cymometer.vhd

一些很好的FPGA设计实例

--文件名：cymometer.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

--说  明：高4位进行动态显示。所显示的结果是数码管显示的数据乘以十的N次方；N对应发光二极

--        管的右边点亮的第几位就是几，如果如果最右边的一个被点亮的话，频率就等于显示的

--        数值乘以10的一次方。频率的测量范围是0～9,999,999HZ。

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity cymometer is
  port ( reset:in std_logic;                      --复位信号,高电平有效
         clk :in std_logic;                       --系统时钟
	    select_sw:in std_logic_vector(1 downto 0 );--选择被测频率是外部输入还是内部输入
         check_clk:in std_logic;                  --外部输入被测信号
	    cs:out std_logic_vector(1 downto 0);      --74HC573的选通信号
         data_led:out std_logic_vector(7 downto 0);    --八段码
         shift:out std_logic_vector(3 downto 0)); --数码管位选信号
end cymometer;
architecture behav of cymometer is
signal cnt1,cnt2,cnt3,cnt4,cnt5,cnt6,cnt7: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 k_1hz :integer range 0 to 50000000;                     --秒分频系数                    

signal en,bclk,clk_shift,check_clk1,check_clk2,check_clk3:std_logic;                                  --使能信号，有效被测信号	，动态扫描分频
signal point : std_logic_vector(3 downto 0);                 --小数点
signal pointout : std_logic_vector(7 downto 0); 
signal bcd0,bcd1,bcd2,bcd3 : std_logic_vector(3 downto 0); --寄存7位十进制计数器中有效的高4位数据
--signal led:std_logic_vector(7 downto 0);  
signal ledfa:std_logic;    
begin
process(clk)										 --分频器；
variable cnt11,cnt22,cnt33 : integer range 0 to 25000000;
begin
   if reset='1' then
	  cnt11:=0;cnt22:=0;cnt33:=0;check_clk1<='0'; check_clk2<='0';check_clk3<='0';
     elsif clk'event and clk='1' then 

        if cnt11=249 then check_clk1<=not check_clk1;cnt11:=0;
	   else cnt11:=cnt11+1; 
	   end if;

	   if cnt22=24999 then check_clk2<=not check_clk2; cnt22:=0;
	   else cnt22:=cnt22+1; 
	   end if;

	   if cnt33=99999 then check_clk3<=not check_clk3; cnt33:=0;
	   else cnt33:=cnt33+1; 
	   end if;
   end if;
end process;

second:process(clk,reset)     --此进程产生一个持续时间为一秒的的闸门信号 
begin
  if reset='1' then k_1hz<=0;
  elsif clk'event and clk='1' then 
     if k_1hz<49999999 then k_1hz<=k_1hz+1;
     else k_1hz<=50000000; 
     end if;
  end if;
  if k_1hz<49999999 and  reset='0' then en<='1';
  else en<='0';
  end if;
end process;


and2:process(en,select_sw,check_clk1,check_clk2,check_clk3,check_clk)    --此进程得到7位十进制计数器的计数脉冲
begin
  if select_sw="00" then
     bclk<=check_clk and en;
  elsif select_sw="01" then
	bclk<=check_clk1 and en;
  elsif select_sw="10" then
	bclk<=check_clk2 and en;
  else
	bclk<=check_clk3 and en;
   end if;
end process;

