sound.vhd

具有多种功能的电子钟：闹钟

library ieee;                         --铃声管理
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity sound is
  port(alarmtime: in std_logic_vector(23 downto 0);  --闹钟预定时间
       clk: in std_logic;
       time:in std_logic_vector(23 downto 0);        --当前时间
	   alarmon :in std_logic;                        --闹钟开关
       houralarmon: in std_logic;                    --报时开关
       sound_signal: out std_logic);                 --闹钟信号
end sound;
architecture s of sound is
  signal alarm: std_logic;
  signal houralarm: std_logic;
  type state is(s0,s1,s2,s3,s4);                     --闹钟状态
  signal pre_state:state:=s0;
  signal next_state:state:=s0;
begin
 process(clk)     --更新
begin
  if(alarmon='0')then
    pre_state<=s0;
  elsif rising_edge(clk)then
     pre_state<=next_state;
  end if;
end process;

process(pre_state,time,alarmtime)
 begin
  case pre_state is
 when s0=>
         if(alarmtime=time)then
          next_state<=s1;
         else
           next_state<=pre_state;
		end if;
 when s1=>
         if(time(6)='1')then
          next_state<=s2;
         else
           next_state<=pre_state;
		end if;
 when s2=>
         if(time(6)='0')then
          next_state<=s3;
         else
           next_state<=pre_state;
		end if;   
when s3=>
         if(time(6)='1')then
          next_state<=s4;
         else
           next_state<=pre_state;
		end if;
when s4=>
         if(time(6)='0')then
          next_state<=s0;
         else
           next_state<=pre_state;
		end if;
when others=>
		next_state<=s0;
end case;
end process;

process(pre_state)  --状态译码
 begin
	if(pre_state=s3 or pre_state=s4)then
		alarm<='1';
     else
		alarm<='0';
end if ;
end process;

process(houralarmon,time)
begin
	if(houralarmon='1' and time(15 downto 0)="0000000000000000")then
           houralarm<='1';
    else
         houralarm<='0';
    end if;
end process;
sound_signal<=alarm or houralarm;
end s;