Chapter 1: Introduction

Digital System Design

Chapter 1. Introduction
Minh-Thuy Le
Department of Instrumentation and Industrial Informatic (3I)
School of Electrical Engineering (SEE)
Thuy.leminh@hust.edu.vn

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 References

• Digital Design: Principles & Practices – John F

Wakerly – Printice Hall
• M. Morris Mano, Digital Design, Prentice-Hall,
3rd - 1996
• Lê Hải Sâm, Điện tử số, NXBDG

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 Course Materials

• Slides at team
• Team name: EE2130E-20231
• Code:
2fp60fa
• Valide in 2 weeks

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 Course outline

I. Basics of Information, the Digital Abstraction,

Assignment 1
II. CMOS, Combinational Logic, Assignment 2
III. Sequential Logic, Finite-state Machines,
Assignment 3
IV. Performance Measures, Design Tradeoffs,
Assignment 4
Bonus: Quiz/Test online or offline can be added

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 ASSESSMENTS AND EXAM

Assessment/ Assessment methods Weight

exam
Mid-term 2 assignments (page 4) or 30%
assessment Project : 50%
Examination: 50%
Final exam Examination 70%

How to practical: design your own digital system/circuit and implement it

Lab Practical is required
How to verify your circuit?
• System test and debug.
• Equipment: oscilloscope at Lab-C1-328/713 room-Ta Quang Buu
building 5
 Chapter 1: Outline

1. Introduction
1.1 Analog versus Digital
1.2 Digital devices
1.3 Logic circuits
1.4 Logic level
1.5 Integrated circuit
1.6 Digital design level

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 Introduction: Design?

• Some tips for engineer to design a digital

system/real application:
– Debugging
– Business requirement and practical
– Risk-taking
– Communication What does it mean?

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 1.1 Analog versus Digital

• Analog: Analog devices and systems process

time-varying signals that can take on any value
across a continuous range of
- voltage, current, or other metric
• Digital: at any time, only two discrete values:
– 0 and 1
– HIGH and LOW
– TRUE and FALSE

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1.1 Analog versus Digital

Hình 1-1: A basic audio public address system

9
Hình 1-2: CD Player function blocs
 1.2 Digital Devices
• Digital devices: basic digital devices are called
gates:
– AND, OR, NOT

Hình 1-3: Digital devices: a) AND gate; b) OR gate; c) NOT or Inverter gate

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 1.3 Logic circuits
• Logic circuits: is an arrangement of the individual logic
functions connected to perform a specified operation or
produce a defined output

• Classification:
– Combinational logic circuit
– Sequential logic circuit
• Gate is considered as a combinational logic circuit.

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 1.3 Logic circuits
• Combinational logic circuit vs. Sequential Logic circuit

In Out
Combinational Combinational
In Logic Out Logic
Circuit Circuit

State
Storage element

Combinational Sequential

Output = f(In) Output = f(In, Previous In)

Output are determined as a function of the Consist of combinational circuit and
inputs and vary as the inputs vary some form of memory
Basic logic AND, OR, NOT gates are
combined to produce more complicated 12
switching circuit
Is This a Combinational Logic Circuit?

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 1.4 Logic Level
• Digital world: discrete-value “0” và “1”
• Representation discrete values as real quantities
like voltage (or current) in electronic circuit
implementation? How to represent?

Digital world

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 1.4 Logic Level
• Digital world: discrete-value “0” và “1”
• Representation discrete values as real quantities
like voltage (or current) in electronic circuit
implementation.
• How represent 0 and 1 as distinct quantities?
– A range of sufficiently high voltage represent a 1
– A range of sufficiently low voltage represent a 0
– Separating the representation of 0 and 1 by a
forbidden zone How many?

