Subprogram declaration

subprogram_specification ;

• entity_declarative_part
• architecture_declarative_part
• package
• package_body
• block_declarative_part
• function_declarative_part
• procedure_declarative_part
• process_declarative_part

procedure designator [ ( formal_parameter_list ) ]

[ pure | impure ] function designator [ ( formal_parameter_list ) ]
return type_mark

A pure function always returns the same value when called different times with the same actual parameters. Impure functions can return different values when called several times with the same actual parameters. This is the case when for example a impure function reads in a text file, which content changes during simulation.

Simple declaration of the procedure thank_you without transfer values

PROCEDURE thank_you ;

Declaration of the procedure test with the transfer value A .

PROCEDURE test( A : Bit ) ;

Declaration of the function convert with the transfer value B and the result type fuzzy_bit .

FUNCTION convert( B : Bit )
      RETURN fuzzy_bit ;

Declaration of the procedure regist with the signals D , CK and Q being transferred.

 PROCEDURE regist(
      SIGNAL D : IN Bit;
      SIGNAL CK : IN Bit;
      SIGNAL Q : OUT Bit ) ;

Declaration of the procedure p with the variable COL and the constant C being transferred.

PROCEDURE p(
      VARIABLE COL : INOUT color;
      CONSTANT C : IN choice ) ;