Table Of ContentThe Checkbook Series
/
Microelectronic
Systems IVI2
Checkbook
R E Vears
Heinemann Professional Publishing
Heinemann Professional Publishing Ltd
Halley Court, Jordan Hill, Oxford 0X2 8EJ
OXFORD LONDON MELBOURNE AUCKLAND
First published by Butterworth & Co. (Publishers) Ltd 1982
Reprinted 1985
First published by Heinemann Professional Publishing Ltd 1986
Second edition 1988
© Heinemann Professional Publishing Ltd 1988
British Library Cataloguing in Publication Data
Vears, R. E.
Microelectronic Systems N2 Checkbook
1. Microcomputers 2. Microprocessors
I. Title
621.3819'58 TK7888.3
ISBN 0 434 92332 X
Printed in Great Britain by Hartnolls Ltd, Bodmin
Note to readers
Checkbooks are designed for students seeking technician or equivalent qualification
through the courses of the Business and Technician Education Council (BTEC), the
Scottish Technical Education Council, Australian Technical and Further Education
Departments, East and West African Examinations Council and other comparable
examining authorities in technical subjects.
Checkbooks use problems and worked examples to establish and exemplify the theory
contained in technical syllabuses. Checkbook readers gain real understanding through
seeing problems solved and through solving problems themselves. Checkbooks do not
supplant fuller textbooks, but rather supplement them with an alternative emphasis and
an ample provision of worked and unworked problems, essential data, short answer and
multi-choice questions (with answers where possible).
Preface
This textbook of worked problems provides coverage of the Business and
Technician Education Council level Nil unit in Microelectronic Systems (syllabus
U86/333). However, it can be regarded as a textbook in microelectronic systems
for a much wider range of studies.
The aim of this book is to provide a foundation in microelectronic systems
hardware and software techniques. Each topic considered in the text is presented
in a way that assumes in the reader only the knowledge attained in BTEC
Information Technology Studies F, Engineering Fundamentals F, or equivalent.
Additional material on the basic ideas of systems, logic functions and numbering
systems is included for the sake of completeness.
This book concentrates on the highly popular 6502, Z80 and 6800
microprocessors and contains approximately 80 tested programs which may be used
with little or no modification on most systems based on these microprocessors. The
text includes over 140 worked problems followed by some 250 further problems.
The author would like to express his thanks to the general editors, J. O. Bird and
A. J. C. May for their helpful advice and careful checking of the manuscript. Finally
the author would like to add a special word of thanks to his wife Rosemary, for her
patience and encouragement during the preparation of this book.
The publishers and author would also like to thank the following firms for
permission to reproduce diagrams and data in this book - Intel; Zilog; MOS
Technology Inc; Mostek UK Ltd; Motorola Semiconductor Products Inc.
R E Vears
Highbury College of Technology
Portsmouth
1 Basic ideas
of systems
A MAIN POINTS CONCERNED WITH THE BASIC IDEAS OF SYSTEMS
1 A system is defined as an orderly arrangement of physical or abstract objects.
Systems have inputs and outputs arranged as shown in Figure 1.
The input signal may cause the system output to change or may cause the operation
of the system to change. Therefore, the input signal is the cause of the change. The
action which occurs as a result of an input signal is called the effect. The response of
the system to an input signal is called the process.
SYSTEM
(Process)
INPUT OUTPUT
Fig 1 (Cause) (Effect)
Figure 2 shows the operation of a simple system. An input signal (voltage) causes
the system to produce an output signal which is twice as large. Note that zero (0 V)
input results in zero output. The output is always an enlarged version of the input
signal, and the system is said to process the input signal. This particular system is
called a voltage amplifier.
The system shown in Figure 3 has three possible inputs, each of which may be
connected to ground (0 V) via switch Sw. When each of the individual inputs is
-|0V-
1 V- SYSTEM
-Γ+
2x1V=2V
Jli
2V- SYSTEM
4-M-
2x2V=4V
INPUT
Figure 2
1
ov
ov
Ground
Figure 3 INPUTS OUTPUT
connected to ground, a particular output signal shape results. To produce each
different shape, a different process takes place within the system. Therefore in this
case, the input signal is causing the system process to change. This particular system
is sometimes called a function generator.
Examples of four other systems are shown in Figure 4.
The input, output and process of each of these systems are:
(a) Lamp dimmer system
input: variable voltage supplied from a
manually operated rotary control. I
output: variable intensity light. dimmer \U he-
process: adjust supply current to lamp contro1 Ψ
according to the setting of the '
dimmer control. Figure 4(a)
(b) Door chime system
input: fixed voltage provided by manually-
operated door switch.
W
output: a sequence of musical notes, or
complete tunes. pDuoshor i
process: upon receipt of an input signal, switch
provide a suitable signal to drive the
loudspeaker, and provide all timing Figure 4(b)
for note pitch and duration.
(c) Coin changer system
input: coins,
output: coins.
process: determine value and validity of 0J U—0-0
input coin(s) and compute amount
of change to be given; may also be
used in vending machines to calcu
late amount of change due when
Figure 4(c)
input coins result in overpayment.