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 1.4 Logic Level
Key idea: encode only one bit of information 2 values
“0” , “1”
Use the same uniform representation convention for
every component and wire in our digital system

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 1.4 Logic Level
• Mapping between analog and digital signals
V
V
out
“ 1” OH
V Slope = -1
V OH
IH
Undefined
Region
Or
forbidden
zone
V
IL
Slope = -1

V
“ 0” V OL
OL
V V V
IL IH in 17
 1.4 Logic Level
• Definition of Noise margins
Noise margin: The difference
between the range boundaries

Undefined region: if input is in

"1" this region we can not know it
V is “1” or “0”
OH Noise margin high
NM H
V
IH
Undefined
Region
NM L V Noise margin low
V IL
OL

"0"
Gate Output Gate Input 18
 1.4 Logic Level
Noise in Digital system

• Will this system work?

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 1.4 Logic Level
Noise in Digital system

• Where does noise come from?

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1.4 Logic Level

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 1.5 Integrated Circuits

• Building Logic with

Transistors?
• Why is designing digital
ICs different today than it
was before?
• Will it change in future?
The Babbage
Difference Engine
(1832)
25,000 parts
cost: £17,470 22
 1.5 Integrated Circuits

ENIAC - The first electronic computer (1946)

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1.5 Integrated Circuits

The Transistor Revolution

First transistor
Bell Labs, 1948
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 1.5 Integrated Circuits

ENIAC - The first Integrated Circuits

Bipolar logic
1960’s

ECL 3-input Gate

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Motorola 1966
 1.5 Integrated Circuits
Intel 4004 Micro-Processor

1971
1000 transistors
1 MHz operation

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 1.5 Integrated Circuits
Intel Pentium (IV) microprocessor

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 1.5 Integrated Circuits

• Moore’s law in Microprocessors

1000

100 2X growth in 1.96 years!

Transistors (MT)

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P6
Pentium® proc
1 486
386
0.1 286
8085 8086
Transistors
0.01 on Lead Microprocessors double every 2 years
8080
8008
4004
0.001
1970 1980 1990 2000 2010
Year 28
 1.5 Integrated Circuits

• Not only Microprocessors

Cell
Phone

Small Power
Signal RF RF

Digital Cellular Market

(Phones Shipped) Power
Management

1996 1997 1998 1999 2000

Analog
Units 48M 86M 162M 260M 435M Baseband

Digital Baseband
(DSP + MCU)

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(data from Texas Instruments)
 1.5 Integrated Circuits
• Integrated Circuit is classification based the
number of gates on chip:
– SSI (small-scale integration): 1 to 20 equivalent gates
per chip.
– MSI (medium-scale integration): 20 to 100 equivalent
gates per chip.
– LSI (large-scale integration): > 100 to 10,000
equivalent gates per chip.
– VLSI ( Very large-scale integration ): 10,000 to
100,000 equivalent gates per chip.
– ULSI (Ultra large-scale integration): more than
100,000 equivalent gates per chip
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• Typical IC gate packages:
– The dual in-line package (DIP) for plug-in or feedthrough
mounting
– The small-outline integrated circuit (SOIC) package for
surface mounting

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1.5 Integrated Circuits

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1.5 Integrated Circuits

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 1.5 Integrated Circuits

Ex.: 74HC00

Logic symbol Logic diagram Pinning

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 1.6 Digital Design level

• Many Digital system design level and

technologies:
1) HDL: hardware Description Language
2) IC level
3) Gate level
4) Transistor level

Key words:

Integrated
Wafer Die IC
circuit (IC)

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1.6 Digital Design Levels

Ex: Digital switch design

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 1.6 Digital Design Levels
1) Hardware Description Language

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 1.6 Digital Design Levels
2) IC function level

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 1.6 Digital Design Levels
3) Gate level

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 1.6 Digital Design Levels
4) Transistor level

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 Summary
• Use voltages to encode information
• Digital encoding:
– Valid voltage levels for representing “0” and “1”
– Forbidden zone avoids mistaking “0” for “1” and vice
versa
– Give rise to notation of signal validity
• Noise:
– Want to tolerate real-world conditions: NOISE
– Key: tougher standards for output and input
– Noise margin
• Integrated circuit
• Digital system design level 41