EX-403 Digital Electronics and Logic Design (DELD) - Jun 2025 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.

   1. i)$(53.625)_{10}$ to $(?)_{2}$
   2. ii)$(3FD)_{16}$ to $(?)_{2}$
   3. iii)$(A69.8)_{16}$ to $(?)_{10}$
   4. iv)$(726.56)_{8}$ to $(?)_{10}$
   How to answer

   • State positional weights for binary, octal, hexadecimal and decimal
   • Convert integer part by repeated division and fractional part by repeated multiplication where applicable
   • Show stepwise conversion for all four parts
   • Write final equivalent values with correct base subscript
2. 7 Marks
   bUsing the tabulation method, obtain the simplified expression in product of sums for the Boolean function $F(w, x, y, z) = \Pi(1, 3, 5, 7, 13, 15)$.
   How to answer

   • List maxterms Pi(1,3,5,7,13,15) for 4 variables w,x,y,z
   • Apply Quine-McCluskey tabulation: grouping, prime implicants, prime implicant chart
   • Select essential prime implicants for POS
   • Write minimal product-of-sums expression
3. 7 Marks
   aExplain the error detection using parity method in digital transmission. Discuss how odd parity error detection carried out for transmitting the letter 'B' in ASCII code.
   How to answer

   • Define parity bit, even vs odd parity
   • Explain error detection principle at transmitter and receiver
   • Give ASCII code of letter 'B' (1000010) and odd parity bit addition
   • Discuss limitation: detects odd number of errors only
4. 7 Marks
   bWhat do you understand by Subtractor Circuit? Design a Half Subtractor circuit with truth table and logic diagram.
   How to answer

   • Define subtractor and need for Difference and Borrow
   • Give truth table of half subtractor for inputs A,B
   • Derive Difference = A xor B, Borrow = A' B
   • Show logic diagram using XOR, NOT, AND gates
5. 7 Marks
   aWhat do you understand by decoder? Design a binary to Gray code Decoder.
   How to answer

   • Define decoder and its n to 2^n function
   • Give binary to Gray conversion relation
   • Derive truth table and output expressions for Gray decoder
   • Show logic diagram implementation
6. 7 Marks
   bWhat is Magnitude comparator? Design a 2 bit magnitude comparator.
   How to answer

   • Define magnitude comparator and outputs A>B, A<B, A=B
   • Write truth table for 2-bit numbers A1A0, B1B0
   • Derive logic expressions for three outputs
   • Show logic diagram
7. 7 Marks
   aDefine the following and explain:

   1. i)State Diagram
   2. ii)State Table
   3. iii)State Equation
   4. iv)State Assignment
   How to answer

   • Define state diagram, state table, state equation, state assignment
   • Explain each with sequential circuit context
   • Give small example representation
   • Mention use in state reduction and flip-flop assignment
8. 7 Marks
   bExplain the working principle of Master Slave flip flop with its Truth Table and Suitable circuit diagram.
   How to answer

   • Explain master-slave configuration to avoid race-around
   • Describe operation on clock phases with SR/JK master and slave
   • Give truth table / characteristic operation
   • Show circuit diagram with two latches and inverter clock
9. 7 Marks
   aWrite logical equation and construct transition table for the circuit output in term of the circuit inputs and secondary variable.

   

   How to answer

   • Identify gates, inputs x, secondary variables y1,y2 and outputs Y1,Y2,z
   • Write Boolean equations for Y1,Y2 and output z
   • Construct transition table for present state, input and next state
   • Mention stable states concept
10. 7 Marks
    bExplain 4-bit synchronous up-down binary counter.
    How to answer

    • Define synchronous up-down counter and control input
    • Explain flip-flop excitation and up/down logic
    • Describe counting sequence 0-15 and reverse
    • Show block diagram / timing concept
11. 7 Marks
    aWhat do you understand by Registers? Discuss about Shift Right and Shift Left with suitable diagram.
    How to answer

    • Define register as group of flip-flops for storage
    • Explain shift right operation with serial shift
    • Explain shift left operation with serial shift
    • Show diagrams of shift registers with clock and data flow
12. 7 Marks
    bWhat is a Counter. Explain the working of Ring counter with suitable diagram.
    How to answer

    • Define counter and classification
    • Explain ring counter as circulating single 1
    • Give 4-bit example sequence and logic
    • Show diagram with shift register and feedback
13. 7 Marks
    aExplain about Read and Write cycles of a static RAM with neat timing waveforms.
    How to answer

    • Define static RAM cell and control signals
    • Explain read cycle timing: address, chip select, output enable
    • Explain write cycle timing: address, write enable, data setup/hold
    • Draw neat timing waveforms for both cycles
14. 7 Marks
    bWith a neat diagram explain in detail about two dimensional memory decoding scheme.
    How to answer

    • Explain 2D decoding concept with row and column decoders
    • Describe address partitioning and memory array selection
    • Discuss advantage of reduced decoder size
    • Show neat diagram of 2D memory decoding scheme
15. 14 Marks
    Write a short note on any two :

    1. a)Priority Encoder
    2. b)Decoding in Counter
    3. c)Programmable Logic Array (PLA)
    4. d)R-2R D to A Converter
    How to answer

    • Select any two topics from four options
    • Give definition, block diagram and working for each
    • Mention applications and key features
    • Conclude with comparison or use-case