pck_crc7_d1.vhd

实现了SD的SPI模式,通过了所有的仿真及测试,支持数据的读和写.对SD卡的SPI模式的绝大多数命令都支持.

-----------------------------------------------------------------------
-- File:  PCK_CRC7_D1.vhd                              
-- Date:  Thu May 22 06:55:50 2008                                                      
--                                                                     
-- Copyright (C) 1999-2003 Easics NV.                 
-- 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 PROVIDED "AS IS" AND WITHOUT ANY EXPRESS
-- OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
-- WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
--
-- Purpose: VHDL package containing a synthesizable CRC function
--   * polynomial: (0 3 7)
--   * data width: 1
--                                                                     
-- Info: [e-mail]
--       http://www.easics.com                                  
-----------------------------------------------------------------------


library IEEE;
use IEEE.std_logic_1164.all;

package PCK_CRC7_D1 is

  -- polynomial: (0 3 7)
  -- data width: 1
  function nextCRC7_D1
    ( Data:  std_logic;
      CRC:   std_logic_vector(6 downto 0) )
    return std_logic_vector;

end PCK_CRC7_D1;

library IEEE;
use IEEE.std_logic_1164.all;

package body PCK_CRC7_D1 is

  -- polynomial: (0 3 7)
  -- data width: 1
  function nextCRC7_D1 
    ( Data:  std_logic;
      CRC:   std_logic_vector(6 downto 0) )
    return std_logic_vector is

    variable D: std_logic_vector(0 downto 0);
    variable C: std_logic_vector(6 downto 0);
    variable NewCRC: std_logic_vector(6 downto 0);

  begin

    D(0) := Data;
    C := CRC;

    NewCRC(0) := D(0) xor C(6);
    NewCRC(1) := C(0);
    NewCRC(2) := C(1);
    NewCRC(3) := D(0) xor C(2) xor C(6);
    NewCRC(4) := C(3);
    NewCRC(5) := C(4);
    NewCRC(6) := C(5);

    return NewCRC;

  end nextCRC7_D1;

end PCK_CRC7_D1;