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--! @file shifter2xstage.vhd

--! @brief RayTrac Arithmetic Shifter 

--! @author Julián Andrés Guarín Reyes

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-- RAYTRAC

-- Author Julian Andres Guarin

-- shifter2xstage.vhd

-- This file is part of raytrac.

-- 

--     raytrac is free software: you can redistribute it and/or modify

--     it under the terms of the GNU General Public License as published by

--     the Free Software Foundation, either version 3 of the License, or

--     (at your option) any later version.

-- 

--     raytrac 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 General Public License for more details.

-- 

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

--     along with raytrac.  If not, see <http://www.gnu.org/licenses/>

library ieee;

use ieee.std_logic_1164.all;

use ieee.math_real.all;

use work.arithpack.all;

entity shifter2xstage is

        generic (

                address_width   : integer := 9;

                width                   : integer := 32

        );

        port (

                data    : in std_logic_vector (width-1 downto 0);

                exp             : out std_logic_vector (2*integer(ceil(log(real(width),2.0)))-1 downto 0);

                add             : out std_logic_vector (2*address_width-1 downto 0);

                zero    : out std_logic

        );

end shifter2xstage;

architecture shifter2xstage_arch of shifter2xstage is

        signal exp0     : std_logic_vector (integer(ceil(log(real(width),2.0)))-1 downto 0);

        signal exp1     : std_logic_vector (integer(ceil(log(real(width),2.0)))-1 downto 0);

        signal add0     : std_logic_vector (address_width-1 downto 0);

        signal add1     : std_logic_vector (address_width-1 downto 0);

        signal szero: std_logic_vector (1 downto 0);

        function exp0StringParam return string is

        begin

                if width rem 2 = 0 then

                        return "NO";

                else

                        return "YES";

                end if;

        end exp0StringParam;

        function exp1StringParam return string is

        begin

                if width rem 2 = 0 then

                        return "YES";

                else

                        return "NO";

                end if;

        end exp1StringParam;

begin

        zero <= szero(1) and szero(0);

        evenS:shifter

        generic map (address_width,width,exp0StringParam)

        port map (data,exp0,add0,szero(0));

        oddS:shifter

        generic map (address_width,width,exp1StringParam)

        port map (data,exp1,add1,szero(1));

        exp(integer(ceil(log(real(width),2.0)))-1 downto 0)<=exp0;

        exp(2*integer(ceil(log(real(width),2.0)))-1 downto integer(ceil(log(real(width),2.0))))<=exp1;

        add(address_width-1 downto 0)<=add0;

        add(2*address_width-1 downto address_width)<=add1;

end shifter2xstage_arch;