Chapter 2: Combinational Circuits

Question 1

What are gates?

Answer 1

combinational logic elements which depend only on the current inputs

Question 2

What are flip-flops?

Answer 2

are sequential logic elements which depend on both the current inputs and previous inputs

Question 3

What are sequential elements a form of?

Answer 3

Memory since they can store values

Question 4

A logical value can be either

Answer 4

0 or 1

Question 5

When does an AND gate return 1

Answer 5

When all inputs are 1

Question 6

When does an AND gate return 0

Answer 6

When any of the inputs are 0

Question 7

What is an AND gate denoted by?

Answer 7

a . (dot)

Question 8

What is an OR gate denoted by?

Answer 8

A + symbol

Question 9

When does an OR gate return 1?

Answer 9

When any of the inputs are 1

Question 10

When does an OR gate return 0?

Answer 10

When all of the inputs are 0

Question 11

What is a NOT gate and what is it represented by?

Answer 11

gate inverts the current value, indicated by the overbar

Question 12

What is a NAND gate?

Answer 12

An AND gate followed by an inverter

Question 13

When does a NAND gate return 1?

Answer 13

When there is any mixture of 0’s and 1’s as input

Question 14

When does a NAND gate return 0?

Answer 14

When all inputs are 1

Question 15

What is a NOR gate?

Answer 15

An OR gate followed by an inverter

Question 16

When does a NOR gate return 1?

Answer 16

When all inputs are 0

Question 17

When does a NOR gate return 0?

Answer 17

When there is any amount of 1s as input

Question 18

What is a XOR gate?

Answer 18

An exclusive OR gate that returns 1 only when an odd number of the inputs are 1

Question 19

What is the boolean expression of a single-bit full adder SUM?

Answer 19

Sum = (A XOR B) XOR Carry in

Question 20

What is the boolean expression of a single-bit full adder CARRY OUT?

Answer 20

(A AND B) OR (A XOR B) OR Carry in

Question 21

What is a decoder?

Answer 21

A combinational logic circuit that converts binary information from the n-bits coded input to a maximum of 2^n unique outputs.

Question 22

What is a multiplexer?

Answer 22

A multiplexer is combinational logic circuit that has up to 2^n binary input lines and n select lines, where the n select-lines are used to forward one of the input values to the output line