CSIT 1st Semester
Digital Logic Board Question Paper 2083 Old Course

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CSC 111-2083 ✡

Tribhuvan University

Institute of Science and Technology

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Bachelor Level/First Year/First Semester/Science
Bachelors in Computer Science and Information Technology (CSC 111)
(Digital Logic)
(Old Course)
Full Marks: 60 Pass Marks: 24 Time: 3 hours

Candidates are required to give their answers in their own words as far as practicable.
The figures in the margin indicate full marks.

Section A
Long Answer Questions
Attempt any Two questions.
[2x10=20]
1.

Design a 3-bit synchronous up counter using T Flip-Flop. Draw the state diagram, transition table, circuit diagram and timing diagram.

2.

Simplify the following Boolean expression using K-Map and realize using NAND gates only:
F(A, B, C, D) = Σ(0, 1, 3, 5, 7, 8, 10, 14, 15) with don't care conditions d(A, B, C, D) = Σ(2,9, 13).

3.

Design full subtractor with truth table, logical expression for output and circuit diagram.

Section B

Attempt any Eight questions

[8×5=40]
4.

Convert the following as indicated:
a) (F4B.B)16 to Decimal
b) (110.625)10 to Binary and Octal

5.

Draw the circuit diagram of a D Flip-Flop. Write its truth table, characteristic equation, and excitation table.

6.

What is a shift register? Explain PISO (Parallel-In Serial-Out) shift register with a neat block diagram and timing diagram.

7.

What is an encoder? Design a 4 to 2 encoder with truth table and logic diagram.

8.

Design a Mod-6 asynchronous counter using JK Flip-Flop. Draw its state diagram and timing diagram.

9.

What is a decoder? Implement a full adder using a 3-to-8-line decoder and OR gates.

10.

State and prove De Morgan's theorems with the help of truth tables and logic circuit.

11.

What is multiplexer? Design a 4 to 1 multiplexer with truth table, logical expression for output and logic circuit.

12.

Write short notes on:
a) Gray Code
b) PLA and PAL