EX-403 Digital Electronics and Logic Design (DELD) - Jun 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aConvert the following to Binary and then to gray code

   1. i)$(AB33)_{16}$
   2. ii)$(3323)_{8}$
   3. iii)$(83.625)_{10}$
   How to answer

   • Convert each given number to binary (hex to 4-bit, octal to 3-bit, decimal fraction by repeated multiply)
   • Write binary equivalents
   • Convert binary to Gray code using G MSB = B MSB, Gi = Bi xor Bi+1
   • List final Gray codes
2. 7 Marks
   bSimplify the following Boolean functions using Karnaugh map: $F(w, x, y, z) = \Sigma m(0, 1, 2, 4, 5, 12, 13, 14) + \Sigma d(6, 8, 9).$
   How to answer

   • Plot 4-variable K-map with minterms 0,1,2,4,5,12,13,14 and don't cares 6,8,9
   • Form largest groups of 1s using don't cares
   • Write prime implicants
   • Give minimized SOP expression
3. 7 Marks
   aDemonstrate by means of truth tables the validity of the De Morgan's theorems for three variables. Find the complement of $F = a(b'c'+bc)$ by applying De Morgan's theorem as many times as necessary.
   How to answer

   • State De Morgan's theorems for three variables
   • Construct 8-row truth tables for LHS and RHS of both theorems
   • Show LHS = RHS to prove validity
   • Apply repeated complementation to find complement of F = a(b'c'+bc)
4. 7 Marks
   bWhat is the need of full adder circuit. Design a Full adder circuit with truth table and logic diagram.
   How to answer

   • Explain need for full adder: addition of two bits with carry-in
   • Give truth table for 3 inputs A,B,Cin and outputs Sum, Cout
   • Derive Sum = A xor B xor Cin and Cout expressions
   • Show logic diagram using XOR, AND, OR gates
5. 7 Marks
   aImplement Boolean function $F(A, B, C, D) = \Sigma m(0, 1, 3, 4, 8, 9, 15)$ using 8:1 multiplexer.
   How to answer

   • Take A,B,C as select lines and D as MUX input variable
   • List minterms 0,1,3,4,8,9,15 in truth table
   • Derive 8 MUX data inputs D0-D7 as function of D
   • Show 8:1 multiplexer connection diagram
6. 7 Marks
   bWhat do you understand by Universal Gates. Realize the NOT, AND, OR, XOR and X-NOR Gates using NAND gates only?
   How to answer

   • Define universal gates: NAND and NOR can realize any function
   • Show NOT, AND, OR using NAND only
   • Show XOR and X-NOR using NAND only
   • Give logic diagrams for each realization
7. 7 Marks
   aWhat is Latch? What are the difference between Latch and Flip Flop? Explain D latch with truth table and logic diagram.
   How to answer

   • Define latch as level-sensitive bistable element
   • Compare latch vs flip-flop on clocking, transparency, edge vs level
   • Explain D latch operation and truth table
   • Show logic diagram using NAND/NOR or SR with enable
8. 7 Marks
   bExplain the working principle of J-K flip flop with its Truth Table and Suitable circuit diagram.
   How to answer

   • Give J-K flip-flop logic symbol and NAND-based circuit
   • Explain J,K = 00 hold, 01 reset, 10 set, 11 toggle
   • Present truth/characteristic table and excitation
   • Explain race-around and master-slave remedy if applicable
9. 7 Marks
   aDerive the State Table and State Diagram for the sequential circuit as shown in figure below.

   How to answer

   • Derive JA,KA,JB,KB input equations from AND gates and present state
   • Use J-K characteristic to get next state A+,B+ for all A,B,x
   • Construct state table including output y
   • Draw state diagram with transitions labelled x/y
10. 7 Marks
    bDesign a synchronous counter with the following repeated binary sequence: 0, 1, 2, 3, 4, 5, 6, use JK flip-flops.
    How to answer

    • Determine number of flip-flops for states 0-6 (3 JK FFs)
    • Draw state diagram for 0 to 6 sequence and excitation table
    • Derive J,K equations via K-maps
    • Show counter logic diagram
11. 7 Marks
    aDescribe shift registers and explain 4-bit bidirectional shift register with parallel load.
    How to answer

    • Define shift register and shift modes
    • Explain bidirectional shifting with control
    • Describe 4-bit register with parallel load inputs
    • Give block/logic diagram and operation table
12. 7 Marks
    bWhat do you understand by counter. Explain the working of Johnson counter with suitable diagram.
    How to answer

    • Define counter and classification
    • Explain Johnson/twisted ring principle with feedback inversion
    • Show 4-bit Johnson sequence of 8 states and timing
    • Give circuit diagram using D/JK flip-flops
13. 7 Marks
    aWhat do you understand by Read-Only-Memory. Explain different types ROMs.
    How to answer

    • Define ROM as non-volatile combinational memory
    • Explain address, data, organization
    • Classify mask ROM, PROM, EPROM, EEPROM, Flash
    • Compare programming/erasing features
14. 7 Marks
    bA combinational circuit is defined by the functions: $F_{1} = m (3, 5, 7)$ $F_{2} = m (4, 5, 7)$ Implement the circuit with a PLA having 3 inputs, 3 product terms and two outputs.
    How to answer

    • Express F1 = m(3,5,7), F2 = m(4,5,7) in terms of 3 variables
    • Find common product term 101? Actually minterm 5 common, minimize to 3 product terms
    • Assign AND-plane fuses for 3 product terms
    • Show PLA diagram with 3 inputs, 3 ANDs, 2 ORs
15. 14 Marks
    Write a short note on any two :

    1. a)Priority Encoder
    2. b)Decoding in Counter
    3. c)Programmable Array Logic (PAL)
    4. d)Successive Approximation A/D Converter
    How to answer

    • Select any two topics from four options
    • Give definition/principle and block diagram for each
    • Mention key features/applications
    • Conclude with uses in digital systems