e) Flip Flops and Adders

What are the 3 circuits in the specification?

Flip flops, half adders and full adders.

Define flip flop

A type of logic circuit which can store the value of one bit.

How many inputs does a flip flop have?

Two - a control signal and a clock input.

Define clock

A regular pulse generated by the CPU which is used to coordinate the computer’s components.

What are the two clock pulses?

Rising edge and falling edge.

Define rising edge

The start of a clock cycle.

Define falling edge

Back half of a clock cycle.

When can the output for a flip flop change?

At the start of a clock tick.

What gates does a D-Type Flip Flop include?

4 NAND gates and a NOT gate.

What can flip flops be combined into?

Registers.

Define adder

A logic circuit which adds together the number of inputs which are true.

What two adder circuits are there?

Half and full.

How many inputs does a half adder have?

Two inputs.

How many outputs does a half adder have?

Sum and carry.

What logic gates form a half adder?

AND and XOR.

What happens when both inputs are true for a half adder?

Carry is true.

How many inputs does a full adder have?

3

Why does a full adder have an additional input?

It allows for a carry in to be represented.

What is a full adder logic circuit formed from?

Two XOR gates, two AND gates and an OR gate.

Why can full adders be combined?

As they have a carry input, they can be chained together to form a ripple adder.

Define ripple adder

When one adder can affect another adder.