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--

-- PIC16xx compatible microcontroller core

--

-- Version : 0146

--

-- Copyright (c) 2001-2002 Daniel Wallner (jesus@opencores.org)

--

-- All rights reserved

--

-- Redistribution and use in source and synthezised forms, with or without

-- modification, are permitted provided that the following conditions are met:

--

-- Redistributions of source code must retain the above copyright notice,

-- this list of conditions and the following disclaimer.

--

-- Redistributions in synthesized form must reproduce the above copyright

-- notice, this list of conditions and the following disclaimer in the

-- documentation and/or other materials provided with the distribution.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE

-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

-- POSSIBILITY OF SUCH DAMAGE.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

-- The latest version of this file can be found at:

--      http://www.opencores.org/cvsweb.shtml/t51/

--

-- Limitations :

--

-- File history :

--

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.numeric_std.all;

entity PPX_ALU is

        generic(

                InstructionLength : integer

        );

        port (

                Clk                     : in std_logic;

                ROM_Data        : in std_logic_vector(InstructionLength - 1 downto 0);

                A                       : in std_logic_vector(7 downto 0);

                B                       : in std_logic_vector(7 downto 0);

                Q                       : inout std_logic_vector(7 downto 0);

                Skip            : in std_logic;

                Carry           : in std_logic;

                Z_Skip          : out std_logic;

                STATUS_d        : out std_logic_vector(2 downto 0);

                STATUS_Wr       : out std_logic_vector(2 downto 0)

        );

end PPX_ALU;

architecture rtl of PPX_ALU is

        procedure AddSub(A : std_logic_vector(3 downto 0);

                                        B : std_logic_vector(3 downto 0);

                                        Sub : std_logic;

                                        Carry_In : std_logic;

                                        signal Res : out std_logic_vector(3 downto 0);

                                        signal Carry : out std_logic) is

                variable B_i            : unsigned(4 downto 0);

                variable Full_Carry     : unsigned(4 downto 0);

                variable Res_i          : unsigned(4 downto 0);

        begin

                if Sub = '1' then

                        B_i := "0" & not unsigned(B);

                else

                        B_i := "0" & unsigned(B);

                end if;

                if (Sub = '1' and Carry_In = '1') or (Sub = '0' and Carry_In = '1') then

                        Full_Carry := "00001";

                else

                        Full_Carry := "00000";

                end if;

                Res_i := unsigned("0" & A) + B_i + Full_Carry;

                Carry <= Res_i(4);

                Res <= std_logic_vector(Res_i(3 downto 0));

        end;

        signal  Do_IDTEST               : std_logic;

        signal  Do_ADD                  : std_logic;

        signal  Do_SUB                  : std_logic;

        signal  Do_DEC                  : std_logic;

        signal  Do_INC                  : std_logic;

        signal  Do_AND                  : std_logic;

        signal  Do_OR                   : std_logic;

        signal  Do_XOR                  : std_logic;

        signal  Do_COM                  : std_logic;

        signal  Do_RRF                  : std_logic;

        signal  Do_RLF                  : std_logic;

        signal  Do_SWAP                 : std_logic;

        signal  Do_BITCLR               : std_logic;

        signal  Do_BITSET               : std_logic;

        signal  Do_BITTESTCLR   : std_logic;

        signal  Do_BITTESTSET   : std_logic;

        signal  Do_CLR  : std_logic;

        signal  Do_PASSA                : std_logic;

        signal  Inst_Top                : std_logic_vector(11 downto 0);

        signal  Bit_Pattern             : std_logic_vector(7 downto 0);

        signal  Bit_Test                : std_logic_vector(7 downto 0);

        signal  IDD                             : std_logic_vector(7 downto 0);

        signal  DC_i                    : std_logic;

        signal  AddSubRes               : std_logic_vector(8 downto 0);

begin

        Inst_Top <= ROM_Data(InstructionLength - 1 downto InstructionLength - 12);

        process (Clk)

        begin

                if Clk'event and Clk = '1' then

                        Do_ADD <= '0';

                        Do_SUB <= '0';

                        Do_AND <= '0';

                        Do_OR <= '0';

                        Do_XOR <= '0';

                        Do_IDTEST <= '0';

                        Do_INC <= '0';

                        Do_DEC <= '0';

                        Do_COM <= '0';

                        Do_RRF <= '0';

                        Do_RLF <= '0';

                        Do_SWAP <= '0';

                        Do_BITCLR <= '0';

                        Do_BITSET <= '0';

                        Do_BITTESTCLR <= '0';

                        Do_BITTESTSET <= '0';

                        Do_CLR <= '0';

                        Do_PASSA <= '0';

                        if Skip = '0' then

                                if InstructionLength = 12 then

                                        if Inst_Top(11 downto 6) = "000111" then

                                                -- ADDWF

                                                Do_ADD <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000010" then

                                                -- SUBWF

                                                Do_SUB <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000101" or Inst_Top(11 downto 8) = "1110" then

                                                -- ANDWF, ANDLW

                                                Do_AND <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000100" or Inst_Top(11 downto 8) = "1101" then

                                                -- IORWF, IORLW

                                                Do_OR <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000110" or Inst_Top(11 downto 8) = "1111" then

                                                -- XORWF, XORLW

                                                Do_XOR <= '1';

                                        end if;

                                else

                                        if Inst_Top(11 downto 6) = "000111" or Inst_Top(11 downto 7) = "11111" then

                                                -- ADDWF, ADDLW

                                                Do_ADD <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000010" or Inst_Top(11 downto 7) = "11110" then

                                                -- SUBWF, SUBLW

                                                Do_SUB <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000101" or Inst_Top(11 downto 6) = "111001" then

