MC68000 MICROPROCESSOR DEVELOPMENT BOARD

CHEONG KEE LOAN

This thesis is submitted as partial fulfillment of the requirements for the award of the

Bachelor Degree of Electrical Engineering (Electronics)

Faculty of Electrical & Electronics Engineering

University Malaysia Pahang

NOVEMBER, 2007

“I hereby acknowledge that the scope and quality of this thesis is qualified for the

award of the Bachelor Degree of Electrical Engineering (Electronics)”

Signature : ___________________________________

Name : MR. SAIFUDIN BIN RAZALI

Date : 23 NOVEMBER 2007

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“All the trademark and copyrights use herein are property of their respective owner.

References of information from other sources are quoted accordingly; otherwise the

information presented in this report is solely work of the author.”

Signature : ____________________________

Author : CHEONG KEE LOAN

Date : 23 NOVEMBER 2007

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DEDICATION

A VERY SPECIAL THANK YOU

TO MY PARENTS, BROTHER, AND

ALL MY BELOVED FRIENDS

FOR THEIR SUPPORT.

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ACKNOWLEDGEMENT

I would like to thank my supervisor Mr. Saifudin bin Razali for his advice

and support throughout this project. Because of his guidance and encouragement, I

am able to strive from the beginning stage of this project until the completion of this

thesis.

I also wish acknowledgement to the people who give support direct or

indirectly to the project and during the thesis writing. Once again, thank you very

much.

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ABSTRACT

The 68000 microprocessor becoming an increasingly important

microprocessor in today's market, as evidenced by the frequent announcements of

products using the 68000. The chip is expandable by design, and Motorola has

produce a full 32-bit version in 1984. The 68000 is considerably more complex than

many of the 16-bit minicomputers popular since the 1970s. The main purpose of the

MC68000 microprocessor development board is to educate the coming generation of

engineers and programmers about the 68000, with the expectation that they will able

to learn, understand, and design their own systems that will be using the 68000

microprocessor. In addition to its intended audience of educators and students, this

board is of interest to both high school student and the others which involved in

learning and developing of the 68000-based system. This system will consist of two

board which is the main board and the application board. The application board

consist of various types of input and output devices such as 4x4 keypad, DIP switch,

traffic light LED, DC motor, 7 segment display, dot matrix, and LCD. This

prototype of 68000 microprocessor based development board will be able to produce

various types of outputs according to the input given where it is able to be

manipulated by programming the memory unit.

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ABSTRAK

Pemproses-mikro 68000 menjadi kian penting dalam pasaran kini dan

buktinya jelas kelihatan melalui kekerapan produk yang menggunakan 68000 yang

semakin meningkat. Chip tersebut boleh dikembangkan melalui rekaan dan

Motorola telahpun menghasilkan versi 32 bit pada tahun 1984. 68000 boleh

dikatakan lebih kompleks daripada banyak komputer mini berciri 16 bit sejak 1970-

an. Tujuan utama papan pambangunan MC68000 pemproses-mikro adalah untuk

mendidik bakal jurutera dan penulis program tentang 68000, dengan harapan mereka

dapat memahami, belajar, dan mereka system mereka sendiri dengan menggunakan

pemproses-mikro 68000. Tambahan untuk pengajar dan pelajar yang berminat, papan

ini sesuai untuk pelajar dan mereka yang terlibat dalam pembelajaran dan

perbangunan sistem berasakan 68000. Sistem ini mengandungi dua papan iaitu papan

utama dan papan aplikasi. Papan aplikasi mengandungi pelbagai jenis input dan

output komponen seperti 4x4 papan kekunci, suis DIP, LED, DC motor, 7-segment

display, dan LCD. Papan prototaip pembangunan berasaskan pemproses-mikro

68000 mampu menghasilkan pelbagai jenis output berdasarkan jenis input yang

diberi, dimana ia mampu dimanipulasi melalui pemprograman unit memorinya.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

