The circuit in Figure 9-8 is defective; data is not appearing on the output lines. A check with the scope shows data pulses on the serial data line and multiplex control lines, S0–S2; no parity error is indicated. A further check with a logic probe indicates that and ground appear to be present. What might be wrong with the circuit?

The parity checker is defective.

The parity generator may be bad.

The parity checker is defective, or the parity generator may be bad.

Refer to the figure given below. The logic function generator being implemented with the multiplexer in this circuit produces a constant LOW on the output. The ABC inputs are checked and appear to be pulsing; also, the 0–7 and EN inputs are checked with the scope and all appear to be at 0 V. A check with the DMM confirms that power is on. What is the problem, and what should be done to correct it?

Power has not been applied to the circuit; apply power.

The output is shorted to Vcc; replace the IC.

The scope's vertical input is in the AC mode and the common connection for the 0,2,3 and 5 inputs is bad. Set the scope's vertical input mode to DC, and repair the bad solder connection.

Power has not been applied to the circuit; apply power.

The output is shorted to ground; replace the IC.

The circuit in Figure 9-8 is defective; data is not appearing on the output lines. A check with the scope shows data pulses on the serial data line and multiplex control lines, S0–S2; no parity error is indicated. A further check with a logic probe indicates that Vcc and ground appear to be present. What might be wrong with the circuit?

The parity checker is defective.

The parity generator may be bad.

The parity checker is defective, or the parity generator may be bad.

It is suspected that the comparator in the figure given below has a problem. The inputs are activated in the table shown below and the corresponding outputs noted. What is most likely wrong with the circuit? For P0 – P3 = 1 and Q0 – Q3 = 0, P > Q = 1, P = Q = 1, P Q = 0, P = Q = 1, P Q = 0, P = Q = 1, P < Q = 0

Nothing is wrong; the circuit is functioning properly.

The P0–P3 inputs are defective.

One or more of the Q inputs is bad.

The P = Q output is shorted to Vcc.

Nothing is wrong; the circuit is functioning properly.

An eight-line multiplexer must have as inputs ________.

eight data inputs and four select inputs

four data inputs and three select inputs

eight data inputs and two select inputs

eight data inputs and three select inputs

eight data inputs and four select inputs

The diagram given below shows a ________ being used as a(n) ________ and Y = ________.

logic function generator, multiplexer, 1467

multiplexer, logic function generator, ABC + ABC + ABC + ABC

logic function generator, multiplexer, 1467

In HDL, the operation of the DEMUX is exactly described using a ________.

number of conditional signal assignment statements

When an application, such as an encoder, calls for a unique response from a circuit corresponding to a combination of its input variables, the two methods that best serve this purpose are the ________ and the ________.

if then statement, elsif statement

105 + Mcqs in Msi Logic Circuits in Digital Electronics Page 1 McqOptions

1.	The circuit in Figure 9-8 is defective; data is not appearing on the output lines. A check with the scope shows data pulses on the serial data line and multiplex control lines, S0–S2; no parity error is indicated. A further check with a logic probe indicates that and ground appear to be present. What might be wrong with the circuit?
A.	The demultiplexer may be bad.
B.	The parity checker is defective.
C.	The parity generator may be bad.
D.	The parity checker is defective, or the parity generator may be bad.
Answer» B. The parity checker is defective.

Discussion

2.	The outputs of the 74138 octal decoder are enabled when the enable inputs are .
A.	True
B.	False
Answer» B. False

Discussion

3.	The 74139 dual four-line demultiplexer functions as a demultiplexer if data input is on the line.
A.	True
B.	False
Answer» B. False

Discussion

4.	In order to select data input of a 74151 eight-line multiplexer, the select inputs must be:
A.	True
B.	False
Answer» B. False

Discussion

5.	When data input I of a 74148 octal-to-binary encoder is active, the data output is: = 1 = 1 = 0
A.	True
B.	False
Answer» B. False

Discussion

6.	All outputs of the 74138 octal decoder are disabled (HIGH) when the enable inputs are:
A.	True
B.	False
Answer» B. False

Discussion

7.	When data input I of a 74148 octal-to-binary encoder is active, the data output is: = 1 = 0 = 0
A.	True
B.	False
Answer» C.

