mti_pkg.vhd

来自「Xilinx Sdram控制器VHDL源代码」· VHDL 代码 · 共 144 行

--*****************************************************************************
--
-- Micron Semiconductor Products, Inc.
--
-- Copyright 1997, Micron Semiconductor Products, Inc.
-- All rights reserved.
--
--*****************************************************************************

LIBRARY work;
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;

PACKAGE mti_pkg IS

    FUNCTION  TO_INTEGER (input : BIT) RETURN INTEGER;
    FUNCTION  TO_INTEGER (input : BIT_VECTOR) RETURN INTEGER;
    FUNCTION  TO_INTEGER (input : STD_LOGIC) RETURN INTEGER;
    FUNCTION  TO_INTEGER (input : STD_LOGIC_VECTOR) RETURN INTEGER;
    PROCEDURE TO_BITVECTOR  (VARIABLE input : IN INTEGER; VARIABLE output : OUT BIT_VECTOR);

END mti_pkg;

PACKAGE BODY mti_pkg IS

    -- Convert BIT to INTEGER
    FUNCTION  TO_INTEGER (input : BIT) RETURN INTEGER IS
    VARIABLE result : INTEGER := 0;
    VARIABLE weight : INTEGER := 1;
    BEGIN
        IF input = '1' THEN
            result := weight;
        ELSE
            result := 0;                                            -- if unknowns, default to logic 0
        END IF;
        RETURN result;
    END TO_INTEGER;

    -- Convert BIT_VECTOR to INTEGER
    FUNCTION  TO_INTEGER (input : BIT_VECTOR) RETURN INTEGER IS
    VARIABLE result : INTEGER := 0;
    VARIABLE weight : INTEGER := 1;
    BEGIN
        FOR i IN input'LOW TO input'HIGH LOOP
            IF input(i) = '1' THEN
                result := result + weight;
            ELSE
                result := result + 0;                               -- if unknowns, default to logic 0
            END IF;
            weight := weight * 2;
        END LOOP;
        RETURN result;
    END TO_INTEGER;

    -- Convert STD_LOGIC to INTEGER
    FUNCTION  TO_INTEGER (input : STD_LOGIC) RETURN INTEGER IS
    VARIABLE result : INTEGER := 0;
    VARIABLE weight : INTEGER := 1;
    BEGIN
        IF input = '1' THEN
            result := weight;
        ELSE
            result := 0;                                            -- if unknowns, default to logic 0
        END IF;
        RETURN result;
    END TO_INTEGER;

    -- Convert STD_LOGIC_VECTOR to INTEGER
    FUNCTION  TO_INTEGER (input : STD_LOGIC_VECTOR) RETURN INTEGER IS
    VARIABLE result : INTEGER := 0;
    VARIABLE weight : INTEGER := 1;
    BEGIN
        FOR i IN input'LOW TO input'HIGH LOOP
            IF input(i) = '1' THEN
                result := result + weight;
            ELSE
                result := result + 0;                               -- if unknowns, default to logic 0
            END IF;
            weight := weight * 2;
        END LOOP;
        RETURN result;
    END TO_INTEGER;

    -- Conver integer to bit_vector
    PROCEDURE  TO_BITVECTOR (VARIABLE input : IN INTEGER; VARIABLE output : OUT BIT_VECTOR) IS
    VARIABLE work,offset,outputlen,j : INTEGER := 0;
    BEGIN
        --length of vector
        IF output'LENGTH > 32 THEN
            outputlen := 32;
            offset := output'LENGTH - 32;
            IF input >= 0 THEN
                FOR i IN offset-1 DOWNTO 0 LOOP
                    output(output'HIGH - i) := '0';
                END LOOP;
            ELSE
                FOR i IN offset-1 DOWNTO 0 LOOP
                    output(output'HIGH - i) := '1';
                END LOOP;
            END IF;
        ELSE
            outputlen := output'LENGTH;
        END IF;
        --positive value
        IF (input >= 0) THEN
            work := input;
            j := outputlen - 1;
            FOR i IN 1 to 32 LOOP
                IF j >= 0 then
                    IF (work MOD 2) = 0 THEN 
                        output(output'HIGH-j-offset) := '0';
                    ELSE
                        output(output'HIGH-j-offset) := '1';
                    END IF;
                END IF;
                work := work / 2;
                j := j - 1;
            END LOOP;
            IF outputlen = 32 THEN
                output(output'HIGH) := '0';
            END IF;
        --negative value
        ELSE
            work := (-input) - 1;
            j := outputlen - 1;
            FOR i IN 1 TO 32 LOOP
                IF j>= 0 THEN
                    IF (work MOD 2) = 0 THEN 
                        output(output'HIGH-j-offset) := '1';
                    ELSE
                        output(output'HIGH-j-offset) := '0';
                    END IF;
                END IF;    
                work := work / 2;
                j := j - 1;
            END LOOP;
            IF outputlen = 32 THEN
                output(output'HIGH) := '1';
            END IF;
        END IF;
    END TO_BITVECTOR;

END mti_pkg;