A switch is a circuit that connects n inputs to n outputs by a one - to - one matching in between inputs and outputs. For instance consider a switch...

A switch is a circuit that connects

n

inputs to

n

outputs by a one

-

to

-

one matching in between inputs and

outputs.

For instance consider a switch for

n = 2

(or

a

2x2 switch). T

here are two inputs (In0, In1

), and two

outputs (Out0, Out1) of this switch. An additional

select input (

sel

)

determines the connectivity between inputs

and outputs

. If the select input is 0

(configuration 0)

, In0 is connected to Out0, and I

n1 is connected to Out1,

whereas if the select input is 1

(configuration 1)

, In0 is connected to Out1, and In1 is connected to Out0.

Note that, a

t any given time, an input can only drive one output

. Likewise, at any given time an output

can only be driven

by one input (

i.e.,

unicast operation).

1.

Write the VHDL code for

a 2x2 Switch using the following entity

ENTITY SW2x2

IS

PORT (

In0

: in STD_LOGIC_VECTOR(

3

DOWNTO 0);

In1

: in STD_LOGIC_VECTOR(

3

DOWNTO 0);

Out0: out

STD_LOGIC_VECTOR(

3

DOWNTO 0);

Out1: out

STD_LOGIC_VECTOR(

3

DOWNTO 0);

Sel:

in

STD_LOGIC

);

END

SW2x2

;

2.

Using SW2x2

components

draw the block diagram and write the VHDL code for

a 4x4 Switch with entity name

SW4x4

.

3.

Using the SW4

x

4

components

draw the block diagram and write the

VHDL code for

a

n

16x16

Sw

itch with entity

name SW

16

x

16

. Each

input should be able

to communicate with every output

at least in one configuration.