Chapter 1.pptx

INTRODUCTION TO
DIGITAL LOGIC
DESIGN

CHAPTER 1
Introductory
Concepts

Definition: Analog & Digital
 Analog
Varies over a continuous range of values
 a variable signal continuous in both time and amplitude
Examples of analog quantities : time, pressure, sound.

• Digital
– A discrete (that is, discontinuous) set of values.
– Varies in discrete (separate) steps.
• The word digital comes from the same source as the word digit and
digitus (the Latin word for finger), as fingers are used for discrete
counting.
… Definition:

Analog vs Digital
Analog
• Use base 10 (decimal)
• Represented by 10 different level:
0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.
• Analog system: A combination of
devices that manipulate values
represented in analog form
Digital
 Use base 2 (binary)
 Represented by 2 different level:
0 and 1 or low and high.
 Digital system: A combination of
devices that manipulate values
represented in digital form.

Digital
• Digital technology is relatively new
compared to analog technology, but a lot
of analog systems has been changed to a
digital systems, Examples:
– Computers
– Manufacturing systems
– Medical Science
– Transportation
– Entertainment
– Telecommunications

The Digital Advantages
 Real world quantities are mostly analog, but why change to
a digital systems?
Because, digital systems has a lot of advantages
 Ease of design
 Ease of storage
 Accuracy and precision are easier to maintain
 Programmable operation
 Less affected by noise
 Ease of fabrication on IC chips
 Thus, the digital systems is more efficient and reliable for:
- Data Processing
- Data Transmission
- Data Storage

The Digital Disadvantages
• But digital systems also has a disadvantages:
– Greater bandwidth (although compression
changing this)
– Sampling error
– Compatibility with existing analog systems
– Short product half life
• But it advantages is a lot more compared to the
disadvantages

System Using Digital
and Analog Methods
• Although a digital systems has many advantages, real
world quantities are analog
– Therefore there is a need to convert between
analog and digital signals

Hybrid System
• The audio CD is a typical hybrid (Analog & Digital)
system.
– Analog sound is converted into analog voltage using a
microphone.
– Analog voltage is changed into digital through an ADC in
the recorder.
– Digital information is stored on the CD .
– At playback the digital information is changed into
analog by a DAC in the CD player.
– The analog voltage is amplified and used to drive a
speaker that produces the original analog sound.

Digits,
Logic Levels
and
Digital Waveform

Representing Digital
Information
• The smallest information that can be represented in
digital systems is binary digit (bit), it can have two
value
– HIGH (bit 1)
– LOW (bit 0)
• This information is represented through electrical
voltage
1010100 represented as electrical signal

Binary Digits
Positive Logic
(active high)
High = 1 (Bit 1)
Low = 0 (Bit 0)
Negative
logic (active
low)
High =0
Low =1

Digital Waveform
• Digital systems usually uses a square wave
– Because square wave represent a binary value (HIGH or
LOW)
• Two type of squarewave
– Periodic
• The signal keep on repeating after a period of time
– Non Periodic
• Doesn’t have a period

Periodic Signal Parameter
 Frequency (f) is the rate at which the signal repeat itself at a
fixed interval. Is measured in cycles per second or Hertz (Hz)
f = 1/T Hz
 Period (T) is the time from the edge of one pulse to the
corresponding edge of the next pulse. Is measured in
second
T = 1/f s
Example:
 clock frequency : f = 100Hz,
so, period : T = 1/100Hz = 0.01s = 0.01x 103 = 10 ms

Pulse Width
• Pulse is a rapid, transient change in the amplitude of a
signal from a baseline value to a higher or lower value,
followed by a rapid return to the baseline value.
• Pulse width (tW): A measure of the duration of the pulse.
• Rise time and fall time is a measure of how fast the
pulse change.
Amplitude
Pulse
Width
Rise Time Fall Time
90%
50%
10%
90%
50%
10%

Duty Cycle
Example : a periodic digital waveform has a pulse width (tw)
1ms and period time (T) 10ms, calculate duty cycle?
Duty cycle = 1ms/10ms * 100% = 10%
Duty cycle is the fraction of time that a system is in an
"active" state (operated), defined as

Timing Diagram
• Is a graph of digital waveform showing the actual time
relationship of two or more waveform and how each
waveform changes in relation to the others.
• In digital systems, the emphasis usually the timing not the
amplitude because amplitude to represent a bit is
predefined.

