DIGITAL LOGIC DESIGN LAB MANUAL PROF VK NAIK

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DIGITAL LOGIC DESIGN
LAB MANUAL
Department of Electronics & Communication Engineering
Prepared By
Prof. (Dr) V. KRISHNANAIK
PROFESSOR ECE
CHAITANYA DEEMED TO BE UNIVERSITY, HYDERABAD

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DIGITAL LOGIC DESIGN LAB MANUAL
HDL Simulation programs
Name:_____________________________________________
H.T.No:____________________________________________
Year/Semester:______________________________________
Department of Electronics & Communication Engineering

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Dept. of Electronics and Communication Engineering
Vision of the institute
To be one of the premier institutes for professional education producing dynamic
and vibrant force of technocrats with competent skills, innovative ideas and leadership qualities
to serve the society with ethical and benevolent approach.
Mission of the institute
Mission_1: To create a learning environment with state-of-the art infrastructure, well equipped
laboratories, research facilities and qualified senior faculty to impart high quality technical
education.
Mission_2: To facilitate the learners to inculcate competent research skills and innovative ideas
by Industry-Institute Interaction.
Mission_3: To develop hard work, honesty, leadership qualities and sense of direction in learners
by providing value based education.
Vision of the department
To develop as a center of excellence in the Electronics and Communication
Engineering field and produce graduates with Technical Skills, Competency, Quality, and
Professional Ethics to meet the challenges of the Industry and evolving Society.
Mission of the department
Mission_1: To enrich Technical Skills of students through Effective Teaching and Learning
practices to exchange ideas and dissemination of knowledge.
Mission_2: To enable students to develop skill sets through adequate facilities, training on core
and multidisciplinary technologies and Competency Enhancement Programs.
Mission_3: To provide training, instill creative thinking and research attitude to the students
through Industry-Institute Interaction along with Professional Ethics and values.
Programme Educational Objectives (PEOs)
PEO 1: To prepare the graduates to be able to plan, analyze and provide innovative ideas to
investigate complex engineering problems of industry in the field of Electronics and
Communication Engineering using contemporary design and simulation tools.
PEO-2: To provide students with solid fundamentals in core and multidisciplinary domain for
successful implementation of engineering products and also to pursue higher studies.
PEO-3: To inculcate learners with professional and ethical attitude, effective communication
skills, teamwork skills, and an ability to relate engineering issues to broader social context at
work place

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Programme Outcomes(Pos)
PO_1 Engineering knowledge: Apply the knowledge of mathematics, science, engineering
fundamentals, and an engineering specialization to the solution of complex engineering problems.
PO_2 Problem analysis: Identify, formulate, review research literature, and analyze complex
engineering problems reaching substantiated conclusions using first principles of mathematics,
natural sciences, and engineering sciences.
PO_3 Design/development of solutions: Design solutions for complex engineering problems and
design system components or processes that meet the specified needs with appropriate
consideration for the public health and safety, and the cultural, societal, and environmental
considerations.
PO_4 Conduct investigations of complex problems: Use research-based knowledge and research
methods including design of experiments, analysis and interpretation of data, and synthesis of the
information to provide valid conclusions.
PO_5 Modern tool usage: Create, select, and apply appropriate techniques, resources, and modern
engineering and IT tools including prediction and modeling to complex engineering activities
with an understanding of the limitations.
PO_6 The engineer and society: Apply reasoning informed by the contextual knowledge to assess
societal, health, safety, legal and cultural issues and the consequent responsibilities relevant to the
professional engineering practice.
PO_7 Environment and sustainability: Understand the impact of the professional engineering
solutions in societal and environmental contexts, and demonstrate the knowledge of, and need
for sustainable development.
PO_8 Ethics: Apply ethical principles and commit to professional ethics and responsibilities and norms
of the engineering practice.
PO_9 Individual and team work: Function effectively as an individual, and as a member or leader in
diverse teams, and in multidisciplinary settings.
PO_10 Communication: Communicate effectively on complex engineering activities with the
engineering community and with society at large, such as, being able to comprehend and write
effective reports and design documentation, make effective presentations, and give and receive
clear instructions.
PO_11 Project management and finance: Demonstrate knowledge and understanding of the
engineering and management principles and apply these to one’s own work, as a member and
leader in a team, to manage projects and in multidisciplinary environments.
PO_12 Life-long learning: Recognize the need for, and have the preparation and ability to engage in
independent and life-long learning in the broadest context of technological change.
Programme Specific Outcome(PSOs)
Higher Education : Qualify in competitive examination for pursuing higher education by
PSO_1
applying the fundamental concepts of Electronics and Communication Engineering domains such
as Analog & Digital Electronics, Signal Processing, Communication & Networking, Embeded
Systems, VLSI Design and Control systems etc.,
Employment: Get employed in allied industries through their proficiency in program specific
PSO_2 domain knowledge, Specalized software packages and Computer programming or became an
entrepreneur.

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II B.Tech. III-Sem (EEE)
DIGITAL LOGIC DESIGN LABORATORY
COURSE OUTCOMES(COS)
CO1 Understand the pin configuration of various digital ICs used in the lab
CO2 Conduct the experiment and verify the properties of various logic circuits.
CO3 Analyze the sequential and combinational circuits.
CO4 Design of any sequential/combinational circuit using Hardware
PART A:
LIST OF EXPERIMENTS:
1. Verification of truth tables of the following Logic gates
Two input (i) OR (ii) AND (iii) NOR (iv) NAND (v) Exclusive-OR (vi) Exclusive-NOR
2. Design a simple combinational circuit with four variables and obtain minimal expression
and verify the truth table using Digital Trainer Kit.
3. Verification of functional table of 3 to 8-line Decoder /De-multiplexer.
4. 4variable logic function verification using 8 to1 multiplexer.
5. Design full adder circuit and verify its functional table.
6. Verification of functional tables of (i) JK Edge triggered Flip–Flop (ii) JK Master Slav
Flip–Flop (iii) D Flip-Flop
7. Design a four-bit ring counter using D Flip–Flops/JK Flip Flop and verify output
8. Design a four bit Johnson’s counter using D Flip-Flops/JK Flip Flops and verify output
9. Verify the operation of 4-bit Universal Shift Register for different Modes of operation.
10. Draw the circuit diagram of MOD-8 ripple counter and construct a circuit using T-Flip-
Flops and Test It with a low frequency clock and sketch the output waveforms.
11.Design MOD–8 synchronous counter using T Flip-Flop and verify the result and sketch
the output waveforms.
12. (a) Draw the circuit diagram of a single bit comparator and test the output
(b) Construct 7 Segment Display Circuit Using Decoder and7 Segment LED and test it.

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Dept. of Electronics and Communication Engineering
(20A04303P) DIGITAL LOGIC DESIGN II B.Tech-I SEM
LIST OF EXPERIMENTS TO BE CONDUCTED
HARDWARE EXPERIMENTS
1. Logic Gates.
2. Design of combinational circuits with four variables.
3. 3 to 8-line Decoder /De-multiplexer.
4. 8 to1 multiplexer.
5. Full adder.
6. Functional tables of (i) JK Edge triggered Flip–Flop (ii) JK Master Slav Flip–Flop (iii) D
Flip-Flop.
7. Four-bit ring counter using D Flip–Flops/JK Flip Flop.
8. Four bit Johnson’s counter using D Flip-Flops/JK Flip Flops.
9. 4-bit Universal Shift Register.
10. MOD-8 ripple counter using T-Flip-Flops.
11. MOD–8 synchronous counter using T Flip-Flop.
12a. single bit comparator
12b. 7 Segment Display Circuit Using Decoder and7 Segment LED
ADDITIONAL EXPERIMENTS:
1. BCD Adder Circuit.
2. 74154 De-Multiplexer using LEDs for outputs.
3 HDL Simulation programs

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CONTENTS
S.NO. NAME OF THE EXPERIMENT PAGE NO
1 Logic Gates.
2 Design of combinational circuits with four variables.
3 3 to 8-line Decoder /De-multiplexer.
4 8 to1 multiplexer.
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Full adder.
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Functional tables of (i) JK Edge triggered Flip–Flop (ii) JK Master
Slav Flip–Flop (iii) D Flip-Flop.
7 Four-bit ring counter using D Flip–Flops/JK Flip Flop.
8 Four bit Johnson’s counter using D Flip-Flops/JK Flip Flops.
9 4-bit Universal Shift Register.
10 MOD-8 ripple counter using T-Flip-Flops.
11 MOD–8 synchronous counter using T Flip-Flop.
A. single bit comparator
12 B.7 Segment Display Circuit Using Decoder and7 Segment LED
ADDITIONAL EXPERIMENTS
1 BCD Adder Circuit.
2 74154 De-Multiplexer using LEDs for outputs.

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DOS & DONTS IN LABORATORY
DO’s
1. Students should be punctual and regular to the laboratory.
2. Students should come to the lab in-time with proper dress code.
3. Students should maintain discipline all the time and obey the instructions.
4. Students should carry observation and record completed in all aspects.
5. Students should be at their concerned experiment table, unnecessary moment is restricted.
6. Students should follow the indent procedure to receive and deposit the components from
lab technician.
7. While doing the experiments any failure/malfunction must be reported to the faculty.
8. Students should check the connections of circuit properly before switch ON the power
supply.
9. Students should verify the reading with the help of the lab instructor after completion of
experiment.
10. Students must endure that all switches are in the lab OFF position, all the connections
are removed.
11. At the end of practical class the apparatus should be returned to the lab technician and
take back the indent slip.
12. After completing your lab session SHUTDOWN the systems, TURNOFF the power
switches and arrange the chairs properly.
13. Each experiment should be written in the record note book only after getting signature
from the lab in charge in the observation notebook.
DON’Ts
1. Don’t eat and drink in the laboratory.
2. Don’t touch electric wires.
3. Don’t turn ON the circuit unless it is completed.
4. Avoid making loose connections.
5. Don’t leave the lab without permission.
6. Don’t bring mobiles into laboratory.
7. Do not open any irrelevant sites on computer.
8. Don’t use a flash drive on computers.

