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--////////////////////////////////////////////////////////////////////
--//                                                              ////
--// search_item.vhd                                              ////
--//                                                              ////
--// This file is part of the open_hitter opencores effort.       ////
--// <http://www.opencores.org/cores/open_hitter/>                ////
--//                                                              ////
--// Module Description:                                          ////
--// This is the multipelexed search's repeated item. The project ////
--// buses perform the multiplex and are experienced by each item ////
--// as b1_* - input to search_item                               ////
--//    b2_* - output from search_item                            ////
--// there is also a small state-machine in each search_item.     ////
--// For now, the count of number of states is fixed, per px_type ////
--//                                                              ////
--// To Do:                                                       ////
--//                                                              ////
--// Author(s):                                                   ////
--// - Stephen Hawes                                              ////
--//                                                              ////
--////////////////////////////////////////////////////////////////////
--//                                                              ////
--// Copyright (C) 2015 Stephen Hawes and OPENCORES.ORG           ////
--//                                                              ////
--// This source file may be used and distributed without         ////
--// restriction provided that this copyright statement is not    ////
--// removed from the file and that any derivative work contains  ////
--// the original copyright notice and the associated disclaimer. ////
--//                                                              ////
--// This source file 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 source 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 source; if not, download it   ////
--// from <http://www.opencores.org/lgpl.shtml>                   ////
--//                                                              ////
--////////////////////////////////////////////////////////////////////
--//
--// \$Id\$  TAKE OUT THE \'s and this comment in order to get this to work
--//
--// CVS Revision History
--//
--// \$Log\$  TAKE OUT THE \'s and this comment in order to get this to work
--//
library ieee;
use ieee.std_logic_1164.all;     
 
entity search_item is
   port (
        RX_CLK: in std_logic;
        -- control flag(s) on the incoming bus
           b1_px_valid: in std_logic;
        -- pxdata: in price_packet
           b1_px_type: out std_logic_vector(4 downto 0);
           b1_buy_sell: out std_logic_vector(2 downto 0);   -- 111 buy, 000 sell
           b1_px: out std_logic_vector(15 downto 0);     -- price
           b1_qty: out std_logic_vector(15 downto 0);    -- quantity
           b1_sec: out std_logic_vector(55 downto 0);    -- 7x 8bits securities identifier
           b1_id: out std_logic_vector(15 downto 0);    -- unique/identifier/counter
        -- pxdata: out price_packet
           b2_px_type: out std_logic_vector(4 downto 0);
           b2_buy_sell: out std_logic_vector(2 downto 0);   -- 111 buy, 000 sell
           b2_px: out std_logic_vector(15 downto 0);     -- price
           b2_qty: out std_logic_vector(15 downto 0);    -- quantity
           b2_sec: out std_logic_vector(55 downto 0);    -- 7x 8bits securities identifier
           b2_id: out std_logic_vector(15 downto 0);     -- unique/identifier/counter
   );
end search_item;
 
architecture search_item_implementation of search_item is
      signal state : integer range 0 to 16 := 16;
   -- pxdata: out price_packet
      signal store_px_type: std_logic_vector(4 downto 0) := (others => '0');
      signal store_buy_sell: std_logic_vector(2 downto 0) := (others => '0');   -- 111 buy, 000 sell
      signal store_px: std_logic_vector(15 downto 0) := (others => '0');     -- price
      signal store_qty: std_logic_vector(15 downto 0) := (others => '0');    -- quantity
      signal store_sec: std_logic_vector(55 downto 0) := (others => '0');    -- 7x 8bits securities identifier
      signal store_id: std_logic_vector(15 downto 0) := (others => '0');     -- unique/identifier/counter
begin
   match: process (RX_CLK) is
   begin
      if rising_edge(RX_CLK) then
         if b1_px_valid then
 
            case b1_px_type is
               when '0000' =>
                   -- do reset store and outputs
                   store_px_type  <= (others => '0');
                   store_buy_sell <= (others => '0');   -- 111 buy, 000 sell
                   store_px       <= (others => '0');   -- price
                   store_qty      <= (others => '0');   -- quantity
                   store_sec      <= (others => '0');   -- 7x 8bits securities identifier
                   store_id       <= (others => '0');   -- unique/identifier/counter
                   --
                   b2_px_type  <= (others => 'Z');
                   b2_buy_sell <= (others => 'Z');   -- 111 buy, 000 sell
                   b2_px       <= (others => 'Z');   -- price
                   b2_qty      <= (others => 'Z');   -- quantity
                   b2_sec      <= (others => 'Z');   -- 7x 8bits securities identifier
                   b2_id       <= (others => 'Z');   -- unique/identifier/counter
                   --
                   b2_px_type <== '0000';
                   state <= 8;
 
               when '0110' =>
                   -- do set store from incoming price 
                   store_px_type  <= b1_px_type;
                   store_buy_sell <= b1_buy_sell;
                   store_px       <= b1_px;
                   store_qty      <= b1_qty;
                   store_sec      <= b1_sec;
                   store_id       <= b1_id;
                   --
                   b2_px_type <== '0000';
                   state <= 8;
 
               when '0101' =>
                   -- incoming price, register it and start the state machine
                   if (store_sec != b1_sec or store_buy_sell == b1_buy_sell or store_px_type != '0110')
                      -- not this store_item instance no action, also stop anything that might be going on
                      state <= 14;
                   elsif (store_qty == 0 or b1_qty == 0 or 
                             (store_buy_sell == '111' and store_px < b1_px) or
                             (store_buy_sell == '000' and store_px > b1_px) )   
                      -- no deal: this is the correct store_item but there's no match
                      b2_px_type <== '0000';
                      state <= 8;
                   else
                      -- send a return order
                      b2_px_type <= '1010';
                      b2_buy_sell <= store_buy_sell;   -- 111 buy, 000 sell
                      b2_px <= b1_px;                   -- price
                      b2_qty <= b1_qty when (b1_qty < store_qty) else store_qty;    -- quantity
                      b2_sec <= store_sec:                                          -- 7x 8bits securities identifier
                      b2_id <= store_id;                                            -- unique/identifier/counter
                      -- update the store
                      store_qty <= (store_qty-b1_qty) when (b1_qty < store_qty) else 0;
                      state <= 1;
                   end if;
 
               when others => null;
            end case;   -- b1_px_type
 
         else     -- b1_px_valid
            -- no incoming b1_px so check for state machine actions
            case state is
               when 1 => 
                   -- sent return order, so clean up
                   b2_px_type  <= (others => 'Z');
                   b2_buy_sell <= (others => 'Z');    -- 111 buy, 000 sell
                   b2_px       <= (others => 'Z');    -- price
                   b2_qty      <= (others => 'Z');    -- quantity
                   b2_sec      <= (others => 'Z');    -- 7x 8bits securities identifier
                   b2_id       <= (others => 'Z'):    -- unique/identifier/counter
                   state <= 16;
 
               when 8 =>
                    -- correct store_item but there was no match
                    b2_px_type <== 'ZZZZ';
                   state <= 16;
 
               when others => null;
            end case;   -- state
 
            if (state < 16) then
               state <= state + 1;
            end if;
 
         end if;     -- b1_px_valid
 
      end if;
   end process match;
 
end search_item_implementation;