EC-303 Digital System Design - 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 Octal numbers into binary, decimal and hexadecimal.

   1. i)426
   2. ii)314.52
   How to answer

   • Convert each octal digit to 3-bit binary for i) 426 and ii) 314.52
   • Convert octal to decimal via positional weights 8^n
   • Convert decimal/binary result to hexadecimal by 4-bit grouping
   • Write final binary, decimal and hexadecimal values
2. 7 Marks
   bWhat is Universal gate? Implement a NOR gate using NAND gate.
   How to answer

   • Define universal gate with NAND and NOR as examples
   • Show why NAND is universal
   • Give step-wise construction of NOR using only NAND gates
   • Draw logic diagram and verify with truth table
3. 7 Marks
   aMinimize the following using Karnaugh map. $F(A,B,C,D) = \sum(0,5,7,9,11,13)$
   How to answer

   • Plot 4-variable K-map for $F(A,B,C,D)=\sum(0,5,7,9,11,13)$
   • Form maximal groups of 1s (pairs/quads)
   • Write prime implicants for each group
   • Give minimized SOP expression
4. 7 Marks
   bSimplify the following using Quine McCluskey method. $f(w,x,y,z) = \sum_m(0,1,3,9,10,12,13,14) + \sum_d(2,5,6,11)$
   How to answer

   • List minterms 0,1,3,9,10,12,13,14 and don't cares 2,5,6,11 by weight
   • Perform Quine-McCluskey tabular combination to get prime implicants
   • Construct prime implicant chart with don't cares
   • Select essential prime implicants and write minimal expression
5. 7 Marks
   aDiscuss about the full subtractor in detail.
   How to answer

   • Define full subtractor with inputs A, B, Bin and outputs Difference, Bout
   • Give truth table for all 8 combinations
   • Derive Boolean expressions for Difference and Bout
   • Show logic diagram using gates
6. 7 Marks
   bExplain the working of BCD adder with diagram.
   How to answer

   • Explain need for BCD correction (sum >9 adds 6)
   • Describe two 4-bit adders with correction logic
   • Draw block diagram of BCD adder
   • Explain working with example
7. 7 Marks
   aDesign and explain a 4 bit priority encoder.
   How to answer

   • Define priority encoder and 4-bit priority concept
   • Give truth table with valid output
   • Derive output equations
   • Show logic diagram and working
8. 7 Marks
   bExplain a 8:1 multiplexer in detail.
   How to answer

   • Define multiplexer and 8:1 selection concept
   • Give block diagram with 8 data inputs and 3 select lines
   • Write truth table / Boolean expression for output
   • Explain working and applications
9. 7 Marks
   aWrite a short note on master slave J-K flip-flop.
   How to answer

   • Define master-slave configuration to avoid race-around
   • Describe master and slave SR/JK stages with clocking
   • Explain working for J=K=1 toggle operation
   • Give circuit diagram and timing behaviour
10. 7 Marks
    bExplain the designing of synchronous FSM.
    How to answer

    • Define synchronous FSM with states, inputs, outputs
    • List design steps: state diagram, state table, encoding, flip-flop selection
    • Explain excitation and output equations
    • Describe implementation with example flow
11. 7 Marks
    aExplain the differences between the synchronous and asynchronous counters.
    How to answer

    • Define synchronous vs asynchronous clocking
    • Compare on clock, speed, power, complexity, glitches
    • Give examples of ripple vs parallel counters
    • Summarize in table
12. 7 Marks
    bWhat are universal shift registers? Explain in detail.
    How to answer

    • Define universal shift register with modes
    • Explain SISO, SIPO, PISO, PIPO operations
    • Describe 4-bit universal register with MUX control
    • Give diagram and applications
13. 7 Marks
    aDraw the circuit of basic ECL inverter and explain its operation.
    How to answer

    • Draw basic ECL inverter with differential pair and emitter follower
    • Explain reference and current-steering operation
    • Describe OR/NOR outputs and non-saturation advantage
    • Mention characteristics and applications
14. 7 Marks
    bDraw and explain TTL NAND gate.
    How to answer

    • Draw multi-emitter TTL NAND circuit with totem-pole output
    • Explain operation for different input combinations
    • Describe transistor states and output levels
    • Mention advantages and limitations
15. 14 Marks
    Write short notes on following: (any two)

    1. a)De-Morgan's theorem
    2. b)Full adder
    3. c)S-R flip-flop
    How to answer

    • State De-Morgan's theorems with expressions
    • Explain full adder truth table and sum/carry equations
    • Describe S-R flip-flop operation and truth table
    • Give diagrams for any two chosen topics