filter.vhd

CPLDFPGA嵌入式应用开发技术白金手册

library ieee;
use ieee.std_logic_1164.all;
package mydefine is
 type def is array (natural range<>) of std_logic_vector(7 downto 0);
 constant rank:integer:=3;
end package;
library	ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use work.mydefine.all;           --使用定义过的数据类型库
entity filter is
port(indata:in std_logic_vector(7 downto 0);
     outdata:out std_logic_vector(rank-1 downto 0);  
     en:in std_logic;
     clk:in std_logic;
     add_en:out std_logic;
     rf:in std_logic);
end filter;

architecture beh of filter is
begin
fil:process
variable count:unsigned(3 downto 0):="0000";
variable temp:def(2 downto 0);
variable s:std_logic;
begin
wait until clk'event and  clk='0'; 
         if(en='1') then
         for i in rank downto 1 loop
	     temp(i):=temp(i-1);
	     end loop;
	     temp(0):=indata;
	     count:="0000";      --读入数据 
         s:='1';
         end if;
case count is
		when "0001"=>for i in rank-1 downto 0  loop    --将读入的数据转换为
		              outdata(i)<=temp(i)(0);         --地址
		              end loop;                     
	                    if s='1' then  
    		                add_en<='1';
        		            end if;
        when "0010"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(1);
		              end loop;
                      s:='0';
        when "0011"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(2);
		              end loop;
        when "0100"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(3);
		              end loop;
		when "0101"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(4);
		              end loop;
        when "0110"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(5);
		              end loop;
        when "0111"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(6);
		              end loop;
        when "1000"=>for i in rank-1 downto 0  loop
		              outdata(i)<=temp(i)(7);
		              end loop;
		when others=> if rf='1' then add_en<='0';
                      end if;
end case;	         
count:=count+1;
end process;
end beh;