Code Converters and Multiplexers

Q1: A principle regarding most IC decoders is that when the correct input is present, the related output will switch:

A
active-HIGH

B
to a high impedance

C
to an open

D
active-LOW

Q2: What control signals may be necessary to operate a 1-line-to-16 line decoder?

A
flasher circuit control signal

B
a LOW on all gate enable inputs

C
input from a hexadecimal counter

D
a HIGH on all gate enable circuits

Q3: How many possible outputs would a decoder have with a 6-bit binary input?

A
16

B
32

C
64

D
128

Q4: The primary use for Gray code is:

A
coded representation of a shaft's mechanical position

B
turning on/off software switches

C
to represent the correct ASCII code to indicate the angular position of a shaft on rotating machinery

D
to convert the angular position of a shaft on rotating machinery into hexadecimal code

Q5: A binary code that progresses such that only one bit changes between two successive codes is:

A
nine's-complement code

B
8421 code

C
excess-3 code

D
Gray code

Q6: How can the active condition (HIGH or LOW) or the decoder output be determined from the logic symbol?

A
A bubble indicates active-HIGH.

B
A bubble indicates active-LOW.

C
A square indicates active-HIGH.

D
A square indicates active-LOW.

Q7: The inputs/outputs of an analog multiplexer/demultiplexer are:

A
bidirectional

B
unidirectional

C
even parity

D
binary-coded decimal

Q8: Use the weighting factors to convert the following BCD numbers to binary. 0101 0011        0010 0110 1000

A
01010011    001001101000

B
11010100    100001100000

C
110101        100001100

D
101011        001100001

Q9: How many exclusive-NOR gates would be required for an 8-bit comparator circuit?

A
4

B
6

C
8

D
10

Q10: How many select lines would be required for an 8-line-to-1-line multiplexer?

A
2

B
3

C
4

D
8

Q11: How many 74184 BCD-to-binary converters would be required to convert two complete BCD digits to a binary number?

A
8

B
4

C
2

D
1

Q12: One application of a digital multiplexer is to facilitate:

A
data generation

B
serial-to-parallel conversion

C
parity checking

D
data selector

Q13: A circuit that responds to a specific set of signals to produce a related digital signal output is called a(n):

A
BCD matrix

B
display driver

C
encoder

D
decoder

Q14: How is an encoder different from a decoder?

A
The output of an encoder is a binary code for 1-of-N input.

B
The output of a decoder is a binary code for 1-of-N input.

Q15: Why is the Gray code more practical to use when coding the position of a rotating shaft?

A
All digits change between counts.

B
Two digits change between counts.

C
Only one digit changes between counts.

Q16: The expansion inputs to a comparator are used for expansion to a(n):

A
4-bit system

B
8-bit system

C
BCD system

D
counter system

Q17: A BCD decoder will have how many rows in its truth table?

A
10

B
9

C
8

D
3

Q18: For the following conditions on a 7485 magnitude comparator, what will be the state of each of the three outputs?
A0 = 0B0 = 1IA < B = 0
A1 = 1B1 = 0IA = B = 1
A2 = 1B2 = 0IA > B = 0
A3 = 0B3 = 0 

A
A = B = 0, A < B = 0, A > B = 1

B
A = B = 0, A < B = 1, A > B = 0

C
A = B = 1, A < B = 0, A > B = 0

D
A = B = 0, A < B = 0, A > B = 0

Q19: If two inputs are active on a priority encoder, which will be coded on the output?

A
the higher value

B
the lower value

C
neither of the inputs

D
both of the inputs

Q20: Most demultiplexers facilitate which type of conversion?

A
decimal-to-hexadecimal

B
single input, multiple outputs

C
ac to dc

D
odd parity to even parity

Q21: How many inputs are required for a 1-of-16 decoder?

A
2

B
4

C
8

D
18

Q22: What is the function of an enable input on a multiplexer chip?

A
to apply Vcc

B
to connect ground

C
to active the entire chip

D
to active one half of the chip

Q23: How many inputs will a decimal-to-BCD encoder have?

A
4

B
8

C
10

D
16

Q24: In a BCD-to-seven-segment converter, why must a code converter be utilized?

A
to convert the 4-bit BCD into 7-bit code

B
to convert the 4-bit BCD into 10-bit code

C
to convert the 4-bit BCD into Gray code

D
No conversion is necessary.

Q25: How many outputs are on a BCD decoder?

A
4

B
16

C
8

D
10

Q26: Why can a CMOS IC be used as both a multiplexer and a demultiplexer?

A
It cannot be used as both.

B
CMOS uses bidirectional switches.

Q27: A truth table with output columns numbered 0–15 may be for which type of decoder IC?

A
hexadecimal 1-of-16

B
dual octal outputs

C
binary-to-hexadecimal

D
hexadecimal-to-binary

Q28: One way to convert BCD to binary using the hardware approach is:

A
with MSI IC circuits

B
with a keyboard encoder

C
with an ALU

D
UART

Q29: How many inputs are required for a 1-of-10 BCD decoder?

A
4

B
8

C
10

D
1

Q30: Which digital system translates coded characters into a more useful form?

A
encoder

B
display

C
counter

D
decoder

Q31: A basic multiplexer principle can be demonstrated through the use of a:

A
single-pole relay

B
DPDT switch

C
rotary switch

D
linear stepper

Q32: How can the active condition (HIGH or LOW) or the decoder output be determined from the logic symbol?

A
A bubble indicates active-HIGH.

B
A bubble indicates active-LOW.

C
A square indicates active-HIGH.

D
A square indicates active-LOW.

Q33: A microcontroller differs from a microprocessor in that it has several ________ ports and ________ built into its architecture, making it better suited for ________ applications.

A
communication, PROMs, control

B
parallel, logic gates, processing

C
input/output, memory, control

D
data, memory, decoding

Q34: What is the status of the inputs S0, S1, and S2 of the 74151 eight-line multiplexer in order for the output Y to be a copy of input I5?

A
S0 = 0, S1 = 1, S2 = 0

B
S0 = 0, S1 = 0, S2 = 1

C
S0 = 1, S1 = 1, S2 = 0

D
S0 = 1, S1 = 0, S2 = 1

Q35: From the following list of input conditions, determine the state of the five output leads on a 74148 octal-to-binary encoder.
I0 = 1 I3 = 1 I6 = 1
I1 = 1 I4 = 0 I7 = 1
I2 = 1 I5 = 1 EI = 0

A
GS = L, A0 = L, A1 = L, A2 = H, EO = H

B
GS = L, A0 = H, A1 = L, A2 = L, EO = H

C
GS = L, A0 = L, A1 = H, A2 = L, EO = H

D
GS = L, A0 = H, A1 = H, A2 = L, EO = H

Q36: Which of the following is not a weighted value positional numbering system:

A
hexadecimal

B
binary-coded decimal

C
binary

D
octal

Q37: When two or more inputs are active simultaneously, the process is called:

A
first-in, first-out processing

B
priority encoding

C
ripple blanking

D
first-in, first-out processing or priority encoding

Q38: What do the mathematical symbols A < b and A > B mean?

A
A < B means A is greater than B. A > B means A is less than B.

B
A > B means A is less than B. A < B means A is greater than B.

C
A < B means A is less than B. A > B means A is greater than B.

Q39: In a Gray code, each number is 3 greater than the binary representation of that number.

A
True

B
False

Q40: Why is a demultiplexer called a data distributor?

A
The input will be distributed to one of the outputs.

B
One of the inputs will be selected for the output.

C
The output will be distributed to one of the inputs.


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