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-- Company: 

-- Engineer: 

-- 

-- Create Date:    15:39:56 08/10/2009 

-- Design Name: 

-- Module Name:    pdp1rotshift - Behavioral 

-- Project Name: 

-- Target Devices: 

-- Tool versions: 

-- Description: 

--

-- Dependencies: 

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-- Revision: 

-- Revision 0.01 - File Created

-- Additional Comments: 

--

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library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.numeric_std.ALL;

entity pdp1rotshift is

    Port ( ac : in  STD_LOGIC_VECTOR (0 to 17);

           io : in  STD_LOGIC_VECTOR (0 to 17);

           right : in  STD_LOGIC;                               -- '0' for left, '1' for right

           shift : in  STD_LOGIC;                       -- '1' for shift, '0' for rotate

           words : in  STD_LOGIC_VECTOR (0 to 1);

           acout : out  STD_LOGIC_VECTOR (0 to 17);

           ioout : out  STD_LOGIC_VECTOR (0 to 17));

end pdp1rotshift;

architecture Behavioral of pdp1rotshift is

        signal input, output: std_logic_vector(0 to 35);

        signal word: std_logic_vector(0 to 17);

        constant use_readable_code: boolean := true;

begin

        cond_gen: if use_readable_code generate

                with words select

                        input <= AC&AC when "01",

                                                IO&IO when "10",

                                                AC&IO when "11",

                                                (others=>'-') when others;

                output <= std_logic_vector(unsigned(input) rol 1) when right='0' and shift='0' else

                                         std_logic_vector(unsigned(input) sll 1) when right='0' and shift='1' else

                                         std_logic_vector(unsigned(input) ror 1) when right='1' and shift='0' else

                                         std_logic_vector(unsigned(input) srl 1) when right='1' and shift='1' else

                                         (others=>'-');

                word <= output(0 to 17) when right='1' else output(18 to 35);

                with words select

                        acout <= word when "01",

                                                output(0 to 17) when "11",

                                                ac when others;

                with words select

                        ioout <= word when "10",

                                                output(18 to 35) when "11",

                                                io when others;

        end generate;

        cond_explicit_rtl: if not use_readable_code generate

                acout(0) <= ac(0) when words(1)='0' else           -- not working on AC

                                                                        ac(1) when right='0' else                                        -- shift/rot left

                                                                        '0' when shift='1' else                                          -- shift right

                                                                        ac(17) when words(0)='0' else             -- rotate ac right

                                                                        io(17) when words(0)='1' else            -- rotate ac&io right

                                                                        '-';

                acout(1 to 16) <= ac(1 to 16) when words(1)='0' else     -- not working on AC

                                                                                                ac(2 to 17) when right='0' else                          -- left

                                                                                                ac(0 to 15) when right='1' else                          -- right

                                                                                                (others=>'-');

                acout(17) <= ac(17) when words(1)='0' else               -- not working on ac

                                                                        ac(16) when right='1' else                                      -- shift/rot right

                                                                        io(0) when words(0)='1' else                      -- shift/rot left ac&io

                                                                        '0' when shift='1' else                                                  -- shift ac left

                                                                        ac(0) when shift='0' else                                 -- rotate ac left

                                                                        '-';

                ioout(0) <= io(0) when words(0)='0' else                            -- not working on IO

                                                                io(1) when right='0' else                                                        -- left

                                                                ac(17) when words(1)='1' else                   -- ac&io right

                                                                '0' when shift='1' else                                                          -- shift io right

                                                                io(17) when shift='0' else                                               -- rotate io right

                                                                '-';

                ioout(1 to 16) <= io(1 to 16) when words(0)='0' else

                                                                                        io(2 to 17) when right='0' else

                                                                                        io(0 to 15) when right='1' else

                                                                                        (others=>'-');

                ioout(17) <= io(17) when words(0)='0' else

                                                                        io(16) when right='1' else

                                                                        '0' when shift='1' else

                                                                        ac(0) when words(1)='1' else

                                                                        io(0) when words(1)='0' else

                                                                        '-';

        end generate;

end Behavioral;