traffic.vhd

一个简单的交通灯程序(包括验证,主程序,和译码程序),在ALTER DE2板上实现

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity traffic is
port(clk,urgency:in std_logic;
     east_west:buffer std_logic_vector(7 downto 0);
     south_north:buffer std_logic_vector(7 downto 0);
     led:buffer std_logic_vector(5 downto 0);
     east_westa : buffer std_logic_vector(3downto 0);
     east_westb : buffer std_logic_vector(3 downto 0);
     south_northa : buffer std_logic_vector(3 downto 0);
     south_northb : buffer  std_logic_vector(3 downto 0)    );
end traffic;
architecture  arch of traffic is
begin 
  process(clk,urgency)
  begin
   if urgency='1' then
     led<="100001";
 elsif(clk'event and clk='1') then
   if(east_west=6 and south_north=1)then
    east_west<="00000101";
    south_north<="00000101";
    led<="100010";
 elsif(east_west=1 and south_north=1 and led(5)='1')then
    East_west<="01000000";
   South_north<="01000101";
   Led<="001001";
 Elsif(east_west=1 and south_north=6) then 
    East_west<="00000101";
   South_north<="00000101";
  Led<="010001";
 Elsif((east_west=1 and south_north=1 and led(0)='1') or east_west=0) then
   East_west<="01000101";
    South_north<="01000000";
     Led<="100100";
 Elsif(east_west(3 downto 0)="0000") then
   East_west<=east_west-7;
    South_north<=south_north-1;
 Elsif(south_north(3 downto 0)="0000") then
   East_west<=east_west-1;
   South_north<=south_north-7;
 Else
   East_west<=east_west-1;
   South_north<=south_north-1;
      End if;
    End if;
     east_westa <= east_west(3 downto 0);
     east_westb <= east_west(7 downto 4)  ; 
     south_northa <= south_north(3 downto 0);
     south_northb<= south_north(7 downto 4); 
  End process;
End arch;