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					                                                                                            Code No.: 207
                                 FACULTY OF ENGINEERING

B.E. II/IV Year (CSE) I Semester          (Main) Examination,         November/December              2008
                               LOGIC AND SWITCHING THEORY

Time:   3 Hours]                                                                       [Max. Marks:        75
                                 Answerall questions of Part A.
                             Answer any five questions from Part B.

                                      Part A - (Marks:         25)

1.   What are universal      gates? Explain    the reasons     that are called universal        gates.      3

2.   Simplify the following Boolean expression.                                                             2
                                 F (A, B, C) = AB + A + B + BC
3.   Distinguish   between    canonical   forms and standard         forms of Boolean equations.            2

4.   Implement x + yz + yz using NOR gates.                                                                 2

5.   Distinguish between a combinational          and sequential      logic circuit.    Draw the block
     diagram of a sequential circuit.                                                                       3
6.   Draw the diagram      of a full adder circuit using two half adders           and other logic
     circuits.                                                                                              3
7. What is a hazard in combinational            network?                                                    2
8.   Draw the excitation     table for a J-K flipflop.                                                      2

9.   Realize a contact network with minimum         number      of contacts    for SO,'I,3 (A, B, C, D).    3
10. Explain the concept of glitches when combinational   circuits                are used in
    conjunction with ripple counters. Give a suitable example.                                              3

                                 Part B - (Marks: 5        x   10 = 50)

11. (a) Prove that the sum of all min. terms of a 3 variable Boolean function is equal
        to 1.
     (b). Convert the following sum of product form to a product of sum form.
                                               -    -       -
                                F (A, B, C) = ABC + ABC + ABC
     (c) Convert the decimal number           5678 to its hexadecimal         equivalent.            3+4+3



                                                                                                    [P.T.O.
                                                     2                                                207

12. (a) Simplify the function       using Karnaugh         map

                           f(A, B, C, D) = L (0, 4, 5,7, 8, 9, 13, 15)
        with minimum       number     of literals.
    (b) Distinguish   between    a prime implicant         and essential    prime implicant.          6+4

13. (a) Distinguish   between    a decoder      and encoder.
    (b) Design a priority encoder with 8 inputs             and 3 outputs    and draw the circuit
        diagram.                                                                                      3+7

14. (a) Distinguish   between    a register     and a latch.
    (b) Convert an SR flipflop to JK flipflop and draw the logic diagram.                             2+8


15. (a) Determine whether the function F (A, B, C) = L (0, 2, 3, 4, 5, 7) is symmetric
        and variables of symmetry.
    (b) Design a mod-5 asynchronous             counter     and draw the concerned      waveforms.
                                                                                                      5+5

16. Design a BCD to decimal decoder            utilizing   the don't care combinations.        Draw
    the relevant diagrams.                                                                             10
                                                                                                            ~


17. Write brief notes on :                                                                        3+3+4

    (a) Parity generator
    (b) Binary multiplier
    (c) Relay contact network.

				
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