cymometer.vhd

在quartus开发环境下

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity cymometer is
port(sysclk:in std_logic;----20mhz 时钟输入
     clkin:in std_logic;-----待测频率信号输入
     seg7:out std_logic_vector(6 downto 0);----7段显示控制信号(abcdefg) 
     scan:out std_logic_vector(7 downto 0));---数码管地址选择信号
end;
architecture one of cymometer is
signal cnt:std_logic_vector(24 downto 0);-----用于分频的计数器
signal clk_cnt :std_logic;
signal cntp1,cntp2,cntp3,cntp4,cntp5,cntp6,cntp7,cntp8:std_logic_vector(3 downto 0);
signal cntq1,cntq2,cntq3,cntq4,cntq5,cntq6,cntq7,cntq8:std_logic_vector(3 downto 0);
signal dat:std_logic_vector(3 downto 0);
begin
---------------------------------------0.5Hz分频---------
process(sysclk)
begin
if sysclk'event and sysclk='1' then
   if cnt=19999999 then clk_cnt<=not clk_cnt;cnt<=(others=>'0');
   else cnt<=cnt+1;
   end if; 
end if;
end process;
--------------------------------在一秒钟内计数-----
process(clkin)
begin
if clkin'event and clkin='1' then
 if clk_cnt='1' then
	if cntp1="1001" then cntp1<="0000";
	  if cntp2="1001" then cntp2<="0000";
	    if cntp3="1001" then cntp3<="0000";
	      if cntp4="1001" then cntp4<="0000";
	        if cntp5="1001" then cntp5<="0000";
	          if cntp6="1001" then cntp6<="0000";
	            if cntp7="1001" then cntp7<="0000";
	              if cntp8="1001" then cntp8<="0000";
	              else cntp8<=cntp8+1;end if;
	            else cntp7<=cntp7+1;end if;
	          else cntp6<=cntp6+1;end if;
	        else cntp5<=cntp5+1;end if;
	      else cntp4<=cntp4+1;end if;
	    else cntp3<=cntp3+1;end if;
	  else cntp2<=cntp2+1;end if;
	else cntp1<=cntp1+1;end if;
  else  
    if  cntp1/="0000" or cntp2/="0000" or cntp3/="0000" or ----对计数值锁存
        cntp4/="0000" or cntp5/="0000" or cntp6/="0000" or
        cntp7/="0000" or cntp8/="0000" then  
	    cntq1<=cntp1;   cntq2<=cntp2;   cntq3<=cntp3;  
	    cntq4<=cntp4;   cntq5<=cntp5;   cntq6<=cntp6;  
	    cntq7<=cntp7;   cntq8<=cntp8; 
	    cntp1<="0000";  cntp2<="0000";  cntp3<="0000";
	    cntp4<="0000";  cntp5<="0000";  cntp6<="0000";
	    cntp7<="0000";  cntp8<="0000";
    end if;
  end if;
end if;
end process;
-----------------------------扫描数码管----
process(cnt(15 downto 13),cntq1,cntq2,cntq3,cntq4,cntq5,cntq6,cntq7,cntq8,dat)
begin
case cnt(15 downto 13) is
	when "000"=>scan<="00000001";dat<=cntq1;  
	when "001"=>scan<="00000010";dat<=cntq2;  
	when "010"=>scan<="00000100";dat<=cntq3;  
	when "011"=>scan<="00001000";dat<=cntq4;  
	when "100"=>scan<="00010000";dat<=cntq5;  
	when "101"=>scan<="00100000";dat<=cntq6;  
	when "110"=>scan<="01000000";dat<=cntq7;  
	when "111"=>scan<="10000000";dat<=cntq8;  
	when others=>null;
end case;
end process;
----------------------------数码管显示译码
process(dat)
begin
case dat is
	when"0000"=>seg7<="1111110";
	when"0001"=>seg7<="0110000";
	when"0010"=>seg7<="1101101";
	when"0011"=>seg7<="1111001";
	when"0100"=>seg7<="0110011";
	when"0101"=>seg7<="1011011";
	when"0110"=>seg7<="1011111";
	when"0111"=>seg7<="1110000";
	when"1000"=>seg7<="1111111";
	when"1001"=>seg7<="1111011";
    when others=>null;
end case;
end process;
end;