plj.txt

基于VHDL的简易数字频率计

--文件名：plj.vhd。 --功能：频率计。具有4位显示，能自动根据7位十进制计数的结果，自动选择有效数据的 
--高4位进行动态显示。小数点表示是千位，即KHz。 
--最后修改日期：2004.4.9。 
library ieee; 
use ieee.std_logic_1164.all; 
use ieee.std_logic_unsigned.all; 
entity plj is port 
( 
start:in std_logic; --复位信号 
clk :in std_logic; --系统时钟 
clk1:in std_logic; --被测信号 
yy1:out std_logic_vector(7 downto 0); --八段码 
w1 :out std_logic_vector(3 downto 0)); --数码管位选信号 
end plj; 
architecture behav of PLj is signal b1,b2,b3,b4,b5,b6,b7:std_logic_vector(3 downto 0); --十进制计数器 signal bcd:std_logic_vector(3 downto 0); --BCD码寄存器 
signal q :integer range 0 to 49999999; --秒分频系数  
signal qq : integer range 0 to 499999; --动态扫描分频系数 
signal en,bclk:std_logic; --使能信号，有效被测信号 
signal sss : std_logic_vector(3 downto 0); --小数点 
signal bcd0,bcd1,bcd2,bcd3 : std_logic_vector(3 downto 0);
--寄存7位十位计数器中有效的高4位数据 
begin 
 
second:process(clk) --此进程产生一个持续时间为一秒的的闸门信号  
begin if start='1' then q<=0;
elsif clk'event and clk='1' then  
if q<49999999 then q<=q+1; 
else q<=49999999;
end if; 
end if; 
if q<49999999 and start='0' then en<='1'; 
else en<='0'; end if; end process;  

and2:process(en,clk1) --此进程得到7位十进制计数器的计数脉冲 begin bclk<=clk1 and en; end process;   
com:process(start,bclk) --此进程完成对被测信号计脉冲数 begin if start='1' then --复位 
b1<="0000";b2<="0000";b3<="0000";b4<="0000";b5<="0000";b6<="0000";b7<="0000";
 elsif bclk'event and bclk='1' then 
 if b1="1001" then b1<="0000"; --此IF语句完成个位十进制计数 
if b2="1001" then b2<="0000"; --此IF语句完成百位十进制计数 
if b3="1001" then b3<="0000"; --此IF语句完成千位十进制计数 
if b4="1001" then b4<="0000"; --此IF语句完成万位十进制计数 
if b5="1001" THEN b5<="0000"; --此IF语句完成十万位十进制计数
 if b6="1001" then b6<="0000"; --此IF语句完成百万位十进制计数
 if b7="1001" then b7<="0000"; --此IF语句完成千万位十进制计数 
else b7<=b7+1;
  end if; 
else b6<=b6+1;
  end if; 
else b5<=b5+1; 
 end if; 
else b4<=b4+1; 
 end if; 
else b3<=b3+1;  
end if; 
else b2<=b2+1; 
end if; else 
b1<=b1+1; 
 end if;  
end if; 
end process;  
process(clk) --此进程把7位十进制计数器有效的高4位数据送如bcd0~3；并得到小数点信息 
begin
if rising_edge(clk) then  
if en='0' then if b7<"0000" then bcd3<=b7; bcd2<=b6; bcd1<=b5; bcd0<=b4; sss<="1110"; 
elsif b6<"0000" then bcd3<=b6; bcd2<=b5; bcd1<=b4; bcd0<=b3; sss<="1101"; 
elsif b5<"0000" then bcd3<=b5; bcd2<=b4; bcd1<=b3; bcd0<=b2; sss<="1011"; 
else bcd3<=b4; bcd2<=b3; bcd1<=b2; bcd0<=b1; sss<="1111"; 
end if;
 end if; 
end if; 
end process;  

weixuan:process(clk) --此进程完成数据的动态显示 
begin 
if clk'event and clk='1' then  
if qq< 99999 then qq<=qq+1;bcd<=bcd3; w1<="0111";  
if sss="0111" then yy1(0)<='0'; 
else yy1(0)<='1'; 
end if; 
elsif qq<199999 then qq<=qq+1;bcd<=bcd2; w1<="1011"; 
if sss="1011" then yy1(0)<='0'; 
else yy1(0)<='1'; 
end if; 
elsif qq<299999 then qq<=qq+1;bcd<=bcd1; w1<="1101"; 
if sss="1101" then yy1(0)<='0';
 else yy1(0)<='1'; 
end if; 
elsif qq<399999 then qq<=qq+1;bcd<=bcd0; w1<="1110";  
if sss="1110" then yy1(0)<='0'; 
else yy1(0)<='1'; 
end if; 
else qq<=0; 
end if; 
end if; 
end process;  

m0: process (bcd) --译码 
begin 
case bcd is 
when "0000"=<yy1(7 downto 1)<="0000001"; 
when "0001"=<yy1(7 downto 1)<="1001111"; 
when "0010"=<yy1(7 downto 1)<="0010010"; 
when "0011"=<yy1(7 downto 1)<="0000110"; 
when "0100"=<yy1(7 downto 1)<="1001100"; 
when "0101"=<yy1(7 downto 1)<="0100100"; 
when "0110"=<yy1(7 downto 1)<="1100000"; 
when "0111"=<yy1(7 downto 1)<="0001111"; 
when "1000"=<yy1(7 downto 1)<="0000000"; 
when "1001"=<yy1(7 downto 1)<="0001100"; 
when others=<yy1(7 downto 1)<="1111111";
end case;
end process;
end behav;