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Welcome to
ENGSCI 232 SC
Computer Systems
Lecture 1
Department of Engineering Science
The University of Auckland
ENGSCI 232SC Lecture 1
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Course Objectives : 1
• Gain an understanding
of
digital
circuit
components,
data
representation,
and
some important aspects
of computer architecture
including memory and
input/output.
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Course Objectives: 2
• Develop skills and
confidence in using
laboratory equipment and
the design and
implementation of
hardware/software
interfaces, in particular
the use of the PC parallel
port to communicate with
external digital logic
circuits via Visual Basic
program code.
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Lecture Topics
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1. Introductory Concepts
2. Digital Gates
3. Combinatory Circuits
4. Synchronous Circuits
5. Data Representation
6. Instruction Sets
7. Memory
8. Input/Output
9. Architecture
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Laboratories
• ENGSCI232 laboratories will begin in Week 2,
Wednesdays 9-11, in 439.433. Completion of lab
work is compulsory. Failure to complete will lead
to a DNC (Did Not Complete) grade.
• Laboratory tasks and associated assignment
questions will contribute 40% to the final mark.
• ENGSCI272 labs will be organised by Dr
Nielsen.
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Exam
• A 2 hour written examination will contribute
60% to the final mark, with the condition
that the final mark cannot exceed the
exam mark by more than 10%.
• No calculators permitted in the exam.
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Resources and Results
• Coursework results, announcements etc
will appear on the course website
• http://www.esc.auckland.ac.nz/teaching/en
gsci232sc
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Course Staff
• Jim Greenslade –
Lecturer, and Course Organiser
Department of Engineering Science
Room 439.233
ext 88390
[email protected]
• Dr Mason will lecture from Week 7
onwards.
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Questions
• Any questions about Course
Organisation?
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Introductory Concepts
• The term “digital” occurs throughout most
areas of everyday life (not only computers
but home appliances, phones,
transportation, entertainment, medical
science and practice etc)
• We will first cover some of the underlying
concepts and terminology on which to
build a good understanding of this area.
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Numerical Representation
• Quantities are measured and represented
in on of two forms:
• 1. Analogue: a quantity represented by a
voltage, current or meter movement
proportional to the value of the quantity.
Eg mercury thermometer, audio mic.
• 2. Digital: quantities represented by digits
rather then proportional quantities.
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• eg Digital watch
• So, analogue=continuous
• Digital = discrete (step by step) and hence
no ambiguity of interpretation.
• Categorise the following:
• Ten-position switch, current flowing from
an electrical outlet, sand grains on the
beach, car speedometer.
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Digital and Analogue Systems
• A digital system is a combination of
devices which manipulate logical
information in digital form (ie discrete
values). May be mechanical, magnetic or
pneumatic but most often electrical.
• Analogue system contains devices which
manipulate quantities that vary over a
continuous range eg simple dimmer
switch, volume output to a radio speaker.
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Advantages of Digital Techniques
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Easier to design
Information storage is easier
Accuracy and precision are greater
Operation can be programmed
Digital circuits are less affected by noise
More digital circuitry can be fabricated on
IC chips
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Limitations of Digital Techniques
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The real world is analogue !!
Often we need to go through conversion steps.
Analogue-to-Digital converter (ADC)
Digital-to-Analogue converter (DAC)
eg music CD. Starts as analogue sound,
digitised onto CD, played in CD player,
converted back to analogue to feed speakers
and hence to your “analogue ear”.
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Decimal Number Systems
• Remember that the decimal number
system comprises 10 digits. When
representing a number, the least
significant digit is on the right and is
weighted as 10^0, the next digit being
weighted 10^1 etc. In counting, when we
reach 9 we need to reset the value of the
current position back to 0 and carry a 1
through to the next (more significant)
position.
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Binary Number System
• Very similar except we are now working in
Base 2 so have only 2 digits (0,1).
• Least significant digit is 2^0, then moving
right to left the weighting increases 2^1,
2^2 etc
• When counting, after reaching 1 we must
reset back to zero and carry 1 through to
the next (more significant) place.
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Revision
• What is the equivalent of the binary
number 1101011 ?
• What is the next binary number after this
number (ie add 1) ?
• How many decimal numbers can be
represented using 7 binary bits ?
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Digital Circuits
• Comprise electronic devices which will
respond predictably to input voltages
which lie within an allowable “zero” range
and allowable “one” range. Subsequent
outputs will also lie within one of these two
ranges.
• Systems may use different voltage levels
eg a 1 may be represented by 3.7 volts or
5 volts depending on the system.
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Logic Circuits
• Basic digital components are really just
switches (individual transistors).
• To be of use they are configured to
perform “logical” operations.
• We will explore and utilise chips which
perform such logical tasks as:
• AND, OR, NOT, XOR
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Integrated Circuits (ICs)
• Various IC technology is available:
• TTL (transistor-transistor logic) uses the
bipolar transistor as its main circuit
element
• CMOS (complementary metal-oxidesemiconductor) uses the enhanced-mode
MOSFET as its principal element.
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Parallel and Serial Transmission
• Computer are constantly transferring
information. This may be over submillimeter ranges within ICs, millimeter
range between functional units within the
computer, meter range between a
computer and locally attached peripheral
devices (scanners printers etc) or long
range between computers world-wide.
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Parallel
• A local printer may be connected using a
parallel cable in which case all 8 bits of a
character can be transmitted
simultaneously (each bits travels on a
separate wire within the cable). This has
the benefit of speed but adds considerable
complexity and is not practical for longer
distance communication.
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Serial
• A serial connection normally involves a
single wire being used to send a stream of
bits (sequentially). This is inherently
slower but is easier and cheaper to
implement and to use over any distance.
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Computer Memory
• Often the main memory (RAM) of a
computer uses ICs containing millions of
“latches” or “flip-flops”. These are capable
of being in only one of 2 states (on or off, 1
or 0) and can change state very quickly
when new data is applied to the data bus
and “latched” into a particular memory
address (or location).
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Major Parts of a Digital Computer
• Input Unit – through which data is feed to the
computer.
• Memory Unit – for storage of instructions and
data.
• Control Unit – to interpret instructions and signal
all other units to achieve execution.
• ALU – Arithmetic and Logical calculations and
decision making.
• Output Unit – displays or prints processed data.
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Next Week
• We will look in more detail at Digital Logic
Gates.
• In the lab this week you will get an
introduction to some logic gates and how
to connect these together.
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