controller.vhd

实现交通灯控制器的vhdl编程

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity controller is
port( clock : in std_logic;    --输入时钟，频率为1Hz
      reset : in std_logic;    --复位信号，高电平有效
      hold  : in std_logic;    --保持信号，高电平有效
      flash : out std_logic;    --转换期间的闪烁信号
      numA,numB : out integer range 0 to 25;
      redA,greenA,yellowA : out std_logic;
      redB,greenB,yellowB : out std_logic);
end entity;
architecture behav of controller is
signal countnum : integer range 0 to 50 ;
begin
  process(clock)
  begin

    if reset='1' then            --复位信号将计数器清零
      countnum<=0;
    elsif rising_edge(clock) then
      if hold='1' then
        flash<='1';
      else   
        flash<='0';
        if countnum=59 then        --计数到50s时，计数器清零
          countnum<=0;
        else
          countnum<=countnum+1;      --正常计数，计脉冲上升沿
        end if;
      end if;
    end if;
  end process;
  process(clock)
  begin
    if rising_edge(clock) then
      if hold='1' then        --hold信号有效期间，两组路灯都为红灯
        redA<='1';
        redB<='1';
        greenA<='0';
        greenB<='0';
        yellowA<='0';
        yellowB<='0';
      else                   --hold无效期间，系统行为：按照一个计数周期（50s）描述灯的动作
        if countnum<=24 then     --前20s，A灯为绿
          numA<=25-countnum;
          redA<='0';
          greenA<='1';
          yellowA<='0';
        elsif (countnum<=29) then     --21～25s，A灯为黄
          numA<=30-countnum;
          redA<='0';
          greenA<='0';
          yellowA<='1';
        else
          numA<=60-countnum;        --26～50s，A灯为红
          redA<='1';
          greenA<='0';
          yellowA<='0';
        end if;
        if countnum<=29 then        --0～25s（A灯为绿、黄期间），B灯为红
          numB<=30-countnum;
          redB<='1';
          greenB<='0';
          yellowB<='0';
        elsif countnum<=54 then     --26～45s，B灯为绿
          numB<=55-countnum;
          redB<='0';
          greenB<='1';
          yellowB<='0';
        else 
          numB<=60-countnum;        --46～50s期间，B灯为红黄
          redB<='0';
          greenB<='0';
          yellowB<='1';
        end if;
      end if;
    end if;
  end process;
end behav;