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SPPU Computer Engineering (Semester 3)
Digital Electronics and Logic Design
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any one question from Q1 and Q2
1 (a) Implement each expression with NAND logic:
i) ABC+DE
ii) ABC+D'+E'
4 M
1 (b) Convert the decimal number 650 to hexadecimal by repeated division by 16.
2 M
1 (c) Draw three input standard TTL NAND gate circuit and explain its operation.
6 M

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 M
2 (b) Prove the following rules of Boolean algebra:
i) A+A' B=A+B
ii) (A+B) (A+C) = A+BC.
2 M
2 (c) Explain the advantages of open collector output.
4 M

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 M
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 M
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 M

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 M
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 M
4 (c) Add the following BCD numbers:
i) 1000+0110
ii) 0111+0101
iii) 0111+0010
iv) 1000+0001.
4 M

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 M
5 (b) What is VHDL? Write a VHDL code for 3:8 decoder using behavioural modelling style.
7 M

6 (a) Explain different modelling style used to VHDL language with example.
6 M
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 M

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 M
7 (b) What is FPGA? Explain in detail the architecture of FPGA.
7 M

8 (a) What is the difference between PAL and PLA with suitable example?
6 M
8 (b) Design a BCD to Excess-3 code converter and implement using suitable PLA.
7 M

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