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END TERM EXAMINATION
Paper Code: BCA-106
SECOND SEMESTER [BCA]
MAY — JUNE 2015

## Subject: Digital Electronics

(Batch 2011 onwards)

Time: 3 Hours Maximum Marks: 75

Note: Attempt any five questions including Q.No 1 which is compulsory.
Select one question from each unit.

Question 1:
(a) State and Prove the Demorgan’s theorems. (4)

(b) Design a full adder using the NAND gates only. (4)

(c) What is a multiplexer? Design a 32 to 1 multiplexer using the 8 to 1 multiplexers. (4)

(d) What is a D ï¬‚ip ï¬‚op? Show how SR ï¬‚ip ï¬‚op can be converted to D flip ï¬‚op.(4)

(e) What is a ripple counter? Explain the difference between the performance of asynchronous and synchronous counters. (4)

(f) Explain the working of bi directional shift register with logic diagram. (5)

UNIT-I
Question 2:
(a) What is Gray code? Why it is important? List features of BCD and Excess3 codes. (6)

(b) What are Universal gate? Obtain EX-OR operation with universal gates. (3.5)

(c) Convert the following octal numbers to hexadecimal numbers: (3)
(i)   137
(ii)  1275
(iii) 673

Question 3:
(a) Simplify the expression Y = Î£m(7,9,10,11,12,13,14,15) using the k-map method.

(b) Realize Y = A + BCD using NAND gates only.

UNIT-II
Question 4:
(a) Design a 4 bit parallel adder circuit. Give the truth table and explain the  operation. (6.5)

(b) What is binary multiplier? Discuss the multiplier using shift method. (6)

Question 5:
(a) Explain the working of BCD to seven segment decoder with diagram. (6)

(b) What is an encoder? Discuss the design of octal to binary encoder. (6.5)

UNIT-III
Question 6:
Discuss and explain the working of master slave JK Flip ï¬‚op. What are its advantages? ( 12.5)

Question 7:
What is shift register? Give its classification and explain the working of each type diagram. (12.5)

UNIT IV

Question 8:
What is modulo counter? Design a MOD-6 counter by giving all design steps. (12.5)

Question 9:
Explain the following: (a) RAM (b) PLA (12.5)