led.vhd

本实验完成发光二极管的循环点亮实验

library IEEE;--library used
use IEEE.STD_LOGIC_1164.all;
use IEEE.STD_LOGIC_unsigned.all;
entity led is--entity 	start	
   port( reset:in   std_logic;
         clk: in   std_logic;
 		 ledout:   out  std_logic_vector(7 downto 0)
        );
end led;--end entity
architecture lxf of led is
signal   count1 : std_logic_vector(2 DOWNTO 0); --start  architecture lxf
begin
--process u1
u1:process(clk,reset)
variable count0:integer RANGE  20000000 DOWNTO 0;
begin
if (reset='1') then --reset pin assigned pin 89
  if ( clk'event and clk = '1') then
		count0 := count0 + 1;
		if (count0 = 12000000) then --fen pin 
			count0 := 0;
			count1<=count1+1; 
		end if ;
   end if;
else count1<="000";
end if;
end process u1;
--process u1
u2:process (count1,clk)
begin
case count1 is
	when "000" =>ledout <= "00000001";
	when "001" =>ledout <= "00000010";
	when "010" =>ledout <= "00000100";
	when "011" =>ledout <= "00001000";
	when "100" =>ledout <= "00010000";
	when "101" =>ledout <= "00100000";
	when "110" =>ledout <= "01000000";
	when "111" =>ledout <= "10000000";
	when others=>null;
end case;
end process u2 ;
end lxf;----end  architecture lxf