Flips-Flops Questions and Answers

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Q51
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 a scope reveals the presence of glitches. What causes the glitches, and how might the problem be corrected?
  • A The PRESET and CLEAR terminals may have been left floating; they should be properly terminated if not being used.
  • B The problem is caused by a race condition between the J and K inputs; an inverter should be inserted in one of the terminals to correct the problem.
  • C A race condition exists between the Q and Q outputs to the AND gate; the AND gate should be replaced with a NAND gate.
  • D A race condition exists between the clock and the outputs of the flip-flop feeding the AND gate; replace the flip-flop with a negative edge-triggered J-K Flip-Flop. Answer & Explanation
Answer: Option D
Q52
Asynchronous inputs will cause the flip-flop to respond immediately with regard to the clock input.
  • A TRUE
  • B FALSE
Answer: Option B
Q53
Which is not a real advantage of HDL?
  • A Using higher levels of abstraction
  • B Tailoring components to exactly fit the needs of the project
  • C The use of graphical tools
  • D Using higher levels of abstraction and tailoring components to exactly fit the needs of the project
Answer: Option C
Q54
Two J-K flip-flops with their J-K inputs tied HIGH are cascaded to be used as counters. After four input clock pulses, the binary count is ________.
  • A 00
  • B 11
  • C 01
  • D 10
Answer: Option A
Q55
Latches constructed with NOR and NAND gates tend to remain in the latched condition due to which configuration feature?
  • A cross coupling
  • B gate impedance
  • C low input voltages
  • D asynchronous operation
Answer: Option A
Q56
In VHDL, how is each instance of a component addressed?
  • A A name followed by a colon and the name of the library primitive
  • B A name followed by a semicolon and the component type
  • C A name followed by the library being used
  • D A name followed by the component library number
Answer: Option A
Q57
The output of a gated S-R flip-flop changes only if the:
  • A flip-flop is set
  • B control input data has changed
  • C flip-flop is reset
  • D input data has no change
Answer: Option B
Q58
In VHDL, in which declaration section is a COMPONENT declared?
  • A Architecture
  • B Library
  • C Entity
  • D Port map
Answer: Option A
Q59
If both inputs of an S-R flip-flop are low, what will happen when the clock goes HIGH?
  • A An invalid state will exist.
  • B No change will occur in the output.
  • C The output will toggle.
  • D The output will reset.
Answer: Option B
Q60
A push-button switch is used to input data to a register. The output of the register is erratic. What could be causing the problem?
  • A The power supply is probably noisy.
  • B The switch contacts are bouncing.
  • C The socket contacts on the register IC are corroded.
  • D The register IC is intermittent and failure is imminent.
Answer: Option B

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