram57
IBM Monochrome Display Adapterblockdiagram57
System Channel Interface58
Lines Used58
Loads58
Special Timing58
Data Rates58
Interrupt and DMA Response Requirements58
Modes of Operation59
Programming Considerations60
Programming the 6845 CRT Controller60
Sequence of Events60
Memory Requirements60
Initialization Parameters60
DMA Channel61
Interrupt Levels61
I/O Address and Bit Map61
IBM Monochrome Display62
Operating Characteristics62
IBM Monochrome Direct Drive Interface and Pin Assignment63
Color/Graphics Monitor Adapter64
Major Components Definitions67
Motorola 6845 CRT Controller67
Mode Set and Status Registers67
Display Buffer67
Character Generator67
Timing Generator67
Composite Color Generator67
Modes of Operation68
Alphanumeric Mode68
Color TV68
Color Monitor69
IBM Monochrome Display Adapter V S. Color/Graphics70
Adapter Attribute Relationship70
Color/Graphics Modes70
Monochrome Vs Color/Graphics Attributes70
Graphics Storage Map71
Description of Basic Operations73
Summary of Available Colors74
Programming Considerations74
Programming the 6845 Controller74
6845 Register Description75
Programming the Mode Control and Status Register76
Color Select Register76
Mode Select Register77
Mode Register Summary78
Status Register78
Sequence of Events79
Memory Requirements79
Interrupt Level79
I/O Address and Bit Map80
Color/Graphics Monitor Adapter Direct Drive, and Composite Interface Pin Assignment81
Color/Graphics Monitor Adapter Auxiliary Video Connectors82
Parallel Printer Adapter84
Parallel Printer Block Diagram85
Programming Considerations86
Parallel Printer Adapter Interface Connector Specifications88
IBM 80 CPS Matrix Printer89
Printer Specifications90
Setting the DIP Switches91
Functions and Conditions of DIP Switch 191
Functions and Conditions of DIP Switch 292
Parallel Interface Description92
Connector Pin Assignment and Descriptions Ofinterface Signals93
Connector Pin Assignment and Description of Interface Signals94
Parallel Interface Timing Diagram96
ASCII Coding Table97
ASCII Control Codes98
Dcl/Dc3 and Data Entry101
Functional Description110
Digital Output Register110
Floppy Disk Controller110
Symbol Description111
Programming Considerations113
Symbol Descriptions113
Command Summary115
Command Status Registers119
Status Register O120
Status Register 1121
Drive Constants123
Comments123
System I/O Channel Interface123
Drive a and B Interface125
Adapter Outputs125
Adapter Inputs126
1/4" Diskette Drive Adapter Internal Interface Specifications127
Specifications127
1/4" Diskette Drive129
Diskettes130
Mechanical and Electrical Specifications131
Memory Expansion Options132
Operating Characteristics132
Memory Module Description133
Memory Module Pin Configuration133
Switch Configurable Start Address134
DIP Module Start Address134
Game Control Adapter136
Game Control Adapter Block Diagram136
Functional Description137
Address Decode137
Data Buss Buffer/Driver137
Trigger Buttons137
Joystick Po~Tions137
I/O Channel Description138
Interface Description138
Asynchronous Communications Adapter142
Asynchronous Communications Adapter Block Diagram143
Modes of Operation144
I/O Decode for Communications Adapter144
I/O Decodes (3F8 - 3FF)144
Interrupts145
Interface Description145
Current Loop Interface146
Voltage Interchange Information147
INS8250 Functional Pin Description148
Input Signals148
Output Signals151
Input/Output Signals152
Programming Considerations152
Asynchronous Communications Reset Functions152
INS 8250 Accessable Registers153
INS8250 Line Control Register153
INS8250 Programmable Baud Rate Generator154
Line Status Register156
Interrupt Identification Register158
Interrupt Enable Register160
Modem Control Register161
Modem Status Register162
Receiver Buffer Register163
Transmitter Holding Register164
Selecting the Interface Format165
Asynchronous Communications Adapter Connector Interface Specifications166
SECTION 3. ROM and SYSTEM USAGE168
Rom Bios169
Use of BIOS169
Parameter Passing169
Interrupt Vector Listing170
Vectors with Special Meaning172
Interrupt 1 CH - Timer Tick172
Interrupt IDH - Video Parameters172
Interrupt Leh - Diskette Parameters172
Interrupt IFH - Graphics Character Extensions173
Other Read/Write Memory Usage173
BIOS Programming Tip173
BIOS Memory Map174
BIOS Cassette Logic175
Interrupt 15175
Cassette Write175
Cassette Read176
Data Record Architecture177
Error Recovery177
Keyboard Encoding and Usage178
Encoding178
Character Codes178
Extended Codes180
Extended Functions180
Shift States181
Shift Key Priorities182
Special Handling182
System Reset182
Break183
Pause183
Print Screen183
Keyboard Usage184
BASIC Screen Editor Special Functions186
DOS Special Functions186
Low Memory Maps188
0-7F Interrupt Vectors188
BASIC and DOS Reserved Interrupts (80-3FF)189
Reserved Memory Locations (400-5FF)189
BASIC Workspace Variables190
Appendices192
Appendix A: ROM BIOS Listing192
Appendix B: Assembly Instruction Set Reference192
Appendix C: Ofcharacters Keystrokes and Color192
Appendix E: Unit Specifications192
System Board309
Keyboard320
IBM Monochrome Display and Parallel Printer Adapter325
IBM Monochrome Display331
Color/Graphics Monitor Adapter332
Parallel Printer Adapter341
32 Kb Memory Expansion350
Game Control Adapter356

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