循环灯控制器，该控制器控制红、绿、黄三个发光管循环发亮（VHDL语言）

设计一个循环灯控制器，该控制器控制红、绿、黄三个发光管循环发亮。要求红发光管亮2秒，绿发光管亮3秒，黄发光管亮1秒。（假设外部提供频率为1MHz的方波信号）

library ieee;
use ieee.std_logic_1164.all;

entity loopled_tb_vhd is
end loopled_tb_vhd;

architecture rtl of loopled_tb_vhd is
  component loopled
    port(
       CLK,CLR:IN STD_LOGIC;
       Red,Green,Yellow:OUT STD_LOGIC
      );
  end component;

  signal clr  :std_logic:='0';
  signal clk  :std_logic:='0';
  signal Red  :std_logic;
  signal Green  :std_logic;
  signal Yellow  :std_logic;

  begin
    uut:loopled port map
    (
      clk=>clk,clr=>clr,Red=>Red,Green=>Green,Yellow=>Yellow
      );
  --clk_gen:process
  --begin
   -- clk <= '1' AFTER 0 ns;
    clr <='1' AFTER 0 ns,

         '0' AFTER 2 ns;

  tb:PROCESS
  BEGIN
    clk<='0';
    LOOP
        clk<='1','0' AFTER 1 ns;
        wait for 2 ns;
    END LOOP;
END PROCESS;

end rtl;