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 -- ***** BEGIN LICENSE BLOCK *****
-- 
-- $Id: ARITHMETICCODER.vhd,v 1.4 2006-10-05 16:17:13 petebleackley Exp $ $Name: not supported by cvs2svn $
-- *
-- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
-- *
-- * The contents of this file are subject to the Mozilla Public License
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-- * with the License. You may obtain a copy of the License at
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-- * Software distributed under the License is distributed on an "AS IS" basis,
-- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
-- * the specific language governing rights and limitations under the License.
-- *
-- * The Original Code is BBC Research and Development code.
-- *
-- * The Initial Developer of the Original Code is the British Broadcasting
-- * Corporation.
-- * Portions created by the Initial Developer are Copyright (C) 2004.
-- * All Rights Reserved.
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-- * Contributor(s): Peter Bleackley (Original author)
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-- * Public License Version 2.1 (the "LGPL"), in which case the provisions of
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
 
--  Uncomment the following lines to use the declarations that are
--  provided for instantiating Xilinx primitive components.
--library UNISIM;
--use UNISIM.VComponents.all;
 
entity ARITHMETICCODER is
    Port ( ENABLE : in std_logic;
           DATA_IN : in std_logic;
			  CONTEXT_ENABLE : in std_logic;
			  CONTEXT_IN : in std_logic_vector (5 downto 0);
			  HALVECOUNTS_IN : in std_logic;
			  FLUSH : in std_logic;
			  RESET : in std_logic;
           CLOCK : in std_logic;
           SENDING : out std_logic;
           DATA_OUT : out std_logic;
			  FLUSH_COMPLETE : out std_logic);
end ARITHMETICCODER;
 
