Name assigned to a specific value of a type
Allow for easy update and readability
Declaration of constant may omit value so that the value assignment may be deferred
- Facilitates reconfiguration
CONSTANT constant_name : type_name [:= value];
CONSTANT PI : REAL := 3.14;
CONSTANT SPEED : INTEGER;
VHDL constants are objects whose values do not change. The value of a constant, however, does not need to be assigned at the time the constant is declared; it can be assigned later in a package body if necessary, for example.
The syntax of the constant declaration statement is shown above. The constant declaration includes the name of the constant, its type, and, optionally, its value.