--------------------------------------------------------------------------------- Title      :  HEC generator-- Project    :  Bluetooth baseband core--------------------------------------------------------------------------------- File        : hec_gen.vhd-- Author      : Jamil Khatib  (khatib@ieee.org)-- Organization: OpenIPCore Project-- Created     : 2000/12/28-- Last update : 2000/12/28-- Platform    : -- Simulators  : Modelsim 5.3XE/Windows98-- Synthesizers: Leonardo/WindowsNT-- Target      : -- Dependency  : ieee.std_logic_1164--------------------------------------------------------------------------------- Description: HEC generator core--------------------------------------------------------------------------------- Copyright (c) 2000 Jamil Khatib-- -- This VHDL design file is an open design; you can redistribute it and/or-- modify it and/or implement it after contacting the author-- You can check the draft license at-- http://www.opencores.org/OIPC/license.shtml--------------------------------------------------------------------------------- Revisions  :-- Revision Number :   1-- Version         :   0.1-- Date            :   28 Dec 2000-- Modifier        :   Jamil Khatib (khatib@ieee.org)-- Desccription    :   Created-- Known bugs      :   -- To Optimze      :  -------------------------------------------------------------------------------library ieee;use ieee.std_logic_1164.all;entity HECgen_ent is  port (    clk    : in  std_logic;                     -- system clock    rst    : in  std_logic;                     -- system reset    header : in  std_logic_vector(9 downto 0);  -- header data    hec    : out std_logic_vector(7 downto 0);  -- HEC 8 bit value    init   : in  std_logic_vector(7 downto 0);  -- init value    load   : in  std_logic);                    -- load headerend HECgen_ent;architecture HECgen_beh of HECgen_ent isbegin  -- HECgen_beh  -- purpose: Generate HEC  -- type   : sequential  -- inputs : clk, rst  -- outputs:   generate_proc : process (clk, rst)    variable lfsr         : std_logic_vector(7 downto 0);  -- LFSR (HEC register)    variable feedback_var : std_logic;  -- feed back variable  begin  -- process generate_proc    if rst = '0' then                   -- asynchronous reset (active low)      lfsr := (others => '0');      HEC  <= (others => '0');    elsif clk'event and clk = '1' then  -- rising clock edge      if load = '1' then        lfsr := init;      else        for i in 9 downto 0 loop          feedback_var := header(i) xor lfsr(7);          lfsr(7) := feedback_var xor lfsr(6);          lfsr(6) := lfsr(5);          lfsr(5) := feedback_var xor lfsr(4);          lfsr(4) := lfsr(3);          lfsr(3) := lfsr(2);          lfsr(2) := feedback_var xor lfsr(1);          lfsr(1) := feedback_var xor lfsr(0);          lfsr(0) := feedback_var;        end loop;  -- i      end if;      HEC <= lfsr;    end if;  end process generate_proc;end HECgen_beh;