4. Definition: Analog & Digital
Varies over a continuous range of values
a variable signal continuous in both time and amplitude
Examples of analog quantities : time, pressure, sound.
5. • 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
6. Analog vs Digital
• 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
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 technology is relatively new
compared to analog technology, but a lot
of analog systems has been changed to a
digital systems, Examples:
– Manufacturing systems
– Medical Science
8. 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
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
9. The Digital Disadvantages
• But digital systems also has a disadvantages:
– Greater bandwidth (although compression
– Sampling error
– Compatibility with existing analog systems
– Short product half life
• But it advantages is a lot more compared to the
10. 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
11. Hybrid System
• The audio CD is a typical hybrid (Analog & Digital)
– Analog sound is converted into analog voltage using a
– Analog voltage is changed into digital through an ADC in
– 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.
13. Representing Digital
• The smallest information that can be represented in
digital systems is binary digit (bit), it can have two
– HIGH (bit 1)
– LOW (bit 0)
• This information is represented through electrical
1010100 represented as electrical signal
15. Digital Waveform
• Digital systems usually uses a square wave
– Because square wave represent a binary value (HIGH or
• Two type of squarewave
• The signal keep on repeating after a period of time
– Non Periodic
• Doesn’t have a period
16. 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
T = 1/f s
clock frequency : f = 100Hz,
so, period : T = 1/100Hz = 0.01s = 0.01x 103 = 10 ms
18. 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
Rise Time Fall Time
19. 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
20. 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
21. 1 2 3 4 5 6 7 8
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
22. Data Transfer
Data refers to groups of bits that convey some type of
Binary data are transferred in two ways: serial
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
23. 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?
26. 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
31. Basic Logic Functions
Any digital systems has one or more of the following
This functions are built from the basic gates.
Code conversion function
Data selection function
Data storage function
34. Code Conversion Function
• A code is a set of bits arranged in a unique
used to represent specified
: BCD, ASCII
• The usage of codes allow a faster and more
efficient data processing.
39. Data Storage Function
• Flip-flop stores a 1 or 0 only
– 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
41. 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
Integrated Circuit (IC)
47. In days of yore…(pre 1960)
before solid state transistors
became commercially chip
Grid current (mA) determines whether current flows cathode anode
(plate)…essentially an electronic on/off switch
48. …the big technological jump occurred in 1950’s as
we moved from from passive to active devices
49. First Transistor
~ a solid state on-off switch
Bardeen Schockley Brattain
Bell Labs 1948
* base control current tiny (pA)
*switching is fast
*solid state allows minaturization
51. Integrated circuits = IC =microchips = chips
Many transistors + …in module to control something
`old timers’ (aka the Doc) called them `bugs’
52. Inside a simple IC: operational amplifier (op amp)
Can use to build/ interface measurement
and control systems of nearly everything
53. Many IC wired to a printed circuit board to perform
54. Simple Integrated Circuit
Chip…with a few hundred
1970s Texas Instruments figures
out how to make many transistors
on an `IC’ (Integrated Circuit)…so
many decisions can be made
55. 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)
59. Overview of PLD
A specific logic function is contained in the IC (hardwired) and
can never be changed.
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
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
60. There Two major categories of user-programmable
logic are PLD (programmable logic device) and
FPGA (field-programmable gate array).
PLDs are either
Types of PLD
61. 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
62. Generic Array Logic (GAL):consists of a reprogrammable
array of AND gates and a fixed array of OR gates with
64. – Much higher capacity than SPLD
• CPLDs can be used to implement any of the logic
• Decoders, encoders, multiplexers, de-multiplexers, etc.
• They are available in variety of configurations, typically
ranging from 44 to 160 pin package
65. 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
Fine grain (smaller logic block)
Coarse grain (large logic block)
67. 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
W=!B & C # !B & D # C & D #A;
X=!A & D # B # C;
Y=!A & !B & D # C;
Z=!B & C # D;
71. Complexity Classifications
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)
72. Advantages of integrated circuits
1. Miniaturization and hence increased
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