architecture RTL of ARITHMETICCODER is
 
	component LIMIT_REGISTER
	generic(CONST: std_logic);
	port(	  LOAD : in std_logic_vector(15 downto 0);
           SET_VALUE : in std_logic;
           SHIFT_ALL : in std_logic;
           SHIFT_MOST : in std_logic;
			  RESET : in std_logic;
           CLOCK : in std_logic;
           OUTPUT : out std_logic_vector(15 downto 0));
	end component LIMIT_REGISTER;
	component FOLLOW_COUNTER
	port	( INCREMENT : in std_logic;
           TEST : in std_logic;
			  RESET : in std_logic;
           CLOCK : in std_logic;
           OUTPUT : out std_logic);
	end component FOLLOW_COUNTER;
	component CONVERGENCE_CHECK
	port	( HIGH_MSB : in std_logic;
           LOW_MSB : in std_logic;
           HIGH_SECONDBIT : in std_logic;
           LOW_SECONDBIT : in std_logic;
           CHECK : in std_logic;
           TRIGGER_OUTPUT : out std_logic;
           TRIGGER_FOLLOW : out std_logic);
	end component CONVERGENCE_CHECK;
	component ARITHMETIC_UNIT
	port	( DIFFERENCE : in std_logic_vector(15 downto 0);
           PROB : in std_logic_vector(7 downto 0);
			  LOW :	in std_logic_vector(15 downto 0);
           ENABLE : in std_logic;
			  RESET :	in std_logic;
           CLOCK : in std_logic;
           DIFFERENCE_OUT0 : out std_logic_vector(15 downto 0);
			  DIFFERENCE_OUT1 : out std_logic_vector(15 downto 0);
           RESULT_OUT0 : out std_logic_vector(15 downto 0);
			  RESULT_OUT1 : out std_logic_vector(15 downto 0);
           DATA_LOAD : out std_logic);
	end component ARITHMETIC_UNIT;
	component OUTPUT_UNIT
	port ( ENABLE : in std_logic;
           DATA : in std_logic;
           FOLLOW : in std_logic;
			  RESET : in std_logic;
           CLOCK : in std_logic;
           SENDING : out std_logic;
			  DATA_OUT : out std_logic;
           FOLLOW_COUNTER_TEST : out std_logic;
           SHIFT : out std_logic);
	end component OUTPUT_UNIT;
	component INPUT_CONTROL
	generic( WIDTH : integer range 1 to 16);
	port( ENABLE : in std_logic;
           DATA_IN : in std_logic_vector(WIDTH - 1 downto 0);
           BUFFER_CONTROL : in std_logic;
           DEMAND : in std_logic;
           RESET : in std_logic;
           CLOCK : in std_logic;
           SENDING : out std_logic;
           DATA_OUT : out std_logic_vector(WIDTH - 1 downto 0));
	end component INPUT_CONTROL;
	component CONTEXT_MANAGER
	port (  CONTEXT_NUMBER : in std_logic_vector(5 downto 0);
				SET : in std_logic;
				UPDATE : in std_logic;
				DATA_IN : in std_logic;
				HALVECOUNTS : in std_logic;
           RESET : in std_logic;
           CLOCK : in std_logic;
           PROB : out std_logic_vector(7 downto 0);
			  READY : out std_logic);
	end component CONTEXT_MANAGER;
	signal HIGH_SET : std_logic;
	signal LOW_SET	: std_logic;
	signal TRIGGER_SHIFT : std_logic;
	signal SHIFT_ALL :	std_logic;
	signal DIFFERENCE_SHIFT_ALL :	std_logic;
	signal SHIFT_MOST :	std_logic;
	signal ZERO_INPUT :	std_logic;
	signal ARITHMETIC_UNIT_ENABLE :	std_logic;
	signal ARITHMETIC_UNIT_DATA_LOAD :	std_logic;
	signal CONVERGENCE_TEST :	std_logic;
	signal TRIGGER_OUTPUT : std_logic;
	signal FOLLOW_COUNTER_TEST :	std_logic;
	signal FOLLOW:	std_logic;
	signal DATA_LOAD: std_logic;
	signal OUTPUT_ACTIVE :	std_logic;
	signal CHECK :	std_logic;
	signal DELAYED_CHECK : std_logic;
	signal DATA_AVAILABLE :	std_logic;
	signal BUFFERED_DATA : std_logic;
	signal BUFFER_INPUT :	std_logic;
	signal NEWCONTEXT : std_logic;
	signal ARITHMETIC_UNIT_DIFFERENCE_OUT0 : std_logic_vector (15 downto 0);
	signal ARITHMETIC_UNIT_DIFFERENCE_OUT1 :	std_logic_vector(15 downto 0);
	signal DIFFERENCE_IN : std_logic_vector (15 downto 0);
	signal ARITHMETIC_UNIT_RESULT_OUT0 :	std_logic_vector (15 downto 0);
	signal ARITHMETIC_UNIT_RESULT_OUT1 : std_logic_vector (15 downto 0);
	signal DIFFERENCE_OUT : std_logic_vector (15 downto 0);
	signal HIGH_OUT : std_logic_vector (15 downto 0);
	signal LOW_OUT : std_logic_vector (15 downto 0);
	signal PROB : std_logic_vector (7 downto 0);
	signal CONTEXT_SELECT : std_logic_vector (5 downto 0);
	signal PROB_AVAILABLE : std_logic;
	signal BUFFERCONTEXT :	std_logic;
	signal DATA_IN2 : std_logic_vector(0 downto 0);
	signal BUFFERED_DATA2 : std_logic_vector(0 downto 0);
	signal CONTEXT_BUFFER_DATA_IN : std_logic_vector(7 downto 0);
	signal CONTEXT_BUFFER_DATA_OUT : std_logic_vector(7 downto 0);
--	signal LAST_FIVE_TRIGGERS : std_logic_vector(4 downto 0);
	signal HALVECOUNTS : std_logic;
	signal BUFFERED_FLUSH : std_logic;
	signal FLUSH_ENCODER : std_logic;
	signal SWITCHED_DATA : std_logic;
	signal CONVERGED : std_logic;
	signal INCREMENT_FOLLOW : std_logic;
	signal ALLOWHALVING : std_logic;
	signal RELEASE_CONTEXT : std_logic;
--	signal FETCH_FLUSH : std_logic;
	signal DEMAND_CONTEXT : std_logic;
	signal LOCK : std_logic;
	signal DEMAND_DATA : std_logic;
	signal HOLDCONTEXT : std_logic;
begin
-- input buffering
INBUFFER:	INPUT_CONTROL
	generic map(WIDTH => 1)
	port map(ENABLE => ENABLE,
	DATA_IN => DATA_IN2,
	BUFFER_CONTROL => BUFFER_INPUT,
	DEMAND => DEMAND_DATA,
	RESET => RESET,
	CLOCK => CLOCK,
	SENDING => DATA_AVAILABLE,
	DATA_OUT => BUFFERED_DATA2);
 
