# Pokhara University Semester Spring 2015 || Digital System || BCIS

### Spring 2015 Digital Systems

This is the question set along with the answers of Spring 2015 Digital Systems which was taken by the Pokhara University (PU).

POKHARA UNIVERSITY(PU)

 Level:  Bachelor Semester – Spring Year: 2015 Program: BCIS Full Marks: 100 Course: Digital Systems Pass Marks: 45 Time:3hrs 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”

 SN Attempt all the questions. 10×2 1 What do you mean by digital system? 2 2 What is bit? 2 3 What is XOR gate? 2 4 What is encoder? 2 5 What is flipflop? 2 6 What do you mean by triggering of flipflop? 2 7 What is memory? 2 8 Explain CMOS. 2 9 What is ALU? 2 10 What is k-map? 2

Section “B”

Attempt any six questions. 6X10

11.Simplify the following expression.

Σm (0, 2, 5, 9, 15) + Σd (1, 4, 7, 12)

Using K-map and draw the logic diagram using

1. Basic gates only
1. NAND gates only

12.Difference between multiplexer and demultiplexer. Design Full Adder using two half adder and OR gate.

1. 13. Write short notes on.
2. Status register

Ii. 4-bits ALU

1. 14. What do you mean by a counter? Design a 3-bit synchronous counter.

15.Explain in detail about the operation of JK flipflop along with truth table, characteristics equation and circuit diagram.

16.Convert the following number from the given base to the other bases indicated.

1. (4F.D2)= ( )8
1. (1101-10116  )2  using 1’s complement method.
1. (762)8 x(345)8
1.   Find base If (211)x = (152)
1. A) State and prove De Morgan’s theorem
2.     B) Prove the universality of NAND and NOR gates?

Section” C

Case Study

1. A BCD to seven segment decoder is a combinational circuit that accepts a decimal in BCD and generates the appropriate outputs decimal digit. The seven outputs of decoder (a, b, c, d, e, f, g) select the corresponding segments in the display. Design the BCD to seven segment decoder circuit (20)

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