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--This library is free software; you can redistribute it and/or

--modify it under the terms of the GNU Lesser General Public

--License as published by the Free Software Foundation; either

--version 2.1 of the License, or (at your option) any later version.

--This library 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

--Lesser General Public License for more details.

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

--License along with this library; if not, write to the Free Software

--Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

-- e_mail : j.l.nunez-yanez@byacom.co.uk

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

--  ENTITY       = CSM         --

--  version      = 4.0         --

--  last update  = 20/04/00    --

--  author       = Jose Nunez --

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

-- FUNCTION

-- control state machine.

--  PIN LIST

--  START        = indicates start of a compress or decompress operation

--  STOP         = forces the end of the current operation

--  COMPRESS     = selects compression mode

--  DECOMPRESS   = selects decompression mode

--  CLEAR        = asyncronous clear

--  END_OF_BLOCK = indicates that a complete block has been processed

--  FLUSH_END    = indicates end of flushing cycle during compression

--  CLK          = master clock

--  COMP         = indicates unit is compressing data

--  DECOMP       = indicates unit is decompressing data

--  FLUSH        = indicates unit is in a flush cycle during compression

--  FINISH       = end of current operation

--  LOAD_BS      = load block size for the current operation

--  INC_TC       = increment tuple counter

--  MOVE_ENABLE  = enable movement logic for the CAM array

--  CLEAR_INT    = asynchronously clear (or preset) all internal storage

library ieee;

use ieee.std_logic_1164.all;

entity CSM_C is

port

(

        START_C : in bit ; -- load BS and start engine => the buffer is ready

        STOP_C : in bit; -- stop engine when parser finish

        FINISH_BUFFER : in bit; -- data exhausted from buffer almost finish wait for parser

        STOP : in bit ;

        FLUSH_END : in bit ;

        CLK : in bit ;

        CLEAR : in bit ;

        COMP : out bit ;

        FLUSH : out bit ;

        MOVE_ENABLE : out bit ;

        RESET : out bit

);

end CSM_C;

architecture STATE of CSM_C is

--State S9 to delay the activation of the counter incrementation due to pipeline

--Now State S6 111001001111 INC disable same as S9

signal CURRENT_STATE : bit_vector(3 downto 0);

signal NEXT_STATE : bit_vector(3 downto 0);

signal CLEAR_AUX : bit;

begin

COMBINATIONAL : process (CURRENT_STATE , START_C , STOP_C, STOP , FLUSH_END)

begin

case CURRENT_STATE is

        -- state S0

        when "1110" =>

                if ((START_C = '1') and (STOP = '1')) then

                        NEXT_STATE <= "1111";   -- goto state S1

                else

                                NEXT_STATE <= CURRENT_STATE;    -- remain in current state

                end if;

        -- state S1

        when "1111" =>

            if (STOP = '0') then

                        NEXT_STATE <= "1110";   -- goto state S0

                elsif (START_C = '1') then

                        NEXT_STATE <= "0101";

                else

                        NEXT_STATE <= CURRENT_STATE;    -- goto state S2

                end if;

        -- state S2

        when "0101" =>

                if (STOP = '0') then -- force stop

                NEXT_STATE <= "1110";

                elsif (START_C = '0' and FINISH_BUFFER = '0') then -- --FINISG_BUFER indicates that all data has been read from buffer wait only for PARSER to finish

                        NEXT_STATE <= "1111"; --wait

            elsif (STOP_C = '1') then -- block is completely finish

                        NEXT_STATE <= "0011";   -- goto state S3 flush

                else

                        NEXT_STATE <= CURRENT_STATE;    -- remain in current state

                end if;

        -- state S3 flushing

        when "0011" =>

                if (FLUSH_END = '1') then

                        NEXT_STATE <= "0111";   -- goto state S4

                else

                        NEXT_STATE <= CURRENT_STATE;    -- goto state S5

                end if;

        -- state S4

        when "0111" =>

                if (FLUSH_END = '0') then

                        NEXT_STATE <= "1110";

                else

                        NEXT_STATE <= CURRENT_STATE;    -- remain in current state

                end if;

        -- anything else (illegal states)

        when others =>

                NEXT_STATE <= "1110";   -- goto state S0

end case;

end process COMBINATIONAL;

FLIP_FLOPS : process(CLK,CLEAR)

begin

if (CLEAR = '0') then

        CURRENT_STATE <= "1110";        -- reset state is S0

elsif ((CLK'event) and (CLK='1')) then

        CURRENT_STATE <= NEXT_STATE;            -- otherwise latch next state

end if;

end process FLIP_FLOPS;

-- assign outputs directly from state register (Moore machine with registered outputs)

COMP <= CURRENT_STATE(3);

FLUSH <= CURRENT_STATE(2);

MOVE_ENABLE <= CURRENT_STATE(1);

RESET <= CURRENT_STATE(0);

end STATE;  -- end of architecture