DE Solution Set QP Code : 00904 1. Attempt any three of the following: 15 a. Define digital signal. (1M) With respect to digital signal explain the terms digits and bits.(2m) Also discuss active high and active low signal. (2M) In binary logic the two levels are logical high and logical low, which generally correspond to a binary 1 and 0 respectively. Signals with one of these two levels can be used in boolean logic for digital circuit design or analysis. The use of either the higher or the lower voltage level to represent either logic state is arbitrary. The two options are active high and active low. Active-high and active-low states can be mixed at will: for example, a read only memory integrated circuit may have a chip-select signal that is active-low, but the data and address bits are conventionally active-high. Occasionally a logic design is simplified by inverting the choice of active level (see De Morgan's theorem). Binary signal representations Logic level Active-high signal Active-low signal Logical high 1 0 Logical low 0 1
The name of an active-low signal is written with a bar above it to distinguish it from an active-high signal. For example, the name Q, read "Q bar" or "Q not", represents an active-low signal. b. What are different numbering systems used(1m)? Convert following numbers to required numbering system (2M each) i) (11001011.01110)2 = ( )10 ii) (1100110.011010)2 = ( )16 A numbering system is defined by digits or numerals. According to the requirement these digits can be arranged in a particular sequence. Based on number of digit identified by a numbering system, there are following numbering systems Decimal identifies 10 digits 0 to 9 used in general. Binary identifies only 2 digits 0 and 1 used by computers Octal identifies 8 digits 0 to 7 used in codes Hexadecimal identifies 16 digits 0 to 9 and A to F. used in assembly language programming. Conversions i) (11001011.01110)2 = (203.4375)10 ii) (1100110.011010)2 = (102.40625)16 c. What are codes? (1M) Where are they used? (2M) Differentiate between weighted and non weighted codes. Give one example of each. (2M)
NOTE use of codes can be written in brief. No marks reserved for dig. Weighted Codes Weighted binary codes are those binary codes which obey the positional weight principle. Each position of the number represents a specific weight. Several systems of the codes are used to express the decimal digits 0 through 9. In these codes each decimal digit is represented by a group of four bits. Non-Weighted Codes In this type of binary codes, the positional weights are not assigned. The examples of non-weighted codes are Excess-3 code and Gray code. d. Explain how negative numbers are represented in binary numbering system. (2M) Discuss properties of 2 s complement.(3m)
e. Perform following arithmetic operations after converting the numbers to binary numbering system i) (10)10 (4)10 (2M) ii) (727)8 (234)8 (2M) iii) (DADA)16 + (BABA)16 (1M) i) (10)10 (4)10 (1010)2 (0100)10 Q = 10 R = 10 ii) (727)8 (234)8 (111010111)2 - (10011100)2 (100111011)2 (473)8 iii) (DADA)16 + (BABA)16
(1101101011011010)2 + (1011101010111010)2 (11001010110010100)2 (19594)16 f. Add following BCD numbers i) (56)10 and (23)10 (2M) ii) (82)10 and (34)10 (3M) i) 0101 0100 + 0010 0011 0111 1001 (79)10 ii) 1000 0010 + 0011 0100 1011 0110 First digit is invalid BCD add 6 (0100) (113)10 2. Attempt any three of the following: 15 a. Draw logic circuit and make truth table to prove the following Boolean theorems i) A. 0 = 0 (2M) ii) (A. B). C = A. (B. C) (3M) i)
ii) (A.B).C = A. (B. C) Associative law. b. Using rules of Boolean algebra, solve y = (x + z)(x + y + z) (3M) Draw a logic circuit using suitable gates to implement the simplified equation. (2M)
c. What is meant by universal logic gate? (1M) Draw logic circuits showing construction of Ex-OR gate using NAND gate and using NOR gate.(2m each) Ex-OR using NAND Ex-OR using NOR d. F(A,B,C,D) = m (0,1,2,5,13,15). Draw k-map (2M + 1M for grouping) and find minimised Boolean expression.(2m)
e. What is meant by don t care conditions? (1M) Explain how are they used in simplifying an expression using a k-map. (1M) Use the following example F(A,B,C,D) = m (1,4, 8, 12, 13, 15) + d (3,14) (3M) f. What are disadvantages of k-map? (1M) Explain the Q M method. (1M) Discuss the terms prime impeccant, code word and reduction table (3M)
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Example not compulsory 3. Attempt any three of the following: 15 a. A 4 bit binary number is represented by A3A2A1A0 where A3, A2, A1 and A0 represent the individual bits with A0 equals to the LSB. Design a logic circuit that will produce a HIGH output whenever binary number is greater than (0010)2 and less than (1000)2. Truth table (2M) K map(1m) equation (1M) dig (1M) b. Convert 4 bit binary number to 4 bit gray. Draw the truth table, (2M) necessary k-maps(2m) and logic circuit. (1M)
c. Design a BCD to 7 segment decoder. (2M) Realize the circuit using NAND gates only. (3M)
Note - K maps not mandatory. Circuit d. Implement 8 bit adder using 4 bit full adder. Logic dig (3M) explaination 2M
e. Draw circuit(3m) and explain working (2M) of BCD subtractor.
f. Write a note on fast multiplier.
4. Attempt any three of the following: 15 a Implement following function using 8:1 Mux F(A,B,C,D) = m (2,4,5,7,10,14) Truth table (3M) ckt dig (2M)
b What are data distributor (demultiplexer)?(1m) dig (1M) explain basic operation of 2 output demultiplexer. (3M)
c Draw block dig (2M)and explain operation of 74180 (2M)monolithic 8 bit checker / generator (what is parity generator 1M)
d Explain the need of preset and clear pins in RS flip flop? (1M) With neat block dig (1M) and truth table (1M) explain the working of RS flip flop.(2m)
e Write a note on master slave JK flip flop.
f Discuss various applications of flip flops List applcations 1M explanation of each 1M Each should be briefly discussed. 5. Attempt any three of the following: 15 a. Explain the working of Asynchronous / ripple counter. Dig 2M working 3 M
b. Design mod 4 regular sequential synchronous up counter using T FF State dig 1 M logic dig 2 M waveforms 1 M working 1 M
c. Write truth table for mod 6 counter in IC 7492. Block schematic 1 M explanation 2 M state table 2 M
d. Explain the difference between serial shifting and parallel shifting of data in shift register.
e. Explain how sequence generator circuit works.(3m) Explain with one example.(2m)
Note - Any one example can be used. f. Write a note on ring counter
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