	DATA_IN2(0) <= DATA_IN;
	BUFFERED_DATA <= BUFFERED_DATA2(0);
	DEMAND_DATA <= ARITHMETIC_UNIT_DATA_LOAD and not LOCK;
 
CONTEXT_BUFFER:	INPUT_CONTROL
	generic map(WIDTH => 8)
	port map(ENABLE => CONTEXT_ENABLE,
	DATA_IN => CONTEXT_BUFFER_DATA_IN,
	BUFFER_CONTROL =>	 BUFFERCONTEXT,
	DEMAND => DEMAND_CONTEXT,
	RESET => RESET,
	CLOCK => CLOCK,
	SENDING => NEWCONTEXT,
	DATA_OUT => CONTEXT_BUFFER_DATA_OUT);
 
	CONTEXT_BUFFER_DATA_IN <= (CONTEXT_IN & HALVECOUNTS_IN & FLUSH);
 
	CONTEXT_SELECT <= CONTEXT_BUFFER_DATA_OUT(7 downto 2);
	HALVECOUNTS <= CONTEXT_BUFFER_DATA_OUT(1) and ALLOWHALVING;
	BUFFERED_FLUSH <= CONTEXT_BUFFER_DATA_OUT(0) and CONVERGENCE_TEST and (CONVERGED nor SHIFT_MOST) and not LOCK;
 
 
 
 
-- Specify the registers
HIGH: LIMIT_REGISTER
	generic map(CONST => '1')
	port map(  LOAD => ARITHMETIC_UNIT_RESULT_OUT0,
           SET_VALUE => HIGH_SET,
           SHIFT_ALL => SHIFT_ALL,
           SHIFT_MOST => SHIFT_MOST,
			  RESET => RESET,
           CLOCK => CLOCK,
           OUTPUT => HIGH_OUT);
 
DIFFERENCE: LIMIT_REGISTER
	generic map(CONST => '1')
	port map(  LOAD => DIFFERENCE_IN,
           SET_VALUE => DATA_LOAD,
           SHIFT_ALL => DIFFERENCE_SHIFT_ALL,
           SHIFT_MOST => '0',
			  RESET => RESET,
           CLOCK => CLOCK,
           OUTPUT => DIFFERENCE_OUT);
 
LOW: LIMIT_REGISTER
	generic map(CONST => '0')
	port map(  LOAD => ARITHMETIC_UNIT_RESULT_OUT1,
           SET_VALUE => LOW_SET,
           SHIFT_ALL => SHIFT_ALL,
           SHIFT_MOST => SHIFT_MOST,
			  RESET => RESET,
           CLOCK => CLOCK,
           OUTPUT => LOW_OUT);
 
-- The arithmetic
 
ARITH: ARITHMETIC_UNIT
	port map(DIFFERENCE => DIFFERENCE_OUT,
           PROB => PROB,
			  LOW => LOW_OUT,
           ENABLE => ARITHMETIC_UNIT_ENABLE,
			  RESET => RESET,
           CLOCK => CLOCK,
           DIFFERENCE_OUT0 => ARITHMETIC_UNIT_DIFFERENCE_OUT0,
			  DIFFERENCE_OUT1 => ARITHMETIC_UNIT_DIFFERENCE_OUT1,
           RESULT_OUT0 => ARITHMETIC_UNIT_RESULT_OUT0,
			  RESULT_OUT1 => ARITHMETIC_UNIT_RESULT_OUT1,
           DATA_LOAD => ARITHMETIC_UNIT_DATA_LOAD);
 
