Digital Systems Engineering
(EEB -4202)
Department of Electrical Power and Engineering
Mbeya University of Science and Technology
Email : dsinkonde2013@gmail
Expected Outcomes
Students can expect to gain the following:
Ability to design and evaluate wide ranges of
numerical control of electrical systems.
Ability to analyze MOSFET and CMOS Circuits
Ability to design and simulate counters,
registers and memories
Assignments and Learning Evaluation
• Mode of Assessment
Continuous Assessment (CA) 40%
Assignments
Total Score = 10% , End of submission on the 6th Week
- 20th April, 2022
Tests
Test to be conducted Starting From Week 7 = 30%
- 27thApril, 2022
University Examination (UE) 60%
Number of Credits : 7
General Course Information
Textbooks/References
1. Rabaey, J.M., (1996), Digital
Integrated Circuits, Prentice-
Hall,
2. Weste, N.,Eshraghain, K.,
Principles of CMOS VILSI Design,
2nd ed. Addison - Wesley
General Course Information
Topic to be Covered
Review of MOSFET operation
CMOS logic gate electrical characteristics
System and single - point noise margin and
noise budgets.
Combinational Logic Circuits Analysis
flip flops, counters, Registers and shift
register, memories (RAM, ROM, PROMS)
Topic to be Covered
Timing, clocking, and clock distribution for
digital circuits Prediction of metastability
error rates and design for acceptable
probability of failure.
Examples and design exercises using systems
and interconnections selected form current
computer practice such as RAMBUS, PCI
bus, GTL, LVDS, and others.
Lecture 1:
Introduction to Digital Systems
Digital Systems Eng
Digital
• Computing and electronics
• Real world information is converted to
binary numeric forms as digital audio and
digital photography.
• Now a day’s digital systems are used in wide
variety of industrial and consumer products
such as automated industrial machinery,
pocket calculators, mobile phone, digital
computers, digital watches, TV games and
signal processing and so on.
Introduction to Digital System
Introduction to Digital System
Introduction to Digital System
Many digital systems are by using these
chips and circuit boards.
VLSI- Very large Scale Integration- Chip
designing
Computer systems are constructed of digital
electronics.
Electronics circuits can only exist in one of
two states.
»On Off
Digital means zeros and ones.
Most Computer Electronics use voltage level
to indicate their present state.
Introduction Contd
Definitions
System- A set of related components
work as whole to achieve a goal.
A System contains
• Inputs
• Behaviours
• Outputs
Analog System- has values from
continuous set
Introduction Contd
Definitions
Digital Systems- are nothing but electronic
systems that use digital signals.
Digital System- Is an interconnection of
digital modules and these digital modules are
nothing but digital circuits.
Used in communications, business, medical
treatment, internet and many other
commercial, industrial and scientific
enterprises.
Digital System- Is a system in which signals
have a finite number of discrete values.
Introduction Contd
Definitions
Mixed Signal System- has both digital and
analogy parts.
Introduction Contd
Systems are constructed from three basic
Components
Introduction to Digital Systems contd..
Digital systems are being used more
than analog systems
Why we are using digital systems more
compared to analog systems?
Digital systems are accurate and reliable.
Surprisingly fast and cheap as compared to
analog systems
Advantages
Easy to design
Store information easily
Less affected by noise
Fabricated on IC chip
Characteristics of Digital systems
• Digital systems manipulate discrete elements
of information.
• Discrete elements are nothing but the digits
such as 10 decimal digits or 26 letters of
alphabets and so on.
• Digital systems use physical quantities called
signals to represent discrete elements. In
digital systems, the signals have two discrete
values and are therefore said to be binary.
• A signal in digital system represents one
binary digit called a bit.
• The bit has a value either 0 or 1.
Digital systems Vs Analog systems
• Analog system process information that varies
continuously i.e; they process time varying signals
that can take on any values across a continuous
range of voltage, current or any physical parameter.
• Digital systems use digital circuits that can process
digital signals which can take either 0 or 1 for binary
system.
Advantages of Digital systems over Analog systems
Advantages of Digital systems over Analog systems
Disadvantages of Digital Systems
Use more energy than analog circuits to
accomplish the same tasks, thus producing
more heat as well.
Digital circuits are often fragile, in that if a
single piece of digital data is lost or
misinterpreted the meaning of large blocks
of related data can completely change.
Digital computer manipulates discrete
elements of information by means of a
binary code.
Quantization error during analog signal
sampling.
Introduction to Digital System
Digital System are classified into two
types
– Combinational circuit
– Sequential Circuit
What is a Combinational Logic Circuit?
A combinational logic circuit as the name
itself indicates that it is the combination of
various kinds of logic gates.
outputs depend only the inputs have been
applied
new outputs appear shortly after changed
inputs (propagation delay)
no feedback loops
no clock
A combinational circuit consists of input variables,
output variables, and logic gates that transform binary
information from the input to the output.
Design Procedure
Design a circuit from a specification.
1. The problem is stated
2. Determine number of required inputs and outputs.
3. Derive truth table
4. Obtain simplified Boolean functions
5. Draw logic diagram and verify correctness
There are two switches S1 and S2 to control a
light bulb (e.g., one switch near each door of a
room w/2 doors). Design a logic circuit so that
the bulb can be controlled (essentially, toggled)
by either switch (i.e., by flicking/pushing either
switch).
Alternate Statement
Design Steps (for small-size designs w/ up to around 6 vars; we will later learn
about hierarchical or divide-and-conquer strategies for larger designs)
1b.
(symbolic)
Classification of Combinational Logic Circuits
Classification of Sequential Logic Circuits
Now, these are types and classifications of Sequential circuits.
Types of Sequential circuits:
The sequential circuits can be event driven, clock driven and pulse
driven.
AB
Drain
Source
Drain
Source
End of segment
