# THE 8080 _ 8085 by Levone

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```									       THE 8080 & 8085

MICROPROCESSORS

AND

PERIPHERALS

Prof. Dr. Dogan Ibrahim

Kaan Uyar
CONTENTS
PREFACE

1.   INTRODUCTION                                       1
1.1   Microcomputers                                     1

1.2   Number Systems                                4
1.2.1 Decimal Number System                   4
1.2.2 Binary Number System                    5
1.2.3 Octal Number System                     5
1.2.5 Converting a Binary Number Into
Decimal                              6
1.2.6 Converting a Decimal Number Into
Binary                               7
1.2.7 Converting a Binary Number Into
1.2.8 Converting a Hexadecimal Number Into
Binary                               10
1.2.9 Converting a Hexadecimal Number Into
Decimal                              11
1.2.10 Converting a Decimal Number Into
1.2.11 Converting an Octal Number Into
Decimal                              13
1.2.12 Converting a Decimal Number Into Octal      14
1.2.13 Converting an Octal Number Into Binary      15
1.2.14 Converting a Binary Numbers Into Octal 16
1.3   Floating Point Numbers                        17
1.3.1 Converting Floating Point Numbers Into
Decimal                              18
1.3.2 Normalizing Floating Point Numbers
1.3.3 Converting Decimal Numbers Into
Floating Point                       20
1.3.4 Multiplication and Division Of Floating
Point Numbers                        22
1.3.5 Addition and Subtraction of Floating
Point Numbers                        23
1.4   Exercises                                     24

2.   THE INTEL 8080 MICROPROCESSOR                      26
2.1   Intel 8080 Microprocessor Registers          26
2.2   Instruction Format                                 28
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2.3   Instruction Set                                    28
2.3.1 Data Transfer Group                          29
2.3.2 Arithmetic Group                             40
2.3.3 Logic Group                                  63
2.3.4 Branch Group                                 72
2.3.5 Stack I/O and Machine Control Group          80
2.4      The Assembly Process                      85
2.5      8080/8085 Assemblers                      86
2.6      Errors in Assembly Programs               90
2.7      Programming Examples
92
2.8    Exercises

3.    THE INTEL 8085 MICROPROCESSOR 121
3.1    The Intel 8085 Architecture           121
3.1.1 Pin Description                 123
3.2    Interrupts                            125
3.2.1 Hardware                        125
3.2.2 Interrupt Priorities            126
3.2.3 Interrupt Driven I/O            128
3.2.4 Interrupt Instruction           129
3.3    SID and SOD Serial I/O Pins           130
3.4    Timing and Delay Programs             138
3.5    Exercises                             147

4.    THE MEMORY INTERFACE                         149
4.1    Semiconductor Memories                149
4.1.1 RAMs                            149
4.1.2 ROMs                            150
4.3    Exercises                             160

5.    INPUT/OUTPUT INTERFACE                       162
5.1    The Intel 8155 Peripheral Interface
5.1.1 8155 Pin functions              164
5.1.2 8155 Selection                  165
5.1.3 8155 Command Register           166
5.1.4 Status Register                 167
5.1.5 The Timer                       171
5.1.6 Switches                        172
5.1.7 Multiplexed Displays            176
5.1.8 Solenoids and Relays            179
Transmitter
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183
5.2.1 8251 USART Pin Descriptions      184
5.3   Exercises                              187

6.   8080/85 CLOCK CIRCUITS                      196
6.1   8080 Microprocessor Clock Circuits    196
6.1.1 Single Stepping the 8080
Microprocessor                 198
6.2   8085 Microprocessor Clock Circuits    199
6.2.1 Single Stepping the 8085
Microprocessor                 200
6.3   Exercises                             201

7.   SOME SPECIAL PERIPHERALS                    203
7.1    Intel 8259A Programmable Interrupt
Controller                            204
7.1.1 Pin Description                 205
7.1.2 Interrupts in Microprocessor
Systems                      205
7.1.3 8259A Functional Description 206
7.1.4 Programming 8259A                208
7.2   Introduction to Direct Memory Access 208
7.3   Programmable Interval Timer            232
Converters With 8-Channel Multiplexer 229
7.5    Dual Channel DAC0800/02 8-Bit Digital
To Analog Converter                   233
7.6    8279 Programmable Keyboard Display
Interface                             235

8.   8080/85 SYSTEM DESIGN                       241
8.1   8080 System Design                    242
8.2   8085 System Design                    250
8.3   Exercises                             259

APPENDIX A – 74LS244 DATA SHEET                       260
APPENDIX B – 82C55 DATA SHEET                         262
APPENDIX C – 27C64 DATA SHEET                         277
APPENDIX D – 6264 DATA SHEET                          279
APPENDIX E – 8254 DATA SHEET                          280
GLOSSARY                                              298
REFERENCES                                            302
INDEX                                                 304
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PREFACE

First generation computers were large machines which occupied big rooms,
and required air-conditioned environment to operate reliably.          These
machines were based on the vacuum technology where several thousand
valves were used in their design. These machines also required very large
power supplies. Valves had limited life times and it was difficult to do any
useful work since the technicians would constantly be stopping the machines

In 1956 after the invention of the transistors the computer technology
entered its second generation where the first all transistor computer was
designed in 1958 by IBM. Using transistors reduced the size of the
computers considerably, improved the reliability, and also reduced the power
supply requirements.

Third generation computer technology started with the invention of the
integrated circuits in early 1960s. With the invention of the integrated circuits
the size of a computer reduced considerably and its reliability increased. In
1964, IBM announced one of the most famous computers ever to be built
using integrated circuits. This was the IBM 360 which could perform
375,000 computations per second.

In 1960s the computer industry began to grow and we see the development
of minicomputers, such as the PDP-8 minicomputer, developed by DEC.
Many other manufacturers also designed and developed minicomputers
during this phase.

In 1970s we see the development of the first microprocessors. Intel 4004
series, followed by Intel 8008, 8080, and 8085 series have been very
popular during this time. Other manufacturers such as Motorola developed
the 6800 series, and Zilog developed the popular Z80 series of
microprocessors. Al of these were 8-bit microprocessors and they have
been mainly used in automatic control and monitoring applications.

In late 1970s and early 1980 we see the development of the 16-bit and 32-
bit microprocessor systems such as the Intel 8086, Motorola 68000 and so
on.

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8085 is an 8-bit powerful microprocessor which is used widely in teaching. Although the 8085 was
originally invented over 20 years ago it is still used in many industrial and teaching applications. The
reason for this is the simplicity of its architecture and the ease of learning its instruction set.

Chapter 1 is an introduction to the microprocessors in general and various parts of a microprocessor
based system are described. The numbering systems are also described in this chapter.

Chapter 2 gives a detailed description of the Intel 8080/85 instruction set. The assembly phase and
assembler programming examples are also given in this chapter.

Chapter 3 is about the 8085 microprocessor architecture. The interrupt facilities, and the serial input
and output instructions are described in this section.

The types of semiconductor memories and their use in 8080/85 microprocessor circuits and address
decoding techniques are described in Chapter 4.

Chapter 5 is an introduction to the input-output systems,

Various 8080/85 clock circuits are described in Chapter 6 with examples. Single stepping techniques
are also described in this chapter.

Special peripheral devices are given in Chapter 7 with programming examples.

Chapter 8 is about 8080/85 microprocessor based systems design. In this chapter various system
examples are given with sample programs.

Finally, the data sheets of commonly used chips in 8080/85 systems are given in the Appendices.

Dogan Ibrahim & Kaan Uyar
July, 2006

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