自动售货机vhdl代码以及解析

奋斗的小孩 · 发表于 2016-7-8 21:24:02

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity drink_auto_sale is
      port(clk: in std_logic;
               reset:in std_logic;
               sw101:in std_logic;
               sw102:in std_logic;
               buy : out std_logic;
               back: out std_logic);
end drink_auto_sale;
architecture Behavioral of drink_auto_sale is
type state_type is(st0,st1);
signal cs ,ns : state_type;
begin
process(clk,reset)
begin
      if(reset = '1') then
               cs <= st0;
      elsif(clk'event and clk = '1') then
               cs <= ns;
      end if;
end process;

process(reset ,cs)
begin
      case cs is
               when st0 =>       if( sw101 = '1') then
                                                               ns <= st1;
                                                               buy<= '0';
                                                               back<= '0';
                                                      elsif(sw102 = '1') then
                                                               ns <= st0;
                                                               buy<= '1';
                                                               back <= '0';
                                                      else
                                                               ns <= st0 ;
                                                               buy <= '0';
                                                               back <= '0';
                                                      end if;
               when st1 => if(sw101 = '1') then
                                                               ns <= st0;
                                                               buy <= '1';
                                                               back <= '0';
                                                      elsif(sw102 = '1') then
                                                               ns <= st0;
                                                               buy <= '1';
                                                               back <= '1';
                                                      end if;
               when others => ns <= st0;
                                                               buy<= '0';
                                                               back <= '0';
      end  case;
end process;
end Behavioral;
设计过程：设定三个状态：0分，5分；当状态为0分时，接收到5分信号脉冲后转为5分；接收到10分信号脉冲时，转到0分状态，同时弹出饮料，不找零；状态为5分时，接受到5分信号，弹出饮料，不找零，返回0分状态；当接受到10分状态时，弹出饮料，找零，并返回零分状态。