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--------------------------------------------------------------------------------

-- Company:        Ferhat Abbas University - Algeria

-- Engineer:       Ibrahim MEZZAH

-- Progect Supervisor: Dr H. Chemali

-- Create Date:    01:16:40 05/16/05

-- Design Name:    Decoder

-- Module Name:    Decoder - Decode

-- Project Name:   Microcontroller IP (MCIP)

-- Target Device:  xc3s500e-4fg320

-- Tool versions:  Xilinx ISE 9.1.03i

-- Description:  This module generate system commands

--                                               by decoding instruction.

-- Revision:             07/07/2008

-- Revision  3.2 - Add description

-- Additional Comments: Decoder is based on instructions classification

--                                                      to optimize the code.

--------------------------------------------------------------------------------

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

entity Decoder is

    Port ( Instruction       : in std_logic_vector(15 downto 0);

                          Status            : in std_logic_vector(4 downto 1);

                          second_inst_ide   : in std_logic_vector(2 downto 0);

                          Command_vector_pc : out std_logic_vector(6 downto 0);

                          Command_vector_opu : out std_logic_vector(13 downto 0);

                          Command_status    : out std_logic_vector(4 downto 0);

                          second_inst_inf   : out std_logic_vector(2 downto 0);

                          Skip_inf          : out std_logic_vector(4 downto 0);

                          read_write        : out std_logic_vector(1 downto 0);

                          call_return       : out std_logic_vector(1 downto 0);

                          bit_op_enable     : out std_logic;

                          load_FREG         : out std_logic;

                          read_result       : out std_logic;

                          WREG_write_enable : out std_logic;

                          MUL_enable        : out std_logic;

                          MOVFF_enable      : out std_logic;

                          load_BSR          : out std_logic;

                          nop_enable        : out std_logic;

--                        retfie            : out std_logic;

                          soft_reset_enable : out std_logic;

                          sleep_mode_enable : out std_logic;

                          clear_watchdog    : out std_logic;

--                        table_read        : out std_logic;

--                        INDFx             : out std_logic;

                          literal_enable    : out std_logic );

end Decoder;

architecture Decode of Decoder is

  constant enable  : std_logic := '1';

  constant disable : std_logic := '0';

  constant Enabled  : std_logic := '1';

  constant Disabled : std_logic := '0';

        subtype Command_vector_opu_type is std_logic_vector(13 downto 0);

        subtype Command_status_type is std_logic_vector(4 downto 0);

        subtype Command_vector_pc_type is std_logic_vector(6 downto 0);

  -- Command vector for calcul unit ----------------------------

  constant NOP     : Command_vector_opu_type := "00011100000110";

  constant ADDWF   : Command_vector_opu_type := "00011110000110";

  constant ADDWFC  : Command_vector_opu_type := "11011110000110";

  constant ANDWF   : Command_vector_opu_type := "00011100001000";

  constant CLRF    : Command_vector_opu_type := "00011100000000";

  constant COMF    : Command_vector_opu_type := "00011100000011";

  constant CPF     : Command_vector_opu_type := "01011101001001";

  constant DECF    : Command_vector_opu_type := "00011111000011";

  constant INCF    : Command_vector_opu_type := "01011100001100";

  constant IORWF   : Command_vector_opu_type := "00011100001110";

  constant MOVF    : Command_vector_opu_type := "00011100001100";

  constant MOVWF   : Command_vector_opu_type := "00011100001010";

  constant NEGF    : Command_vector_opu_type := "01011100000011";

  constant RLCF    : Command_vector_opu_type := "11011111000000";

  constant RLNCF   : Command_vector_opu_type := "10011111000000";

  constant RRCF    : Command_vector_opu_type := "10101111000000";

  constant RRNCF   : Command_vector_opu_type := "10111111000000";

  constant SETF    : Command_vector_opu_type := "00011100001111";

  constant SUBFWB  : Command_vector_opu_type := "11011100101001";

  constant SUBWF   : Command_vector_opu_type := "01011101001001";

  constant SUBWFB  : Command_vector_opu_type := "11011101001001";

  constant SWAPF   : Command_vector_opu_type := "00010100001100";

  constant TSTF    : Command_vector_opu_type := "00011100001100";

  constant XORWF   : Command_vector_opu_type := "00011100000110";

  constant BCF     : Command_vector_opu_type := "00000000001100";

  constant BSF     : Command_vector_opu_type := "00010000001100";

  constant BTF     : Command_vector_opu_type := "00011000001100";

  constant BTG     : Command_vector_opu_type := "00011000001100";

  constant DAW     : Command_vector_opu_type := "00000110000110";

