Digital Electronics- MSI Logic Circuits
Digital Electronics- MSI Logic Circuits
11. Why are control inputs included in an HDL magnitude comparator?
- For cascading the chips
- For control signal input
- For signal control
- For internal interconnections
12. What VHDL techniques are used to describe a priority encoder?
- Integer outputs and priority coding
- Signal outputs and priority coding
- Tristate outputs and priority coding
- Variables and priority coding
13. What is an important attribute of the conditional signal assignment statement?
- Its tristate outputs
- Its sequential evaluation
- Its use of library components
- Its fast activation times
14. There appears to be a problem with a 7-segment display on a DMM sometimes skipping certain numbers. How would you test the display?
- Remove the display unit and check each segment diode with an ohmmeter. Replace the defective segments.
- 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.
- 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.
- 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.
15. What is the purpose of a decoder's inputs?
- To allow the decoder to respond to the inputs to activate the correct output gate.
- To disable the decoder outputs so that all outputs will be inactive.
- To disable the inputs and activate all outputs.
- To allow the decoder to respond to the inputs to activate the correct output gate, and to disable the inputs and activate all outputs.
16. The circuit in Figure 9-8 is defective; data is not appearing on the output lines. A check with the scope shows data pulses on the serial data line and multiplex control lines, S0–S2; no parity error is indicated. A further check with a logic probe indicates that Vcc and ground appear to be present. What might be wrong with the circuit?
- The demultiplexer may be bad.
- The parity checker is defective.
- The parity generator may be bad.
- The parity checker is defective, or the parity generator may be bad.
17. A device that selects one of several inputs to be placed on the output is a multiplexer.
- TRUE
- FALSE
18. A device that selects one of several inputs to be placed on the output is a multiplexer.
- TRUE
- FALSE
19. A VARIABLE can be thought of as a piece of scrap paper used to write down some numbers that can be used later.
- TRUE
- FALSE
20. When data input I1 of a 74148 octal-to-binary encoder is active, the data output is:
A0 = 0
A1 = 0
A2 = 1
A0 = 0
A1 = 0
A2 = 1
- TRUE
- FALSE