JNTU
JNTU B.Tech II DIGITAL LOGIC DESIGN Previous Question Paper (August/September - 2022 - R13)
Answer any five questions
All questions carry equal marks
Main
Explain BCD codes, Excess-3 code, Gray code, and ASCII codes used in digital systems.
Answer
BCD (Binary Coded Decimal): Represents each decimal digit (0-9) using a 4-bit binary sequence. It is weighted (8-4-2-1) and used for decimal arithmetic.
Excess-3 Code: A non-weighted code derived by adding 3 to the BCD value of a digit. It is a self-complementing code, useful for subtraction via 9's complement.
Gray Code: A unit-distance code where consecutive numbers differ by only one bit. It is used in encoders and K-maps to minimize transition errors.
ASCII (American Standard Code for Information Interchange): A 7-bit character encoding scheme representing alphanumeric characters, punctuation, and control codes for data communication.
Write about error detecting codes and error correcting codes used in digital systems.
Answer
Error Detecting Codes: These codes include redundant bits to identify if a transmission error occurred. The most common example is the Parity Bit (Even or Odd parity), which detects single-bit errors but cannot locate them.
Error Correcting Codes: These codes contain sufficient redundant information to not only detect but also locate and fix errors. The Hamming Code is the standard method, using multiple parity bits placed at power-of-two positions to identify the specific bit in error.
Convert (i) 68BE16 to Binary and then Octal (ii) Convert 34510 to binary and hexadecimal.
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Explain the axiomatic definition of Boolean algebra by taking two and three variables.
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Explain the characteristics of the logic families (i) TTL (ii) ECL (iii) MOS (iv) CMOS.
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Explain the methods of simplification of Boolean expression using Karnaugh methods by taking 4 variable function that includes Don’t care conditions.
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Simplify the following four variable Boolean function and implement the same using NAND logic. F (A, B, C, D) = ∑m (0, 2, 4, 5, 7, 8, 10, 13, 15), ∑ d(3,6,11,12).
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Minimize the following multiple output functions using SOP: f1 =∑m(0,1,2,4,6,7,10) f2 =∑m(2,4,10,12,14)
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Explain the construction of Karnaugh’s maps with five variables and simplify the Boolean function F(A,B,C,D, E) = ∑m(0,1,2,4,5,7,11,15, 18, 20, 23, 25,26,27, 30).
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Discuss the analysis and design procedure and draw the logic diagram of a 4 bit BCD adder/subtractor.
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Explain functions of Multiplexers and Decoders. Design combinational circuits for 4/1 line multiplexers using logic gates.
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Construct a 4 bit 2’s complement adder and a BCD adder using full adders and perform addition and subtraction by taking 4-bit numbers with examples.
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Draw the logic diagrams of 4 bit magnitude comparator and explain its working with typical examples.
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Draw the logic diagram of a 4-bit binary ripple counter with parallel load and explain its working with its function table.
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Design a 4 bit synchronous counter with JK flip - flops and explain its working with the help of state diagrams and state tables.
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Given 32 × 8 ROM with enable input, Show the external connections necessary to construct a 128 × 8 ROM with 4 chips and a decoder.
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What are PLAs? Explain the working of a PLA with a schematic and implement the following two Boolean functions with a PLA: F1 (A, B, C) = ∑ (0, 1, 2, 4) and F2 (A, B, C) = ∑ (0, 5, 6, 7).
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