expwave.vhd

很精典的一个分频程序

--指数波模块
library ieee;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;                                         
entity ExpWave is                                                    
  port(clk : in std_logic;
       outp: out std_logic_vector(9 downto 0));
end ExpWave;
architecture Exp_arc of ExpWave is
signal d:integer;
begin
outp<=conv_std_logic_vector(d,10);
  process(clk)
    variable tmp:integer range 0 to 63;
  begin
  
     if clk'event and clk='1' then
        if tmp=63 then
           tmp:=0;
        else
           tmp:=tmp+ 1;
        end if;
        case tmp is
           when 00=>d<=1023;  when 01=>d<=990;  when 02=>d<=959;
           when 03=>d<=930;  when 04=>d<=903;  when 05=>d<=878;
           when 06=>d<=855;  when 07=>d<=832;  when 08=>d<=812;
           when 09=>d<=792;  when 10=>d<=774;  when 11=>d<=757;
           when 12=>d<=742;  when 13=>d<=727;  when 14=>d<=713;
           when 15=>d<=700;  when 16=>d<=688;  when 17=>d<=677;
           when 18=>d<=666;   when 19=>d<=656;   when 20=>d<=647;
           when 21=>d<=638;   when 22=>d<=630;   when 23=>d<=622;
           when 24=>d<=615;   when 25=>d<=609;   when 26=>d<=602;
           when 27=>d<=597;   when 28=>d<=591;    when 29=>d<=586;
           when 30=>d<=581;    when 31=>d<=577;    when 32=>d<=1;
           when 33=>d<=34;    when 34=>d<=65;    when 35=>d<=94;
           when 36=>d<=121;   when 37=>d<=146;   when 38=>d<=170;
           when 39=>d<=192;   when 40=>d<=212;   when 41=>d<=232;
           when 42=>d<=250;   when 43=>d<=267;   when 44=>d<=282;
           when 45=>d<=297;   when 46=>d<=311;  when 47=>d<=324;
           when 48=>d<=336;  when 49=>d<=348;  when 50=>d<=358;
           when 51=>d<=368;  when 52=>d<=377;  when 53=>d<=386;
           when 54=>d<=394;  when 55=>d<=402;  when 56=>d<=409;
           when 57=>d<=416;  when 58=>d<=422;  when 59=>d<=428;
           when 60=>d<=433;  when 61=>d<=438;  when 62=>d<=443;
           when 63=>d<=447;
           when others=>null;
        end case;
     end if;
  end process;
end Exp_arc;