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--
-- This VHDL file was generated by EASE/HDL 7.4 Revision 4 from HDL Works B.V.
--
-- Ease library  : work
-- HDL library   : work
-- Host name     : S212065
-- User name     : df768
-- Time stamp    : Tue Aug 19 08:05:18 2014
--
-- Designed by   : L.Maarsen
-- Company       : LogiXA
-- Project info  : eSoC
--
--------------------------------------------------------------------------------
 
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-- Object        : Entity work.esoc_search_engine_da
-- Last modified : Mon Apr 14 12:50:04 2014.
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library ieee, std, work;
use ieee.std_logic_1164.all;
use std.textio.all;
use ieee.numeric_std.all;
use work.package_hash10_24b.all;
use work.package_esoc_configuration.all;
 
entity esoc_search_engine_da is
  port(
    clk_search           : in     std_logic;
    reset                : in     std_logic;
    search_eof           : in     std_logic;
    search_key           : in     std_logic_vector(63 downto 0);
    search_port_stalled  : in     std_logic_vector(esoc_port_count-1 downto 0);
    search_result        : out    std_logic_vector(esoc_port_count-1 downto 0);
    search_result_av     : out    std_logic;
    search_sof           : in     std_logic;
    search_table_address : out    STD_LOGIC_VECTOR(12 downto 0);
    search_table_data    : out    STD_LOGIC_VECTOR(79 downto 0);
    search_table_q       : in     STD_LOGIC_VECTOR(79 downto 0);
    search_table_rden    : out    STD_LOGIC;
    search_table_wren    : out    STD_LOGIC);
end entity esoc_search_engine_da;
 
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-- Object        : Architecture work.esoc_search_engine_da.esoc_search_engine_da
-- Last modified : Mon Apr 14 12:50:04 2014.
--------------------------------------------------------------------------------
 
 
architecture esoc_search_engine_da of esoc_search_engine_da is
 
type   search_states is (idle, wait_hash, compare);
signal search_state: search_states;
 
signal search_table_address_i: std_logic_vector(search_table_address'high downto 0);
signal search_result_i: std_logic_vector(esoc_port_count-1 downto 0);
signal search_port_stalled_sync : std_logic_vector(2*esoc_port_count-1 downto 0);
 
signal search_table_coll_cnt: integer range esoc_search_engine_col_depth downto 0 ;
signal search_hash_delay_cnt: integer range esoc_search_engine_hash_delay downto 0;
 
signal search_key_i: std_logic_vector(59 downto 0);
 
begin
 
--=============================================================================================================
-- Process		  : proces search requests for destination MAC address
-- Description	: 
--=============================================================================================================    
search_da:  process(clk_search, reset)
            begin
              if reset = '1' then
                search_table_coll_cnt <= 0;
                search_hash_delay_cnt <= 0;
 
                search_key_i           <= (others => '0');
                search_table_address_i <= (others => '0');
                search_table_rden      <= '0';             
                search_result_i        <= (others => '0');
                search_result_av       <= '0';
 
                search_port_stalled_sync <= (others => '0');
 
              elsif clk_search'event and clk_search = '1' then
                -- clear one-clock active signals
                search_result_av  <= '0';
                search_table_rden <= '0';             
 
                -- synchronise port stalled information with this clock
                search_port_stalled_sync(esoc_port_count-1 downto 0)                 <= search_port_stalled_sync(2*esoc_port_count-1 downto esoc_port_count);
                search_port_stalled_sync(2*esoc_port_count-1 downto esoc_port_count) <= search_port_stalled;
 
                -- process new search requests 
                case search_state is
                  when idle       =>  -- wait for start of frame, first data is VID + DA, calculate hash pointer (additional delay may be required after synthesis, due to large XOR tree)
                                      if search_sof = '1' then
 