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SCHEME OF EVALUATION
Marks Awarded
Total
S.No Program Date Record Obs. Viva Attd. 35(M)
(10M) (15M) (5M) (5M)
1 Logic Gates.
2
Design of combinational
circuits with four
variables.
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3 to 8-line Decoder /De-
multiplexer.
4 8 to1 multiplexer.
5 Full adder.
Functional tables of (i)
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JK Edge triggered Flip–
Flop (ii) JK Master Slav
Flip–Flop (iii) D Flip-
Flop.
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Four-bit ring counter
using D Flip–Flops/JK
Flip Flop.
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Four bit Johnson’s
counter using D Flip-
Flops/JK Flip Flops.
9 4-bit Universal Shift
Register.
10 MOD-8 ripple counter
using T-Flip-Flops.
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MOD–8 synchronous
counter using T Flip-
Flop.
A. single bit comparator
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B.7 Segment Display
Circuit Using Decoder
and7 Segment LED
1 BCD Adder Circuit.
2 74154 De-Multiplexer
using LEDs for outputs.
Signature of Lab In-charge

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DLD/DE LABORATORY II B.Tech III Sem
LOGIC DIAGRAMS:
NOT GATE
OR GATE
AND GATE
NAND GATE
CHAITANYA DEEMED TO BE UNIVERSITY, Dept of ECE. Page 1

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EXP.NO : DATE:
LOGIC GATES
AIM: Verification of Truth Table for AND, OR, NOT, NAND, NOR and EX-OR gates.
APPARATUS REQUIRED:
Sl. No Name of the Gates IC number Qty
1 AND gate 7408 2
2 OR gate 7432 2
3 Not gate 7404 2
4 EXOR gate 7486 2
5 NAND gate 7400 2
6 NOR gate 7402 2
7 EX-NOR gate 4077 1
8 Patch chords few
9 Trainer Kit
THEORY:
The basic logic gates are the building blocks of more complex logic circuits. These logic
gates perform the basic Boolean functions, such as AND, OR, NAND, NOR, Inversion,
Exclusive-OR, Exclusive-NOR. Fig. below shows the circuit symbol, Boolean function, and
truth. It is seen from the Fig that each gate has one or two binary inputs, A and B, and one
binary output, C. The small circle on the output of the circuit symbols designates the logic
complement. The AND, OR, NAND, and NOR gates can be extended to have more than
two inputs. A gate can be extended to have multiple inputs if the binary operation it
represents is commutative and associative.

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NOR GATE
XOR GATE
EX-NOR GATE

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PROCEDURE:
1. Fix the I.C on the I.C trainer kit.
2. Connections are made as shown, using the pin details of the gates. Toggle switches and
3. Switch on the supply on the trainer and verify the truth table of the gates
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. Why NAND & NOR gates are called universal gates?
2. Realize the EX – OR gates using minimum number of NAND gates?
3. Give the truth table for EX-NOR and realize using NAND gates?
4. What is the principle of logic gates?
5. Which is the most commonly used logic family?

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LOGIC DIAGRAM:
FIG: 8:1 MULTIPLEXER
FUNCTION TABLE
SELECTION
STROBE
LINES OUTPUTS
C B A E Y Y
X X X 1 0 1
0 0 0 0 D0 D0
0 0 1 0 D1 D1
0 1 0 0 D2 D2
0 1 1 0 D3 D3
1 0 0 0 D4 D4
1 0 1 0 D5 D5
1 1 0 0 D6 D6
1 1 1 0 D7 D7
X = don’t care condition.

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EXP NO : DATE:
REALIZATION OF BOOLEAN EXPRESSION USING 8:1 MULTIPLEXER 74151
AIM:-Verification of 4variable logic function using 8 to1 multiplexer.
APPARATUS REQUIRED:
Digital trainer board, IC 74151, IC 7404, IC 7432, patch cords, + 5V Power supply
THEORY:
1 .What is multiplexer?
Multiplexer is a digital switch which allows digital information from several sources to
be routed onto a single output line. Basic multiplexer has several data inputs and a single
output line. The selection of a particular input line is controlled by a set of selection line.
There are 2n input lines & n is the number of selection line whose bit
combinations determines which input is selected .It is “Many into One”.
Strobe: - It is used to enable/ disable the logic circuit OR ‘E’ is called as enable I/P which
is generally active LOW. It is used for cascading MUX is a single pole multiple way switch.
2. Necessity of multiplexer?
In most of the electronic systems, digital data is available on more than one lines. It is necessary
to route this data over a single line. It select one of the many I/P at a time.
Multiplexer improves the reliability of digital system because it reduces the number of
external wire connection.
Enlist significance and advantages of Multiplexer
• It doesn‘t need K-map & logic simplification.
• The IC package count is minimized.
• It simplifies the logic design.
• In designing the combinational circuit
• It reduces the complexity & cost.
• To minimize number of connections in communication system were we need to
handle thousands of connections. Ex.Telephone exchange.

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Example:
Function = Sum of Product (SOP) Y = ∑m (1, 2, 3, 4, 5, 6, 7)
SELECTION STROB
LINES E OUTPUTS
C B A Y Y
0 0 0 0 0 1
0 0 1 0 1 0
0 1 0 0 1 0
0 1 1 0 1 0
1 0 0 0 1 0
1 0 1 0 1 0
1 1 0 0 1 0
1 1 1 0 1 0
SOP realization Diagram
SOP Y = ∑m (1, 2, 3, 4, 5, 6, 7)
Solution:- Since there are 3 variable, the multiplexer have 3 select I/P should be used. Hence one
8:1 mux should be used.
Ste p 1:-Identify the number decimal corresponding to each minterm.
Here 1,2,3,4,5,6,7
Step 2:-Connect the data input lines 1,2,3,4,5,6,7 to logic 1(+Vcc) &
remaining input line 0 to logic 0(GND)
Step 3:-Connect variables A, B & C to select input.

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RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What are the different methods to obtain minimal expression?
2. What is a Min term and Max term?
3. State the difference between SOP and POS?
4. How do you realize a given function using multiplexer?
5. What is a multiplexer?
LOGIC DIAGRAM:

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FIG: 3:8 DECODER
TRUTH TABLE FOR DECODER:

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EXP. NO: DATE:
3 TO 8-LINE DECODER /DE-MULTIPLEXER
AIM:-Verification of functional table of 3 to 8-line Decoder /De-multiplexer.
APPARATUS REQUIRED:
IC 7447, 7-segment display, IC 74139 and connecting leads.
THEORY:
ENCODER:
An encoder is a device, circuit, transducer, software program, algorithm or person that converts
information from one format or code to another, for the purposes of standardization, speed,
secrecy, security, or saving space by shrinking size. An encoder has M input and N output
lines. Out of M input lines only one is activated at a time and produces equivalent code on
output N lines. If a device output code has fewer bits than the input code has, the device is
usually called an encoder. For example Octal-to-Binary Encoder take 8 inputs and provides 3
outputs, thus doing the opposite of what the 3-to-8 decoder does. At any one time, only one
input line has a value of 1. The figure below shows the truth table of an Octal-to-binary
encoder.
For an 8-to-3 binary encoder with inputs I0-I7 the logic expressions of the outputs Y0-
Y2 are:
Y0=I1+I3+I5+I7Y1=I2+I3+I6+I7Y2=I4+I5+I6+I7
DECODER:
A decoder is a device which does the reverse operation of an encoder, undoing the encoding so
that the original information can be retrieved. The same method used to encode is usually just
reversed in order to decode. It is a combinational circuit that converts binary information from
n input lines to a maximum of 2n
unique output lines. In digital electronics, a decoder can take
the form of a multiple-input, multiple-output logic circuit that converts coded inputs into coded
outputs, where the input and output codes are different. e.g. n-to-2n
, binary-coded decimal
decoders. Enable inputs must be on for the decoder to function, otherwise its outputs assume a
single "disabled" output code word. In case of decoding all combinations of three bits eight
(23
=8) decoding gates are required. This type of decoder is called 3-8 decoder because 3 inputs
and 8 outputs. For any input combination decoder outputs are 1.

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LOGIC DIAGRAM:
FIG: 1:4 DEMUX
TRUTH TABLE FOR DEMUX:

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DEMULTIPLEXER:
Demultiplexer means generally one into many. A demultiplexer is a logic circuit
with one input and many outputs. By applying control signals, we can steer the
input signal to one of the output lines. The ckt has one input signal, m control
signal and n output signals. Where 2n
= m. It functions as an electronic switch to
route an incoming data signal to one of several outputs.
PROCEDURE:
1) Connect the circuit as shown in figure.
2) Apply Vcc & ground signal to every IC.
3) Observe the input & output according to the truth table.
PRECAUTIONS:
1) Make the connections according to the IC pin diagram.
2) The connections should be tight.
3) The Vcc and ground should be applied carefully at the specified pin only.
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What do you understand by decoder?
2. What is demultiplexer?
3. What do you understand by encoder?
4. What is the main difference between decoder and demultiplexer?
5. Why Binary is different from Gray code?

