船舶控制：1正车指令；2倒车指令；档位（3前进+1，4后退+1，5停止）；控制指令：（6驾控，7集控，8机控）；9紧急停车；10越控；11消音；12试验；一共12个按键，帮忙把下面程序改一下，谢谢谢谢。。。。。
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.std_logic_arith.ALL;
USE ieee.std_logic_unsigned.ALL;
ENtiTY anjian IS
  PORT(
       pq:in std_logic_vector(1 to 12);
       clk:in std_logic;
       clr:in std_logic;
    aa: out std_logic_vector(7 downto 0)   
  );
END anjian;
ARCHITECTURE anjian_encoder OF anjian IS
BEGIN
  PROCESS(clk,clr)
  BEGIN
      IF (clk'event and clk='1')THEN
   IF (clr='1' ) THEN
          aa<="00000000";
    ELSE      
    CASE pq IS
        WHEN "100010000000"=> aa <="00010001";
         WHEN "100001000000"=> aa <="00010010";
        WHEN "100000100000"=> aa <="00010011";
        WHEN "100000010000"=> aa <="00010100";
          WHEN "100000001000"=> aa <="00010101";
         WHEN "100000000100"=> aa <="00010110";
         WHEN "100000000010"=> aa <="00010111";
         WHEN "100000000001"=> aa <="00011000";
      WHEN "010010000000"=>aa<="00100001";
      WHEN "010001000000"=>aa<="00100010";
      WHEN "010000100000"=>aa<="00100011";
      WHEN "010000010000"=>aa<="00100100";
      WHEN "010000001000"=>aa<="00100101";
      WHEN "010000000100"=>aa<="00100110";
      WHEN "010000000010"=>aa<="00100111";
      WHEN "010000000001"=>aa<="00101000";
      WHEN "001010000000"=>aa<="00110001";
      WHEN "001001000000"=>aa<="00110010";
      WHEN "001000100000"=>aa<="00110011";
      WHEN "001000010000"=>aa<="00110100";
      WHEN "001000001000"=>aa<="00110101";
      WHEN "001000000100"=>aa<="00110110";
      WHEN "001000000010"=>aa<="00110111";
      WHEN "001000000001"=>aa<="00111000";
      WHEN "000110000000"=>aa<="01000001";
      WHEN "000101000000"=>aa<="01000010";
      WHEN "000100100000"=>aa<="01000011";
      WHEN "000100010000"=>aa<="01000100";
      WHEN "000100001000"=>aa<="01000101";
      WHEN "000100000100"=>aa<="01000110";
      WHEN "000100000010"=>aa<="01000111";
      WHEN "000100000001"=>aa<="01001000";
      WHEN "110010000000"=>aa<="01010001";
      WHEN "001101000000"=>aa<="01010010";
      WHEN OTHERS =>aa<="00000000";
      END CASE;
      END IF;
  END IF;
    END PROCESS;
  END anjian_encoder;