Discussion

8.	Output 3 of a 74138 octal decoder is selected when it is enabled by a data input of: = 1 = 1 = 0
A.	True
B.	False
Answer» B. False

Discussion

9.	In order to select data input I5 of a 74151 eight-line multiplexer, the select inputs must be ________.
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

10.	When data input I6 of a 74148 octal-to-binary encoder is active, the data output is ________.
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» D. [D].

Discussion

11.	When data input I1 of a 74148 octal-to-binary encoder is active, the data output is: A0 = 0 A1 = 0 A2 = 1
A.	True
B.	False
Answer» C.

Discussion

12.	The outputs of a 7485 four-bit magnitude comparator when the inputs are A = 0110 and B = 1010 are:A < B is 1 A = B is 0 A > B is 1
A.	True
B.	False
Answer» C.

Discussion

13.	Output 6 of a 74138 octal decoder is selected when it is enabled by a data input of:A0 = 1 A1 = 1 A2 = 0
A.	True
B.	False
Answer» C.

Discussion

14.	Output 5 of a 74138 octal decoder is selected when it is enabled by a data input of:
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

15.	For the input values (A0–A3, B0–B3, Data Select = 1) given for the circuit given below, what will be indicated on the displays?
A.	A = 0, B = 5
B.	A = 5, B = 0
C.	A = 6, B = 0
D.	A = 0, B = 6
Answer» E.

Discussion

16.	Refer to the figure given below. The logic function generator being implemented with the multiplexer in this circuit produces a constant LOW on the output. The ABC inputs are checked and appear to be pulsing; also, the 0–7 and EN inputs are checked with the scope and all appear to be at 0 V. A check with the DMM confirms that power is on. What is the problem, and what should be done to correct it?
A.	The output is shorted to Vcc; replace the IC.
B.	The scope's vertical input is in the AC mode and the common connection for the 0,2,3 and 5 inputs is bad. Set the scope's vertical input mode to DC, and repair the bad solder connection.
C.	Power has not been applied to the circuit; apply power.
D.	The output is shorted to ground; replace the IC.
Answer» C. Power has not been applied to the circuit; apply power.

Discussion

17.	The circuit in Figure 9-8 is defective; data is not appearing on the output lines. A check with the scope shows data pulses on the serial data line and multiplex control lines, S0–S2; no parity error is indicated. A further check with a logic probe indicates that Vcc and ground appear to be present. What might be wrong with the circuit?
A.	The demultiplexer may be bad.
B.	The parity checker is defective.
C.	The parity generator may be bad.
D.	The parity checker is defective, or the parity generator may be bad.
Answer» B. The parity checker is defective.

Discussion

18.	It is suspected that the comparator in the figure given below has a problem. The inputs are activated in the table shown below and the corresponding outputs noted. What is most likely wrong with the circuit? For P0 – P3 = 1 and Q0 – Q3 = 0, P > Q = 1, P = Q = 1, P < Q = 0 For P0 – P3 = 0 and Q0 – Q3 = 1, P > Q = 0, P = Q = 1, P < Q = 1 For P0 – P3 = 1 and Q0 – Q3 = 1, P > Q = 0, P = Q = 1, P < Q = 0
A.	The P0–P3 inputs are defective.
B.	One or more of the Q inputs is bad.
C.	The P = Q output is shorted to Vcc.
D.	Nothing is wrong; the circuit is functioning properly.
Answer» D. Nothing is wrong; the circuit is functioning properly.

Discussion

19.	A multiplexer is a device that converts some code into a recognizable number or character.
A.	1
B.
Answer» C.

Discussion

20.	The device that places its input data onto one of several outputs is a ________.
A.	demultiplexer
B.	multiplexer
C.	comparator
D.	counter
Answer» B. multiplexer

Discussion

21.	The select inputs to a multiplexer may also be called address lines.
A.	1
B.
Answer» B.

Discussion

22.	A typical AHDL comparator follows an algorithm described as ________.
A.	FUNCTION constructs
B.	CASE constructs
C.	IF/ELSE constructs
D.	PROCESS constructs
Answer» D. PROCESS constructs

Discussion

23.	The device shown in below is a ________ and for the waveforms shown in the accompanying diagram, the ________ output at point X will be ________ and all others will be ________.
A.	multiplexer, D4, HIGH, LOW
B.	demultiplexer, D3, LOW, HIGH
C.	demultiplexer, D3, HIGH, LOW
D.	decoder, D12, LOW, LOW
Answer» C. demultiplexer, D3, HIGH, LOW

