MSI Logic Circuits Questions

• Multiplexing of digital signals is usually required when:
• What must be done in the given figure in order to use two 7485 4-bit comparators to compare two 8-bit numbers?
• 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?
• Which statement below best describes the function of a decoder?
• Determine the correct output for the multiplexer and its associated timing diagram given below.
• 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?
• There appears to be a problem with a 7-segment display on a DMM sometimes skipping certain numbers. How would you test the display?
• How is the number one (1) indicated on the outputs of a 7447 BCD-to-seven-segment code converter?
• What is the HDL key issue in the design of the MUX and DEMUX?
• One can safely state that the output lines for a demultiplexer are under the direct control of the:
• 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?
• Why are control inputs included in an HDL magnitude comparator?
• The data transmission system shown in below has a problem; the parity error output is always high. A logic analyzer is used to examine the system and shows that the DATA IN on the left matches the DATA OUT on right. What might be causing the problem?
• What are the outputs of a 7485 four-bit magnitude comparator when the inputs are A = 1001 and B = 1010?
• Refer to the figure given below. The logic function generator being implemented with the multiplexer in this circuit produces a constant LOW on the output. The ABC inputs are checked and appear to be pulsing; also, the 0–7 and EN inputs are checked with the scope and all appear to be at 0 V. A check with the DMM confirms that power is on. What is the problem, and what should be done to correct it?
• Which statement best describes the given figure, and what is the function of the terminal labeled EN?
• What is the purpose of a decoder's inputs?
• Referring to the figure given below, what output code will appear on the output (A3,A2,A1,A0) when the 5 key is pressed?
• 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
• Refer to the keyboard encoder in figure (a). Sometimes when the 5 key is pressed, the system attached to the keypad does not respond. The 5 input on the 74147 is monitored with a digital storage scope while repeatedly pressing the 5 key, and the waveform in figure (b) is obtained; the P above the trace indicates the points at which the technician pressed the key. What is most likely wrong with the circuit?