  --------------------------------------------------------------

  -- Command vector for status ---------------------------------

  constant allv                : command_status_type := "11111";

  constant ZN                  : command_status_type := "10100";

  constant CZN                 : command_status_type := "10101";

  constant C                   : command_status_type := "00001";

  constant Z                   : command_status_type := "00100";

  constant none                : command_status_type := "00000";

  --------------------------------------------------------------

  -- Command vector for program counter ------------------------

  constant increment      : Command_vector_pc_type := "0001010";

  constant branch_con     : Command_vector_pc_type := "0001100";

  constant branch_inc     : Command_vector_pc_type := "0001110";

  constant CALL1          : Command_vector_pc_type := "1001010";

  constant CALL2          : Command_vector_pc_type := "1111010";

  constant GOTO1          : Command_vector_pc_type := "1001010";

  constant GOTO2          : Command_vector_pc_type := "1101010";

  constant RCALL          : Command_vector_pc_type := "0011110";

  constant POP            : Command_vector_pc_type := "0010010";

  constant PUSH           : Command_vector_pc_type := "0011010";

  constant retur_n        : Command_vector_pc_type := "0010011";

  --------------------------------------------------------------

  -- second instruction information ----------------------------

  constant sec_disable  : std_logic_vector(2 downto 0) := "011";

  constant sec_MOVFF    : std_logic_vector(2 downto 0) := "100";

--  constant sec_LFSRx    : std_logic_vector(2 downto 0) := "101";

  constant sec_GOTO     : std_logic_vector(2 downto 0) := "110";

  constant sec_CALL     : std_logic_vector(2 downto 0) := "111";

  --------------------------------------------------------------

  -- Skip information ------------------------------------------

  constant not_skip   : std_logic_vector(4 downto 0) := "00011";

  constant CPFSEQ     : std_logic_vector(4 downto 0) := "11010";

  constant CPFSGT     : std_logic_vector(4 downto 0) := "10011";

  constant CPFSLT     : std_logic_vector(4 downto 0) := "10111";

  constant SZ         : std_logic_vector(4 downto 0) := "11010";

  constant SNZ        : std_logic_vector(4 downto 0) := "10010";

  constant BTFSC      : std_logic_vector(4 downto 0) := "10001";

  constant BTFSS      : std_logic_vector(4 downto 0) := "10101";

  --------------------------------------------------------------

  -- call-return -----------------------------------------------

  constant none_action   : std_logic_vector(1 downto 0) := "01";

  constant call_action   : std_logic_vector(1 downto 0) := "10";

  constant return_action : std_logic_vector(1 downto 0) := "11";

  --------------------------------------------------------------

  -- load FSRx -------------------------------------------------

--  constant load_disable  : std_logic_vector(1 downto 0) := "01";

--  constant enable_1stcyc : std_logic_vector(1 downto 0) := "10";

--  constant enable_2ndcyc : std_logic_vector(1 downto 0) := "11";

  --------------------------------------------------------------

  alias read_D  : std_logic is read_write(1);

  alias write_D : std_logic is read_write(0);

  alias d     : std_logic is Instruction(9);

  alias s1    : std_logic is Instruction(8);

  alias s2    : std_logic is Instruction(0);

  signal not_d : std_logic;

  signal BC   : Command_vector_pc_type;

  signal BNC  : Command_vector_pc_type;

  signal BN   : Command_vector_pc_type;

  signal BNN  : Command_vector_pc_type;

  signal BOV  : Command_vector_pc_type;

  signal BNOV : Command_vector_pc_type;

  signal BZ   : Command_vector_pc_type;

  signal BNZ  : Command_vector_pc_type;

begin

  not_d <= '1'                                                           when Instruction(9) = '0' else

                          '0';