Declaration i

Dedication ii

Acknowledgement iii

Abstract iv

Abstrak v

Table of Contents vi

List of Tables ix

List of Figures x

List of Appendices xi

1 INTRODUCTION

1.1 Overview 1

1.2 Problem Statement 2

1.3 Objective 3

1.4 Scope 3

1.5 Thesis Outline 4

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2 LITERATURE REVIEW

2.1 Microprocessor Development Board 5

2.2 Hardware Analysis 6

2.2.1 Memory Unit 7

2.2.2 Input & Output Device 9

2.3 Software Analysis 11

3 MC68000 MICROPROCESSOR BOARD:

HARDWARE & SOFTWARE DEVELOPMENT

3.1 Overview of MC68000 Educational Development Board 13

3.2 Operation of Microprocessor Development System 15

3.3 Process Methodology 17

3.3.1 Hardware Development 19

3.3.2 Software Development 22

4 RESULTS AND DISCUSSION

4.1 General Description and Analysis 24

4.2 Hardware Part 24

4.2.1 Microprocessor Main Board 26

4.2.2 Input Module 28

4.2.3 Output Module 30

4.2.3.1 Integration Output Result 33

4.3 Manual Guide 36

4.4 Software 36

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5 CONCLUSION AND RECOMMENDATION

5.1 Conclusion 39

5.2 Recommendation for Future Project 41

5.2.1 Costing & Commercialization 41

REFERENCES 43

APPENDICES A - M 44-84

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LIST OF TABLES

TABLE NO. TITLE PAGE

1 Types of common devices for development board 10

2 Types of module being activated by DIP switch 34

3 Types of output being activated by keypad switch 34

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LIST OF FIGURE

FIGURE NO. TITLE PAGE

3.1 MC68000 Development Systems 14

3.2 Flow of the operating system 16

3.3 Steps towards project completion 18

3.4 Power Circuit 20

3.5 Reset Circuit 20

3.6 Clock Circuit 21

3.8 MC68000 basic operation system 22

4.1 The Complete Main Board of MC68000 Development Board 25

4.2 The Complete Application Board of MC68000 Board 25

4.3 Output waveform from the pin A18 (pin 46) of MC68000P10 27

4.4 The example of DIP switches and the schematic of DIP module 28

4.5 The keypad module that been used and its schematic 29

4.6 The flow chart of the microprocessor board’s development 30

4.7 Output modules along with its schematic diagram 31

4.8 Output modules along with its schematic diagram 32

4.9 Output result: (a) LED, (b) 7 Segment Display, 35

(c) Dot Matrix, (d) and (e) Motor, and (f) LCD display

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LIST OF APPENDICES

APPENDIX NO. TITLE PAGE

A Software program of the MC68000 Microprocessor 43

Development Board

B Schematic of MC68000 Development Board 48

C Manual Guide of MC68000 Development Board 55

D Data sheet of the MC68000 Microprocessor 70

E Data sheet of the EPROM M27C64A 75

F Data sheet of the RAM 6264 76

G Data sheet of the Address Decoder SN74LS138 77

H Data sheet of the Buffer 74LS244 78

I Data sheet of the Latch 74LS374 79

J Data sheet of the Keypad Encoder MM74C922 80

K Data sheet of the Motor Driver L293D 81

L Data sheet of the voltage regulator 7805 82

M Data sheet of the Dot Matrix 83

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CHAPTER 1

INTRODUCTION

1.1 Overview

Microprocessor is an integrated circuit built on a tiny piece of silicon which

contains thousand or even millions of transistor which interconnected via superfine

traces of aluminum. The microprocessor MC68000 has been introduced in 1979 by

MACSS (Motorola Advanced Computer System on Silicon). It is a 16 bit

microprocessor with 16 bit data bus and can operate with 32 bit. It is capable of

supporting multi-tasking and applicable for high level language. Originally it is used

for household products but later on been used for the design of computers like Apple

Macintosh, Commodore Amiga, and Atari ST.

The microprocessor is the heart of a computer (general known as CPU or

central processing unit) which contains all circuitry for fetching and interpreting

instructions and for controlling and performing various operations. It is an intelligent

processing system which able to perform certain task in response to given input

through the data that have been stored. In order to enable a microprocessor to

operate, it is essentially a need of supporting component such as memory unit like

RAM and ROM, input devices like switch, and output devices like Dot matrix.

