原创 模拟交通灯控制

        此程序设计的是模拟交通灯系统的控制，其中状态：ally是东西南北方向都亮黄灯，sny、sng分别为南北方向亮黄、绿灯，同样，ewy和ewg分别为东西方向亮黄、绿灯。

       本设计假设南北方向为主干道，通行时间为60秒，东西方向为次干道，通行时间为30秒，在两干道交替通行时有5秒的时间，此时两条干道的黄灯都要闪，在这个时候，原来通行的干道上的车应准备等待，原来在等待的车辆则可准备行驶；

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
entity traffic is
  port(clk:in std_logic;
       rst:in std_logic;
        pout:out std_logic_vector(12 downto 1));
end traffic;
architecture one of traffic is
type state is (ally,sng,sny,ewg,ewy);
signal ct:state:=ally;
signal nt:state;
signal pp :std_logic_vector(12 downto 1);
signal maxtime:bit;
signal mediatime:bit;
signal mintime:bit;
signal mintime1:bit;
signal a:bit;
signal time:integer range 0 to 60;
signal time1:integer range 0 to 30;
signal time2:integer range 0 to 5;
signal time3:integer range 0 to 5;
begin
neg:process(clk,rst) is
    begin
      if rst='1' then
         ct<=ally;
      elsif (clk'event and clk='1') then
        ct<=nt;
      end if;
    end process neg;
com:process(ct,clk) is
       begin
     if rising_edge(clk) then
        case ct is
         when ally => pp<="100100100100";
                      nt<=sng;
         when sng =>  pp<="010001010001";mediatime<='0';time1<=time1+1;
                          if time1=29 then mediatime<='1';end if;
                      if mediatime='1'then
                         nt<=sny;
                       end if;
        when sny =>  mintime<='0';time2<=time2+1;
                      if a='0' then pp<="110001110001";
                         else pp<="010001010001";
                      end if;
                        if time2=4 then mintime<='1';end if;
                      if mintime='1' then
                         nt<=ewg;
                      end if;
         when ewg =>  pp<="001010001010";maxtime<='0';time<=time+1;
                       if time="59" then maxtime<='1';end if;
                      if maxtime='1' then
                         nt<=ewy;
                      end if;
         when ewy => mintime1<='0';time3<=time3+1;
                      if a='0' then pp<="001110001110";
                         else pp<="001010001010";
                      end if;
                         if time3=4 then mintime1<='1';end if;
                      if mintime1='1' then
                        nt<=sng;
                      end if;
         when others => nt<=ally;
                  end case;
               end if;
    end process com;
la:process(ct)
begin
         if rising_edge(clk) then
              a<=not a;
    end if;
end process la;
    pout<=pp;
end one;
         本人水平十分有限，错误之处难免，望大家指正。