3.6.4.1 Logic Gates. Flashcards

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1
Q

Define a logic gate.

A

Devices which apply logical operations to one or more Boolean inputs in order to produce a single output.

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2
Q

What name is given to a collection of connected logic gates?

A

Logic circuit.

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3
Q

What is the purpose of a logic circuit?

A

To perform more complex operations like binary addition.

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4
Q

How many outputs do logic gates have?

A

One.

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5
Q

Define the purpose of a truth table.

A

To show every possible combination of inputs and the corresponding output for a logic gate or logical circuit.

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6
Q

How are the inputs on a truth table labelled?

A

Alphabetically, starting with A with the output usually labelled as Q.

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7
Q

Outline a NOT gate.

A

One input and one output.
Output is the opposite of the input.
Truth table has two columns, labelled A and Q.

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8
Q

Outline the Boolean algebra equation for NOT.

A

_

A = A

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9
Q

Outline an AND gate.

A

Two inputs, out output.
Output is the product of the inputs.
Only outputs true (1) when or one, or both, inputs are true, otherwise it outputs false.

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10
Q

Outline the Boolean equation for AND.

A

Q = A x B

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11
Q

Outline an OR gate.

A

Two inputs, out output.
Input + input = output.
Only outputs false (0) when both inputs are false, otherwise it outputs true.

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12
Q

Outline the Boolean equation for OR.

A

Q = A + B

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13
Q

Outline a XOR gate.

A

Aka exclusively or.
Outputs true when strictly one of its inputs are true.
Outputs false when both inputs are true.
Used in the vernam cipher.

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14
Q

Outline the Boolean equation for XOR.

A

Q = A ⊕ B

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15
Q

Outline a NAND gate.

A

Aka not and.
Combination of the NOT and AND gates.
Only outputs false (1) when or one, or both, inputs are false, otherwise it outputs
true.

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16
Q

Outline the Boolean equation for NAND.

A

____

Q = A × B

17
Q

Outline a NOR gate.

A

Aka not or.
Combination of NOT and OR.
Both inputs must be false to elicit a positive output.

18
Q

outline the Boolean equation for NOR.

A

____

Q = A + B

19
Q

Outline a full adder.

A

Three inputs and two outputs, enabling it to input two Boolean values and a carry bit from the previous, less significant operation.

20
Q

In a full adder, outline what A, B and Cin stand for.

A

Carry in.

21
Q

In a full adder, outline what S stands for.

A

Sum.

22
Q

In a full adder, outline what Cout stands for.

A

Carry out.

23
Q

Define an Edge-triggered D-type flip-flop.

A

A logic circuit which can be used as a memory unit for storing the value of a single bit.

24
Q

How many inputs does an Edge-triggered D-type flip-flop have?

A

Two, one for data and one for clock signal.

25
Q

How many outputs does an Edge-triggered D-type flip-flop have?

A

One, which always holds the value of a stored bit.

26
Q

How is clock signal generated in an How many inputs does an Edge-triggered D-type flip-flop?

A

Generated by the computer and alternates between 0 and 1 at a set frequency.
The value of the stored bit is set to the value of the data input with each change
of the clock signal

27
Q

What other purpose does clock signal have?

A

The clock signal can also be used to synchronise numerous flip-flops when they form part
of a larger system such as a shift register.