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The MC68000 microprocessor development board has been designed to aid

the teaching of microprocessor interfacing from simple switch and lamp input/output

through to more complex closed-loop and open-loop control systems. The learning

experience for the student will build a level of competency required in understanding

microprocessors and microprocessor based systems and how to program them in the

various high and low level dialects. The student can use the various elements and

I/O to design and implement hardware and software applications to a specification,

an important area of knowledge for engineers. Simple or complex experiments are

possible by linking the range of devices and sensors to the MC68000. The layout

enables students or beginner to easily understand how a processor works upon. The

wide array of features incorporated into the board include digital switches such as

DIP switch, 4x4 keypad, traffic light colored LED, Dot matrix, DC motor, LCD

display.

1.2 Problem Statement

Nowadays, the technology is getting more advance from day to day and

basically the most important element in it is the more advance intelligent system.

The root of all the intelligent systems is come from the basic microprocessor itself. It

is important for us to keep on passing this knowledge to the next generation. There

are many universities in the world which offer the knowledge of the microprocessor

but most of them is only through theory or the mostly will only cover till the

programming. Therefore, it is essential for us to provide or give the younger

generation the knowledge and skills along by offer them a chance to build their own

intelligent systems or at least giving them an opportunity to see the result of their

own programming skills on a real board. And to achieve that, they need education

guidance as example which is the MC68000 microprocessor development board.

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1.3 Objective

The objective of this project is to design an educational microprocessor

development board will

i. Become a main educational guidance for the future engineer, student, and

beginners to understand more how a processor works before proceed into

more complex devices such as microcontroller.

ii. Enable the students to understand how and why the hardware connected to

the main processor in an arranged order and the function & characteristic of

other supporting component like RAM, ROM, BUFFER, many more.

iii. Give a clear idea and understanding about the effect and function of

programming and the assembly language.

1.4 Scope

There are some scopes that are needed in order to achieve the objective of

this project:

a) The design for this development board must be using MC68000

microprocessor.

b) The programming of the data and instruction must be in assembly language

instead of high level language.

c) This development board is design only for educational purpose.

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1.5 Thesis Outline

This thesis consists of 5 chapters. Chapter 1 cover on introduction of the

project, problem statement, project objectives and scopes of the project. Chapter 2 is

the literature review of this project. The chapter will discuss and review the example

and history of MC68000 microprocessor development board system, the supporting

memory device such as ROM, the variable types of input and output device, and the

software being used. Chapter 3 focuses on the methodology of the whole system of

the MC68000 microprocessor development board. While Chapter 4 discusses all the

result obtained. All discussions concentrate based on the result and the performance

of the system. And Chapter 5 will discuss about the conclusion of the project and

suggestions for further development of the project.

CHAPTER 2

LITERATURE REVIEW

2.1 Microprocessor Development Board

The Motorola MC68000 family of microprocessors is widely recognised as

an industry standard for industrial control and multi-user computer systems requiring

the speed and power of an advanced 16/32-bit microprocessor. For this reason the

68000 is the number one choice for teaching microprocessor and control principles to

students on electronic engineering and computing courses at all levels.

The 68000 may be used to teach advanced microprocessor principles, yet the

orthogonal architecture and uniform addressing modes make it a very straightforward

processor to learn. This, combined with the ease of use of the Flite FLT-68K, make

the system suitable for teaching of microprocessors at introductory level through to

advanced applications. The system makes an ideal platform both for the taught

environment of the classroom and self-teach use by individual users. It also makes

an ideal development/target board for control applications based on the MC68000

[1].

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From the development board, we will be able to understand and see by

ourselves how the microprocessor works along with the component. This will made

the learning process easier since the prototype is a very good example to display the

output from every used component and from that, the understanding of the

functionality of every component can be enhanced.

The MC68000 microprocessor development board is a widely-used tool in

the teaching process for all the students of Electrical & Electronics at all level. The

development board makes an ideal platform for both teaching and learning process

whether in a classroom or in a self-taught environment.

2.2 Hardware Analysis

Many of the 68000’s hardware features are now brought together in a case

study of a complete 68000-based single board computer. It is called the 68KMB.

