Question 1

A positive edge- triggered J- K flip- flop is used to produce a two- phase clock. However, when the circuit is operated it produces erratic results. Close examination with an oscilloscope reveals the presence of glitches. What might be the source of these glitches?

Accepted Answer

A)   A race condition exists between the J and K inputs.
B)   The PRESET and CLEAR terminals may have been left floating.
C)   A race condition exists between the Q and Q outputs to the AND gate.
D)   A race condition exists between the CLOCK and the outputs of the flip- flop feeding the AND gate.E) B) and D)
F) A) and D)

Question 2

The symbol for an edge- triggered flip- flop has a triangle on its clock input.

Accepted Answer

A) True 
 B)False  True

Question 3

What symbol is used to identify edge- triggered flip- flops?

Accepted Answer

A)   An inverted "L" on the output
B)   The letter E on the Enable input
C)   A triangle on the Clock input
D)   A bubble on the Clock inputE) A) and D)
F) C) and D)

Question 4

A J- K flip- flop is being used as a divide- by- 2 circuit when _________.

Accepted Answer

A)   the J and K inputs are tied to Vcc
B)   the reset is tied to the clock
C)   the J and K inputs are tied to ground
D)   all the inputs are connected to the presetE) B) and C)
F) All of the above

Question 5

When both inputs of a J- K pulse- triggered FF are high, and the clock cycles, the output wil_________

Accepted Answer

A)   remain unchanged
B)   be invalid
C)   toggle
D)   not changeE) None of the above
F) C) and D)

Question 6

The asynchronous inputs to a flip- flop are normally labeled_____and________ , and are normally active_______inputs.

Accepted Answer

A)   START, STOP, low
B)   SET, RESET, high
C)   PRE, CLR, low
D)   ON, OFF, highE) B) and C)
F) A) and B)

Question 7

The J- K flip- flop toggles when both inputs are high during the transition of the clock signal.

Accepted Answer

A) True 
 B)False

Question 8

All multivibrators require feedback.

Accepted Answer

A) True 
 B)False

Question 9

A one- shot is a multivibrator that must be triggered to produce each output pulse.

Accepted Answer

A) True 
 B)False

Question 10

How is the invalid input state problem associated with the S- R flip- flop overcome?

Accepted Answer

A)   The R terminal is eliminated.
B)   A single input terminal is used (
D)  .
C)   The R input is fed through an inverter.
D)   Both B and C are correct.E) B) and D)
F) A) and D)

Question 11

The ON time of a 555 monostable multivibrator is determined by tw = 1.1RC.

Accepted Answer

A) True 
 B)False

Question 12

An astable multivibrator is a circuit that _________.

Accepted Answer

A)   has two stable states
B)   has one stable state
C)   produces a continuous output signal
D)   Both B and C are correct.E) A) and B)
F) B) and C)

Question 13

The L in 74L71 stands for _______.

Accepted Answer

A)   low power
B)   the type of package
C)   lock- out flip- flop
D)   low frequencyE) C) and D)
F) A) and D)

Question 14

A push- button switch is used to input data to a register. The output of the register is erratic. Which of the following could be the cause of the problem?

Accepted Answer

A)   The power supply is probably noisy.
B)   The socket contacts on the register IC are corroded.
C)   The switch contacts are bouncing.
D)   The register IC is intermittent and failure is imminent.E) None of the above
F) All of the above

Question 15

All multivibrators are level triggered.

Accepted Answer

A) True 
 B)False

Question 16

What primary advantage does the J- K flip- flop have over the S- R flip- flop?

Accepted Answer

A)   The J- K flip- flop does not have propagation delay problems.
B)   The J- K flip- flop does not have an invalid input state.
C)   The J- K flip- flop is much faster.
D)   The J- K flip- flop only needs one output.E) A) and B)
F) A) and C)

Question 17

Which of the following is correct for a gated D latch?

Accepted Answer

A)   The output toggles if one of the inputs is held high.
B)   Only one of the inputs can be high at a time.
C)   Q output follows the input D when the ENABLE is high.
D)   The output complement follows the input when enabled.E) C) and D)
F) B) and D) C

Question 18

A diode can be added to the discharge path for a 555 astable multivibrator to obtain duty cycles that are less than 50%.

Accepted Answer

A) True 
 B)False

Question 19

These waveforms are applied to a gated D latch, which is initially RESET. Which of the areas identified on the Q waveform is incorrect?

Accepted Answer

A)   Area a
B)   Area b
C)   Area c
D)   Area dE) None of the above
F) A) and D) C

Question 20

An active- HIGH input S- R latch has a 1 on the S input and a 0 on the R input. What state is the latch in?

Accepted Answer

A)   Q = 0,  = 1
B)   Q = 1,  = 0
C)   Q = 1,  = 1
D)   Q = 0,  = 0E) C) and D)
F) A) and B)

Exam 7: Latches, Flip-Flops, and Timers

A positive edge- triggered J- K flip- flop is used to produce a two- phase clock. However, when the circuit is operated it produces erratic results. Close examination with an oscilloscope reveals the presence of glitches. What might be the source of these glitches?

Correct AnswerverifiedShow Answer

The symbol for an edge- triggered flip- flop has a triangle on its clock input.

Correct AnswerverifiedTrue

What symbol is used to identify edge- triggered flip- flops?

Correct AnswerverifiedShow Answer

A J- K flip- flop is being used as a divide- by- 2 circuit when _________.

Correct AnswerverifiedShow Answer

When both inputs of a J- K pulse- triggered FF are high, and the clock cycles, the output wil_________

Correct AnswerverifiedShow Answer

The asynchronous inputs to a flip- flop are normally labeled_____and________ , and are normally active_______inputs.

Correct AnswerverifiedShow Answer

The J- K flip- flop toggles when both inputs are high during the transition of the clock signal.

Correct AnswerverifiedShow Answer

All multivibrators require feedback.

Correct AnswerverifiedShow Answer

A one- shot is a multivibrator that must be triggered to produce each output pulse.

Correct AnswerverifiedShow Answer

How is the invalid input state problem associated with the S- R flip- flop overcome?

Correct AnswerverifiedShow Answer

The ON time of a 555 monostable multivibrator is determined by tw = 1.1RC.

Correct AnswerverifiedShow Answer

An astable multivibrator is a circuit that _________.

Correct AnswerverifiedShow Answer

The L in 74L71 stands for _______.

Correct AnswerverifiedShow Answer

A push- button switch is used to input data to a register. The output of the register is erratic. Which of the following could be the cause of the problem?

Correct AnswerverifiedShow Answer

All multivibrators are level triggered.

Correct AnswerverifiedShow Answer

What primary advantage does the J- K flip- flop have over the S- R flip- flop?

Correct AnswerverifiedShow Answer

Which of the following is correct for a gated D latch?

Correct AnswerverifiedC

A diode can be added to the discharge path for a 555 astable multivibrator to obtain duty cycles that are less than 50%.

Correct AnswerverifiedShow Answer

These waveforms are applied to a gated D latch, which is initially RESET. Which of the areas identified on the Q waveform is incorrect?

Correct AnswerverifiedC

An active- HIGH input S- R latch has a 1 on the S input and a 0 on the R input. What state is the latch in?

Correct AnswerverifiedShow Answer

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True

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The asynchronous inputs to a flip- flop are normally labeled_and , and are normally active___inputs.

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The ON time of a 555 monostable multivibrator is determined by t_w= 1.1RC.

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C

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C

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