(d) Oven control system
input: variable voltage from manually-
adjusted temperature setting
control and oven temperature
sensing device. OVESNY CSTOENMTR OL EHLEOEAVMTEEINNNG T
output: heat at controlled temperature,
process: compare actual oven temperature
with the desired (target) tempera
ture and adjust the heating element
current to maintain these two Figure 4(d)
temperatures as close as possible
to one another.
In many systems, the input signal alone has insufficient power to operate the output
device. In this case, an additional input to the system is required, that is, a power
supply. The input signal then controls the flow of current between this additional
input and the system output. One method by which this is achieved is shown in
Figure 5.
ADDITIONAL
INPUT
240 V
-7-
Switches operated
INPUT L by input signal
(Controls
additional
input)
240 V r\J
OUTPUT
Figure 5
The input and output signals of a system are energy sources. An electronic system
requires an input of electrical energy, but the input energy source is in all probability
not electrical. The output from the system is in the form of electrical energy, but in
most cases, the output required is some other form of energy, for example, heat,
light or mechanical. Therefore, devices which are capable of converting energy from
one form into another are an essential part of most systems. These devices are called
transducers, and examples of typical transducers are illustrated in Figures 6 and 7.
A thermistor is a device often found in temperature measuring systems. It
consists of a piece of special material to which two connecting wires are fixed,
and has the characteristic that its electrical resistance changes according to its
temperature. Two types of thermistor action are available:
3
(a) (b) (c)
Bead type thermistor, General purpose Specially insulated thermistor,
responds rapidly to thermistor used where environment
temperature changes due dictates use of better encapsulation
to its small physical size
£^ ^Z-
(e)
(d) Circuit symbol, positive
Circuit symbol, negative temperature coefficient
temperature coefficient thermistor
thermistor
Resistance
(Ω) i I Rneessiisstt ance ,
(Ω)
OK 10K
5K
4K
3K
2K
1K
" i ll i r i i ^
0 20 40 60 100 120 140
temp
CO
(f)
Characteristics of a negative temperature Characteristics of a positive temperature
coefficient thermistor coefficient thermistor
Figure 6
(a) increase in resistance as temperature increases, which is known as a positive
temperature coefficient of resistance (PTC thermistor)
(b) reduction in resistance as temperature increases, which is known as a negative
temperature coefficient of resistance (NTC thermistor)
Thus, the thermistor may be used as a transducer to convert heat energy into an
equivalent electrical signal.
Some systems need to know when liquid in a container reaches a predeter
mined level. Figure 7 shows two methods by which this may be accomplished. In
Figure 7(a), the rising liquid level causes the air pressure in the lower part of the
transducer to increase. This, in turn, puts pressure on a spring-loaded diaphragm
to which an electrical contact is fitted. At a predetermined pressure (and hence,
4
Spring loaded
Air compresses flexible diaphragm
as liquid level \
rises X
-----ΐΐ: Liqu id i^irCr-E-E1 :Ε:ΕΪΕΪΕ=Ξ:=:ί=:Ε§ϊ§ΐί|
(a) Figure 7
liquid level) the diaphragm suddenly springs across and causes the diaphragm to
touch the fixed contact, thus completing the circuit to which it is connected.
An alternative method is shown in Figure 7(b) in which a small pool of mercury
is used to complete the circuit between two fixed contacts. The contacts and
mercury are housed in a small container, which is attached to a float and pivot
assembly. The float rises with the liquid level, and at a predetermined level, the
angle of the mercury container is such that the pool of mercury rolls down the
container and makes an electrical connection between the two fixed contacts
(note: mercury is a good conductor of electricity).
SYMBOL MEANING
PROCESSOR ACTION
INPUT OR OUTPUT
O
DECISION
O CONNECTOR
(^ ) START OR STOP
FLOW DIRECTION
Figure 8
7 The manner in which a system operates is determined by the functions performed
by each of its blocks and by the sequence in which they are operated. This
operating sequence may be represented by means o fa flow chart which is drawn
using symbols similar to those shown in Figure 8.
B WORKED PROBLEMS ON THE BASIC IDEAS OF SYSTEMS
Problem 1 What is the basic function of a photo-electric device? Describe,
using diagrams, three practical applications for photo-electric devices in
systems.
The basic function of a photo-electric device is to convert light energy into a cor
responding electrical signal. There are several different types of photo-electric
devices. Some types have an electrical resistance which varies according to the
amount of light falling on them, whilst other types generate an electrical potential
(voltage). Examples of applications of the photo-electric device in practical
systems are as follows:
(a) Conveyor belt control The conveyor belt drive motor operates until an object
arrives to break the beam between the light source and the photo-electric device.
The drive belt then stops, and work may be carried out on the stationary object.
The belt drive may be restarted by several methods. Examples include manually
moving the object clear of the beam, or electrical override of the system, or a
\vr \ halt period with automatic restart (see Figure 9).
Object on
belt
To belt drive
Figure 9 motor
6
