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Chapter 1
Introduction: Digital Systems &
Logic Design
By Taweesak Reungpeerakul
Digital Systems
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Digital and Analog Quantities
Parameters of Pulse Waveform
Basic Logic
Combinational Logic
Digital Integrated Circuits
An example of Digital System
Design Flow
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1.1 Digital & Analog Quantities
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Analog Quantity?
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Digital Quantity?
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Continuous Values
Discrete Set of Values
Which one has more advantages?
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Digital Quantity (process & transmit)
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Efficiency
Reliability
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Analog & Digital Example
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Analog & Mixed System
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Analog System
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Digital and Analog System
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1.2 Binary Digits, Logic Levels,
and Digital Waveforms
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Binary Digits: 0  Low,
1  High
Code:
Group of Bits
Logic Level:
represented by voltages
Volts
VH (max)
VH (min)
Logic 1
(high)
5.0
2.0
Undefined
VL (max)
VL (min)
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Volts(TTL)
Logic 0
(low)
0.8
0.0
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Digital Waveforms
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Pulse
H
L
H
L
Positive-going pulse
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Negative-going pulse
Waveform Characteristic
f = 1/T
T = 1/f
90%
tW : pulse width
tr : rise time
tf : fall time
T : period
f : frequency
90%
50%
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tW
Duty Cycle =
( tw / T ) 100%
10%
10%
tr
tr
0 10
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tW
50%
Question
tf
T
T
60
tf
110
Time(µs)
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Clock and Bits Waveforms
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Clock
is a periodic waveform (signal) in which each interval
between pulse equals the time for one bit
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Timing Diagrams
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How 2 or more waveforms change and relate
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1.3 Basic Logic Operations
NOT
AND
OR
Symbol
Truth
Table
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In
0
1
Out
1
0
In1
0
0
1
1
In2 Out
0
0
1
0
0
0
1
1
In1
0
0
1
1
In2 Out
0
0
1
1
0
1
1
1
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1.4 Basic Logic Functions
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Basic Logic Functions (cont)
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Mux
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Demultiplexer
Multiplexer
2n
S0
S1
S2
S3
D
C0 C1 En
Demux
O0
O1
O2
O3
D
C0 C1 En
n
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Basic Logic Functions (cont)
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Flip-flops
SET
D
CLK
D
SET
Q
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Q
D
CLK
D
SET
CLR
CLR
Q
Registers
Q
Q
D
SET
CLR
Q
Q
D
SET
CLR
Q
Q
D
SET
CLR
Q
OUT
Q
Q
CLR
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Counters
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1.5 Digital Integrated Circuits
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IC Packages: DIP, SMT, SOIC, PLCC,
LCCC, FP
IC Complexity Classifications
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SSI: gate ≥ 12, basic gates & flip-flops
MSI: 12 ≤ gate ≥ 99, logic functions
LSI: 100 ≤ gate ≥ 9999, including memory
VLSI: 10,000 ≤ gate ≥ 99,999
ULSI: gate ≥ 100,000
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Integrated Circuit Technologies
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Types of Transistors
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Bipolar Junction Transistors
MOSFETs (metal-oxide semiconductor
field-effect transistors)
Bipolar used in: transistor-transistor logic
(TTL) and emitter-couple logic (ECL)
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MOSFETs used in: complementary MOS
(CMOS) and n-channel MOS (NMOS)
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1.6 Testing and Troubleshooting
Instruments
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Oscilloscope
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Analog
Digital
Logic Analyzer
DC Power Supply
Function Generator
Digital Multimeter
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1.7 Digital System Application
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Design Flow
Concept
Behavioral
Description
Behavioral
Synthesis
Floor Planning
RTL
Description
Technology
Dependent Network
Layout
Mask Data
Manufacturing
Logic Synthesis
Product
Gate
Description
Technology
Mapping
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Testing
Good Product
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