The goal in designing 68KMB was to provide a powerful tool to study the 68000

microprocessor as well as interfacing to input/output devices. A parallel goal was to

design a 68000-based system with a minimum number of ICs that could be

prototyped and manufactured as cheaply as possible. The following features are

supported:

• 68000 microprocessor

• 16K bytes EPROM

• 16K RAM

• 8-bit parallel output port

• 6-bit parallel input port

• easy expansion for RAM, EPROM, or I/O devices

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Perhaps the reader will extend the design for a custom application with a

different memory configuration or with different I/O features. Also, since the

68KMB is small and inexpensive, it is relatively easy to construct a prototype and

gain hands-on experience through monitor program and interfacing example [2].

68000 development board is actually a single-board computer 6-1/2 by 10-1/2

inches with general component, containing a 68000 microprocessor running at 4

MHz; 16K-byte monitor ROM; 32K-byte dynamic RAM [3].

The MC68000 educational board will consist of three general main parts

which is memory unit, I/O devices, and supporting device [2, 3, 7]. Mainly the input

signal will be generated by the input devices before it is transfer to the

microprocessor. The microprocessor will interface with the memory unit which will

provide data and instruction, and the result will be display as the output on the output

devices.

2.2.1 Memory Unit

The 32K bytes of RAM are located in the lowest memory space and consist

of sixteen 16K by 1-bit dynamic RAM chips. The monitor program, which resides in

two 8K by 8-bit ROMs, is located in address space 8000 to BFFF (hexadecimal),

making it awkward to expand the RAM because any additional memory will be

noncontiguous with the original RAM. It should be no more difficult to have the

monitor resides at higher memory [3].

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Memory systems are used to store data and instruction. There are two types

of memory which is:

1) ROM (Read Only Memory):

• Programmable Maskable ROM- Very cheap and normally programmed in

factory for mass production. One time written and widely used in game

cassette.

• Programmable ROM (PROM)- One time written and can be programmed by

using PROM programmer

• One-Time PROM (OTPROM)- Cheap version of PROM with plastic packed.

• Erasable PROM (EPROM)- Like OTPROM but with glass window. Can be

programmed using EPROM programmer. Can be written thousand times and

erased by using Ultra-violet devices.

• Electrically-Erasable PROM (EEPROM)- Like EPROM, can be written

thousand times using EPROM programmer or in circuit. Electrically erased

but more expensive than its counter part.

• Flash Memory- Like EEPROM, but erasing process involves block by block

Common industrial PROM:

• 2716 2kbyte

• 2732 4kbyte

• 2764 8kbyte

• 27128 16kbyte

• 27256 32kbyte

2) RAM (Random Access Memory):

• Static RAM (SRAM)- Easy to be used and requires an internal flip-flop to

store each bit. Normally used in personal computer

• Dynamic RAM (DRAM)- Cheaper as dynamic RAM uses a single transistor

that acts like a charged capacitor to store each bit.

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Common industrial RAM:

• 6116 2kbyte

• 6164/6264 8kbyte

• 43256/6625 32kbyte

The most general types of ROM and RAM to be used for educational is 2764

type of ROM and 6264 type pr RAM [4].

There are many types of memory unit like ROM and RAM and each of them

have different in terms of functionality, ratings, size, handling method, and many

more [4, 7]. The memory unit that used for this project is EPROM and RAM. The

EPROM has been chosen since it is easily to be program and erasable. The model of

the ROM that have been chosen is 2764 which its size is 8Kbyte while the chosen

RAM is 6264 with size of 8Kbyte. That size was chosen since there will be 2 ROM

and 2 RAM which total up the size to 16Kbyte and this amount will provide

sufficient memory for the programming and data that need to be used.

2.2.2 Input & Output Device

The new microprocessor development board layout enable students to easily

understand each experiment section as it is worked upon. The wide array of features

incorporated into the board include digital switches, traffic light coloured LED

displays, temperature, light, and optical position/speed sensors, a heater, a DC motor,

an LED bargraph, and a potentiometer. A screw terminal is also provided for

external analogue input [1].

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The 68000 microprocessor development board should be designed to teach a

wide variety of control experiments. The circuits provided must include:

Table 1: Types of common devices for development board

ITEM DESCRIPTION

Eight digital switches Generally also known as DIP switch

Temperature sensor Use to detect heat

Optical sensor Use to detect light

Potentiometer Mainly for support other application

External analogue input To detect non-digital input signal

DC motor To operate as one type of output

LED To operate as one of the output

Bargraph Indicator of analogue output

Heater To control the temperature as output

Analogue output To produce non-digital output

The microprocessor development board should also include a power supply

adapter, user’s manual, and an experiment manual with eighteen easy to use

programs specifically for use with the microprocessor board. The manual must also

contain sixteen questions with fully worked answers [5].

