**GTU Last Year question papers**

**GUJARAT TECHNOLOGICAL UNIVERSITY**

**B.E. Sem-III Remedial Examination May 2011**

**Subject code: 130701 **

**Subject Name: Digital Logic Design**

** **

**Instructions:**

**1. Attempt all questions.**

**2. Make suitable assumptions wherever necessary.**

**3. Figures to the right indicate full marks.**

**Q.1 **Answer the following

(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

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

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

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

**OR**

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

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

with don’t care conditions d( w,x,y,z ) = Σ( 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

output is the 2’s complement of the input binary number.

**07**

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

**OR**

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

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

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

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

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

F1(A,B,C) = Σ( 3 , 5 , 6, 7 )

F2(A,B,C) = Σ( 0 , 2 , 4, 7 )

Implement the circuit with PLA having three inputs ,four product term andtwo outputs

** **

**OR**

**Q.4 (a) **Give classification of counters and explain asynchronous ** **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 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 microprograme control.

**OR**

**Q.5 (a) **Simplify the following Boolean function using tabulation Method and

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

**(b) **Explain working of master-slave JK flip-flop with necessary logic diagram , state equation and state diagram

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