CRC模块设计

--sdata:12位待发送信息；
--datald：sdata的装载信号；
--datafini：数据接收校验完成；
--error：误码警告信号；
--rdata：接收模块接收的12位有效信息数据；
--clk：时钟信号；
--datacrc：附加5位CRC校验码的17位CRC码，在生成模块被发送，在接收模块被接收；
--hsend，hrecv：生成、检验模块的握手信号，协调相互之间关系。

LIBRARY ieee;
USE ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;

entity crcm is
port
 (
 clk,hrecv,datald :in std_logic;
 sdata :in std_logic_vector(11 downto 0);
 datacrci:in std_logic_vector(16 downto 0);
 datacrco:out std_logic_vector(16 downto 0);
 rdata :out std_logic_vector(11 downto 0);
 datafini:out std_logic;
 erroro,hsend:out std_logic
 );
end crcm;

architecture comm of crcm is
 CONSTANT multi_coef:std_logic_vector(5 downto 0)  :="110101";
 SIGNAL dtemp,sdatam,rdtemp:std_logic_vector(11 downto 0);
 SIGNAL cnt,rcnt:std_logic_vector(4 downto 0);
 SIGNAL rdatacrc:std_logic_vector(16 downto 0);
 SIGNAL st,rt:std_logic;
begin
 process(clk)
 variable crcvar:std_logic_vector(5 downto 0);
 begin
  if clk'event and clk='1' then
   if st='0' and datald='1' then--存储待发送数据
    dtemp <= sdata;
    sdatam <= sdata;
    cnt <= (others=>'0');
    hsend <='0';
    st <= '1';
   elsif st='1' and cnt < 7 then--计算CRC码
    cnt <= cnt+1;
    if dtemp(11)='1' then
     crcvar := dtemp(11 downto 6)xor multi_coef;
     dtemp <= crcvar(4 downto 0)& dtemp(5 downto 0) & '0';
    else
     dtemp <= dtemp(10 downto 0)& '0';
    end if;
   elsif st='1' and cnt=7  then
    datacrco <= sdatam & dtemp(11 downto 7);--信息码+CRC码
    hsend <= '1';
    cnt <= cnt+1;
   elsif st='1' and cnt=8 then--发送数据：信息码+CRC码
    hsend <= '0' ;
    st <= '0';
   end if;
  end if;
 end process;
 
 process(hrecv,clk)
  variable rcrvar :std_logic_vector(5 downto 0);
 begin
  if clk'event and clk='1' then--save data+crc dode
   if rt='0' and hrecv='1' then
    rdtemp <= datacrci(16 downto 5);
    rdatacrc <= datacrci;
    rcnt <= (others => '0');
   elsif rt='1' and rcnt < 7 then--check CRC code
    datafini <= '0';
    rcnt <= rcnt+1;
    rcrvar := rdtemp(11 downto 6) xor multi_coef;
    if dtemp(11)='1' then
     rdtemp <= rcrvar(4 downto 0)& rdtemp(5 downto 0)& '0';
    else
     rdtemp <= rdtemp(10 downto 0) & '0';
    end if;
   elsif rt='1' and rcnt =7 then --output data and judge weather error
    rdata <= rdatacrc(16 downto 5);
    rt <= '0';
    if rdatacrc(4 downto 0) /= rdtemp(11 downto 7) then
     erroro <='1';
    end if;
   end if;
  end if;
 end process;
end comm;