There are also input devices like optical fibre, 8-bit digital switch, numerical

keypad, optical sensor, temperature sensor. As for the output device, there are variety

types of it like optical fibre transmitter, stepper motor, multi colour LED, and

speaker [6].

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There are many types of input and output devices that exist and in order to

choose the most suitable and proper for this project, we need to stick to the objective

[5, 6] Since the development board is specific for educational purpose, we must

choose a most common, general, easy, and yet simple types of input/output devices

so that the learning process will begin at a low level. The planned input device is

DIP switch and 4x4 keypad. As for the output device, the planned device is traffic

colour LED, 7 segment displays, DC motor, Dot Matrix, and LCD display. This

device have been chosen because of their function and characteristic which suitable

for teaching and learning aspect especially for displaying output that manipulated by

programmed software.

2.3 Software Analysis

The designers attempted to make the assembly language orthogonally. That

is, instructions were divided into operations and address modes, and almost all

address modes were available for almost all instructions. Many programmers

disliked the "near" orthogonality, while others were grateful for the attempt.

At the bit level, the person writing the assembler would clearly see that these

"instructions" could become any of several different op-codes. It was quite a good

compromise because it gave almost the same convenience as a truly orthogonal

machine, and yet also gave the CPU designers freedom to fill in the op-code table.

With only 56 instructions the minimal instruction size was huge for its day at

16 bits. Furthermore, many instructions and addressing modes added extra words on

the back for addresses, more address-mode bits, etc.

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Many designers believed that the MC68000 architecture had compact code

for its cost, especially when produced by compilers. This belief in more compact

code led to many of its design wins, and much of its longevity as an architecture [7].

The 16K-byte monitor ROM with most of the functions of the Motorola

Macsbug plus interpretative assembler, dis-assembler, printer and tape recorder

functions, and a series of TRAP #14 functions that allows user program access to

most of the monitor data conversion and I/O routines [8].

In order to activate the function of the microprocessor, it is a must to do the

programming in order to store data and instruction to the memory unit [7, 8]. This

instruction will inform the microprocessor what to do, when, and how to act in

response to the given input signal. There are more than 256 instruction set that been

used to write the program in assemble language. The assembly language can be

converted to machine language by using assembler like A68k. This is necessary

since the computer only recognize machine language that either in 0 or 1 logic.

The whole and fully function 68000 microprocessor development board

should at least consist of few chosen variable of inputs and outputs to be integrated

with the suitable program that written in either high level language or assembly

language. The hardware and software is needed to integrate together in oreder to

produce certain desired result.

CHAPTER 3

MC68000 MICROPROCESSOR BOARD:

HARDWARE & SOFTWARE DEVELOPMENT

3.1 Overview of MC68000 Educational Development Board

The main component that play the most important which are the

microprocessor MC68000 which function as the heart of the whole system. It is

generally known as Central Processing Unit or CPU. There are many others

supporting devices that must be used in order to create a simple computer system that

been used on this development board. This includes memory unit, input devices, and

output devices. Beside than that, there are others component that must also be

included so that the system will operate without any problem. For example, the

buffer and latch is required in order to connect the input and output together.

The component that been used for the memory unit for this project is

EPROM and RAM. The EPROM is used to as a storage device that store all the data

and instruction which will be used when the system has been activated. The RAM or

Random Access Memory is used as a temporarily memory device that store the data

temporarily when a program is executed and data storage of certain information is

required. There will be two ROM and RAM that will be used in this project since

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the data reading and writing will be operated at the rate of 16 bit in an instance. The

block diagram for the MC68000 educational development board is as shown in

Figure 3.1.

