Subversion Repositories xucpu

-- Copyright 2015, Jürgen Defurne

--

-- This file is part of the Experimental Unstable CPU System.

--

-- The Experimental Unstable CPU System Is free software: you can redistribute

-- it and/or modify it under the terms of the GNU Lesser General Public License

-- as published by the Free Software Foundation, either version 3 of the

-- License, or (at your option) any later version.

--

-- The Experimental Unstable CPU System is distributed in the hope that it will

-- be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of

-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser

-- General Public License for more details.

--

-- You should have received a copy of the GNU Lesser General Public License

-- along with Experimental Unstable CPU System. If not, see

-- http://www.gnu.org/licenses/lgpl.txt.

LIBRARY ieee;

USE ieee.STD_LOGIC_1164.ALL;

USE ieee.NUMERIC_STD.ALL;

ENTITY alu IS

  GENERIC(

    w_data : NATURAL RANGE 1 TO 32 := 16);

  PORT(

    op : IN  STD_LOGIC_VECTOR(3 DOWNTO 0);

    A  : IN  STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0);

    B  : IN  STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0);

    Y  : OUT STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0));

  FUNCTION alu_add (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0);

    SIGNAL B : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR;

  FUNCTION alu_add(

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0);

    SIGNAL B : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR IS

  BEGIN  -- alu_add

    RETURN STD_LOGIC_VECTOR(UNSIGNED(A) + UNSIGNED(B));

  END alu_add;

  FUNCTION alu_sub (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0);

    SIGNAL B : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR;

  FUNCTION alu_sub(

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0);

    SIGNAL B : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR IS

  BEGIN  -- alu_sub

    RETURN STD_LOGIC_VECTOR(UNSIGNED(A) - UNSIGNED(B));

  END alu_sub;

  FUNCTION alu_inc (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR;

  FUNCTION alu_inc (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR IS

  BEGIN

    RETURN STD_LOGIC_VECTOR(UNSIGNED(A) + 1);

  END alu_inc;

  FUNCTION alu_dec (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR;

  FUNCTION alu_dec (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR IS

  BEGIN

    RETURN STD_LOGIC_VECTOR(UNSIGNED(A) - 1);

  END alu_dec;

  FUNCTION shift_left (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR;

  FUNCTION shift_left (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR IS

  BEGIN

    RETURN STD_LOGIC_VECTOR(shift_left(UNSIGNED(A), 1));

  END shift_left;

  FUNCTION shift_right (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR;

  FUNCTION shift_right (

    SIGNAL A : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0))

    RETURN STD_LOGIC_VECTOR IS

  BEGIN

    RETURN STD_LOGIC_VECTOR(shift_right(UNSIGNED(A), 1));

  END shift_right;

END ENTITY alu;

ARCHITECTURE Behavioral OF alu IS

  CONSTANT ZERO : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0)

    := STD_LOGIC_VECTOR(TO_UNSIGNED(0, w_data));

  CONSTANT ONE : STD_LOGIC_VECTOR(w_data - 1 DOWNTO 0)

    := STD_LOGIC_VECTOR(TO_UNSIGNED(1, w_data));

BEGIN  -- ARCHITECTURE Behavioral

  WITH op SELECT

    y <=

    alu_inc(A)     WHEN "0000",

    alu_dec(A)     WHEN "0001",

    ZERO           WHEN "0010",         -- Place holder

    ONE            WHEN "0011",         -- Place holder

    B WHEN "0100",

    A WHEN "0101",                      -- Place holder

    A WHEN "0110",                      -- Place holder

    alu_add(A, B)  WHEN "0111",

    alu_sub(A, B)  WHEN "1000",

    A WHEN "1001",                      -- Place holder

    A AND B        WHEN "1010",

    A OR B         WHEN "1011",

    A XOR B        WHEN "1100",

    NOT A          WHEN "1101",

    shift_left(A)  WHEN "1110",

    shift_right(A) WHEN "1111",

    A WHEN OTHERS;

END ARCHITECTURE Behavioral;