Shifter

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--  Barrelshifter fuer LSL, LSR, ASR, ROR mit Shiftweiten von 0 bis 3 (oder
--  generisch n-1) Bit.
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--  Datum:      ??.??.2013
--  Version:    ?.?
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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_signed.all;
--use ieee.math_real.all;

entity ArmBarrelShifter is
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--  Breite der Operanden (n) und die Zahl der notwendigen
--  Multiplexerstufen (m) um Shifts von 0 bis n-1 Stellen realisieren zu
--  koennen. Es muss gelten: ???
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    generic (OPERAND_WIDTH : integer := 4;
             SHIFTER_DEPTH : integer := 2;
     );
    port (  OPERAND     : in std_logic_vector(OPERAND_WIDTH-1 downto 0);
            MUX_CTRL    : in std_logic_vector(1 downto 0);
            AMOUNT      : in std_logic_vector(SHIFTER_DEPTH-1 downto 0);
            ARITH_SHIFT : in std_logic;
            C_IN        : in std_logic;
            DATA_OUT    : out std_logic_vector(OPERAND_WIDTH-1 downto 0);
            C_OUT       : out std_logic
    );
end entity ArmBarrelShifter;

architecture structure of ArmBarrelShifter is

signal data: std_logic_vector(OPERAND_WIDTH-1 downto 0);

begin


    --Linksshifter
    lsl_k : for k in 0 to SHIFTER_DEPTH-1 generate
    --erste ebene
        lsl_i : for i in 0 to OPERAND_WIDTH-1 generate

    		С_OUT <= C_IN when C_IN = '0' else
					data(OPERAND_WIDTH); --MSB
            data(i) <=  OPERAND(i) when AMOUNT(k) = '0' else
                    C_IN when i <= k else
                    OPERAND(i-1);


        end generate;

    end generate;

       --Rechtsshifter hier benutzen wir OPERAND(i) wobei es eig data(i) sein muss damit es auch bei ebenen > 1 funktioniert
     lsr_k :  for k in 0 to SHIFTER_DEPTH-1 generate
     --erste ebene
         lsr_i: for i in OPERAND_WIDTH-1 downto 0 generate

			 С_OUT <= C_IN when C_IN = '0' else
					data(0); --LSB
             data(i) <=  OPERAND(i) when AMOUNT(k) = '0' else
                     C_IN when i > (SHIFTER_DEPTH - k) else
                     OPERAND(i+1);

         end generate;

     end generate;

       --Rechtsshifter A
   asr_k :  for k in 0 to SHIFTER_DEPTH-1 generate
   --erste ebene
       asr_i: for i in OPERAND_WIDTH-1 downto 0 generate

           data(i) <=  OPERAND(i) when AMOUNT(k) = '0' else
                   OPERAND(OPERAND_WIDTH-1) when i > (SHIFTER_DEPTH - k) else
                   OPERAND(i+1);

       end generate;

   end generate;


--ROTATION
 rotate_k : for k in 0 to SHIFTER_DEPTH-1 generate
  -- Erste Ebene
  rotate_i : for i in 0 to OPERAND_WIDTH-1 generate

	С_OUT <= C_IN when C_IN = '0' else
			data(0); --LSB
    data(i) <= OPERAND(i) when AMOUNT(k) = '0' else
               OPERAND((i + 1 + k) mod OPERAND_WIDTH);
  end generate;
end generate;

DATA_OUT <= data;
end architecture structure;