Subversion Repositories epc_rfid_transponder

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--     Politecnico di Torino                                              

--     Dipartimento di Automatica e Informatica             

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--

--     Title          : EPC Class1 Gen2 RFID Tag - CRC16 encoder/decoder

--

--     File name      : crc16encdec.vhd 

--

--     Description    : Tag CRC16 encoder/decoder    

--

--     Authors        : Erwing R. Sanchez <erwing.sanchezsanchez@polito.it>

--

--     Rev. History   : 10 July 06  

--                                 

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library IEEE;

use IEEE.STD_LOGIC_1164.all;

use IEEE.std_logic_unsigned.all;

use IEEE.STD_LOGIC_ARITH.all;

entity crc16encdec is

  generic(

    PRESET_CRC16 : integer := 65535);  -- X"FFFF"

  port (

    clk   : in  std_logic;

    rst_n : in  std_logic;

    init  : in  std_logic;

    ce    : in  std_logic;

    sdi   : in  std_logic;

    cout  : out std_logic_vector(15 downto 0));

end crc16encdec;

architecture CRC16beh of crc16encdec is

  signal crc16reg : std_logic_vector(15 downto 0);

begin  -- CRC16beh

  process (clk, rst_n)

  begin  -- process

    if rst_n = '0' then                 -- asynchronous reset (active low)

      crc16reg <= (others => '0');

    elsif clk'event and clk = '1' then  -- rising clock edge

      if init = '1' then

        crc16reg <= conv_std_logic_vector(PRESET_CRC16,16);

      elsif ce = '1' then

        crc16reg(0)            <= crc16reg(15) xor sdi;

        crc16reg(4 downto 1)   <= crc16reg(3 downto 0);

        crc16reg(5)            <= crc16reg(15) xor sdi xor crc16reg(4);

        crc16reg(11 downto 6)  <= crc16reg(10 downto 5);

        crc16reg(12)           <= crc16reg(15) xor sdi xor crc16reg(11);

        crc16reg(15 downto 13) <= crc16reg(14 downto 12);

      end if;

    end if;

  end process;

  cout <= crc16reg;

end CRC16beh;