  BC   <= branch_con                                             when Status(1) = '1' else

                         increment;

  BNC  <= branch_con                                             when Status(1) = '0' else

                         increment;

  BN   <= branch_con                                             when Status(4) = '1' else

                         increment;

  BNN  <= branch_con                                             when Status(4) = '0' else

                         increment;

  BOV  <= branch_con                                             when Status(3) = '1' else

                         increment;

  BNOV <= branch_con                                             when Status(3) = '0' else

                         increment;

  BZ   <= branch_con                                             when Status(2) = '1' else

                         increment;

  BNZ  <= branch_con                                             when Status(2) = '0' else

                         increment;

control : process(Instruction, Status, second_inst_ide, not_d,

                                                BC, BNC, BN, BNN, BOV, BNOV, BZ, BNZ)

  begin

        case Instruction(15 downto 12) is

        when "0000" =>                                                           -- class 0

         case Instruction(11 downto 10) is

         when "00" =>                                                            -- class 0:0

          case Instruction(9) is

          when '1' =>                                   -- MULWF

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

--                retfie                                                <= disabled;

                  read_D                                                <= enabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= enabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= enabled;

                  MOVFF_enable                          <= disabled;

--                load_FSRx                                     <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

--                table_read                            <= disabled;

--                INDFx                                         <= enabled;

          when others =>

          case Instruction(8) is

          when '1' =>

          case Instruction(7 downto 4) is

          when "0000" =>                                -- MOVLB

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= enabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when others =>                                -- NOP

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          end case;

          when others =>

          case Instruction(7 downto 0) is

          when "00000100" =>                    -- CLRWDT

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= enabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00000111" =>                    -- DAW

                  Command_vector_opu            <= DAW;

                  Command_vector_pc             <= increment;

                  Command_status                        <= C;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= enabled;

                  WREG_write_enable             <= enabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00000110" =>                    -- POP

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= POP;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00000101" =>                    -- PUSH

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= PUSH;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00000011" =>                    -- SLEEP

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= enabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00001000" =>                    -- TBLRD*

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= enabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= enabled;

                  -- INDFx                                              <= disabled;

          when "00001001" =>                    -- TBLRD*+

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= enabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= enabled;

                  -- INDFx                                              <= disabled;

          when "00001010" =>                    -- TBLRD*-

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= enabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= enabled;

                  -- INDFx                                              <= disabled;

          when "00001011" =>                    -- TBLRD+*

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= enabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= enabled;

                  -- INDFx                                              <= disabled;

          when "11111111" =>                    -- RESET

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= enabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00010000" =>                    -- RETFIE

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= retur_n;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= s2&'1';

                  nop_enable                            <= enabled;

                  -- retfie                                             <= enabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00010001" =>                    -- RETFIE

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= retur_n;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= s2&'1';

                  nop_enable                            <= enabled;

                  -- retfie                                             <= enabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00010010" =>                    -- RETURN

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= retur_n;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= s2&'1';

                  nop_enable                            <= enabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when "00010011" =>                    -- RETURN

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= retur_n;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= s2&'1';

                  nop_enable                            <= enabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;

          when others =>                                -- NOP

                  Command_vector_opu            <= NOP;

                  Command_vector_pc             <= increment;

                  Command_status                        <= none;

                  second_inst_inf                       <= sec_disable;

                  Skip_inf                                      <= not_skip;

                  call_return                           <= none_action;

                  nop_enable                            <= disabled;

                  -- retfie                                             <= disabled;

                  read_D                                                <= disabled;

                  write_D                                               <= disabled;

                  load_FREG                                     <= disabled;

                  read_result                           <= disabled;

                  WREG_write_enable             <= disabled;

                  bit_op_enable                 <= disabled;

                  literal_enable                        <= disabled;

                  MUL_enable                            <= disabled;

                  MOVFF_enable                          <= disabled;

                  -- load_FSRx                                  <= load_disable;

                  load_BSR                                      <= disabled;

                  soft_reset_enable             <= disabled;

                  sleep_mode_enable             <= disabled;

                  clear_watchdog                        <= disabled;

                  -- table_read                         <= disabled;

                  -- INDFx                                              <= disabled;