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Home ‣ Digital Electronics ‣ Digital System Projects Using HDL See What Others Are Saying!
  • Question

  • A frequency counter is a circuit that can measure and display the frequency of a signal.


  • Options
  • A. True
  • B. False

  • Correct Answer
  • True 

    • More questions

    • 1. 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


    • Options
    • 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.
      • Discuss
    • 2. Refer to the display multiplexer given below. The MSD display is blank, while the LSD seems to be OK. The input and output lines to the 74157 and 7449 are checked with a scope and can be seen changing levels. The A input on the 74139 also changes; however, the 0 output on the 74139 is always LOW and the 1 output is always HIGH. The B and EN inputs on the 74139 are always LOW. What could cause the problem and what should be done to correct it?


    • Options
    • A. The 74139 is defective; replace it.
    • B. The EN pin on the 74139 could have a bad connection; check the connection.
    • C. The 74139 is defective and must be replaced; or the EN pin on the 74139 could have a bad connection, which should be checked.
    • D. The MSD display is bad; replace it.
      • Discuss
    • 3. The circuit given below fails to produce data output. The individual flip-flops are checked with a logic probe and pulser, and each checks OK. What could be causing the problem?


    • Options
    • A. The data output line may be grounded.
    • B. One of the clock input lines may be open.
    • C. One of the interconnect lines between two stages may have a solder bridge to ground.
    • D. One of the flip-flops may have a solder bridge between its input and Vcc.
      • Discuss
    • 4. When is LOW, the data are shifted one bit per clock pulse.

    • Options
    • A. True
    • B. False
      • Discuss
    • 5. The output of a NAND gate is LOW if ________.

    • Options
    • A. all inputs are LOW
    • B. all inputs are HIGH
    • C. any input is LOW
    • D. any input is HIGH
      • Discuss
    • 6. A port can be ________.

    • Options
    • A. strictly for input
    • B. strictly for output
    • C. bidirectional
    • D. all of the above
      • Discuss
    • 7. A positive edge-triggered flip-flop will accept inputs only when the clock ________.

    • Options
    • A. is LOW
    • B. changes from HIGH to LOW
    • C. is HIGH
    • D. changes from LOW to HIGH
      • Discuss
    • 8. The high input impedance of MOSFETs:

    • Options
    • A. allows faster switching
    • B. reduces input current and power dissipation
    • C. prevents dense packing
    • D. creates low-noise reactions
      • Discuss
    • 9. Which of the following is an example of a counter with a truncated modulus?

    • Options
    • A. 8
    • B. 13
    • C. 16
    • D. 32
      • Discuss
    • 10. Bidirectional means having two states.

    • Options
    • A. True
    • B. False
      • Discuss

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