Figure 3.1: MC68000 Development Systems

There are two types of input devices that will be used in this project and it is

DIP switch and 4x4 Keypad. The DIP switch that consists of 8 small turn on-off

button is connected to the 68000 microprocessor and the connection to the voltage

source and terminal ground is required. The 4x4 keypad which consist of 16 key/

button which consist of digit numbers (0 to 9), symbols like star (*)and hash (#), and

alphabet (A, B, C, D). There are 8 terminals that used to connect to microprocessor

through a keypad encoder. The DIP switch is used to activate the types of output

devices while the keypad is used later to determine the output’s pattern.

The types of output devices that have been chosen are traffic light LED, 7

segment display, Dot Matrix, DC motor, and LCD. The traffic light LED consists of

8 LED which is in red, yellow, and green color. The 8x8 Dot matrix will be used to

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display words that able to be scrolled while the DC motor will be turning forward

and backward in different period. Each of those outputs will display different pattern

of result depend on the determined input.

There are devices like buffer and latch which will become the medium of

connection between the 68000 microprocessor and the I/O devices. The buffer is the

device that connects the input devices to the microprocessor while the latch will

connect the outputs. This is because the microprocessor can only communicate with

one device at one time leaving the others in high impedance state. The buffer and

latch is the devices that used to configure the I/O devices into tri-state since the I/O is

a bi-state device originally.

3.2 Operation of Microprocessor Development System

Initially the whole system will not be activate if there is no power supply

being supplied to the system. After the power being supplied to the system, the CPU

will start fetching the instruction from the ROM where the instructions have stored

inside it through program burner. After the instruction being fetched, usually the

microprocessor will temporarily store the fetch data into its internal register before it

is transfer to the Arithmetic Logic Unit (ALU) to perform arithmetic operation to

execute the instruction. The whole process is as shown as the Figure 3.2.

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Figure 3.2: Flow of the operating system

Normally the instruction will command the microprocessor to scan whether

there are any input signal has been detected. If there is no input signal being

detected, the scanning process will repeat again and again until there is an input

signal except the whole system has been turn off by removing the power source. By

turning on the input devices like DIP, there will be an input signal from the device

that sends to the microprocessor.

After the microprocessor has detect the input signal, it will starting to give

response by access the ROM again to fetch the new instruction and data before store

it to the data registers. Then the data will be transfer from the register to the ALU to

perform the data analysis and produce the output. Then the output will be display as

result in the output device according to the activated input.

START (By keypad/DIP)

Microprocessor detect input signal

Data and instruction fetching from memory unit

Data Analysis by ALU

Result (By output like LED)

17

During the whole process, the types of input or output device or the memory

unit that been chosen to activate is determine by the stored instruction in along with

the devices like address decoder which is connected to each of that devices through

the address bus.

3.3 Process Methodology

The best way to ensure success of the project, before any design,

construction, or simulation had been done, it is essentially to collect enough data and

information first. Therefore, the literature review process must be go through precise

and carefully.

This process must go along with the information gathering and from that, the

information such as the required component, techniques, project’s standard, software,

and example can be gathered. This is important in order to create a standard project

with the most efficient way in the shortest time with the best precision. The whole

process is illustrated in Figure 3.3.

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Figure 3.3: Steps towards project completion

After enough information has been gathered, the construction of the project

can be started. The developments of the whole project consist of two parts which is

the hardware part and the software part. The hardware part will be elaborated further

in next sub chapter while the software part will be elaborated in chapter after that.

These two parts can be done together or one by one.

START

Designing the hardware

Writing the data and the instruction set

Information Collect & Literature Review

Hardware testing plus troubleshooting

Create the hardware and connect it to various outputs Software testing

and assembling

Hardware and software combination

Final Testing & Troubleshooting

END

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After the hardware and software have been completed, the combination

process can begin where the software’s program have to be download to the memory

unit, ROM before the project’s testing can be proceed. Then, the testing process will

begin at the simplest level where the manipulation of the input devices like DIP and

keypad will produce various output on the traffic light LED. And after that, the

testing process will move to others device begin with 7 segment display, then DC

motor, dot matrix, and finally the LCD display. If any problem occurs during the

process, the troubleshooting will begin and this will be continue before we proceed

to next device.

3.3.1 Hardware Development

The hardware part can begin with the circuit’s designation process. For this

process, the design can be done whether manually (which mean by using paper and

writing tools) or by using software such as PSPICE. Although the schematic design

of the hardware can be done by using PSPICE, the whole project’s functionality

can’t be done since the whole functionality required the software to work along with.

