Transcript Slide 1

ECA1212
Introduction to Electrical &
Electronics Engineering
Chapter 10: Digital Systems
by Muhazam Mustapha, December 2011
Learning Outcome
By the end of this chapter students are
expected to:
• Understand the basics of computer system
• Be able to explain the circuits of
electronics instrumentation
Chapter Content
• Computer System Architecture
• Instrumentation
Computer System
Architecture
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Microcomputers
• Microcomputers are the results of the
integration of a very large number of digital
electronics components on an integrated circuit
to perform intelligent and systematic tasks
through the use of programs
• They can be categorized into 2 groups:
– Microprocessor: more for general purpose use
• e.g.: Intel Pentium, i3, AMD Athlon, Sempron, etc
– Microcontroller: for a specific use
• e.g.: Intel 8051, PIC16x84, Atmel AVR, etc
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Microprocessors
• Since it is for a general purpose computing,
microprocessor has the following generic
architecture:
Text book Figure 14.30
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Microprocessors
• In the previous slide, the input sensors are the
common devices like keyboard, mouse,
touchpad, cameras, etc
• While the outputs are also common like VGA
screen, speaker, disk drives, etc
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Microcontrollers
• Since it is for a specific purpose, microcontroller
has the following generic architecture:
Text book Figure 14.33 (a)
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Microcontrollers
• In the previous slide, the input sensors and
output actuators are for that specific task meant
for the system
• For example, if the system is for temperature
controller, the input must include a temperature
sensor, and the actuator or output must include
some device to indicate the temperature value
or to activate something to lower or higher the
temperature
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Components
• Based on the previous slides, the core
components of a computing system can be
listed as follows:
– Central Processing Unit (CPU)
– Memory
– Program
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Central Processing Unit
• CPU is the heart of a microprocessor
• It performs the computation that is kept in the
memory as program code and then transfer the
input or output to the outside system as
necessary
• To perform the task it uses a collection of
registers, mostly accumulator, to compute basic
Boolean processing like AND-ing, OR-ing, rotate,
shift, as well as the arithmetic ones like, adding,
subtracting, etc
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Memory
• Normally called RAM (random access memory)
• Memory is an electronic device that keeps
Boolean values:
– as flip-flops: SRAM (static)
– as charge on capacitor: DRAM (dynamic)
• Mass storage is also a kind of memory but it is
significantly larger than the memory and nonvolatile (keeps value even though when
powered off):
– harddisk, thumb drive
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Program
• Computer program is a sequence of 1-s and 0-s
kept in memory to instruction the computer
about what to do
• Two types of programs:
– High-level: coded using human friendly words –
C/C++, Java, C#, etc
– Low-level: coded using mnemonics or code that is
more computer friendly – assembly language
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Assembly Language
• It is a low level programming language to
program microprocessor using mnemonics
• Operation code (opcode) is the sequence of 1-s
and 0-s that correspond to a specific instruction
• Each instruction in assembly language then has
a 1-to-1 mapping to opcode
• Look at one assembly language example in text
book Example 14.6
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Assembly Language
• Another example:
MOV A, H40;
load 40 hex to accumulator
MOV B, [H0032]; load reg B with content from memory
addr 32 hex
SUB A, B;
JZ Error;
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Instrumentation
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Measurement System
• Measurement system can be built using a
microcontroller system with transducers as
inputs
– nowadays some system are built on general purpose
microprocessors
• Transducers are devices that convert nonelectrical energy into electrical energy (signals)
– normally in analog form
• The signal has to be converted to digital first so
that is can be used in computing systems
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Measurement System
Transducer
Analog
Digital
Text book Figure 15.1
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Measurement Quality
Text book page 761
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Accuracy – closeness to the true value
Precision – no. significant digits in the measure
Resolution – smallest measurable increment
Error – difference from the true value
Linearity – conformity to straight line graph if we
plot a graph of the non-electrical energy vs the
corresponding electrical signal
• Span – range of linearity
• Range – high and low limits of measure
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Measurement Devices
• Text book Table 15.1 page 762 list out all
measurement devices for mechanical and civil
engineering that it covers
• For your class we will cover briefly all in pages
761 – 765
• Read those pages for your examination
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Mechanical Measures
• Absolute position: change in resistance,
Wheatstone bridge
• Displacement & velocity: magnetic effect
• Acceleration & jerk: optical signal, image
processing and piezoelectric material
• Force, torque & pressure: piezoelectric, load
cell, diaphragm, strain gauge
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Fluid Measures
• Differential pressure:
Text book Figure 15.2 (a)
• Turbine flow meter:
Text book Figure 15.2 (c)
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Fluid Measures
• Hot-wire anemometer:
– a resistor that is a part of a
Wheatstone bridge is place
in flow tube
– all resistors heat up due to
the electric current, but the
one in the fluid flow will
cool down and causes its
resistance to get out of
balanced with the rest, and
thus disrupting the
balanced voltage on the
bridge
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Text book Figure 15.2 (b)
Temperature Measures
• Thermocouple:
Text book Figure 15.3
– built based on the
physical property that 2
different touching metals
will generate potential
difference that also
changes due to
temperature
• Thermistors:
Text book Figure 15.4
– built based on the physical property that
metal changes resistance due to
temperature
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