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  • Question

  • There appears to be a problem with a 7-segment display on a DMM sometimes skipping certain numbers. How would you test the display?


  • Options
  • A. Remove the display unit and check each segment diode with an ohmmeter. Replace the defective segments.
  • B. Apply 5 V directly to each segment of the display and check for individual segment operation. Replace any segment that has voltage applied but is not lit.
  • C. Tie all of the segments together and connect to Vcc; the number 8 should appear on the display. Now check the display supply voltage to determine if the display is receiving the correct voltage.
  • D. Connect the DMM to a variable supply and very slowly increase the voltage, while observing for missing digits. Then check the segment voltage to determine whether the display or the display driver is bad.

  • Correct Answer
  • Connect the DMM to a variable supply and very slowly increase the voltage, while observing for missing digits. Then check the segment voltage to determine whether the display or the display driver is bad. 

    • MSI Logic Circuits problems

    Search Results

    • 1. A 16-input multiplexer is to be used to perform parallel-to-serial data conversion. Which of the following counters would be required to provide the data select inputs?

    • Options
    • A. MOD 8
    • B. MOD 16
    • C. MOD 4
    • D. MOD 2
      • Discuss
    • 2. Determine the correct output for the multiplexer and its associated timing diagram given below.


    • Options
    • A. Ya
    • B. Yb
    • C. Yc
    • D. Yd
      • Discuss
    • 3. Which statement below best describes the function of a decoder?

    • Options
    • A. A decoder will convert a decimal number into the proper binary equivalent.
    • B. A decoder will convert a binary number into a specific output representing a particular character or digit.
    • C. Decoders are used to prevent improper operation of digital systems.
    • D. Decoders are special ICs that are used to make it possible for one brand of computer to talk to another.
      • Discuss
    • 4. A breadboard-circuit design using a BCD-to-decimal decoder has a problem wherein the operation of the system is erratic. The technician uses his scope to examine the waveforms throughout the system and doesn't really see any problems. While he's scratching his head, what helpful advice can you offer him as to what might be wrong and what to do to correct the problem?

    • Options
    • A. The decoder is thermally intermittent; replace it.
    • B. There is probably a bad connection on the wire wrap protoboard; recheck the wiring.
    • C. Glitches are probably the culprit; strobe the decoder.
    • D. The decoder is thermally intermittent and must be replaced; or there is probably a bad connection on the wire wrap protoboard, and the wiring must be rechecked.
      • Discuss
    • 5. What must be done in the given figure in order to use two 7485 4-bit comparators to compare two 8-bit numbers?


    • Options
    • A. The P < Q, P = Q, and P > Q outputs of COMP A must be connected to the same outputs of COMP B.
    • B. The P < Q, P = Q, and P > Q outputs of COMP A must be connected to the <, =, and > inputs of COMP B.
    • C. The = input of COMP A must be connected to Vcc, and the < and > inputs must be connected to ground.
    • D. The P < Q, P = Q, and P > Q outputs of COMP A must be connected to the <, =, and > inputs of COMP B, the = input of COMP A must be connected to Vcc, and the < and > inputs must be connected to ground.
      • Discuss
    • 6. How is the number one (1) indicated on the outputs of a 7447 BCD-to-seven-segment code converter?

    • Options
    • A. Segment a is active.
    • B. Segment b is active.
    • C. Segments a and b are active.
    • D. Segments b and c are active.
      • Discuss
    • 7. What is the HDL key issue in the design of the MUX and DEMUX?

    • Options
    • A. Having the MUX and DEMUX part of the library
    • B. Using the case statement in the process
    • C. Describing the functions
    • D. Assigning signals under certain conditions
      • Discuss
    • 8. One can safely state that the output lines for a demultiplexer are under the direct control of the:

    • Options
    • A. input data select lines.
    • B. the internal AND gates.
    • C. the internal OR gate.
    • D. Input data line.
      • Discuss
    • 9. The BCD/DEC decoder shown in figure (a) is examined with a logic analyzer and the results are shown in the waveforms in figure (b). What, if anything, is wrong with the circuit?


    • Options
    • A. The "2" output is shorted to Vcc.
    • B. The A1 input is internally open.
    • C. The A1 input node is internally stuck LOW.
    • D. Nothing is wrong with the circuit.
      • Discuss
    • 10. Why are control inputs included in an HDL magnitude comparator?

    • Options
    • A. For cascading the chips
    • B. For control signal input
    • C. For signal control
    • D. For internal interconnections
      • Discuss

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