# Sathyabama University Exam Papers

# Digital Logic Theory and Design BE Third Sem

(Established under section 3 of UGC Act, 1956)

Course & Branch: B.E – EIE

Semester: III Max. Marks: 80

Sub.Code: 6C0065 Time: 3 Hours

Date: 06-05-2008 Session: AN

PART – A (10 x 2 = 20)

Answer All the Questions

1. Express the following decimal numbers in 2421 and 5421 code (i)

1993

2. State Demorgan’s theorem.

3. Give two advantages and one disadvantages of the totem pole

arrangement.

4. What is a tri-state gate?

5. Compare Encoder and decoder.

6. What is meant by a magnitude comparator?

7. Draw the logic diagram of a master – slave D-flip flop using NAND

gate.

8. What do you mean by critical and Non-critical races? How can they

be avoided?

9. Why are shift registers considered to be basic memory devices?

10. How can essential hazards be eliminated?

PART – B (5 x 12 = 60)

Answer All the Questions

11. Using the K-map method, Simplify the following functions into

minimal sum of products

F(u,w,x,y,z)= (0.2,5,7,9,11,13,15,16,18,21,23,25,27,29,31)

(or)

12. Find the minimal sum of products for the Boolean expression,

F(a,b,c,d) = (1,2,3,7,8,9,10,11,14,15)

13. Discuss about the various parameters of TTL.

(or)

14. (a) Draw the basic BICMOS inverter, NAND and NOR gates and

explain its operation.

(b) Draw and explain the circuit diagram of a 3-input I2L NOR gate.

15. Explain briefly about the BCD – Seven Segment decoder.

(or)

16. Draw and explain the basic block diagram of PLA and what are the

steps used for implementing combinational circuit using PLA.

17. Design a synchronous counter with the following sequence counter

0000 0100 0100 0110 1000 1010 1100 1110 0000.

(or)

18. (a) Explain the working of serial in parallel out shift register with

logic diagram and waveforms.

(b) Explain about the various applications of flip-flops.

19. Obtain a static hazard free asynchronous circuit for the following

switching function.

F = (0,2,4,5,8,10,14)

(or)

20. Design an asynchronous circuit that will output only the first pulse

received whatever a control input is asserted from LOW to HIGH

state. Any future pulses will be ignored.

(ii) Timing Diagram