Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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1.
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Which logic gate performs the
comparator function?
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2.
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A logic circuit which
determines if one input is equal to another is called
a. | a
comparator. | c. | a
decoder. | b. | an adder. | d. | a multiplexer. |
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3.
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What are the outputs of a 7485
four-bit magnitude comparator when the inputs are A = 1001 and B = 1010?
a. | A < B is 0
A = B is 1
A
> B is 0 | b. | A < B is 1
A = B is 0
A > B is 1 | c. | A < B is 0
A = B is 0
A > B is
1 | d. | A < B is 1
A = B is 0
A
> B is 0 |
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4.
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What are the outputs of a 7485
four-bit magnitude comparator when the inputs are A = 0011 and B = 0010?
a. | A < B is 1
A = B is 0
A
> B is 0 | b. | A < B is 1
A = B is 0
A > B is 1 | c. | A < B is 0
A = B is 0
A > B is
1 | d. | A < B is 0
A = B is 1
A
> B is 0 |
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5.
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A device which determines which
of two numbers is greater is a
a. | counter. | c. | decoder. | b. | comparator. | d. | multiplexer. |
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6.
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Output 6 of a 74138 octal
decoder is selected when it is enabled by a data input of
a. | A0 = 1
A1 = 0
A2 =
0 | b. | A0 = 1
A1 = 1
A2 =
0 | c. | A0 = 0
A1 = 0
A2 =
1 | d. | A0 = 0
A1 = 1
A2 =
1 |
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7.
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All outputs of the 74138 octal
decoder are disabled (HIGH) when the enable inputs are ________.
a. |  1 = 1,  2 = 1, and E3 = 0 | c. |  1 = 0,  2 = 1, and E3
= 1 | b. |  1 = 0,  2 = 0, and E3
= 0 | d. | all of the
above |
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8.
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A decimal-to-BCD encoder has
________ data inputs.
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9.
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A binary code which is used to
indicate the position of a rotating shaft is the
a. | octal
code. | c. | BCD
code. | b. | Gray code. | d. | ASCII code. |
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10.
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What is the binary value of the
BCD number: 1000 0001 (81)?
a. | 0100
0001 | c. | 0110
0011 | b. | 1000 0000 | d. | 0101 0001 |
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11.
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A multiplexer is a device
which
a. | selects one of several inputs to be
placed onto one output line. | b. | converts some code into a recognizable number or
character. | c. | routes a single data input onto one of several data
outputs. | d. | generates an encoded output from a numeric
input. |
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12.
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An everyday illustration of a
multiplexer is
a. | the treble-bass control on a stereo
receiver. | b. | the balance control on a stereo receiver. | c. | the function switch on a stereo
receiver. | d. | the volume control in a stereo
receiver. |
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13.
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A multiplexer is also known as
a(n)
a. | code
converter. | c. | decoder. | b. | encoder. | d. | data selector. |
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14.
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A four-line multiplexer must
have
a. | four data inputs and four select
inputs. | c. | two data inputs
and four select inputs. | b. | two data inputs and two select inputs. | d. | four data inputs and two select
inputs. |
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15.
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In order to select data input
I5 of a 74151 eight-line multiplexer, the select inputs must be
a. |  = 0
S0 =
1
S1 = 1
S2 = 0 | b. |  = 0
S0 = 1
S1 = 0
S2 =
1 | c. |  = 0
S0 =
0
S1 = 0
S2 = 1 | d. |  = 1
S0 = 1
S1 = 1
S2 =
0 |
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16.
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A circuit that connects one of
several inputs to its output is a
a. | decoder. | c. | multiplexer. | b. | counter. | d. | comparator. |
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17.
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A demultiplexer is a device
which
a. | generates an encoded output from a
numeric input. | b. | routes a single data input onto one of several data
outputs. | c. | converts some code into a recognizable number or
character. | d. | selects one of several inputs to be placed onto one output
line. |
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18.
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If the inputs of a 74139 dual
four-line demultiplexer are as shown below, which output is correct?
 a =
data  b = data
A0a =
1 A0b = 0
A1a = 0 A1b =
0
a. | 1a = data
1b =
data | b. | 0a = data
1b = data | c. | 2a = data
2b = data | d. | 1a = data
0b =
data |
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19.
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A VHDL comparator uses a(n)
________ comparison
a. | IF-THEN-ELSE | c. | IF-THEN | b. | PLA | d. | SPLD |
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20.
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In VHDL, grouped inputs are
called vectors, but a single
output is a ________ quantity.
a. | scalar | c. | unique | b. | phasor | d. | mono |
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