                                        -- send result (all ports) immediately if destination address is a BC or MC, if UC start search action.
                                        -- the BC/MC detection is part of the search engine and not part of port because you still need to learn the SA!
                                        if search_key(esoc_search_bus_mac+esoc_ethernet_uc_mc_bc) = '0'then
                                          search_key_i(esoc_search_entry_vlan+11 downto esoc_search_entry_vlan) <= search_key(esoc_search_bus_vlan+11 downto esoc_search_bus_vlan);
                                          search_key_i(esoc_search_entry_mac+47 downto esoc_search_entry_mac)   <= search_key(esoc_search_bus_mac+47 downto esoc_search_bus_mac);
                                          search_table_address_i                                                <= CALC_HASH10_24b(search_key(esoc_search_bus_mac+23 downto esoc_search_bus_mac)) & "000";
                                          search_table_rden                                                     <= '1';
                                          search_table_coll_cnt                                                 <= 0;
 
                                          -- use delay mechanism to give the hash function - large xor tree - time to provide stable result
                                          -- depends on target speed, use target timing analysis result to optimze this delay! At least one clock
                                          -- delay due to RAM latency
                                          search_hash_delay_cnt <= esoc_search_engine_hash_delay-1;
                                          search_state          <= wait_hash;
 
                                        else
                                          search_result_av  <= '1';
                                          search_result_i   <=  (others => '1'); 
                                        end if;
                                      end if;
 
                  when wait_hash  =>  -- hash result stable?  
                                      if search_hash_delay_cnt = 0 then
                                        search_table_address_i  <= std_logic_vector(to_unsigned(to_integer(unsigned(search_table_address_i))+1,search_table_address_i'length));
                                        search_state <= compare;
                                      else
                                        search_hash_delay_cnt <= search_hash_delay_cnt-1;
                                      end if;
 
                                      search_table_rden <= '1';
 
                  when compare  => -- there is a hit on DA and VID
                                   if search_table_q(esoc_search_entry_vlan+11 downto esoc_search_entry_vlan) = search_key_i(esoc_search_entry_vlan+11 downto esoc_search_entry_vlan) and
                                     search_table_q(esoc_search_entry_mac+47 downto esoc_search_entry_mac) = search_key_i(esoc_search_entry_mac+47 downto esoc_search_entry_mac) then
 
                                    -- entry valid, provide destination information else return broadcast as result
                                    if search_table_q(esoc_search_entry_valid) = '1' then
                                      search_result_av  <= '1';
                                      search_result_i   <= search_table_q(esoc_search_entry_destination+esoc_port_count-1 downto esoc_search_entry_destination);
                                      search_state      <= idle;
                                    else
                                      search_result_av  <= '1';
                                      search_result_i   <= (others => '1');
                                      search_state      <= idle;
                                    end if;
 
                                  -- there is no hit on DA and VID
                                  else
                                    -- End of collision buffer reached, no increment address for next entry else return result
                                    if search_table_coll_cnt < esoc_search_engine_col_depth then    
                                      search_table_coll_cnt  <= search_table_coll_cnt + 1;      
                                      search_table_address_i <= std_logic_vector(to_unsigned(to_integer(unsigned(search_table_address_i))+1,search_table_address_i'length)); 
                                      search_table_rden      <= '1';
 
                                    -- end of collission buffer, no hit, return broadcast as result
                                    else
                                      search_result_av  <= '1';
                                      search_result_i   <=  (others => '1');
                                      search_state      <= idle;
                                    end if;
                                  end if;
 
                  when others =>  search_state <= idle;
                end case;
              end if;
            end process;
 
            search_table_wren    <= '0';    
            search_table_data    <= (others => '0');
            search_table_address <= search_table_address_i;
 
            -- provide search result, but use port stall info to avoid use of data bus to stalled ports, waste of bus usage
            search_result <= search_result_i and not(search_port_stalled_sync(esoc_port_count-1 downto 0));
 
end architecture esoc_search_engine_da ; -- of esoc_search_engine_da