max.vhd

数字逻辑基础与Verilog设计,针对verilog语言的特点

LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;

PACKAGE example IS
        FUNCTION maximum (a,b  : integer) RETURN integer;
        FUNCTION maximum (a,b,c  : integer) RETURN integer;
        FUNCTION maximum (a,b,c,d  : integer) RETURN integer;
END example;

PACKAGE BODY example IS
           FUNCTION maximum (a,b  : integer) RETURN integer IS
                VARIABLE  temp  : integer;
           BEGIN
                IF (a > b) THEN
                   temp := a;
                ELSE
                   temp := b;
                END IF;
                RETURN (temp);
           END maximum;

           FUNCTION maximum (a,b,c: integer) RETURN integer IS
                VARIABLE  temp1, temp2  : integer;
           BEGIN
                IF (a > b) THEN
                   temp1 := a;
                ELSE
                   temp1 := b;
                END IF;
                IF (temp1 > c) THEN
                   temp2 := temp1;
                ELSE
                   temp2 := c;
                END IF;
                RETURN (temp2);
           END maximum;

           FUNCTION maximum (a,b,c,d: integer) RETURN integer IS
                VARIABLE  temp1,temp2,temp3 : integer;
           BEGIN
                IF (a > b) THEN
                   temp1 := a;
                ELSE
                   temp1 := b;
                END IF;
                IF (temp1 > c) THEN
                   temp2 := temp1;
                ELSE
                   temp2 := c;
                END IF;
                IF (temp2 > d) THEN
                   temp3 := temp2;
                ELSE
                   temp3 := d;
                END IF;
                RETURN (temp3);
           END maximum;
END example;

LIBRARY IEEE;
USE IEEE.std_logic_1164.ALL;
USE WORK.example.ALL;

ENTITY max IS 
           PORT (a1,b1 : IN  integer;
                 a2,b2,c2 : IN  integer;
                 a3,b3,c3,d3 : IN  integer;
                 o1    : OUT integer;
                 o2    : OUT integer;
				 o3    : OUT integer);
END max;

ARCHITECTURE max_arc OF max IS
BEGIN
         o1 <= maximum (a1,b1);
         o2 <= maximum (a2,b2,c2);
         o3 <= maximum (a3,b3,c3,d3);
END max_arc;