1 2 3 4 5 6 7 8
A
B
C
C l o c k
A , B a n d C H I G H
A = 1 , B = 1 , C = 1
A ? B ? C ?
B i t
t i m e 7
Example: Timing Diagram

Data Transfer
 Data refers to groups of bits that convey some type of
information.
 Binary data are transferred in two ways: serial
and parallel
 Serial: During the time interval from t0 to t1, the first bit is transferred. During
the time interval from t1 to t2, the second bit is transferred.
 Parallel: all the bits in a group are sent out on separate lines at the same

Example: (a) Determine the total time required to serially transfer the
eight bits contained in
waveform A of Figure below, and indicate the sequence of bits. The
left-most bit is
the first to be transferred. The 1 MHz clock is used as reference.
(b) What is the total time to transfer the same eight bits in parallel?

Introduction
to
Logic Operations

LOGIC GATES
The NOT operation: changes one logic level to
the opposite logic level (inverter).
The AND operation: produces a HIGH outputonly
if all the inputs are HIGH.
The OR operation: produces a HIGH output when
any of the inputs is HIGH.
Gate is the most basic building block of a digital
systems, and the 3 most basic are

NOT
operation
Truth table shows the relationship between output and the input.
Truth Table for NOT
X Z
0 1
1 0
X Z
NOT
X Z

AND
operation
X Y Z
0 0 0
0 1 0
1 0 0
1 1 1
Truth TableAND
AND

O
R
operation
X Y Z
0 0 0
0 1 1
1 0 1
1 1 1
Truth Table OR
OR

Basic Logic Functions
 Any digital systems has one or more of the following
function.
 This functions are built from the basic gates.
 Comparison Function
 Arithmetic Functions
 Code conversion function
 Encoding function
 Decoding function
 Data selection function
 Data storage function
 Counting function

Arithmetic Functions
 Adder
 Subtractor
 Multiplier
 Division

Code Conversion Function
• A code is a set of bits arranged in a unique
pattern and
information.
– Examples
used to represent specified
: BCD, ASCII
• The usage of codes allow a faster and more
efficient data processing.

Data Selection Function
(MUX & DeMUX )
Multiplexer and Demultiplexer

Data Storage Function
• Flip-flop stores a 1 or 0 only
• Registers
– Formed by combining several flip-flops
– 8-bit register  from 8 flip-flops
• Semiconductor Memories
– e.g. RAM, ROM, Flash
• Magnetic/Optical Memories
– For mass storage  e.g. hard disk, tape, DVD, Blu-Ray

Counting Function
• Counter
– To count the occurrence at the input.
– to initiate a controller after a certain
(period).
count

 An integrated circuit (IC) is a miniature ,low cost
electronic circuit consisting of active and passive
components fabricated together on a single
crystal of silicon.
 The active components are transistors and diodes
and passive components are resistors and
capacitors.
Integrated Circuit (IC)

•Resistors
•Capacitors
•Inductors
•Diodes and LED
•Transistors
•Chips = Integrated Circuits (IC) by
wiring together all of the above
(gates, op amps, timers…)
Semiconductor
device=active
elements
Passive
elements

RESISTORS ( R )
Units in Ohms ()
fixed
variable
Dial to
change R

CAPACITORS (C)
Units in Farads (Coulombs/Volt)
Non-polarized, fixed
polarized, fixed
variable
(can shaped, higher
C attained. Contains
electrolytes) (Flattened)
(has dial)

INDUCTORS (L)
Units in Henries (H)
fixed variable
Harder to spot
variable ones
Slot for screw driver
adjust

PIV
=Vf
DIODES
(one way current filters)
Rated for PIV and Vf
regular diodes
Light
emitting
diodes (LED)
regular LED

In days of yore…(pre 1960)
before solid state transistors
became commercially chip
and available
Grid current (mA) determines whether current flows cathode anode
(plate)…essentially an electronic on/off switch
grid

…the big technological jump occurred in 1950’s as
we moved from from passive to active devices
R,C, L….+
`vacuum’ tubes

First Transistor
~ a solid state on-off switch
Bardeen Schockley Brattain
Bell Labs 1948
Key advantages
* base control current tiny (pA)
*switching is fast
*solid state allows minaturization

Emitter Base Collector
TRANSISTORS
voltage controlled
current switch
Almost always
characterized
by 3 prongs
Small base current
controls much larger
current from CE

Integrated circuits = IC =microchips = chips
Many transistors + …in module to control something
`old timers’ (aka the Doc) called them `bugs’

Inside a simple IC: operational amplifier (op amp)
Can use to build/ interface measurement
and control systems of nearly everything