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LOGIC DIAGRAM:
FIG: 8:1 MULTIPLEXER
FUNCTION TABLE
SELECTION STROBE
LINES OUTPUTS
C B A E Y Y
X X X 1 0 1
0 0 0 0 D0 D0
0 0 1 0 D1 D1
0 1 0 0 D2 D2
0 1 1 0 D3 D3
1 0 0 0 D4 D4
1 0 1 0 D5 D5
1 1 0 0 D6 D6
1 1 1 0 D7 D7
X = don’t care condition.
EXP NO: DATE:

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8:1 MULTIPLEXER
AIM: 3 variable logic function verification using 8 to1 multiplexer.
APPARATUS REQUIRED:
Digital Trainer Kit 01
NOT Gate IC 7404 01
81 MUX IC 74151 01
Patch chords / Connecting wires 20
THEORY:
The Multiplexers or data selector is a logic circuit that selects one out of several
inputs to a single output. The input selected is controlled by a set of select lines. For selecting
one output line from n-input lines, a set of m-select lines is required. The relationship
between the number of input lines and the select lines is given by 2 m
= n.
PROCEDURE:
1. Connections are made as shown in the logic diagram using the pin details of the
gates.
2. Connect Vcc and GND to respective pins of each IC.
3. Connect the data, select and enable inputs to the toggle switches and outputs to the
LED‟s
4. Switch on the Trainer
5. Verify the truth table of the Multiplexer.
FUll Adder using MUX
INPUTS OUTPUTS
X Y CIN
S COUT
(Sum) (Carry)
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
Implementation table for Sum and Carry:

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Sum = Σm (1,2,4,7)
Carry = Σm (3,5,6,7)
LOGIC DIAGRAM FOR CARRY:
LOGIC DIAGRAM FOR SUM:
RESULT :

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CONCLUSION:
VIVA QUESTIONS:
1. What is a multiplexer?
2. What are the applications of multiplexer and de-multiplexer?
3. What is a de-multiplexer?
4. In 2n to 1 multiplexer how many selection lines are there?
5. Implement an 8:1 mux using 4:1 muxes?

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CIRCUIT DIAGRAM:
TRUTH TABLE
X Y Z Sum (S) Carry (C)
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1

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Exp No: Date:
FULL ADDER
AIM: To verify the truth tables of Full Adder.
APPARATUS REQUIRED:
S.NO APPARATUS RANGE QUANTITY
1
IC’s 74LS08, 74LS32, 74LS04,
1
74LS00, 74LS02, 74LS86
2 Light Emitting Diode (LED) 1
3 Bread board 1
4 Connecting wires REQUIRED
5 Fixed Power Supply (0-5v) 1
THEORY:
Full adder
A Full adder is a combinational circuit that performs addition of three input bits. Half adder
has inputs X, Y, Z and outputs sum (S) and carry(C). The truth table is
X Y Z Sum (S) Carry (C)
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1

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The simplified Boolean expressions are
The logic circuit to implement is as shown below

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FULL ADDER USING TWO HALF ADDERS AND OR GATE
A full adder can also be implemented using two half adders and one OR gate as shown in
fig.The sum output from second half adder is
S=x EXOR y EXOR z S=x’y’z’+x’yz’+xy’z’+xyz
C=xy+yz+xz
PROCEDURE:
1. The IC’s are placed on the bread board.
2. A voltage of +5V is applied to pin no.14 and –Ve is applied to pin no.7.
3. Inputs and Outputs are connected according the gates which are taken. 10.
For the input 1 we have to connect the input terminal to +5V and for 0 to –Ve.
4. Output is verified in LED. If the LED is ON the output is 1, if OFF it is 0.According to
the Logic gates truth table we have to verify the inputs and outputs.
RESULT:
CONCLUSION
VIVA QUESTIONS:
1. What is use of Full adder?
2. What is difference between the half and full adder?
3. How many half adders required to make a full adder?
4. In full adder how many types of gates are required?
5. Draw full adder circuit?

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CIRCUIT IMPLEMENTATION:
FIG: J – K FLIP – FLOP CIRCUIT
Where
Q Present State
Q t + 1 Next State
Characteristic eqn Q t + 1 = J Q + K Q
i)Implementation of JK Flip-Flop Design:
IC – 74LS76: Dual –ve edge triggered J – K Flip – Flop
Inputs Outputs
Q J K Qt + 1
0 0 0 0
0 0 1 0
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 0
1 1 0 1
1 1 1 0

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Truth Table of JK Flip – Flop Fig: Pin diagram of 7476
Exp No: Date:
JK & D FLIPFLOP
AIM: Verification of functional tables of (i) JK Edge triggered Flip–Flop (ii) JK Master Slav Flip–
Flop (iii) D Flip-Flop
APPARATUS REQUIRED:
7485,7408, 8411,7421, 7432, digital IC Trainer Kit, Patch Chord.
THEORY:
Basically Flip-Flops are the bistable multivibrators that stores logic 1 and logic 0.Shift
registers, memory, and counters are built by using Flip – Flops. Any complex sequential
machines are build using Flip – Flops. Sequential circuit (machine) output depends on the
present state and input applied at that instant.
Mealy Machine is one whose output depends on both the present state and the input.
Moore machines one whose output depends only on the present state of the sequential circuit.
Note that the truth table of J – K Flip – Flop is same as the Master – Slave.
J – K Flip Flop and they must be remain same because IC – 7476is –ve edge trigged flip
– flop and we know that race around condition is eliminated by edge triggered flip – flop.
Another way of eliminating race around condition is by using Master – Slave J –K Flip – Flop.
When J = K = 1 (logic HIGH), J – K Flip – Flop changes output many times for single clock
pulse, it is Smaller than width of the clock pulse.

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ii) Master Slave J K Flip – Flop:
IC – 74107: Dual – Master – Slave J-K Flip - Flop
FIG: PIN DIAGRAM
FIG: MASTER – SLAVE J –K FLIP – FLOP CIRCUIT.

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Truth Table of Master – Slave – JK Flip – Flop:
Where
Q Present State
Q t + 1 Next State
Input Outputs
s
Q J K Qt + 1
0 0 0 0
0 0 1 0
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 0
1 1 0 1
Characteristic eqn Q t + 1 = J Q + K Q
1 1 1 0
PROCEDURE:
1) Connections are made as per the circuit diagram.
2) Apply the –ve edge triggered, +ve edge triggered and level sensitive
clock pulses as required.
3) Verify the truth table of all the Flip – Flops.
4) Switch - off the power supply and disconnect the circuit.
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What is flip-flop?
2. How many types of flip-flop are used?
3. What are the characteristic equation for T flip-flop?
4. What is full form of T flip-flop?
5. Which Gates are used in SR flip flops to a JK flip-flop?

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iii) D – Flip – Flop:
IC – 7474: Dual + ve edge triggered D- Flip-Flop:
FIG: PIN DIAGRAM
FIG: D –FLIP – FLOP
Truth Table of D – Flip – Flop:
Inputs Outputs
Q J Qt + 1
0 0 0
0 1 1
1 0 0
1 1 1
Where
Q Present State
D Data Input
Qt + 1 Next State
Characteristic eqn Qt + 1 = D

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LOGIC DIAGRAM:
FIG: RING COUNTER

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Exp No: Date:
RING COUNTER
AIM: Design a four-bit ring counter using D Flip–Flops/JK Flip Flop.
APPARATUS REQUIRED:
Digital IC trainer kit, IC 7476
THEORY:
Ring counter and Johnson counters are basically shift registers Ring
Ring counter:
It is made by connecting Q&Q‟ output of one JK FF to J&K input of next FF respectively.
The output of final FF is connected to the input of first FF. To start the counter the first
FF is set by using preset facility and the remaining FF are reset input. When the clock arrives
the set condition continues to shift around the ring ,
As it can be seen from the truth table there are four unique output stages for this counter. The
modulus value of a ring counter is n, where n is the number of flip flops. Ring counter is
called divided by N counter where N is the number of FF
PROCEDURE:
1. Set up the ring counter and set clear Q outputs using PRESET and apply mono pulse.
2. Note down the state of the ring counter on the truth table for successive clock 0.

37
RESULT:
COCLUSION:
VIVA QUESTIONS:
1. What do you mean by Counter?
2. What is the ring counter?
3. What are the types of Counters? Explain each
4. Why asynchronous counters are called as ripple counters?
5. What are the applications of asynchronous counters?

38
Exp No: Date:
JOHNSON’S COUNTER
AIM: Design a four bit Johnson’s counter using D Flip-Flops/JK Flip Flops.
APPARATUS REQUIRED:
Digital IC trainer kit, IC 7476
THEORY:
Ring counter and Johnson counters are basically shift registers
Johnson counter (Twisted ring counter)
The modulus value of a ring counter can be doubled by making a small change in the ring counter circuit.
The Q‟ and Q of the last FFS are connected to the J and K input of the first FFrespectively. This is the
Johnson counter.
Initially the FFs are reset. After first clock pulse FF0 is set and the remaining FFs are reset.
After the eight clock pulse all the FFS are reset. There are eight different conditions creating a
mode 8 Johnson counter. Johnson counter is called a twisted ring counter or divide by 2N
counter.
PROCEDURE:
1. Set up the Johnson counter and set clear Q outputs using PRESET and apply mono
pulse.
2. Note down the state of the Johnson counter on the truth table for successive clock 0.

39
LOGIC DIAGRAM:
FIG: JOHNSON COUNTER

40
RESULT:
COCLUSION:
VIVA QUESTIONS:
1. What is the Johnson counter?
2. What is the difference between the counting sequence of an up counter and a down
counter?
3. What down you mean by down counter?
4. What is the advantage of Ripple counter over Synchronous Counter?
5. What are the applications of the counters?

