controller.vhd

基于VHDL实现的十字路口交通灯功能

library ieee;
use ieee.std_logic_1164.all;

entity controller is
port
(clk:in std_logic;
hold:in std_logic;
num:buffer integer range 0 to 49;
a1,b1:out integer range 0 to 25;
red1,green1,yellow1:out std_logic;
red2,green2,yellow2:out std_logic;
shanshuo:out std_logic);
end;

architecture b_controller of controller is
begin
  process(clk)
begin
if falling_edge(clk) then
  if hold='1' then
    red1<='1';
    red2<='1';
    green1<='0';
    green2<='0';
    yellow1<='0';
    yellow2<='0';
    shanshuo<='1';
else
    shanshuo<='0';

  if  num<=19  then      
     a1<=20-num;
     green1<='1';
     red1<='0';
     yellow1<='0';
  elsif (num>19 and num<=24) then
     a1<=25-num;
     yellow1<='1';
     red1<='0';
     green1<='0';
else
   a1<=50-num;
   red1<='1';
   green1<='0';
   yellow1<='0';
end if;

if num<=24 then
   b1<=25-num;
   red2<='1';
   green2<='0';
   yellow2<='0';
elsif (num>24 and num<=44) then
  b1<=45-num;
  green2<='1';
  yellow2<='0';
  red2<='0';
else
 b1<=50-num;
 yellow2<='1';
 red2<='0';
 green2<='0';
end if;
end if;
end if;
end process;
end b_controller;