Discussion

24.	An eight-line multiplexer must have as inputs ________.
A.	four data inputs and three select inputs
B.	eight data inputs and two select inputs
C.	eight data inputs and three select inputs
D.	eight data inputs and four select inputs
Answer» D. eight data inputs and four select inputs

Discussion

25.	For the inputs shown in the given figure, the output is ________.
A.	1
B.	0¬†
Answer» C.

Discussion

26.	A demultiplexer takes an input and turns it into a binary number.
A.	1
B.
Answer» C.

Discussion

27.	The 74139 dual four-line demultiplexer functions as a demultiplexer if data input is on the line.
A.	1
B.
Answer» B.

Discussion

28.	A circuit that converts some binary code into a singular active output representing its numerical value is a comparator.
A.	1
B.
Answer» C.

Discussion

29.	The device that is an application of SOP logic is a multiplexer.
A.	1
B.
Answer» B.

Discussion

30.	It is normal for more than one decoder output to be active at the same time.
A.	1
B.
Answer» C.

Discussion

31.	A decimal-to-BCD encoder has ________ data inputs.
A.	two
B.	four
C.	five
D.	ten
Answer» E.

Discussion

32.	The diagram given below shows a ________ being used as a(n) ________ and Y = ________.
A.	multiplier, divider, 2.25
B.	multiplexer, encoder, 7641
C.	multiplexer, logic function generator, ABC + ABC + ABC + ABC
D.	logic function generator, multiplexer, 1467
Answer» D. logic function generator, multiplexer, 1467

Discussion

33.	When outputs a, b, c, d, and g of a 7447 BCD-to-seven-segment code converter are active, the number displayed is 5.
A.	1
B.
Answer» C.

Discussion

34.	Another name for a multiplexer is ________.
A.	encoder
B.	decoder
C.	code converter
D.	data selector
Answer» E.

Discussion

35.	In HDL, a process is usually thought of as a wire connecting two points in a circuit.
A.	1
B.
Answer» C.

Discussion

36.	A demultiplexer is a device that converts some code to a recognizable number or character.
A.	1
B.
Answer» C.

Discussion

37.	A device that determines which of two numbers is greater is a comparator.
A.	1
B.
Answer» B.

Discussion

38.	A 75154 1-of-16 decoder has 16 outputs and decodes an input of ________ bits.
A.	two
B.	three
C.	four
D.	six
Answer» D. six

Discussion

39.	When data input I4 of a 74148 octal-to-binary encoder is active, the data output is: A0 = 1 A1 = 1 A2 = 0
A.	1
B.
Answer» B.

Discussion

40.	In HDL, the operation of the DEMUX is exactly described using a ________.
A.	function
B.	process
C.	variable type
D.	number of conditional signal assignment statements
Answer» E.

Discussion

41.	Basically, a multiplexer changes parallel data inputs to a serial output.
A.	1
B.
Answer» B.

Discussion

42.	A very important attribute of the conditional signal assignment statement is its sequential operation.
A.	1
B.
Answer» B.

Discussion

43.	A 1-of-8 octal decoder has eight outputs and decodes an input of ________ bit(s).
A.	three
B.	two
C.	four
D.	one
Answer» B. two

Discussion

44.	A(n) ________ display controls the reflection of available light.
A.	MOS
B.	LCD
C.	LED
D.	LSC
Answer» C. LED

Discussion

45.	The outputs of the 74138 octal decoder are enabled when the enable inputs are .
A.	1
B.
Answer» B.

Discussion

46.	When an application, such as an encoder, calls for a unique response from a circuit corresponding to a combination of its input variables, the two methods that best serve this purpose are the ________ and the ________.
A.	CASE construct, truth TABLE
B.	if then statement, elsif statement
C.	VARIABLE, PROCESS
D.	FUNCTION, TYPE
Answer» B. if then statement, elsif statement

Discussion

47.	Incandescent 7-segment displays are especially well suited for use in portable battery-operated devices.
A.	1
B.
Answer» C.

Discussion

48.	An octal-to-binary encoder has eight data inputs and encodes an output of ________ bits.
A.	two
B.	three
C.	four
D.	five
Answer» C. four

Discussion

49.	In an AHDL BCD to binary coded converter, multiplication by 10 is performed by ________.
A.	a multiplication operator
B.	shifting bits
C.	a library function
D.	a variable type
Answer» B. shifting bits

Discussion

50.	The binary value of the BCD number 1000 0001 (81) is ________.
A.	0101 0001
B.	0110 0011
C.	0100 0001
D.	1000 0000
Answer» B. 0110 0011

Discussion

Explore topic-wise MCQs in Digital Electronics.