41
LOGIC DIAGRAM:
FIG: UNIVERSAL SHIFT REGISTER DIAGRAM

42
Exp No: Date:
UNIVERSAL SHIFT REGISTER
AIM: Verify the operation of 4-bit Universal Shift Register for different Modes of operation.
APPARATUS REQUIRED: IC 74291, IC 74395
THEORY:
Shift registers are the sequential logic circuits that can store the data temporarily and provides the
data transfer towards its output device for every clock pulse. These are capable of
transferring/shifting the data either towards the right or left in serial and parallel modes. Based on
the mode of input/output operations, shift registers can be used as a serial-in-parallel-out shift
register, serial-in-serial-out shift register, parallel-in-parallel-out shift register, parallel-in-
parallel-out shift register. Based on shifting the data, there are universal shift registers and
bidirectional shift registers. Here is a complete description of the universal shift register.
What is a Universal Shift Register?
Definition: A register that can store the data and /shifts the data towards the right and left along
with the parallel load capability is known as a universal shift register. It can be used to perform
input/output operations in both serial and parallel modes. Unidirectional shift registers and
bidirectional shift registers are combined together to get the design of the universal shift register.
It is also known as a parallel-in-parallel-out shift register or shift register with the parallel load.
Universal shift registers are capable of performing 3 operations as listed below.
• Parallel load operation – stores the data in parallel as well as the data in parallel
• Shift left operation – stores the data and transfers the data shifting towards left in the
serial path
• Shift right operation – stores the data and transfers the data by shifting towards right in
the serial path.
Hence, Universal shift registers can perform input/output operations with both serial and parallel
loads.
• Serial input for shift-right control enables the data transfer towards the right and all the
serial input and output lines are connected to the shift-right mode. The input is given to
the AND gate-1 of the flip-flop -1 as shown in the figure via serial input pin.
• Serial input for shift-left enables the data transfer towards the left and all the serial input
and output lines are connected to shift-left mode.
• In parallel data transfer, all the parallel inputs and outputs lines are associated with the
parallel load.
• Clear pin clears the register and set to 0.
• CLK pin provides clock pulses to synchronize all the operations.
• In the control state, the information or data in the register would not change even though
the clock pulse is applied.
• If the register operates with a parallel load and shifts the data towards the right and left,
then it acts as a universal shift register.
• From the above figure, selected pins the mode of operation of the universal shift register.
Serial input shifts the data towards the right and left and stores the data within the register.

43
FIG: UNIVERSAL SHIFT REGISTER DESIGN
FUNCTION TABLE:
S0 S1 Mode of Operation
0
0 Locked state (No change)
0
1 Shift-Left
Shift-Right
1 0
Parallel Loading
1 1
CHAITANYA DEEMED TO BE UNIVERSITY, Dept of
ECE. Page 34

44
• Clear pin and CLK pin are connected to the flip-flop.
• M0, M1, M2, M3 are the parallel inputs while F0, F1, F2, F3 are the parallel outputs of
flip-flops
• When the input pin is active HIGH, then the universal shift register loads / retrieve the
data in parallel. In this case, the input pin is directly connected to 4×1 MUX
• When the input pin (mode) is active LOW, then the universal shift register shifts the data.
In this case, the input pin is connected to 4×1 MUX via NOT gate.
• When the input pin (mode) is connected to GND (Ground), then the universal shift
register acts as a Bi-directional shift register.
• To perform the shift-right operation, the input pin is fed to the 1st AND gate of the 1st
flip-flop via serial input for shit-right.
• To perform the shift-left operation, the input pin is fed to the 8th AND gate of the last
flip-flop via input M.
• If the selected pins S0= 0 and S1 = 0, then this register doesn’t operate in any mode. That
means it will be in a Locked state or no change state even though the clock pulses are
applied.
• If the selected pins S0 = 0 and S1 = 1, then this register transfers or shifts the data to left
and stores the data.
• If the selected pins S0 = 1 and S1 = 0, then this register shifts the data to right and hence
performs the shift-right operation.
• If the selected pins S0 = 1 and S1 = 1, then this register loads the data in parallel. Hence it
performs the parallel loading operation and stores the data.
PROCEDURE:
1. S0 and S1 are the selected pins that are used to select the mode of operation of this
register. It may be shift left operation or shift right operation or parallel mode.
2. Pin-0 of first 4×1Mux is fed to the output pin of the first flip-flop. Observe the
connections as shown in the figure.
3. Pin-1 of the first 4X1 MUX is connected to serial input for shift right. In this mode, the
register shifts the data towards the right.
4. Similarly, pin-2 of 4X1 MUX is connected to the serial input for shift-left. In this mode,
the universal shift register shifts the data towards the left.
5. M1 is the parallel input data given to the pin-3 of the first 4×1 MUX to provide parallel
mode operation and stores the data into the register.
6. Similarly, remaining individual parallel input data bits are given to the pin-3 of related
4X1MUX to provide parallel loading.
7. F1, F2, F3, and F4 are the parallel outputs of Flip-flops, which are associated with the 4×1
MUX.

45
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What do you mean by shift register?
2. Explain the operation of a left shift register & a right shift register?
3. What is the difference between a register and shift register?
4. What is meant by universal shift register?
5. Explain the various modes in which the data can be entered or taken out from a register?

46
Exp No: Date:
MOD-8 RIPPLE COUNTER
AIM: Draw the circuit diagram of MOD-8 ripple counter and construct a circuit using T-Flip-Flops
and Test It with a low frequency clock and sketch the output waveforms.
APPARATUS REQUIRED:
IC 7474 (T- Flip-flop), Digital Trainer Kit, patch cords, +5V power supply.
THEORY:
Asynchronous counter:
A digital counter is a set of flip flop. An Asynchronous counter uses T flip flop to perform a
counting function. The actual hardware used is usually J-K flip-flop connected to logic 1.
In ripple counter, the first flip-flop is clocked by the external clock pulse & then each successive
flip-flop is clocked by the Q or /Q‘ output the previous flip-flop. Therefore in an asynchronous
counter the flip-flop are not clocked simultaneously. The input of MS-JK is connected to VCC
because when both inputs are one output is toggled. As MS-JK is negative edge triggered at each
high to low transition the next flip-flop is triggered. On this basis the design is done for MOD-8
counter.
1) Up Counter:
Fig shows 3 bit Asynchronous Up Counter. Here Flip-flop A act as a MSB Flip-flop and
Flip-flop C can act as a LSB Flip-flop. Clock pulse is connected to the Clock of flip-flop C.
Output of Flip-flop C (Qc) is connected to clock of next flip-flop(i.e. Flip-flop B) and so on. As
soon as clock pulse changes output is going to -change(at the negative edge of clock pulse) as a
Up count sequence. For 3 bit Up counter Truth table is as shown below.
2) Down Counter:
Fig shows 3 bit Asynchronous Down Counter. Here Flip-flop a act as a MSB Flip-flop and Flip-
flop C can act as a LSB Flip-flop. Clock pulse is connected to the Clock of flip-flop C. Output of
Flip-flop C (Qc‘) is connected to clock of next flip- flop (i.e. Flip-flop B) and so on. As soon as
clock pulse changes output is going to change(at the negative edge of clock pulse) as a down
count sequence. For 3 bit down counter Truth table is as shown below.

47
Truth Table:
Up Counter
Counter States F/F Output
QA QB QC
0 0 0 0
1 0 0 1
2 0 1 0
3 0 1 1
4 1 0 0
5 1 0 1
6 1 1 0
7 1 1 1
LOGIC DIAGRAM:
Down Counter
Counter States F/F Output
QA QB QC
7 1 1 1
6 1 1 0
5 1 0 1
4 1 0 1
3 0 1 1
2 0 1 0
1 0 0 1
0 0 0 0
FIG: 3- BIT ASYNCHRONOUS UP COUNTER
FIG: 3- BIT ASYNCHRONOUS DOWN COUNTER

48
TIMING DIAGRAM:
1. 3 Bit Asynchronous Up Counter
CLK
Qa 0 0 0
3 1
Qb 0 0 1 1 0
Qc 0 0 0 0 1
2. 3 Bit Asynchronous Down Counter:
CLK
0 0
Qc 1 0 1
Qb 0 1 1 0 0
Qa 0
1 1 1 1
1
0
1
1
1
0
0
1
1
0
1
0
1
1
1
1
0
0

49
PROCEDURE:
1. Make the connections as per the logic diagram.
2. Connect +5v and ground according to pin configuration.
3. Apply diff combinations of inputs to the i/p terminals.
4. Note o/p for summation.
5. Verify the truth table.
PRECAUTIONS:
1. Make the connections according to the IC pin diagram.
2. The connections should be tight.
3. The Vcc and ground should be applied carefully at the specified pin only.
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What do you understand by counter?
2. What is asynchronous counter?
3. What is synchronous counter?
4. Which flip flop is used in asynchronous counter?
5. Which flip flop is used in synchronous counter?

50
Exp No: Date:
MOD–8 SYNCHRONOUS COUNTER
AIM: To Design MOD–8 synchronous counter using T Flip-Flop.
APPARATUS REQUIRED:
IC 7474 (T- Flip-flop), Digital Trainer Kit, patch cords, +5V power supply.
THEORY:
A counter in which each flip-flop is triggered by the output goes to previous flip-flop. As all the
flip-flops do not change states simultaneously in asynchronous counter, spike occur at the
output. To avoid this, strobe pulse is required. Because of the propagation delay the operating
speed of asynchronous counter is low. This problem can be solved by triggering all the flip-flops
in synchronous with the clock signal and such counters are called synchronous counters.
PROCEDURE:
• Check all the components for their working.
• Insert the appropriate IC into the IC base.
• Make connections as shown in the circuit diagram.
• Verify the Truth Table and observe the outputs.

