Download AKTU B-Tech 3rd Sem 2016-2017 NEC 309 Digital Logic Design Question Paper

Section - A

1. Attempt all questions in brief. (10×2=20)
   1. Perform 2's complement subtraction of 010110-100101.
   2. What is the feature of gray code?

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   3. Write the logic equation and draw the internal logic diagram for a 4 to 1 mux.
   4. What is a priority encoder?
   5. List the major differences between PLA and PAL.
   6. Define a Bus. What are the different types of buses?
   7. Give the comparison between combinational circuits and sequential circuits.

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   8. What are the different types of flip-flop?
   9. Give the comparison between synchronous & asynchronous sequential circuits.
   10. What is Ram? Explain the different types of RAM in detail.
   11. When does race condition occur?

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Section - B

2. Attempt any three of the following: (3×10=30)
   1. Reduce the Boolean function using k-map technique and implement using gates f (w,x,y,z) = ?m(0,1,4,8,9,10) which has the don't cares condition d(w, x, y, z) = ?m(2,11)
   2. Implement the following multiple output combinational logic circuit using a 3 to 8 decoder.
      1. f1 = ?m(1,2,3,5,7)
      2. f2 = ?m(0,3,6)
      3. f1 = ?m(0,2,4,6)

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   3. 1. Realize a JK flip flop using SR flip flop.
      2. A SR flip flop using NAND gates and explain its operation.

Section - C

3. Attempt any one part of the following (1×10=10)
   1. Detect and correct error (if any) in the following received even parity Hamming code word 00111101010.

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   2. Minimize the given Boolean function using Quine Mc Clusky method f(A,B,C,D) = ? m(0,1,2,4,5,8,9,11,15) and implement the simplified function using NOR gates only.

4. Attempt any one part of the following (1×10=10)
   1. 1. Obtain the simplified Boolean expression for the output F and G in terms of the input variables in the circuit of fig. 1
         
      2. Implement the full adder and full subtractor using decoder.

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   2. 1. Design a combinational circuit that compares the magnitude of two 3 bit numbers and its output indicates whether A>B, A =B, A<B.
      2. Construct a BCD to excess 3 code converter with a 4 bit adder. What must be done to change the circuit to an excess 3 to BCD code converter?

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5. Attempt any one part of the following (1×10=10)
   1. Design a combinational circuit using a ROM. The circuit accepts a three-bit number and outputs a binary number equal to the square of the input number.
   2. Draw a PLA circuit to implement the functions f1 = A'B + AC' + A'BC', f2 = (AC + AB + BC)', f3 = BC + AC + A'BC'

6. Attempt any one part of the following (1×10=10)
   1. A sequential circuit has three flip flop A,B and C; one input x in and one output y out. The state diagram is shown in fig2. The circuit is to be designed by treating the unused states as don't-care conditions. Use T flip flop in the design.
      

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   2. Design a 4 bit binary synchronous counter with D flips flop.

7. Attempt any one part of the following (1×10=10)
   1. Derive the transition table for the asynchronous sequential circuit shown in fig.3 determine the sequence of internal states Y, Y2 for the following sequence of input XX2: 00,10;,11,01,11,10,00.
      
   2. An asynchronous sequential circuit is described by the excitation function Y = x^x + (x + x)y and z = y
      1. Draw the logic diagram of the circuit

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      2. Drive the transition table and output map.