msi-logic-circuits digital-electronics question and answers -Page first

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Home Aptitude

1. Multiplexing of digital signals is usually required when:
Options
A. moving data internally within a microprocessor.
B. moving data between memory and storage registers in a microprocessor.
C. moving data over long distance transmission lines.
D. moving data internally within a microprocessor or between memory and storage registers.

2. 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 V_cc, 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 V_cc, and the < and > inputs must be connected to ground.

3. 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.

4. 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.

6. 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

7. 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 V_cc; 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.

8. 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.

10. 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.

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