51
MOD 8 COUNTER:
LOGIC DIAGRAM:
TRUTH TABLE:
FIG: 3 BIT SYNCHRONOUS COUNTER
Present count Next count
QC QB QA
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
0 0 0
QC QB QA
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
QC QB QA
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
0 0 0
T-FLIPFLOP EXCITATION TABLE:
States Input
Present Next T
0 0 0
0 1 1
1 0 1
1 1 0

52
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What are synchronous counters?
2. What are the advantages of synchronous counters?
3. What is an excitation table?
4. Write the excitation table for D, T FF?
5. Design mod-5 synchronous counter using T FF?

53
LOGIC DIAGRAM:
_
Fig: 1- BIT COMPARATOR
TRUTH TABLE
INPUTS OUTPUTS
A B A > B A = B A < B A>B = AB
0 0 0 1 0 _
A<B = AB
0 1 0 0 1 _ _
A=B=A B+AB
1 0 1 0 0
1 1 0 1 0

54
Exp No: Date:
A. COMPARATOR
AIM: Draw the circuit diagram of a single bit comparator and test the output.
APPARATUS REQUIRED:
IC 7400, IC 7410, IC 7420, IC 7432, IC 7486, IC 7402, IC 7408, IC 7404, IC 7485, Patch
Cords & ICTrainer Kit.
THEORY:
Magnitude Comparator is a logical circuit, which compares two signals A and B and generates
three logical outputs, whether A > B, A = B, or A < B. IC 7485 is a high
speed 4-bit Magnitude comparator , which compares two 4-bit words . The A = B Input must be
held high for proper compare operation.
PROCEDURE:
1. Check all the components for their working.
2. Insert the appropriate IC into the IC base.
3. Make connections as shown in the circuit diagram.
4. Verify the Truth Table and observe the outputs.

55
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What is a comparator?
2. What are the applications of comparator?
3. Derive the Boolean expressions of one bit comparator and two bit comparators.
4. How do you realize a higher magnitude comparator using lower bit comparator
5. Design a 2 bit comparator using a single Logic gates?

56
Exp No: Date:
B. 7 SEGMENT DISPLAY
AIM: Construct 7 Segment Display Circuit Using Decoder and7 Segment LED and test it.
APPARATUS REQUIRED:
S.No Name Quantity
1. Digital Trainer 1
2. IC 7447 1
3. IC FND 507 1
THEORY:
The functions of LT, RBI, RBO and BI are given below. LT This is called the LAMP TEST
terminal and is used for segment testing. If it is connected to logic ‘0’ level, all the segements of
the display connected to the decoder will be ON. For normal decoding operation, this terminal is
to be connected to logic ‘1’ level. RBI For normal decoding operation, this is connected to logic
‘1’ level. If it is connected to logic ‘0’, the segment outputs will generate the data for normal 7-
segment decoding, for all BCD inputs except Zero. Whenever the BCD inputs correspond to
Zero, the 7-segment display switches off. This is used for zero blanking in multi-digit displays.
BI If it is connected to logic ‘0’ level, the display is switched-off irrespective of the BCD inputs.
This is used for conserving the power in multiplexed displays. RBO This output is used for
cascading purposes and is connected to the RBI terminal of the succeeding stage.
PROCEDURE:
• Set up the Ckt as shown in fig.
• Apply logic ‘0’ level to LT and observe the seven segments of the LED. All
the segments must be ON.
• Apply logic ‘0’ level to BI/RBO and observe the seven segments of the LED. All the
segments must be OFF.
• Apply logic ‘1’ to LT and RBI and observe the number displayed on the LED for
all the inputs 0000 through 1111. This is the normal decoding mode.
• Apply logic ‘1’ to LT and logic ‘0’ to RBI, and observe the BI/RBO output and the
number displayed on the LED for all the inputs 0000 through 1111. This is the normal
decoding mode with zero blanking.

57
CIRCUIT DIAGRAM:
FIG: SEVEN SEGMENT DISPLAY
TRUTH TABLE :
D C B A a b c d e f g
Display
Number
0 0 0 0 0 0 0 0 0 0 1
0 0 0 1 1 0 0 1 1 1 1
0 0 1 0 0 0 1 0 0 1 0
0 0 1 1 0 0 0 0 1 1 0
0 1 0 0 1 0 0 1 1 0 0
0 1 0 1 0 1 0 0 1 0 0
0 1 1 0 1 1 0 0 0 0 0
0 1 1 1 0 0 0 1 1 1 1
1 0 0 0 0 0 0 0 0 0 0
1 0 0 1 0 0 0 1 1 0 0
CHAITANYA DEEMED TO BE UNIVERSITY, Dept of
ECE. Page 48

58
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What are the applications of seven segment display?
2. Can you use the segments outputs of 7448 decoder directly to drive a 7-Segment LED? If
not suggest a suitable interface?
3. Describe the operation performed by the decoder?
4. What is the function of RBI input?
5. What is the difference between common anode & common cathode display?

59

60
CIRCUIT DIAGRAM:
FIG: FOR INVALID BCD DETECTION
TABLE OF BCD ADDER:
INPUT OUTPUT
1st
Operand 2nd
Operand MSD LSD
A3 A2 A1 A0 B3 B2 B1 B0 Cout S3 S2 S1 S0
(MSB) (LSB) (MSB) (LSB) (MSB) (LSB)

61
Exp No: Date:
BCD ADDER
AIM: Design BCD Adder Circuit and Test the Same using Relevant IC.
APPARATUS REQUIRED:
Digital Trainer Kit, IC 7483, 7432 7408, Patch Cord ,+ 5V Power Supply
THEORY:
Carry Save Adder:
A carry save adder is just a set of one bit full adder, without any carry chaining. Therefore n-bit
CSA receivers three n-bit operands, namely A(n-1),A(0) and CIN(n-1)CIN(0) and generate two
n-bit result values, sum(n-1)-----------sum(0) and count(n-1)count(0).
Carry Propagation Adder:
The parallel adder is ripple carry type in which the carry output of each full adder stage is
connected to the carry input of the next highest order stage.
Therefore, the sum and carry outputs of any stage cannot be produced until the carry occurs.
This leads to a time delay in addition process.
This is known as Carry Propagation Delay.
BCD Adder:
It is a circuit that adds two BCD digits & produces a sum of digits also in BCD.
Rules for BCD addition:
1. Add two numbers using rules of Binary addition.
2. If the 4 bit sum is greater than 9 or if carry is generated then the sum is
invalid. To correct the sum add 0110 i.e. (6)10 to sum. If carry is
generated from this addition add it to next higher order BCD digit.
3. If the 4 bit sum is less than 9 or equal to 9 then sum is in proper form.
The BCD addition can be explained with the help of following 3cases

62
TruthTable:-
For design of combinational circuit for BCD adder to check invalid BCD
INPUT OUTPUT
S3 S2 S1 S0 Y
0 0 0 0 0
0 0 0 1 0
0 0 1 0 0
0 0 1 1 0
0 1 0 0 0
0 1 0 1 0
0 1 1 0 0
0 1 1 1 0
1 0 0 0 0
1 0 0 1 0
1 0 1 0 1
1 0 1 1 1
1 1 0 0 1
1 1 0 1 1
1 1 1 0 1
1 1 1 1 1
K-map:-
For reduced Boolean expressions of output
Y= S3S2+S3S1

63
✓
CASE I: Sum <= 9 & carry = 0.
Add BCD digits 3 & 4
1. 0011
+ 0100
0111
Answer is valid BCD number = (7) BCD & so 0110 is not added.
CASE II: Sum > 9 & carry = 0.
1. 0110
+ 0101
1011
Invalid BCD (since sum > 9) so 0110 is to be added
2. 1011
+ 0110
1 0001
(1 1)BCD
Valid BCD result = (11) BCD

64
CIRCUIT DIAGRAM FOR BCD ADDER :
FIG: BCD ADDER

65
CASE III: Sum < = 9 & carry = 1.
1. 1001
+1001
10010
Invalid BCD (since Carry = 1) so 0110 is to be added
2. 1 0010
+ 0110
11000
(1 8)BCD
Valid BCD result = (18) BCD
Design of BCD adder :
1. 4 bit binary adder is used for initial addition. i.e. binary addition of two 4 bit numbers.(
with Cin = 0 ),
2. Logic circuit to sense if sum exceeds 9 or carry = 1, this digital circuit will produce
high output otherwise its output will be zero.
3. One more 4-bit adder to add (0110)2 in the sum is greater than 9 or carry is 1.

66
RESULT:
CONCLUSION:
VIVA QUESTIONS:
1. What is the need of code converters?
2. What is BCD Adder?
3. What is invalid BCD?
4. What are weighted codes and non-weighted codes?
5. What are applications of Gray code?