After the design is finished, the next process which is hardware production

can connection with other components can be begin. The basic connection of the

microprocessor with the others component are as follow:

• ROM (even)- D15-D8 UDS

• ROM (odd)- D7-D0 LDS

• RAM (even)- D15-D8 A23-A21

• RAM (odd)- D7-D0 A23-A21

• Address Decoder- A23-A21

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• Buffer D0-D7 (Pin From Address Decoder)

• Latch D0-D7 (Pin From Address Decoder)

• Clock Circuit Pin 15

• Reset Circuit Pin 17&18

• Power Circuit Pin 14&49

Figure 3.4: Power Circuit

MC68000 needs a constant 5VDC to operate, so as the other integrated

circuits. To ensure the microprocessor and the other integrated circuits are supplied

with 5VDC, a voltage regulator of 5VDC must be built up. In this case, a 7805 is

used to regulate the voltage. Figure 3.4 is showing the schematic diagram for

voltage regulator.

Figure 3.5: Reset Circuit

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Once the power supply is regulated at 5 VDC, reset circuit is constructed.

Figure 3.5 are showing the schematic diagram of reset circuit. The reset pin is an

active low logic. To reset the microprocessor, it is mandatory to drive the reset pin

low at a desire time. Based on the Figure 3.5, once the push button is pressed, the

current flows through the LED path as it is a short circuit. Thus, it is predicted there

is no current flow through the reset pin. Once the push button is released, the current

flows through the reset pin and drive it high in a short period. This is because the

capacitor is charging to 5 VDC in a very short time.

Figure 3.6: Clock Circuit

The clock circuit is an important element of MC68000 since the

microprocessor works digitally based on generated clock. The rate of the clock is

determined by a crystal that is connected to the clock logic pins. The crystal that

used in this project is at rate of 4 MHz. This is shown by Figure 3.6.

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Figure 3.7: MC68000 basic operation system

After the hardware been construct, the hardware testing can be conduct by

download the testing software’s program that been searched from the reference

source [4] and others internet site. If the hardware can work along with the software,

the hardware considers success and if not, troubleshooting is required until the

hardware part finish. The figure 3.7 shows the schematic of the MC68000 basic

operation system.

3.3.2 Software Development

The software used is categorized to two parts which are software for

assembles and program download into internal EPROM of microprocessor unit.

Initially the program is written by using normal window’s notepad. Then the written

program can be converted by using ASM68K assembler to ensure our program didn’t

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have any error before we download the software’s program to the EPROM by using

the WP11 software.

The purpose of using ASM68K assembler is to create the hex file. Before

assemble the program, the program was saved in (.asm) extension. The assemblers

ASM68K only assemble the program that does not have error. Therefore, it checks

whether the program is right or wrong. The assembler will notify the part of error if

the program has error.

This assembler also converts the programming language into the machine

language. After the program was assembled, the extension (hex) will created and

shown up as a new file. The hex) file which contains the machine language is used

to download into both of the EEPROM.

WP11 is the software used to download the (hex) file format to the EPROM.

The software also allows the operator to perform many other useful programming

functions such as erasing, blank checking & verifying devices, displaying, editing,

exporting and changing the format of the object code files.

In order to successfully construct this project, it is essentially to gain full

understanding of the project and choose the best strategy by always follow up the

determined plan. The hardware and software that been chosen have been go through

screening and analysis process to ensure it success.

CHAPTER 4

RESULTS AND DISCUSSION

4.1 General Description & Analysis

The main objective of this project is to become an education guide for those

who learning microprocessor. The main and most important criteria that must been

fulfilled in order to fully master the microprocessor is to understand how the

microprocessor works, its hardware designation which will be connected with others

component, and the way to program and write command to the microprocessor.

Most of the information about how a microprocessor works is already clearly stated

in previous chapter. So, for this chapter, it is mainly divided into two parts which is

the hardware part and the software part.

4.2 Hardware Part

The hardware parts consist of discussion and analysis about the result after

the project being completed successfully. Basically, the whole hardware will be

divided into 3 main categories, which is main system module, input module, and

output module. The whole project consists of two boards, which is main board and