Important Questions in

**Digital electronics****147302**subject for NOV/DEC 2011 ANNA UNIVERSITY OF TECHNOLOGY EXAMINATIONS FOR SECOND YEAR THIRD SEMESTER ECE Students

**147302 - Digital electronics**

**UNIT I**

**1.**Obtain the standard POS for f(A,B,C ) = (A+B

^{’}) (B+C)(A+ C

^{’})

**2.**Simplify the following Boolean function by Quine Mc cluskey method

F(A,B,C,D)= ∑(0,2,3,6,7,8,10,12,13)

**3.**Reduce the following function suing K- map

F(A,B,C,D)= π (0,3,4,7,8,10,12,14) + d(2,6)

**4.**Using Quine Mc cluskey method to simplify the Boolean expression

F(A,B,C,D,E) = ∑ m (0,1,4,5,16,17,21,25,29)

**5.**Using K –map method obtain the minimal SOP and POS expressions

for the function F(W,X,Y,Z) = ∑ m (1,3,4,5,6,7,9,12,13)

UNIT II

1. Design a excess 3 to BCD code convertor

2. Design a combinational circuit that generates the 9’s complement of a BCD digit

3. Design a seven segment decoder circuit to display the numbers 0 to 3

4. Realize F(W,X,Y,Z) = ∑ m (1,4,6,7,8,9,10,11,15) using 4 to 1 MUX

5. Explain the operation of carry look ahead adder with neat diagram

UNIT III

1. Explain the operation of universal shift register with neat block diagram

2. With a neat state diagram and logic diagram ,design and explain the sequence of states of BCD counter

3. Explain in detail the operation of 4 bit ripple counter

4. How will you convert a D flip flop into JK flip flop

UNIT IV

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. Explain read and write operation of memory with timing waveforms

3. A combinational circuit is defined by functions F

_{1}(A,B,C) =∑ M(0,1,6,7)F

_{2}(A,B,C) =∑ M(2,3,5,7)Implement the circuit with a PLA having three inputs , three product terms and twoinputs

4. Write a note on RAM

UNIT V

1. Describe the hazards that could occur in asynchronous sequential circuits. What are the ways in which they are eliminated

2. Design negative edge triggered T flip flop from logic gates

3. Write a verilog coding for full adder

4. Give hazard free realization for the following Boolean function

F(A,B,C,D)= ∑ m (1,3,6,7,13,15)

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