67
BLOCK DIAGRAM:
FIG: 74154 4-TO-16 DEMULTIPLEXER
PIN CONFIGURATION:
FUNCTION TABLE:
S1 S0 INPUT
0 0 D0=XS1’S0
0 1 D1=XS1’S0
1 0 D2=XS1S0’
1 1 D3=XS1S0
Y=XS1’S0+XS1’S0+XS1S0’+XS1S0
CIRCUIT DIAGRAM:
FIG: CIRCUIT DIAGRAM

68
Exp No: Date:
74154 DE-MULTIPLEXER USING LEDS
AIM: - Verification of the truth table of the De-Multiplexer 74154.
APPARATUS REQUIRED: -
Logic trainer kit, IC- 74154, wires.
THEORY:
A Demultiplexer performs the reverse operation of a Multiplexer. It accepts a single input and
distributes it over several outputs. The SELECT input code determines to which output the data
input will be transmitted. The Demultiplexer becomes enabled when the strobe signal is active
LOW.
This circuit can also be used as binary-to-decimal decoder with binary inputs applied at the select
input lines and the output will be obtained on the corresponding line. These devices are available
as 2-line-to-4-line decoder, 3-line-to- 8-line decoder, 4-line-to-16-line decoder. The output of
these devices is active LOW. Also there is an active low enable/data input terminal available.
Figure below shows the block diagram of a Demultiplexer.
In this diagram the inputs and outputs are indicated by means of broad arrows to indicate that
there may be one or more lines. Depending upon the digital code applied at the SELECT inputs,
one data is transmitted to the single output channel out of many. The pin out of a 16:1
Demultiplexer IC 74154 is shown above. The output of this circuit is active low. This is a 24-pin
DIP.
PROCEDURE: -
1) Assemble the circuit on bread board, as per above Pin diagram.
2) Give the logical inputs and check for the proper output, as per the truth table.
PRECAUTIONS:
• All connections should be made neat and tight.
• Digital lab kits and ICs should be handled with utmost care.
• While making connections main voltage should be kept switched off.
• Never touch live and naked wires.

69
PIN DIAGRAM:
TRUTH TABLE:
TRUTH TABLE
INPUT OUTPUT
S1 S0 I/P D0 D1 D2 D3
0 0 0 0 0 0 0
0 0 1 1 0 0 0
0 1 0 0 0 0 0
0 1 1 0 1 0 0
1 0 0 0 0 0 0
1 0 1 0 0 1 0
1 1 0 0 0 0 0
1 1 1 0 0 0 1

70
RESULT:
CONCLUSION:
VIVAQUESTIONS:
1. Why is a demultiplexer called data distributor?
2. How does a demux works?
3. Which IC is used for demux?
4. What is difference between MUX and DEMUX?
5. Can decoder be used as demux?

71
HDL Simulation programs
Programming can be done using any compiler. Download the programs on FPGA / CPLD
boards and performance testing may be done using pattern generator / logic analyzer apart
from verification by simulation using Cadence / Mentor Graphics / Synopsys / Equivalent
front end CAD tools.
1. HDL code to realize all the logic gates
2. Design of 2-to-4 Decoder
3. Design of 8-to-3 Encoder
4. Design of Priority Encoder
5. Design of 8-to-1 Multiplexer
6. Design of 1 x 8 De-Multiplexer.
7. Design of 4-bit Binary to Gray Code Converter
8. Design of 2-bit Comparator
9. Design of Full Adder using 3 modeling styles
10. Design of Full Subtractor
11. Design of SR, JK, T & D Flip Flops

72
INTRODUCTION-XILINX
Xilinx ISE is a software tool produced by Xilinx for synthesis and analysis of HDL designs, which
enables the developer to synthesize ("compile") their designs, perform timing analysis, examine
RTL diagrams, simulate a design's reaction to different stimuli, and configure the target device
with the programmer.
Inour Lab, the scope is limited to design and analyze the design using testbenches & simulation.
The following is the step by step procedure to design in the XilinxISE simulator tool:
9. New Project Creation
Once the Xilinx ISE Design suite is started, open a new project &enter your design name and the
location path. By default "HDL" is selected as the top-level source type. (If not, please select
Top-level source type as "HDL").

73
DLD/DE LABORATORY CDU- ECE
3 Continue to the next window and check if the Preferred Language is selected as ‘Verilog’.
3. Proceed by clicking ‘Next’ and create a "New Source" using the "Create New Source"
Window.

74
4. Select the source type as ‘Verilog Module’ and input a filename and proceed to ‘Next’. In the
next window ‘Define Module’ enter the ports.
5. Finish with the Newproject setup with the ‘Summary’ window.

75
6. Once ‘Finish’ is selected a pop-up appears to create the directory. Select ‘yes’.
6. Then proceed to ‘Next’ in the “New Project Wizard’ to ‘Add Existing Sources’. ‘Add source’ if
an existing source is available, If not proceed to ‘Next’ and finish with the ‘Project Summary’
window.

76
8. Design Entry and Syntax Check:
The ports defined during the ‘Project Creation’ are defined as a module in the ‘filename.v’ file.
9. In put your design (verilog code) within the module definition.

77
• Select the design from the ‘Hierarchy‘ window. In the below window of Processes
‘Implement Design‘ would be orange (in color) ready for implementation.
6. Double click on implement design, it turns green (in color) once the design is implemented
successfully and the Summary report is displayed.

78
12. Test-Bench creation, Simulation &Verification:
To add a test-bench to the existing design, right click on the‘.v’ file from the Hierarchy window
and select ‘New Source’.
13. Select ‘Verilog Text Fixture’ from the Select Source Type and name theTest-Bench.

79
4 Continue to ‘Finish’ and a test bench is added in the project area.
4) Edit the test bench as per your simulation requirements and select ‘Behavioral Simulation’
in the ‘Design Window’.
5) In the Processes window Isim Simulator would be displayed. First Proceed with the
Behavioral Check Syntax.

80
EXPERIMENT- 1
HDL CODE TO REALIZE ALL LOGIC GATES
AIM: To develop the source code for logic gates by using VERILOG and obtain the simulation
results.
SOFTWARE & HARDWARE:
4) XILINX9.2i
5) FPGA-SPARTAN-3E
LOGIC DIAGRAMS:
AND GATE:
LOGIC DIAGRAM TRUTH TABLE
A B Y=AB
0 0 0
0 1 0
1 0 0
1 1 1
OR GATE:
A B Y=A+B
0 0 1
0 1 0
1 0 0
1 1 0
NOT GATE:
A Y=A'
0 1
1 0

81
NAND GATE:
A B Y=(AB)'
0 0 1
0 1 1
1 0 1
1 1 0
NOR GATE:
A B Y=(A+B)'
0 0 1
0 1 0
1 0 0
1 1 0
XOR GATE:
A B
0 0 0
0 1 1
1 0 1
1 1 0
XNOR GATE:
A B
0 0 1
0 1 0
1 0 0
1 1 1

82
VERILOG SOURCE CODE:
module logicgates1(a, b, c);
input a;
input b;
output [6:0] c;
assign c[0]= a & b;
assign c[1]= a | b;
assign c[2]= ~(a & b);
assign c[3]= ~(a | b);
assign c[4]= a ^ b;
assign c[5]= ~(a ^ b);
assign c[6]= ~ a;
endmodule
TEST BENCH CODE:
module allgtb;
6. Inputs
reg a; reg
b;
7. Outputs
wire [6:0] c;
8. Instantiate the Unit Under Test (UUT)
logicgates1 uut (
.a(a),
.b(b),
.c(c)
);
initial begin
6. Initialize Inputs
a = 0;b = 0;
#5 a = 0;b = 1;
#5 a = 1;b = 0;
#5 a = 1;b = 1;
#5 $finish;
end
initial $monitor($time, " a=%b,b=%b,c=%b",a,b,c);
endmodule

83
SIMULATION OUTPUT:
RESULT:

84
EXPERIMENT-2
DESIGN OF 2-TO-4 DECODER
AIM: To develop the source code for 2 to 4 Decoder by using VERILOG and obtain the
simulation.
6. XILINX9.2i
7. FPGA-SPARTAN-3E
LOGIC DIAGRAM:
TRUTH TABLE:

85
module decoder24_assign(en,a,b,y);
5. declare input and output ports
input en,a,b;
output [3:0]y;
6. supportive connection required
wire enb,na,nb;
assign enb = ~en;
assign na = ~a;
assign nb = ~b;
7. assign output value by referring to logic diagram
assign y[0] = ~(enb&na&nb);
assign y[1] = ~(enb&na&b);
assign y[2] = ~(enb&a&nb);
assign y[3] = ~(enb&a&b);
endmodule
TEST BENCH CODE
module tb;
6. input port are declared in reg(register)
reg a,b,en;
7. output port are declared in wire(net)
wire [3:0]y;
8. instantiate design block
decoder24_assign dut(en,a,b,y);
initial
begin
$monitor("en=%b a=%b b=%b y=%b",en,a,b,y);
ii) with reference to truth
iii) table provide input
values
en=1;a=1'bx;b=1'bx;#5
en=0;a=0;b=0;#5

86
en=0;a=0;b=1;#5
en=0;a=1;b=0;#5
en=0;a=1;b=1;#5
// terminate simulation using $finish system task
$finish;
end
initial $monitor($time, " en=%b,a=%b,b=%b,y=%b",en,a,b,y);
endmodule
SIMULATION OUTPUT:
RESULT:

87
EXPERIMENT-3
DESIGN OF 8-TO-3 ENCODER
AIM: To develop the source code for 8 to 3 decoder by using VERILOG and obtain the
simulation.
iii)XILINX9.2i
iv)FPGA-SPARTAN-3E
LOGIC DIAGRAM:
TRUTH TABLE:
D7 D6 D5 D4 D3 D2 D1 D0 X Y Z
d[7] d6] d[5] d[4] d[3] d[2] d[1] d[0] a b c
0 0 0 0 0 0 0 1 0 0 0
0 0 0 0 0 0 1 0 0 0 1
0 0 0 0 0 1 0 0 0 1 0
0 0 0 0 1 0 0 0 0 1 1
0 0 0 1 0 0 0 0 1 0 0
0 0 1 0 0 0 0 0 1 0 1
0 1 0 0 0 0 0 0 1 1 0
1 0 0 0 0 0 0 0 1 1 1

