# GTU Digital Logic Design Question Paper May 2011

Table of Contents

## Digital Logic Design

Subject code: 130701     Subject Name: Digital Logic Design

Total Marks: 70

Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1             Answer the following                                                                                             14

(i)   Draw symbol and construct the truth table for three input Ex-OR gate.

(ii)   What is the principle of Duality Theorem?

(iii)   Explain briefly: standard SOP and POS forms.

(iv)   What are Minterms and Maxterms ?

(v)  Define: Noise margin , Propagation delay

(vi)   Give comparison between combinational and Sequential logic circuits

(vii)   What is race-around condition in JK flip-flop?

Q.2 (a) (i) Explain NAND and NOR as an universal gates                                      (04) 07

(ii) Convert decimal 225.225 to binary ,octal and hexadecimal (03)

(b) (i) Implement Boolean expression for Ex-OR gate using NAND gates only 07

(04)

(ii) convert decimal 8620 into BCD , excess-3 code and Gray code.

(03)

OR

(b) (i) Simplify the following Boolean function using K-map                                        07

F( w,x,y,z) = £( 1 , 3 , 7 , 11 , 15 )                                                     (04)

with don’t care conditions d( w,x,y,z ) = £( 0, 2 ,5 )

(ii) Draw logic diagram , graphical symbol , and

Characteristic table for clocked D flip-flop                                        (03)

Q.3 (a) Design a combinational circuit whose input is four bit binary number and 07 output is the 2’s complement of the input binary number.

(b) Design a full-adder with two half-adders and an OR gate                                         07

OR

Q.3 (a) Design a BCD to decimal decoder                                                                                07

(b) What is multiplexer? Implement the following function with a multiplexer: 07

F(A,B,C,D) = (0 , 1 , 3 , 4 , 8 , 9 ,15 )

Q.4 (a) Write short note on : Read Only Memory (ROM)                                                         07

(b) A combinational circuit is defined by functions:                                                      07

F1(A,B,C) = ( 3 , 5 , 6, 7 )

F2(A,B,C) = ( 0 , 2 , 4, 7 )

Implement the circuit with PLA having three inputs four product term and two outputs

OR=

Q.4 (a) Give classification of counters and explain asynchronous                                            07

4-bit binary ripple counter

(b) Explain briefly:

(i)   logic and shift micro-operations

(ii)   fixed-point binary data and floating-point data

Q.5 (a) Draw block diagram of a 4-bit arithmetic logic unit. Design an 07 adder/subtractor circuit with one selection variable S and two inputs A and B .when S = 0 circuit performs A+B, when S = 1 circuit performs A – B by taking the 2’s complement of B

(b) Draw and explain block diagram of microprogramming

control.                                                                                                                                     07

OR

Q.5 (a) Simplify the following Boolean function using tabulation Method and 07 draw logic diagram

using NOR gates only F(w,x,y,z ) = X( 0 ,1 , 2 , 8 ,10 ,11,14,15 )

(b) Explain working of master-slave JK flip-flop with necessary logic diagram 07 ,

state equation and state diagram.