Final answer:
In VHDL, the entity specifies the interface or external inputs and outputs of a digital circuit. The entity declaration includes port declarations, which define the interface of the entity. Each port can be an input, an output, or a bidirectional signal. The data type of each port is also specified.
Step-by-step explanation:
In VHDL, the entity specifies the interface or external inputs and outputs of a digital circuit. It describes the inputs and outputs of the circuit, as well as the modes of operation and the type of data that can be used.
The entity declaration includes port declarations, which define the interface of the entity. Each port can be an input, an output, or a bidirectional signal. The data type of each port is also specified.
For example, consider an entity declaration for a simple adder circuit:
entity Adder is
port (
A, B: in std_logic;
CLK: in std_logic;
SUM: out std_logic
);
end entity Adder;
In this example, the entity declaration specifies that the circuit has two input signals (A and B) of type std_logic, one input signal (CLK) of type std_logic, and one output signal (SUM) of type std_logic.