88
module endoder(input [7:0]d, output x,y,z);
assign x=d[4]|d[5]|d[6]|d[7];
assign y=d[2]|d[3]|d[6]|d[7];
assign z=d[1]|d[3]|d[5]|d[7];
endmodule
TEST BENCH CODE:
module enctest;
5) Inputs
reg [7:0] d;
6) Outputs
wire x;
wire y;
wire z;
7) Instantiate the Unit Under Test (UUT)
endoder uut (
.d(d),
.x(x),
.y(y),
.z(z)
);
initial begin
6. Initialize Inputs
d =8'd1;
#5 d=8'd2;
#5 d=8'd4;
#5 d=8'd8;
#5 d=8'd16;
#5 d=8'd32;
#5 d=8'd64;
#5 d=8'd128;
#5 $finish;
end
initial $monitor($time, " d=%b x=%b y=%b z=%b",d,x,y,z);
endmodule

89
SIMULATION OUTPUT:
RESULT:

91
EXPERIMENT-4
DESIGN OF PRIORITY ENCODER
AIM: To develop the source code for Priority Encoder by using VERILOG and obtain
the simulation.
GG XILINX9.2i
HH FPGA-SPARTAN-3E
LOGIC DIAGRAM: 8 To 3 priority encoder:
TRUTH TABLE: 8 to 3 priority encoder
Input Output
en i7 i6 i5 i4 i3 i2 i1 i0 y2 y1 y0
0 x x x x x x x x z z z
1 0 0 0 0 0 0 0 1 0 0 0
1 0 0 0 0 0 0 1 x 0 0 1
1 0 0 0 0 0 1 x x 0 1 0
1 0 0 0 0 1 x x x 0 1 1
1 0 0 0 1 x x x x 1 0 0
1 0 0 1 x x x x x 1 0 1
1 0 1 x x x x x x 1 1 0
1 1 x x x x x x x 1 1 1

92
module priorityenoder83_dataflow(en,i,y);
3. declare port list via input and output
input en;
input [7:0]i;
output [2:0]y;
4. check the logic diagram and assign the outputs
assign y[2]=i[4] | i[5] | i[6] | i[7] &en;
assign y[1]=i[2] | i[3] | i[6] | i[7] &en;
assign y[0]=i[1] | i[3] | i[5] | i[7] &en;
endmodule
TEST BENCH CODE:
module tb;
reg en;
reg [7:0]i;
wire [2:0]y;
6. instantiate the model: creating
7. instance for block diagram
priorityenoder83_dataflow dut(en,i,y);
initial
begin
monitor is used to display the information.
$monitor("en=%b i=%b y=%b",en,i,y);
since en and i are input values,
provide values to en and i.
en=1;i=128;#5
en=1;i=64;#5
en=1;i=32;#5
en=1;i=16;#5
en=1;i=8;#5
en=1;i=4;#5
en=1;i=2;#5
en=1;i=1;#5

93
en=0;i=8'bx;#5
$finish;
end
endmodule
SIMULATION OUTPUT:
RESULT:

95
EXPERIMENT-5
DESIGN OF 8X1 MULTIPLEXER
AIM: To develop the source code for 8X1 Multiplexer by using VERILOG and obtain the
simulation.
3. XILINX9.2i
4. FPGA-SPARTAN-3E
THEORY:
A digital multiplexer is a combinational circuit that selects binary information from one of many
input lines and directs it to a single output line. Multiplexing means transmitting a large number
of information units over a smaller number of channels or lines. The selection of a particular
input line is controlled by a set of selection lines. Normally, there are 2
n
input lines and n
selection lines whose bit combinations determine which input is selected. A multiplexer is also
called a data selector, since it selects one of many inputs and steers the binary information to
the output lines. Multiplexer ICs may have an enable input to control the operation of the unit.
When the enable input is in a given binary state (the disable state), the outputs are disabled,
and when it is in the other state (the enable state), the circuit functions as normal multiplexer.
The enable input (sometimes called strobe) can be used to expand two or more multiplexer ICs
to digital multiplexers with a larger number of inputs. The size of the multiplexer is specified by
the number 2
n
of its input lines and the single output line. In general, a 2
n
to 1 line multiplexer
is constructed from an n to 2
n
decoder by adding to it 2
n
input lines, one to each AND gate.
The outputs of the AND gates are applied to a single OR gate to provide the 1 – line output.

96
LOGIC DIAGRAM:
TRUTH TABLE:

97
module m81(output out, input D0, D1, D2, D3, D4, D5, D6, D7, S0, S1, S2);
wire w0,w1,w2,w3,w4,w5,w6,w7;
assign w0=(D0 & ~S2 & ~S1 & ~S0);
assign w1=(D1 & ~S2 & ~S1 & S0) ;
assign w2=(D2 & ~S2 & S1 & ~S0);
assign w3=(D3 & ~S2 & S1 & S0);
assign w4=(D4 & S2 & ~S1 & ~S0);
assign w5=(D5 & S2 & ~S1 & S0);
assign w6=(D6 & S2 & S1 & ~S0);
assign w7=(D7 & S2 & S1 & S0);
assign out = w0 | w1 | w2 | w3 | w4 | w5 | w6 | w7 ;
endmodule
TEST BENCH CODE:
module top;
wire out;
reg D0, D1, D2, D3, D4, D5, D6, D7, S0, S1, S2;
m81 name(.D0(D0), .D1(D1), .D2(D2), .D3(D3), .D4(D4), .D5(D5), .D6(D6), .D7(D7), .S0(S0),
.S1(S1), .S2(S2), .out(out));
initial
begin
D0=1'b0; D1=1'b0; D2=1'b0; D3=1'b0; D4=1'b0; D5=1'b0; D6=1'b0; D7=1'b0;S0=1'b0; S1=1'b0;
S2=1'b0;
#500 $finish;
end
always #1 D0=~D0;
always #2 D1=~D1;
always #3 D2=~D2;
always #4 D3=~D3;
always #5 D4=~D4;
always #6 D5=~D5;
always #7 D6=~D6;
always #8 D7=~D7;
always #9 S0=~S0;
always #10 S1=~S1;
always #11 S2=~S2;

98
always@(D0 or D1 or D2 or D3 or D4 or D5 or D6 or D7 or S0 or S1 or S2)
$monitor("At time = %t, Output = %d", $time, out);
endmodule
SIMULATION OUTPUT:
RESULT:

99
EXPERIMENT-6
DESIGN OF 1X8 DEMULTIPLEXER
AIM: To develop the source code for 1x8 De-multiplexer by using VERILOG and obtain the
simulation.
6. XILINX9.2i
7. FPGA-SPARTAN-3E
LOGIC DIAGRAM:

100
TRUTH TABLE:
module demux_1_8(y,s,a);
output reg [7:0]y;
input [2:0]s;
input a;
always @(*)
begin
y=0;
case(s)
3'd0: y[0]=a;
3'd1: y[1]=a;
3'd2: y[2]=a;
3'd3: y[3]=a;
3'd4: y[4]=a;
3'd5: y[5]=a;
3'd6: y[6]=a;
3'd7: y[7]=a;
endcase
end
endmodule
TEST BENCH:
module TestModule;
Inputs
reg in;

101
reg s0;
reg s1;
reg s2;
Outputs
wire d0;
wire d1;
wire d2;
wire d3;
wire d4;
wire d5;
wire d6;
wire d7;
Instantiate the Unit Under Test (UUT)
Demultiplexer uut (
.in(in),
.s0(s0),
.s1(s1),
.s2(s2),
.d0(d0),
.d1(d1),
.d2(d2),
.d3(d3),
.d4(d4),
.d5(d5),

102
.d6(d6),
.d7(d7)
);
initial begin
// Initialize Inputs
in = 0;s0 = 0;s1 = 0;s2 = 0;
Wait 100 ns for global reset to finish
#100;in = 1;s0 = 0;s1 = 1;s2 = 0;
Wait 100 ns for global reset to finish
#100;
Add stimulus here
end
endmodule
SIMULATION OUTPUT:
RESULT:

103
EXPERIMENT-7
DESIGN OF 4 BIT BINARY TO GRAY CODE CONVERTER
AIM: To develop the source code for 4 Bit Binary to Gray Code Converter by using VERILOG and
obtain the simulation.
8. XILINX9.2i
9. FPGA-SPARTAN-3E
LOGIC DIAGRAM:
TRUTH TABLE:

104
//Verilog Code 4-bit Binary to Gray by using Data Flow Modelling
module Binary_to_Gray ( input [3:0] b, output [3:0] g); assign
g[0]=b[1]^b[0];
assign g[1]=b[2]^b[1];
assign g[2]=b[3]^b[2];
assign g[3]=b[3];
endmodule
//Verilog Code 4-bit Binary to Gray by using Structural Modelling
module Binary_to_Gray( input [3:0] b, output [3:0] g); xor
A1(g[0],b[1],b[0]);
xor A2(g[1],b[2],b[1]);
xor A3(g[2],b[3],b[2]);
buf A4(g[3],b[3]);
endmodule
//Verilog Code 4-bit Binary to Gray by using Behavioural Modelling
module Binary_to_Gray( input [3:0] b, output reg[3:0] g);
always@(b)
begin
g[0]=b[1]^b[0];
g[1]=b[2]^b[1];
g[2]=b[3]^b[2];
g[3]=b[3];
end
endmodule
TECHTBENCH
module tb();
reg [3:0] bin;
wire [3:0] G,bin_out;
6. instantiate the unit under test's (uut)
bin2gray uut1(bin,G);
gray2bin uut2(G,bin_out);