                                                -- ANDWF, ANDLW

                                                Do_AND <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000100" or Inst_Top(11 downto 6) = "111000" then

                                                -- IORWF, IORLW

                                                Do_OR <= '1';

                                        end if;

                                        if Inst_Top(11 downto 6) = "000110" or Inst_Top(11 downto 6) = "111010" then

                                                -- XORWF, XORLW

                                                Do_XOR <= '1';

                                        end if;

                                end if;

                                if Inst_Top(11 downto 9) = "001" and Inst_Top(7 downto 6) = "11" then

                                        -- INC/DEC w conditional skip

                                        Do_IDTEST <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "001010" or Inst_Top(11 downto 6) = "001111" then

                                        -- INCF, INCFSZ

                                        Do_INC <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "000011" or Inst_Top(11 downto 6) = "001011" then

                                        -- DECF, DECFSZ, 

                                        Do_DEC <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "001001" then

                                        -- COMF

                                        Do_COM <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "001100" then

                                        -- RRF

                                        Do_RRF <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "001101" then

                                        -- RLF

                                        Do_RLF <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "001110" then

                                        -- SWAPF

                                        Do_SWAP <= '1';

                                end if;

                                if Inst_Top(11 downto 8) = "0100" then

                                        -- BCF

                                        Do_BITCLR <= '1';

                                end if;

                                if Inst_Top(11 downto 8) = "0101" then

                                        -- BSF

                                        Do_BITSET <= '1';

                                end if;

                                if Inst_Top(11 downto 8) = "0110" then

                                        -- BTFSC

                                        Do_BITTESTCLR <= '1';

                                end if;

                                if Inst_Top(11 downto 8) = "0111" then

                                        -- BTFSS

                                        Do_BITTESTSET <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "000001" then

                                        -- CLRF, CLRW

                                        Do_CLR <= '1';

                                end if;

                                if Inst_Top(11 downto 6) = "001000" then

                                        -- MOVF

                                        Do_PASSA <= '1';

                                end if;

                        end if;

                        case Inst_Top(7 downto 5) is

                        when "000" =>

                                Bit_Pattern <= "00000001";

                        when "001" =>

                                Bit_Pattern <= "00000010";

                        when "010" =>

                                Bit_Pattern <= "00000100";

                        when "011" =>

                                Bit_Pattern <= "00001000";

                        when "100" =>

                                Bit_Pattern <= "00010000";

                        when "101" =>

                                Bit_Pattern <= "00100000";

                        when "110" =>

                                Bit_Pattern <= "01000000";

                        when others =>

                                Bit_Pattern <= "10000000";

                        end case;

                end if;

        end process;

        IDD <= std_logic_vector(unsigned(A) + 1) when Do_INC = '1' else

                        std_logic_vector(unsigned(A) - 1) when Do_DEC = '1' else "ZZZZZZZZ";

        Q <= IDD when Do_INC = '1' or Do_DEC = '1' else "ZZZZZZZZ";

        Q <= AddSubRes(7 downto 0) when (Do_ADD = '1' OR Do_SUB = '1') else "ZZZZZZZZ";

        AddSub(A(3 downto 0), B(3 downto 0), Do_SUB, Do_SUB, AddSubRes(3 downto 0), DC_i);

        AddSub(A(7 downto 4), B(7 downto 4), Do_SUB, DC_i, AddSubRes(7 downto 4), AddSubRes(8));

        Q <= (A and B) when Do_AND = '1' else

                (A or B) when Do_OR = '1' else

                (A xor B) when Do_XOR = '1' else "ZZZZZZZZ";

        Q <= (not A) when Do_COM = '1' else "ZZZZZZZZ";

        Q <= Carry & A(7 downto 1) when Do_RRF = '1' else "ZZZZZZZZ";

        Q <= A(6 downto 0) & Carry when Do_RLF = '1' else "ZZZZZZZZ";

        Q <= A(3 downto 0) & A(7 downto 4) when Do_SWAP = '1' else "ZZZZZZZZ";

        Q <= ((not Bit_Pattern) and A) when Do_BITCLR = '1' else "ZZZZZZZZ";

        Q <= (Bit_Pattern or A) when Do_BITSET = '1' else "ZZZZZZZZ";

        Q <= "00000000" when Do_CLR = '1' else "ZZZZZZZZ";

        Q <= A when Do_PASSA = '1' else "ZZZZZZZZ";

        Bit_Test <= Bit_Pattern and A;

        Z_Skip <= '1' when (Do_IDTEST = '1' and IDD = "00000000") or

                                        (Bit_Test /= "00000000" and Do_BITTESTSET = '1') or

                                        (Bit_Test = "00000000" and Do_BITTESTCLR = '1') else '0';

        STATUS_d(2) <= '1' when Q(7 downto 0) = "00000000" else '0';

        STATUS_d(1) <= DC_i;

        STATUS_d(0) <= A(0) when Do_RRF = '1' else

                                        A(7) when Do_RLF = '1' else

                                        AddSubRes(8);

        -- Z

        STATUS_Wr(2) <= '1' when Do_SUB = '1' or Do_ADD = '1' or

                ((Do_DEC = '1' or Do_INC = '1') and Do_IDTEST = '0') or

                Do_AND = '1' or Do_OR = '1' or Do_XOR = '1' or

                Do_CLR = '1' or Do_COM = '1' or Do_PASSA = '1' else '0';

        -- DC

        STATUS_Wr(1) <= '1' when Do_SUB = '1' or Do_ADD = '1' else '0';

        -- C

        STATUS_Wr(0) <= '1' when Do_SUB = '1' or Do_ADD = '1' or Do_RRF = '1' or Do_RLF = '1' else '0';

end;