HW 8 - Functions of Logic

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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Name: _____________________________ Date:___________

MULTIPLE CHOICE. Circle or underline the one alternative that best completes the statement or

answers the question. USE A PENCIL!

1) The carry output of a half-adder circuit can be expressed as ________.

A) = AB B) = A + B C) = A ⊕ B D) None of these

2) The expression A ⊕ B represents ________.

A) The summing output of a half-adder B) The carry output of a half-adder

C) The summing output of a full-adder D) The carry output of a full-adder

Refer to the figure below to answer the following question(s).

Figure 8-1

3) The symbol in Figure 8-1 represents a(n) ________.

A) AND function B) Half-adder C) Full-adder D) PLD

4) Refer to the symbol in Figure 8-1. When A = 0 and B = 1, ________.

A) Σ = 0, Cout = 0 B) Σ = 0, Cout = 1 C) Σ = 1, Cout = 0 D) Σ = 1, Cout = 1

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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5) Referring to the symbol in Figure 8-1, which set of outputs is very unlikely to ever occur?

A) Σ = 0, Cout = 0 B) Σ = 0, Cout = 1 C) Σ = 1, Cout = 0 D) Σ = 1, Cout = 1

6) What is the major difference between half-adders and full-adders?

A) Nothing basically; full-adders are made up of two half-adders.

B) Full-adders can handle double digit numbers.

C) Full-adders have a carry input capability.

D) Half-adders can only handle single digit numbers.

7) Which of the following is correct for full-adders?

A) Full-adders have the capability of directly adding decimal numbers.

B) Full-adders are used to make half-adders.

C) Full-adders are limited to two inputs, since there are only two binary digits.

D) In a parallel full-adder, the first stage may be a half-adder.

8) The expression (A ⊕ B) ⊕ Cin represents ________.

A) The summing output of a half-adder B) The carry output of a half-adder

C) The summing output of a full-adder D) The carry output of a full-adder

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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9) The expression AB + (A ⊕ B) ⊕ Cin represents ________.

A) The summing output of a half-adder B) The carry output of a half-adder

C) The summing output of a full-adder D) The carry output of a full-adder

Refer to the figure below to answer the following question(s).

Figure 8-2

10) The symbol in Figure 8-2 represents a(n) ________.

A) And function B) Half-adder C) Full-adder D) PLD

11) Refer to the symbol in Figure 8-2. What are the outputs when A = 1, B = 1, Cin = 0?

A) Σ = 0, Cout = 0 B) Σ = 1, Cout = 0 C) Σ = 0, Cout = 1 D) Σ =1, Cout = 1

12) Refer to the symbol in Figure 8-2. What are the output when A = 1, B = 1, Cin = 1?

A) Σ = 0, Cout = 0 B) Σ = 1, Cout = 0 C) Σ = 0, Cout = 1 D) Σ =1, Cout = 1

13) What is one disadvantage of the ripple-carry adder?

A) The interconnections are more complex. B) More stages are required to a full-adder.

C) It is slow, due to propagation time. D) All of the above are correct.

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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14) What distinguishes the look-ahead-carry adder?

A) It is slower than the ripple-carry adder.

B) It is easier to implement logically than a full-adder.

C) It is faster than a ripple-carry adder.

D) It requires advance knowledge of the final answer.

15) Which of the following is true for IC comparator circuits?

A) Comparators can compare only 2 bits at a time.

B) Comparators can compare only two values at a time.

C) All comparators have outputs for indicating A<B, A>B, and A=B.

D) None of these.

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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Figure 8-3

16) The circuit in Figure 8-3 can be used as a(n) ________.

A) 8-bit comparator B) 4-bit comparator

C) 4-bit half-adder D) Dual 4-line multiplexer

17) Which statement below best describes the function of a decoder?

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.

18) The function 𝐴 ∙ 𝐵 ∙ 𝐶 ∙ 𝐷 can be decoded with ________.

A) One 4-input AND gate and one inverter B) One 4-input AND gate and two inverters

C) Two 2-input OR gates and one inverter D) Two 2-input OR gates and two inverters

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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Refer to the figure below to answer the following question(s).

Figure 8-4

19) The output of the decoder in Figure 8-4 will be 1 only when ________.

A) A = 0, B = 0, C= 0, D = 0 B) A = 1, B = 1, C= 1, D = 1

C) A = 0, B = 1, C= 0, D = 1 D) A = 1, B = 0, C= 1, D = 0

20) The Boolean expression for the decoder output X in Figure 8-4 is ________.

A) 𝐴 ∙ 𝐵 ∙ 𝐶 ∙ 𝐷 B) 𝐴 ∙ 𝐵 ∙ 𝐶 ∙ 𝐷 C) 𝐴 ∙ 𝐵 ∙ 𝐶 ∙ 𝐷 D) None of these

21)

A 1-of-16 decoder IC has ________ data input connection(s).

A) 1 B) 4 C) 8 D) 16

22)

A BCD-to-decimal decoder has ________ data input lines and ________ data output lines.

A) 4; 10 B) 7; 9 C) 1; 10 D) 10; 10

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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Figure 8-5

23) This circuit in Figure 8-5 is most likely a ________.

A) full-adder B) comparator C) multiplexer D) demultiplexer

24) What is another name used for a multiplexer?

A) demultiplexer B) data selector C) attenuator D) multiplier

25) A multiplexer with four select, or address, lines can select one of ________ inputs.

A) 3 B) 7 C) 15 D) 16

Figure 8-6

26) The circuit in Figure 8-6 is most likely a ________.

A) full-adder B) comparator C) multiplexer D) demultiplexer

ELN-133 Chapter 8 Homework Spring 2015 Functions of Logic

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27) A breadboarded circuit design using a 7447 TTL BCD-to-seven segment decoder has a problem

wherein the output of the 5 digits of the display flickers erratically. 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?

A) The decoder is thermally intermittent; replace it.

B) There is probably a bad connection on the wire wrap proto board; recheck the wiring.

C) Counter Ripple is probably the culprit; strobe the decoder.

D) Either A or B is correct.