105
6. stimulus
always
begin
bin <= 0; #10;
bin <= 1; #10;
bin <= 2; #10;
bin <= 3; #10;
bin <= 4; #10;
bin <= 5; #10;
bin <= 6; #10;
bin <= 7; #10;
bin <= 8; #10;
bin <= 9; #10;
bin <= 10; #10;
bin <= 11; #10;
bin <= 12; #10;
bin <= 13; #10;
bin <= 14; #10;
bin <= 15; #10;
#100;
$stop;
end
endmodule
SIMULATION OUTPUT:
RESULT:

106

107
EXPERIMENT-8
DESIGN OF 2 BIT COMPARATOR
AIM: To develop the source code for 4 Bit Comparator by using VERILOG and obtain the
simulation.
4. XILINX9.2i
5. FPGA-SPARTAN-3E
LOGIC DIAGRAM: TRUTH TABLE:
The specification of the 2-bit comparator is as follows:
Input: 2-bit A and B for comparison
Output:
A_greater_B: high if A > B else low
A_equal_B: high if A = B else low
A_less_B: high if A<B else low

108
module comparator(input [1:0] A,B, output A_less_B, A_equal_B, A_greater_B);
wire tmp1,tmp2,tmp3,tmp4,tmp5, tmp6, tmp7, tmp8; // A = B output
xnor u1(tmp1,A[1],B[1]);
xnor u2(tmp2,A[0],B[0]);
and u3(A_equal_B,tmp1,tmp2);
// A less than B output
assign tmp3 = (~A[0])& (~A[1])& B[0];
assign tmp4 = (~A[1])& B[1];
assign tmp5 = (~A[0])& B[1]& B[0];
assign A_less_B = tmp3 | tmp4 | tmp5;
// A greater than B output
assign tmp6 = (~B[0])& (~B[1])& A[0];
assign tmp7 = (~B[1])& A[1];
assign tmp8 = (~B[0])& A[1]& A[0];
assign A_greater_B = tmp6 | tmp7 | tmp8;
endmodule
Test Bench Code:
module cmp24tst;
6. Inputs
reg [1:0] A;
reg [1:0] B;
7. Outputs wire
A_less_B; wire
A_equal_B; wire
A_greater_B;
comparator uut (
.A(A),
.B(B),
.A_less_B(A_less_B),
.A_equal_B(A_equal_B),

109
.A_greater_B(A_greater_B)
);
initial begin
A=0; B=0;
#5 A=2'b01; B=2'b10;
#5 A=2'b11; B=2'b10;
#5 A=2'b10; B=2'b10;
#5 A=2'b01; B=2'b10;
#5 A=2'b11; B=2'b01;
#5 A=2'b11; B=2'b11;
#5 $finish;
end
initial $monitor($time, " A=%b,B=%b A_less_B=%b, A_equal_B=%b,
A_greater_B=%b",A,B,A_less_B, A_equal_B, A_greater_B);
endmodule
SIMULATION OUTPUT:
RESULT:

111
EXPERIMENT-9
DESIGN OF FULL ADDER USING 3 MODELING STYLES
AIM: To develop the source code for Full Adder using 3 modeling styles in VERILOG and obtain
the simulation.
XILINX9.2i
FPGA-SPARTAN-3E
LOGIC DIAGRAM:
TRUTH TABLE:
A B C SUM CARRY
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1

112
Dataflow Modeling:
module fulladder(input a,b,c, output sum,cout);
assign sum=(a^b)^c;
assign cout=(a&b)|(b&c)|(c&a);
endmodule
Behavioral Modeling:
module fulladder(input a,b,c, output reg sum,cout);
always@(a,b,c)
begin
sum=(a^b)^c;
cout=(a&b)|(b&c)|(c&a);
end
endmodule
Structural Modeling:
module fulladder(input a,b,c, output sum,cout);
wire p,q,r;
xor x1(sum,a,b,c);
and a1(p,a,b);
and a2(q,b,c);
and a3(r,c,a);
or r1(cout,p,q,r);
endmodule
TEST BENCH CODE:
module fulladdtst;
6. Inputs
reg a; reg
b; reg c;
7. Outputs
wire sum;
wire cout;
fulladder uut (
.a(a),

113
.b(b),
.c(c),
.sum(sum),
.cout(cout)
);
initial begin
a = 0; b = 0; c = 0;
#5 a = 0; b = 0; c = 1;
#5 a = 0; b = 1; c = 0;
#5 a = 0; b = 1; c = 1;
#5 a = 1; b = 0; c = 0;
#5 a = 1; b = 0; c = 1;
#5 a = 1; b = 1; c = 0;
#5 a = 1; b = 1; c = 1;
#5 $finish;
end
initial $monitor($time, " a=%b,b=%b, c=%b, sum=%b,cout=%b ",a,b,c,sum,cout);
endmodule
SIMULATION OUTPUT:
RESULT:

114

115
EXPERIMENT-10
DESIGN OF FULL SUBTRACTOR
AIM: To develop the source code for Full Subtractor by using VERILOG and obtain the
simulation.
5. XILINX9.2i
6. FPGA-SPARTAN-3E
LOGIC DIAGRAM:
TRUTH TABLE:

116
module full_subtractor(input a, b, Bin, output D, Bout);
assign D = a ^ b ^ Bin;
assign Bout = (~a & b) | (~(a ^ b) & Bin);
endmodule
TEST BENCH:
module Full_Subtractor_3_tb;
wire D, B;
reg X, Y, Z;
Full_Subtractor_3 Instance0 (D, B, X, Y, Z);
initial begin
X=0;Y=0;Z=0;
#1 X=0;Y=0;Z=1;
#1 X=0;Y=1;Z=0;
#1 X=0;Y=1;Z=1;
#1 X=1;Y=0;Z=0;
#1 X=1;Y=0;Z=1;
#1 X=1;Y=1;Z=0;
#1 X=1;Y=1;Z=1;
end
initial begin
$monitor ("%t, X = %d| Y = %d| Z = %d| B = %d| D = %d", $time, X, Y, Z, B, D);
end
endmodule
SIMULATION OUTPUT:
RESULT:

117
EXPERIMENT-11
DESIGN OF SR, JK, T & D Flip Flops
AIM: To develop the source code for SR, JK, T & D Flip Flops by using VERILOG and obtain
the simulation.
6. XILINX9.2i
7. FPGA-SPARTAN-3E
LOGIC DIAGRAM:
SR FLIPFLOP:
TRUTH TABLE:
Q(t) S R Q(t+1)
0 0 0 0
0 0 1 0
0 1 0 1
0 1 1 X
1 0 0 1
1 0 1 0
1 1 0 1
1 1 1 X

118
module srflipflop (s, r, clk, rst, q, qbar);
input s, r, clk, rst;
output q, qbar;
reg q, qbar;
always@(posedge(clk) or posedge(rst))
begin
if(rst==1'b1)
begin
q=1'b0;
qbar=1'b1;
end
elseif(s==1'b0 &&r==1'b0)
begin
q=q;
qbar=qbar;
end
else if(s==1'b0&& r==1'b1)
begin
q=1'b0;
qbar=1'b1;
end
elseif(s==1'b1 && r==1'b0)
begin
q=1'b1;
qbar=1'b0;
end
else
begin
q=1'bx;
qbar=1'bx;
end
end
endmodule
SIMULATION OUTPUT:

119
JKFLIPFLOP:
TRUTH TABLE:
Q(t) J K Q(t+1)
0 0 0 0
0 0 1 0
0 1 0 1
0 1 1 1
1 0 0 1
1 0 1 0
1 1 0 1
1 1 1 0
module jkff(j,k,clk,rst,q,qbar);
input j, k, clk, rst;
output q, qbar;
reg q, qbar;
always@(posedge (clk) or posedge (rst))
begin
if(rst==1'b1)
begin
q=1'b0;
qbar=1'b1;
end
elseif(j==1'b0 && k==1'b0)
begin

120
q=q;
qbar=qbar;
end
elseif(j==1'b0&&k==1'b1)
begin
q=1'b0;
qbar=1'b1;
end
elseif(j==1'b1&&k==1'b0)
begin
q=1'b1;
qbar=1'b0;
end
else
begin
q=~q;
qbar=~qbar;
end
end
endmodule
SIMULATION OUTPUT:
T-FLIPFLOP:

121
TRUTH TABLE:
module t_flip_flop(t,clk,reset,dout);
output dout ;
input t, clk;
always@(posedge (clk))
begin
if(reset)
dout <= 0;
else
begin
if(t)
dout <= ~dout;
end
end
endmodule
SIMULATION OUTPUT:

122
D FLIP FLOP:
LOGIC DIAGRAM:
TRUTH TABLE:

123
Behavioral Model:
module d_flip_flop (Q,D,clk,reset);
input D;
input clk;
input reset;
output reg Q;
always @(posedge clk or posedge reset)
begin
if (reset == 1'b1 )
Q <= 1'b0;
else
Q<=D;
end
endmodule
TEST BENCH:
initial
begin
clk = 1'b0;
forever #20 clk = ~clk ;
end
initial
begin
reset = 1'b1;
#40;
reset = 1'b0;
#40;
D = 1'b0;
#40;
D = 1'b1;
#40;
$finish ;
end
endmodule

124
SIMMULATION RESULT:
RESULT:
Thus the OUTPUT’s of SR, JK, T & D Flip Flops are verified by simulating the VERILOG code.

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