dengjingdupinglvji.txt

设计一个用等精度测频原理的频率计。 频率测量范围1~9999； 其精度为 ； 用4位带小数点数码管显示其频率； 并且具有超量程、欠量程提

VHDL语言设计如下所示:
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
entity a is
   port(clk:in std_logic;
            tclk:in std_logic;
            start:in std_logic;
            alarm0,alarm1:out std_logic;
            dian:out std_logic_vector(3 downto 0);
            data1:out integer range 0 to 9999);
end a;
architecture behav of a is
signal q:integer range 0 to 9999;
signal q1:integer range 0 to 10000;
signal q2:integer range 0 to 20000;
signal en,en1:std_logic;
signal qq,qqq:integer range 0 to 200000000;
signal data0:integer range 0 to 9999;
begin
process(clk)

begin 
   if clk'event and clk='1' then
       if start='1' then q<=0;en<='0';
       elsif q=9999 then q<=9999;en<='0';
       else q<=q+1;en<='1';
       end if;
   end if;
end process;
process(tclk)
 
begin
  if tclk'event and tclk='1' then
      if start='1' then q1<=0;en1<='0';
      elsif en='1' then q1<=q1+1;en1<='1';
      else en1<='0';
      end if;
  end if;
end process;
process(clk)

begin
  if clk'event and clk='1' then
      if start='1' then q2<=0;
      elsif en1='1' then
            if q2=20000 then q2<=20000;
            else q2<=q2+1;
            end if;
      end if;
  end if;
end process;
process(clk)
begin
  if clk'event and clk='1' then
      if start='1' then data0<=0;dian<="0000";alarm0<='0';alarm1<='0';qqq<=0;qq<=00;
      elsif en1='0' then 
          if q1>=1000 then qq<=q1*10000;
             if qqq<qq then qqq<=qqq+q2;data0<=data0+1;dian<="0000";
             elsif data0>=10000 then alarm0<='1';
             else data1<=data0;
             end if;
          elsif q1>=100 then qq<=q1*100000;
             if qqq<qq then qqq<=qqq+q2;data0<=data0+1;
             elsif data0>=10000 then data1<=1000;dian<="0000";
             else data1<=data0;dian<="0010";
             end if;
   elsif q1>=10 then qq<=q1*1000000;
             if qqq<qq then qqq<=qqq+q2;data0<=data0+1;
             elsif data0>=10000 then data1<=1000;dian<="0010";
             else data1<=data0;dian<="0100";
             end if;
          elsif q1>=1 then qq<=q1*10000000;
             if qqq<qq then qqq<=qqq+q2;data0<=data0+1;
             elsif data0>=10000 then data1<=1000;dian<="0100";
             else data1<=data0;dian<="1000";
             end if;
           end if;
        elsif q2>19999 then alarm1<='1';
        else alarm1<='0';
        end if;
     end if;
end process; 
end behav;