2.txt

ISE9.1的开发环境编写的程序啊,是个很有用的东西,大家认真看一下.

entity count is
    Port ( clk : in  STD_LOGIC;
           reset : in  STD_LOGIC;
           clkout : out  STD_LOGIC;
           s1 : out  STD_LOGIC;
           s2 : out  STD_LOGIC);
end count;

architecture Behavioral of count is
signal s1n,s2n : std_logic;
signal cnt   : integer range 0 to 4;
begin
process(clk,reset)                                       
   begin
if reset='1' then
cnt<=0;
elsif clk'event and clk='1' then
if cnt=4 then
    cnt<=0;
else
    cnt<=cnt+1;
end if;
end if;
   end process;
  

p1:process(clk,reset)                                     
   begin
if reset='1' then
s1n<='0';
elsif clk'event and clk='1' then
if cnt=0 then
    s1n<=not s1n;
else
    s1n<=s1n;
end if;
end if;
   end process;
  

p2:process(clk,reset)                                    
   begin
if reset='1' then
s2n<='0';
elsif clk'event and clk='0' then
if cnt=3 then
    s2n<=not s2n;
else
    s2n<=s2n;
end if;
end if;
s1<=s1n;
s2<=s2n;
end process;

clkout<= s1n xor s2n;                                        


end Behavioral;