traffic.vhd

实现得失一个交通灯。利用vhdl语言

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.all;

ENTITY traffic IS

  PORT(clk,clr,en,em:IN STD_LOGIC;

       ewr,ewy,ewg,nsr,nsy,nsg:OUT STD_LOGIC);

END traffic;

ARCHITECTURE rtl OF traffic IS

SIGNAL a:STD_LOGIC_VECTOR(5 DOWNTO 0);

BEGIN

  ewr<=a(0);

  ewy<=a(1);

  ewg<=a(2);

  nsr<=a(3);

  nsy<=a(4);

  nsg<=a(5);

  PROCESS(clr,clk)

  variable i:std_logic;
  
  BEGIN
    
    iF(clr='1')THEN

       a<="000000";

    ELSIF(clk'EVENT AND clk='1')THEN
     
       if(en='1')then

         
          IF(clk'EVENT AND clk='1')THEN

                   a<="100001";

              if(a="100001")then
     
                IF(clk'EVENT AND clk='1')THEN

                   a<="010010";

                end if;

              end if;
  
              if(a="010010")then
     
                IF(clk'EVENT AND clk='1')THEN

                     a<="001100";
     
                end if;
  
              end if;
  
              if(a="001100")then
     
                IF(clk'EVENT AND clk='1')THEN

                      a<="100001";
     
                end if;
  
               end if;
  
            end if;

              
       if(em='1')then
      
         a<="100100";
     

       end if ;
    
     end if;  
  
   end if;


END PROCESS;

END rtl;