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Bangladesh University of Engineering and Technology
CSE 206 (Digital Logic Design Sessional) Quiz
Full Marks 50 Time: 50 minutes
Student No.: Date:
1. State True/False on the left side of each of the following
sentences. 10x1=10
a. Any combinational circuit can be implemented using NAND gates
only. T b. There are 16 output lines in an encoder with 4 input
lines. F c. Any binary number from 0 to 19 can be converted to BCD
by adding 6 to the binary number. F d. IC 74153 is a dual 3x 8
decoder. T
e. For n variables, there are different switching functions. T
f. A sequential circuit may not contain a feedback path. F g.
Flip-flops are used as storage elements in sequential circuits. T
h. A decoder with an enable line can function as a demultiplexer. T
i. F j. IC 7447 is a Binary to BCD converter. F
2. ing MCQs. 10x1=10
i.
The logic circuit above is used to compute two unsigned 2-bit
numbers,
X1X0=X and Y1Y0=Y, where X0 and Y0 are the least significant
bits. Which
of the following always makes the output Z have the value 1?
a. X>Y b. X=Y
d. X=Y
ii. It is not possible to invert a signal using only a. an XOR
gate b. an OR gate
c. a 2 1 MUX
d. a 4 1 MUX
iii. To construct a 32x1 Mux using 4x1 Muxs we need minimum
a. Ten 4x1 Muxs
b. Eleven 4x1 Muxs
c. Twelve 4x1 Muxs
d. Thirteen 4x1 Muxs
iv. if A B=C, then
a. A
b. A
c. A C=B
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d. B C=AB
v. Simplified form of
a. b. ab+ bc + d+e c. ab+a d. It cannot be simplified
vi. Suppose a BCD-to-7 segment decoder has 0100 on its inputs.
The active outputs are
a. a, c, f, g
b. b, c, f, g
c. b, c ,e, f
d. d, b, f, g
vii. The 7483 IC is a 4-bit full adder. To expand this device to
a 8-bit adder you must-
a. Use two adders with no interconnection.
b. Use two adders and connect the sum outputs of one to the bit
inputs of the other.
c. User four adders with no interconnection.
d. Use two adders with the carry output of one connected to the
carry input of the other.
viii. What does the following circuit do?
a. BCD to Binary
b. BCD to Gray code
c. BCD to Excess-3
d. BCD to Excess-12
ix. What will be the output of a 4 to 2 priority encoder if the
given input is 0000. a. Zero b. Floating
A2
A1
A3 A4
B2
B1
B3 B4
1
0
Cin
Cout
S2 S1
S3 S4
BCD
input
Output
????
(MSB)
7483
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c. Unknown d. Tristate
x. How many clock cycle/ cycles does a master slave JK Flip-flop
require to operate?
a) 1
b) 2
c) 3
d) 4
3. Answer the following Short Questions 5x6=30
a. Using two 3 to 8 decoders and basic gates as required, design
a circuit that takes as input a number between 0-15 and produces as
output 1 if the input is a prime number and 0 otherwise. (The
outputs of the decoders
are active low)
b. Design a 3 input NOR gate using only one 4x1 Mux.
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c. Design an arithmetic unit which takes two 4-bit numbers A
&B and performs the following functions based on the values of
S1 and S0.
S1 S0 Output function
0 0 A+B'
0 1 A+B
1 0 A+B'+1
1 1 A+B+1
-bit adder) and XOR gates.
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d. Construct a J K flip -flop using D flip -flop, a 2-to-1-line
multiplexer and an inverter.
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e. Assume a system gets series of numbers as input. If an odd
number comes after an even number, then output indicates 1 and vice
versa. Otherwise, the output will be 0 (i.e. odd after odd and even
after even). Design a
circuit that will fulfill the above requirement.
