Digital System Design ( EC302)

Dr. Hasanujjaman
Assistant Professor
Department of Electronics & Communication Engineering
Kalyani Government Engineering College

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 EC392 Digital System Design Lab 0L:0T:2P 1 credits

• 1. Introduction to Digital Electronics Lab- Nomenclature of Digital Ics, Specifications, Study of

• the Data Sheet, Concept of Vcc and Ground, Verification of the Truth Tables of Logic Gates
• using TTL ICs.
• 2. Implementation of the Given Boolean Function using Logic Gates in Both Sop and Pos Forms.
• 3. Verification of State Tables of Rs, J-k, T and D Flip-Flops using NAND & NOR Gates
• 4. Implementation and Verification of Decoder/De-Multiplexer and Encoder using Logic Gates.
• 5. Implementation of 4x1 Multiplexer using Logic Gates.
• 6. Implementation of 4-Bit Parallel Adder Using 7483 IC.
• 7. Design , and Verify the 4- Bit Synchronous Counter
• 8. Design, and Verify the 4-Bit Asynchronous Counter.
• 9. Simulation of MOS Inverter with different loads using PSPICE software
• 10. Simulation of CMOS Inverter for different parameters Kn, Kp as a design variable in
suitable
• circuit simulator software.
• 11. Design of a 4-bit Multiplexer using VHDL\Verilog
• 12. Design of a decade counter using VHDL\Verilog.
• 13. Design of a 3-input NAND gate and its simulation using suitable logic simulator

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 Virtual Lab

• https://de-iitr.vlabs.ac.in/

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 Circuits
• Circuits can be Combinational or Sequential
• Combinational logic circuits produce a specified output
(almost) at the instant when input values are applied.
• The addition of a memory device to a combinational circuit
allows the output to be fed back into the input: Sequential
circuit
Combinational circuit

Input(s) Output(s)
circuit

memory
Sequential circuit
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 Digital Devices
• Combinational circuit
– Gates
– Multiplexer
– Demultiplexer
– Adders
– Encoder
– Decoder
• Sequential circuit
– Flip-Flops
– Registers
– Counters
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 Gates
• The most basic digital devices are called gates.
• Gates got their name from their function of
allowing or blocking (gating) the flow of digital
information.
• A gate has one or more inputs and produces an
output depending on the input(s).
• A gate is called a combinational circuit.
• Three most important gates are: AND, OR, NOT

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 NOT Gate
•A NOT gate accepts one input signal (0 or 1)
and returns the opposite signal as output

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 AND Gate
•An AND gate accepts two input signals
•If both are 1, the output is 1; otherwise the
output is 0

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 OR Gate
•An OR gate accepts two input signals
•If both are 0, the output is 0; otherwise, the
output is 1

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 XOR Gate
• An XOR gate accepts two input signals
• If both are the same, the output is 0; therwise,
the output is 1

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 NAND Gate
•The NAND gate accepts two input signals
•If both are 1, the output is 0; otherwise, the
output is 1

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 NOR Gate
•The NOR gate accepts two input
signals
•If both are 0, the output is 1; otherwise,
the output is 0

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 Universal Gates

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 Adders
• At the digital logic level, addition is performed
in binary.
• Addition operations are carried out
by special circuits called, appropriately,
adders.

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 Adders
• The result of adding two binary digits could
produce a carry value.
• Recall that 1 + 1 = 10 in base two.
• A circuit that computes the sum of two bits
and produces the correct carry bit is called a
half adder.

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Adder Truth Table
• Examine the adder’s
truth table carefully.
• The Sum column has
the same results as the
XOR gate.
• The Carry column has
the same results as the
AND gate.

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Adders

• This circuit diagram

represents a half
adder.
• As do these two
Boolean expressions:
sum = A  B
carry = AB

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 Adders

• A circuit called a full adder takes the carry-in

value into account.

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 Combinational Circuits
• Gates are combined into circuits by using the output
of one gate as the input for another.

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 Combinational Circuits

• Because there are three inputs to this circuit, eight

rows are required to describe all possible input
combinations.

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 Combinational Circuits
• This same circuit using Boolean algebra:

AB + AC

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 Combinational Circuits
• Now let’s go the other way; let’s take a Boolean expression
and draw its circuit and its Truth Table.

• Consider the following Boolean expression:

A(B + C)
• What does it mean?

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 Combinational Circuits
A (B + C)

Can you create its Truth Table?

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 A (B + C)

A B C B+C A(B + C)
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
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 A (B + C)

A B C B+C A(B + C)
0 0 0 0
0 0 1 1
0 1 0 1
0 1 1 1
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1
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 A (B + C)

A B C B+C A(B + C)
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 1 0
1 0 0 0 0
1 0 1 1 1
1 1 0 1 1
1 1 1 1 1
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 Combinational Circuits
• Now compare the final result column in this truth table to the
truth table for the previous example:

A(B+C) (AB + AC)

Their result columns are identical. 27
 Combinational Circuits
• We have therefore just demonstrated circuit
equivalence.
– That is, both circuits produce the exact same output for
each input value combination.
• Boolean algebra allows us to apply provable
mathematical principles to help us design
logical circuits.

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Properties of Boolean Algebra

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 • Thank You

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