Entity

A VHDL entity specifies the name of the entity, the ports of the entity, and entity-related information. All designs are created using one or more entities.
Let’s take a look at a simple entity example:

ENTITY mux IS

// start of an entity statement ; name of the entity is mux.

//STANDARD package are shown in ALL CAPITAL letters
PORT ( a, b, c, d : IN BIT; // four data input ports (a, b, c, d) are of type BIT
s0, s1 : IN BIT; //two multiplexer select inputs, s0 and s1, are also of type BIT 
x, : OUT BIT); // output port is of type BIT
END mux;

The entity describes the following:-

(i) interface to the outside world.

(ii) It specifies

(iii) the number of ports

(iv) the direction of the ports

(v) the type of the ports

QUIZ

  1. Why ENTITY is used in the CAPITAL LETTERS?

(a) It is a STANDARD PACKAGE

(b) It is a Keyword

(c) It is a Type

(d) It is a Keyword in STANDARD PACKAGE

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