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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_D is
port
(
	START_C : in bit; -- start test mode
	START_D : in bit; -- load BS
	START_D_ENGINE : in bit; -- start engine
	STOP : in bit ;
	END_OF_BLOCK : in bit ;
	CLK : in bit ;
	CLEAR : in bit ;
	DECOMP : out bit ;
	FINISH : out bit ;
	MOVE_ENABLE : out bit ;
	RESET : out bit 
);
 
 
end CSM_D;
 
architecture STATE of CSM_D 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, START_D, START_D_ENGINE, STOP , END_OF_BLOCK)
begin
 
case CURRENT_STATE is
	-- state S0
	when "1110" =>
			if (((START_C = '0') or (START_D = '0'))) then
				NEXT_STATE <= "1111";	-- goto state S10 load the BS
			else
				NEXT_STATE <= CURRENT_STATE;	-- remain in current state
			end if;
 
	-- I am going to set bits 1 and 3 to 1 to activate the count for decompressing later due to pipelining
	-- state S6
	when "1011" =>
			NEXT_STATE <= "1001";	-- goto state S7
 
	-- state S7
	when "1001" =>
		if ((END_OF_BLOCK = '0')) then
			NEXT_STATE <= "0110";	-- goto state S8
		else
		     NEXT_STATE <= CURRENT_STATE;	-- remain in current state
		end if;
 
	-- state S8
	when "0110" =>
			NEXT_STATE <= "1110";	-- goto state S0
 
	-- state S11 wait for the order to start decompression engine
	when "1111"=>
		if ((START_D_ENGINE = '0')) then
				NEXT_STATE <= "1011";	-- goto state S6 
			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 
	if ( STOP = '0') then
			CURRENT_STATE <= "1110";	-- reset state is S0
  else
	     CURRENT_STATE <= NEXT_STATE;		-- otherwise latch next state
  end if;
end if;
 
end process FLIP_FLOPS;
 
-- assign outputs directly from state register (Moore machine with registered outputs)
 
FINISH <= CURRENT_STATE(3) and END_OF_BLOCK;
DECOMP <= CURRENT_STATE(2);
MOVE_ENABLE <= CURRENT_STATE(1);
RESET <= CURRENT_STATE(0);
 
 
end STATE;  -- end of architecture