 
com:process(en,reset,bclk)  --此进程完成对被测信号计脉冲数
begin
  if reset='1' then                             --复位
cnt1<="0000";cnt2<="0000";cnt3<="0000";cnt4<="0000";cnt5<="0000";cnt6<="0000";cnt7<="0000";
  elsif bclk'event and bclk='1' then  
     if cnt1="1001" then cnt1<="0000";                   --此IF语句完成个位十进制计数
        if cnt2="1001" then cnt2<="0000";                --此IF语句完成百位十进制计数
           if cnt3="1001" then cnt3<="0000";             --此IF语句完成千位十进制计数
              if cnt4="1001" then cnt4<="0000";          --此IF语句完成万位十进制计数
                 if cnt5="1001" THEN cnt5<="0000";       --此IF语句完成十万位十进制计数
                    if cnt6="1001" then cnt6<="0000";    --此IF语句完成百万位十进制计数
                       if cnt7="1001" then cnt7<="0000"; --此IF语句完成千万位十进制计数
                       else cnt7<=cnt7+1; 
                       end if;
                    else cnt6<=cnt6+1; 
                    end if;
                 else cnt5<=cnt5+1; 
                 end if;
              else cnt4<=cnt4+1; 
              end if;
           else cnt3<=cnt3+1; 
           end if;
        else cnt2<=cnt2+1;
        end if;
     else cnt1<=cnt1+1; 
     end if; 
  end if;
end process;

process(clk,en) --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 cnt7>"0000" then bcd3<=cnt7; bcd2<=cnt6; bcd1<=cnt5; bcd0<=cnt4; point<="0111";
        elsif cnt6>"0000" then bcd3<=cnt6; bcd2<=cnt5; bcd1<=cnt4; bcd0<=cnt3; point<="1011";
        elsif cnt5>"0000" then bcd3<=cnt5; bcd2<=cnt4; bcd1<=cnt3; bcd0<=cnt2; point<="1101";
 	    else bcd3<=cnt4; bcd2<=cnt3; bcd1<=cnt2; bcd0<=cnt1; point<="1111";
	    end if;
     end if;
   end if;
end process;

process(clk)										 --分频器；
variable cnt : integer range 0 to 50000;
begin
   if clk'event and clk='1' then cnt:=cnt+1;
      if cnt<2500 then clk_shift<='1';
		elsif cnt<50000 then clk_shift<='0';
		else cnt:=0;clk_shift<='0';
		end if;
   end if;
end process;

process(clk_shift,reset)		--此进程完成数据的动态显示	 ,数据的赋植提前了一个时钟，原因是译码模块使得数据传输延迟了一个时钟；
variable cnt : std_logic_vector(2 downto 0);
begin
  if reset='1' then
     cnt:="000";cs<="00";shift<="1111";
   elsif clk_shift'event and clk_shift='1' then 
         cnt:=cnt+1;
			if cnt="001" then
			   ledfa<='0';	
			   cs<="11";
				shift<="1111";
				bcd<="1111";		--发光二极管、数码管全灭；
			elsif cnt="010" then 
				cs<="00";
				shift<="1111";
				bcd<=bcd3;	   
			elsif cnt="011" then 
				cs<="01";
				shift<="0111";
				bcd<=bcd2; 	   
			elsif cnt="100" then 
				cs<="01";
				shift<="1011";
				 bcd<=bcd1; 	
			elsif cnt="101" then
				cs<="01";
				shift<="1101";
				 bcd<=bcd0;   	
			elsif cnt="110" then
				cs<="01"; 
				shift<="1110";	
				ledfa<='1';
			 	pointout<='1'&'1'&'1'&'1'&point;
			elsif cnt="111" then
				cs<="10";
				bcd<="1111";							
				shift<="1111";
				 
			end if;
		
   end if;
end process;


 process (clk_shift,bcd)               --译码
  begin
  if clk_shift'event and clk_shift='1' then
     if ledfa='1' then
      data_led<=pointout;
       else
        case bcd is
         when"0000"=>data_led<="11000000";--0
	    when"0001"=>data_led<="11111001";--1
	    when"0010"=>data_led<="10100100";--2
	    when"0011"=>data_led<="10110000";--3
	    when"0100"=>data_led<="10011001";--4
	    when"0101"=>data_led<="10010010";--5
	    when"0110"=>data_led<="10000010";--6
	    when"0111"=>data_led<="11111000";--7
	    when"1000"=>data_led<="10000000";--8
	    when"1001"=>data_led<="10010000";--9
	    when others=>data_led<="11111111";--No signal; 
       end case;
  	end if;
  end if;
end process;
end behav;