The outputs of the 74138 octal decoder are enabled when the enable inputs are .

The 74139 dual four-line demultiplexer functions as a demultiplexer if data input is on the line.

In order to select data input of a 74151 eight-line multiplexer, the select inputs must be:

When data input I of a 74148 octal-to-binary encoder is active, the data output is: = 1 = 1 = 0

All outputs of the 74138 octal decoder are disabled (HIGH) when the enable inputs are:

When data input I of a 74148 octal-to-binary encoder is active, the data output is: = 1 = 0 = 0

Output 3 of a 74138 octal decoder is selected when it is enabled by a data input of: = 1 = 1 = 0

In order to select data input I5 of a 74151 eight-line multiplexer, the select inputs must be ________.

When data input I6 of a 74148 octal-to-binary encoder is active, the data output is ________.

When data input I1 of a 74148 octal-to-binary encoder is active, the data output is: A0 = 0 A1 = 0 A2 = 1

The outputs of a 7485 four-bit magnitude comparator when the inputs are A = 0110 and B = 1010 are:A < B is 1 A = B is 0 A > B is 1

Output 6 of a 74138 octal decoder is selected when it is enabled by a data input of:A0 = 1 A1 = 1 A2 = 0

Output 5 of a 74138 octal decoder is selected when it is enabled by a data input of:

For the input values (A0–A3, B0–B3, Data Select = 1) given for the circuit given below, what will be indicated on the displays?

A multiplexer is a device that converts some code into a recognizable number or character.

The device that places its input data onto one of several outputs is a ________.

The select inputs to a multiplexer may also be called address lines.

A typical AHDL comparator follows an algorithm described as ________.

The device shown in below is a ________ and for the waveforms shown in the accompanying diagram, the ________ output at point X will be ________ and all others will be ________.

An eight-line multiplexer must have as inputs ________.

For the inputs shown in the given figure, the output is ________.

A demultiplexer takes an input and turns it into a binary number.

The 74139 dual four-line demultiplexer functions as a demultiplexer if data input is on the line.

A circuit that converts some binary code into a singular active output representing its numerical value is a comparator.

The device that is an application of SOP logic is a multiplexer.

It is normal for more than one decoder output to be active at the same time.

A decimal-to-BCD encoder has ________ data inputs.

The diagram given below shows a ________ being used as a(n) ________ and Y = ________.

When outputs a, b, c, d, and g of a 7447 BCD-to-seven-segment code converter are active, the number displayed is 5.

Another name for a multiplexer is ________.

In HDL, a process is usually thought of as a wire connecting two points in a circuit.

A demultiplexer is a device that converts some code to a recognizable number or character.

A device that determines which of two numbers is greater is a comparator.

A 75154 1-of-16 decoder has 16 outputs and decodes an input of ________ bits.

When data input I4 of a 74148 octal-to-binary encoder is active, the data output is: A0 = 1 A1 = 1 A2 = 0

In HDL, the operation of the DEMUX is exactly described using a ________.

Basically, a multiplexer changes parallel data inputs to a serial output.

A very important attribute of the conditional signal assignment statement is its sequential operation.

A 1-of-8 octal decoder has eight outputs and decodes an input of ________ bit(s).

A(n) ________ display controls the reflection of available light.

The outputs of the 74138 octal decoder are enabled when the enable inputs are .

When an application, such as an encoder, calls for a unique response from a circuit corresponding to a combination of its input variables, the two methods that best serve this purpose are the ________ and the ________.

Incandescent 7-segment displays are especially well suited for use in portable battery-operated devices.

An octal-to-binary encoder has eight data inputs and encodes an output of ________ bits.

In an AHDL BCD to binary coded converter, multiplication by 10 is performed by ________.

The binary value of the BCD number 1000 0001 (81) is ________.

The device shown in below is a and for the waveforms shown in the accompanying diagram, the output at point X will be and all others will be .

The diagram given below shows a being used as a(n) and Y = .

When an application, such as an encoder, calls for a unique response from a circuit corresponding to a combination of its input variables, the two methods that best serve this purpose are the and the .