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Digital Electronics and Logic Design : Question Paper Dec 2015 - Computer Engineering (Semester 3) | Pune University (PU)

## Digital Electronics and Logic Design - Dec 2015

### Computer Engg (Semester 3)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.

### Solve any one question from Q1 and Q2

1 (a) Implement each expression with NAND logic:
i) ABC+DE
ii) ABC+D'+E'
(4 marks)
1 (b) Convert the decimal number 650 to hexadecimal by repeated division by 16.(2 marks) 1 (c) Draw three input standard TTL NAND gate circuit and explain its operation.(6 marks) 2 (a) Using K-map convert the following standard POS expression into a minimum POS expression, a standard SOP expression and minimum SOP expression: (A'+B'+C+D) (A+B'+C+D) (A+B+C+D') (A+B+C'+D') (A'+B+C+D') (A+B+C'+D).(6 marks) 2 (b) Prove the following rules of Boolean algebra:
i) A+A' B=A+B
ii) (A+B) (A+C) = A+BC.
(2 marks)
2 (c) Explain the advantages of open collector output.(4 marks)

### Solve any one question from Q3 and Q4

3 (a) Design a synchronous counter for
4->6->7->3->1->4....
Avoid lockout condition. Use JK flip flop for design.
(6 marks)
3 (b) What are the full adder's inputs that will produce each of the following outputs?
i) ∑=0, Cout=0
ii) ∑=1, Cout=0
iii) ∑=1, Cout=1
iv) ∑=0, Cout=1.
(2 marks)
3 (c) Explain the logic required to convert 6-bit binary number to gray code. Use that logic to convert the following binary numbers to gray code:
i) 101010
ii) 111111
iii) 000111
iv) 111000.
(4 marks)
4 (a) Design a SEQUENCE DETECTOR using JK Flip-Flop to detect the following sequence, .... 1001 .... Use state table diagram, state transition table and K-map as design tools. Remove all redundant states and draw the final circuit diagram.(6 marks) 4 (b) Determine the output for the following input states:
D0=0, D1=1, D2=1, D3=0, s0=1, s1=0. Use 4:1 MUX.
(2 marks)
4 (c) Add the following BCD numbers:
i) 1000+0110
ii) 0111+0101
iii) 0111+0010
iv) 1000+0001.
(4 marks)

### Solve any one question from Q5 and Q6

5 (a) What is ASM chart? Give its application and explain the MUX controller method with the suitable example.(6 marks) 5 (b) What is VHDL? Write a VHDL code for 3:8 decoder using behavioural modelling style.(7 marks) 6 (a) Explain different modelling style used to VHDL language with example.(6 marks) 6 (b) Draw an ASM chart for the 2-bit counter with the following specifications:
i) It will court UP if X=1
ii) It will maintain the state if X=0
iii) Produces output = 1.
If the counter bits are equal unconditionally, otherwise output = 0 unconditionally. X is an external input.
(7 marks)

### Solve any one question from Q7 and Q8

7 (a) Show how PAL is programmed for the following 3 variable logic function:
i) X=AB'C+A'BC'+A'B'+AC
ii) Y=A'B'C+AB'C+A+AB.
(6 marks)
7 (b) What is FPGA? Explain in detail the architecture of FPGA.(7 marks) 8 (a) What is the difference between PAL and PLA with suitable example?(6 marks) 8 (b) Design a BCD to Excess-3 code converter and implement using suitable PLA.(7 marks)

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