Many IC wired to a printed circuit board to perform
complex tasks
How
many IC
do you
count ?
Probably
computer “chip”
(zillions of
transistors)

Simple Integrated Circuit
Chip…with a few hundred
transistors
1970s Texas Instruments figures
out how to make many transistors
on an `IC’ (Integrated Circuit)…so
many decisions can be made

DE-9 serial port (RS-232)
(printers, projectors…for PC)
RJ 45 `ether
net cable’ (for LAN)
Mini DIN -8 serial
port ( for Macs)
USB = Universal Serial Bus
Getting information to and from computer device…thru a `BUS’: some connector types
25 pin parallel port
DB 25 (many current printer ports)

More input/output cabling types
(Video)

Central Processing
Unit (CPU)
motherboard
Hard Drive
What are these ???

Programmable
Logic Devices (PLD)

Overview of PLD
 Fixed function
A specific logic function is contained in the IC (hardwired) and
can never be changed.
 PLD
Programmable logic requires both hardware and software.
Logic function programmed by the user. Some, can be
reprogrammed many times.
Programmable logic devices can be programmed to perform
specified logic functions and operations by the manufacturer or
by the user.
PLDs use much less board space for an equivalent amount of
logic
designs can be readily changed without rewiring or replacing
components if PLDs are used.
a logic design can generally be implemented faster and with
less cost with programmable logic than with fixed-function
logic.

 There Two major categories of user-programmable
logic are PLD (programmable logic device) and
FPGA (field-programmable gate array).
 PLDs are either
 Simple (SPLDs)
 Complex (CPLDs)
Types of PLD

1. Simple Programmable Logic Devices (SPLD)
• The SPLD was the original PLD and is still available
for small-scale applications.
• Generally, an SPLD can replace up to ten fixed-
function ICs and their interconnections, depending
on the type of functions and the specific SPLD.
• Most SPLDs are in one of two categories:
• Programmable Array Logic (PAL): consists of a
reprogrammable array of AND gates and a fixed
array of OR gates and it can be programmable one
time.

 Generic Array Logic (GAL):consists of a reprogrammable
array of AND gates and a fixed array of OR gates with
programmable outputs,

Complex Programmable Logic Devices (CPLD)
 The CPLD is device containing multiple SPLDs and can
replace many fixed-function ICs.

– Much higher capacity than SPLD
• CPLDs can be used to implement any of the logic
function.
• Decoders, encoders, multiplexers, de-multiplexers, etc.
• They are available in variety of configurations, typically
ranging from 44 to 160 pin package

Field-Programmable Gate Arrays (FPGA)
 Different internal organization than SPLD and CPLD
 Greatest logic capacity
 Consist of 64- thousands logic block(logic gate groups)
 The FPGA is composed of:
 The logic block
 The programmable interconnection,
 And the input/output(I/O) blacks
 Classes
 Fine grain (smaller logic block)
 Coarse grain (large logic block)

PLD Programming
• Logic circuit entered using 2 basic method
– Graphical entry
• schematic diagram
– Text-based entry (language based entry)
• Using Hardware Description Language (HDL)
– Eg . ABEL, CUPL, WinCUPL
– Becoming widely used
especially for CPLD and FPGA
» VHDL
» Verilog
MODULE decoder
TITLE 'decoder'
A,B,C,D pin
W,X,Y,Z pin
1,2,3,4;
14,15,16,17;
equations
W=!B & C # !B & D # C & D #A;
X=!A & D # B # C;
Y=!A & !B & D # C;
Z=!B & C # D;

IC package showing the chip mounted
inside, with
connection to input an output pins.

Complexity Classifications
for ICs
The size and complexity of ICs have increased rapidly
• A) Invention of Transistor 1947
• B) Development of silicon transistor 1955-1959
• C) Silicon planar technology 1959
• D) First ICs , Small Scale Integration (SSI) 1960-1965
• E) Medium scale Integration (MSI) 1965-1970
• F) Large scale integration (LSI) 1970- 1980
• G)Very Large scale integration (VLSI) 1980- 1990
• H) Ultra Large scale integration (ULSI) 1990-2000
• I) Giant - scale integration (GSI)

Advantages of integrated circuits
1. Miniaturization and hence increased
equipment density.
2. Cost reduction due to batch processing.
3. Increased system reliability due to the
elimination of soldered joints.
4. Improved functional performance.
5. Matched devices.
6. Increased operating speeds.
7. Reduction in power consumption

Chapter 1.pptx

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