VHDL Programming

Advanced Topics 209

The types of the parameters can be the same, but the number of

parameters can be different. This is shown by the following example:

LIBRARY IEEE;

USE IEEE.std_logic_1164.ALL;

PACKAGE p_addr_convert IS

FUNCTION convert_addr(a0, a1 : std_logic) return integer;

FUNCTION convert_addr(a0, a1, a2 : std_logic)return

integer;

FUNCTION convert_addr(a0, a1, a2, a3 : std_logic) return

integer;

END p_addr_convert;

PACKAGE BODY p_addr_convert IS

FUNCTION convert_addr(a0, a1 : std_logic) RETURN

INTEGER IS

VARIABLE result : INTEGER := 0;

BEGIN

IF (a0 = ‘ 1 ’) THEN

result := result + 1;

END IF;

IF (a1 = ‘ 1 ’) THEN

result := result + 2;

END IF;

RETURN result;

END convert_addr;

FUNCTION convert_addr(a0, a1, a2 : std_logic) RETURN

INTEGER IS

VARIABLE result : INTEGER := 0;

BEGIN

result := convert_addr(a0, a1);

IF (a2 = ‘ 1 ’) THEN

result := result + 4;

END IF;

RETURN result;

END convert_addr;

FUNCTION convert_addr(a0, a1, a2, a3 : std_logic) RETURN

INTEGER IS

VARIABLE result : INTEGER := 0;

BEGIN

result := convert_addr(a0, a1, a2);

IF (a3 = ‘ 1 ’) THEN