VHDL交通灯

好的，这是一个IT类问题。下面是VHDL交通灯的代码：

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity traffic_light is
port(clk: in std_logic;
reset: in std_logic;
traffic_light_out: out std_logic_vector(3 downto 0));
end traffic_light;

architecture Behavioral of traffic_light is
signal cnt: integer range 0 to 1000000000 := 0;
signal state: integer range 0 to 3 := 0;

begin

process(clk, reset)
begin
if reset = '1' then
cnt <= 0;
state <= 0;
elsif rising_edge(clk) then
cnt <= cnt + 1;

if cnt >= 50000000 then
cnt <= 0;

case state is
when 0 =>
traffic_light_out <= "0001";
state <= 1;
when 1 =>
traffic_light_out <= "0010";
state <= 2;
when 2 =>
traffic_light_out <= "0100";
state <= 3;
when 3 =>
traffic_light_out <= "0010";
state <= 0;
end case;
end if;
end if;
end process;

end Behavioral;

以上是一个简单的VHDL交通灯代码，可以在FPGA或CPLD等可编程逻辑器件上实现交通灯的控制。