--The convergence checks
 
CONVERGE: CONVERGENCE_CHECK
	port map(HIGH_MSB => HIGH_OUT(15),
           LOW_MSB => LOW_OUT(15),
           HIGH_SECONDBIT => HIGH_OUT(14),
           LOW_SECONDBIT => LOW_OUT(14),
           CHECK => CONVERGENCE_TEST,
           TRIGGER_OUTPUT => CONVERGED,
           TRIGGER_FOLLOW => SHIFT_MOST);
 
				TRIGGER_OUTPUT <= CONVERGED or FLUSH_ENCODER;
--The Follow Counter
 
FC:	FOLLOW_COUNTER
	port map( INCREMENT => INCREMENT_FOLLOW,
           TEST => FOLLOW_COUNTER_TEST,
			  RESET => RESET,
           CLOCK => CLOCK,
           OUTPUT => FOLLOW);
		INCREMENT_FOLLOW <= SHIFT_MOST or BUFFERED_FLUSH;
--The output unit
 
OUTPUT:	OUTPUT_UNIT
	port map(ENABLE => TRIGGER_OUTPUT,
           DATA => SWITCHED_DATA,
           FOLLOW => FOLLOW,
			  RESET => RESET,
           CLOCK => CLOCK,
           SENDING => OUTPUT_ACTIVE,
			  DATA_OUT => DATA_OUT,
           FOLLOW_COUNTER_TEST => FOLLOW_COUNTER_TEST,
           SHIFT => TRIGGER_SHIFT);
 
	SENDING <= OUTPUT_ACTIVE;
 
	SHIFT_ALL <= TRIGGER_SHIFT and not FLUSH_ENCODER;
 
-- Input logic
 
	DATA_LOAD <= DATA_AVAILABLE and ARITHMETIC_UNIT_DATA_LOAD;
	HIGH_SET <= ZERO_INPUT and DATA_LOAD;
	ZERO_INPUT <= not BUFFERED_DATA;
	LOW_SET <= BUFFERED_DATA and DATA_LOAD;
 
FLUSH_SWITCH : process (FLUSH_ENCODER,LOW_OUT,HIGH_OUT)
begin
	if FLUSH_ENCODER = '1' then
		SWITCHED_DATA <= LOW_OUT(14);
	else
		SWITCHED_DATA <= HIGH_OUT(15);
	end if;
end process FLUSH_SWITCH;
 
-- Control logic for DIFFERENCE register
 
	DIFFERENCE_SHIFT_ALL <= SHIFT_ALL or SHIFT_MOST;
 
-- Control logic for convergence check
 
	CHECK <= DIFFERENCE_SHIFT_ALL or DATA_LOAD;
 
CONVERGENCE_TEST_DELAY:	process (CLOCK)
	begin
	if CLOCK'event and CLOCK = '1' then
		DELAYED_CHECK <= CHECK;
	end if;
	end process CONVERGENCE_TEST_DELAY;
 
	CONVERGENCE_TEST <= DELAYED_CHECK or FOLLOW_COUNTER_TEST;
 
-- Control logic for arithmetic unit
 
	ARITHMETIC_UNIT_ENABLE <= PROB_AVAILABLE and not(OUTPUT_ACTIVE or DIFFERENCE_SHIFT_ALL or DATA_LOAD);
 
-- Control Logic for input control
 
	BUFFER_INPUT <= OUTPUT_ACTIVE or not ARITHMETIC_UNIT_DATA_LOAD;
 
-- Select the new difference value
 
NEWDIFF : process(BUFFERED_DATA,ARITHMETIC_UNIT_DIFFERENCE_OUT0,ARITHMETIC_UNIT_DIFFERENCE_OUT1)
	begin
		if(BUFFERED_DATA = '1') then
			DIFFERENCE_IN <= ARITHMETIC_UNIT_DIFFERENCE_OUT1;
		else
			DIFFERENCE_IN <= ARITHMETIC_UNIT_DIFFERENCE_OUT0;
		end if;
	end process NEWDIFF;
 
-- Select the context
 
PROBABILITY : CONTEXT_MANAGER
			port map(CONTEXT_NUMBER => CONTEXT_SELECT,
			SET => NEWCONTEXT,
			UPDATE => DATA_LOAD,
			DATA_IN => BUFFERED_DATA,
			HALVECOUNTS => HALVECOUNTS,
			RESET => RESET,
			CLOCK => CLOCK,
			PROB => PROB,
			READY => PROB_AVAILABLE);
 
 
 
FLUSH_CONTROL : process (CLOCK)
begin
	if CLOCK'event and CLOCK = '1' then
		if RESET = '1' then
			FLUSH_ENCODER <= '0';
		elsif BUFFERED_FLUSH = '1'  then
			FLUSH_ENCODER <= '1';
		elsif TRIGGER_SHIFT = '1' then
			FLUSH_ENCODER <= '0';
		end if;
	end if;
end process	FLUSH_CONTROL;
 
FLUSH_COMPLETE <= FLUSH_ENCODER and TRIGGER_SHIFT;
 
LIMITHALVING : process (CLOCK)
begin
	if CLOCK'event and CLOCK='1' then
		if RESET='1' then
			ALLOWHALVING <= '1';
		else
			ALLOWHALVING <= not CONTEXT_BUFFER_DATA_OUT(1);
		end if;
	end if;
end process LIMITHALVING;
 
RELEASE_CONTEXT <= RESET or DEMAND_CONTEXT;
 
CONTEXTS_SHOULD_BE_BUFFERED : process (RELEASE_CONTEXT,CLOCK)
begin
	if CLOCK'event and CLOCK = '1' then
		if NEWCONTEXT = '1' then
			HOLDCONTEXT <= '1';
		elsif RELEASE_CONTEXT = '1' then
		  	HOLDCONTEXT <= '0';
		end if;
	end if;
end process CONTEXTS_SHOULD_BE_BUFFERED;
 
BUFFERCONTEXT <= HOLDCONTEXT and not RELEASE_CONTEXT;
 
--STORE_TRIGGERS : process (CLOCK)
--begin
--	if CLOCK'event and CLOCK='1' then
--		if RESET='1' then
--			LAST_FIVE_TRIGGERS <= "11111";
--		else
--			LAST_FIVE_TRIGGERS <= LAST_FIVE_TRIGGERS(3 downto 0) & (DATA_AVAILABLE or OUTPUT_ACTIVE or DIFFERENCE_SHIFT_ALL);
--		end if;
--	end if;
--end process STORE_TRIGGERS;
 
--GET_FLUSH_SIGNAL : process (LAST_FIVE_TRIGGERS)
--begin
--	if LAST_FIVE_TRIGGERS = "00000" then
--		FETCH_FLUSH <= '1';
--	else
--		FETCH_FLUSH <= '0';
--	end if;
--end process GET_FLUSH_SIGNAL;
 
LOCK_ENCODER : process (CLOCK)
begin
	if CLOCK'event and CLOCK='1' then
		if RESET = '1' then
			LOCK <= '0';
		elsif BUFFERED_FLUSH='1' then
			LOCK <= '1';
		end if;
	end if;
end process LOCK_ENCODER;
 
DEMAND_CONTEXT <= DATA_LOAD; -- or FETCH_FLUSH;--DATA_LOAD or FETCH_FLUSH or AFTER_RESET;
 
--DELAY_RESET: process (CLOCK)
--begin
--	if CLOCK'event and CLOCK='1' then
--		AFTER_RESET <= RESET;
--	end if;
--end process DELAY_RESET;
--
 
end RTL;