-- 向蜂鳴器發(fā)送一定頻率的方波可以使蜂鳴器發(fā)出相應(yīng)的音調(diào)，該實(shí)驗(yàn)通過設(shè)計(jì)一個(gè)狀態(tài)機(jī)和分頻
-- 器使蜂鳴器發(fā)出"多來咪發(fā)梭拉西多"的音調(diào)。
-- 
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY buzzer IS
   PORT (
      clk  : IN std_logic;   
      rst  : IN std_logic;   
      out_bit  : OUT std_logic);   
END buzzer;

ARCHITECTURE arch OF buzzer IS


   SIGNAL clk_div1   :  std_logic_vector(3 DOWNTO 0);   --基頻分頻計(jì)數(shù)器，基頻為4M
   SIGNAL clk_div2   :  std_logic_vector(12 DOWNTO 0);  --音階分頻計(jì)數(shù)器，由基頻分頻產(chǎn)生各個(gè)音階 
   SIGNAL cnt        :  std_logic_vector(21 DOWNTO 0);  --各音階發(fā)聲時(shí)間長(zhǎng)短計(jì)數(shù)器 
   SIGNAL state      :  std_logic_vector(2 DOWNTO 0);   
   --各個(gè)音調(diào)的分頻系數(shù)
   CONSTANT  duo   :  std_logic_vector(12 DOWNTO 0) :="0111011101110";     
   CONSTANT  lai  :  std_logic_vector(12 DOWNTO 0) := "0110101001101";    
   CONSTANT  mi   :  std_logic_vector(12 DOWNTO 0) := "0101111011010";    
   CONSTANT  fa    :  std_logic_vector(12 DOWNTO 0) := "0101100110001";    
   CONSTANT  suo   :  std_logic_vector(12 DOWNTO 0) := "0100111110111";    
   CONSTANT  la    :  std_logic_vector(12 DOWNTO 0) := "0100011100001";    
   CONSTANT  xi    :  std_logic_vector(12 DOWNTO 0) := "0011111101000";    
   CONSTANT  duo1   :  std_logic_vector(12 DOWNTO 0) := "0011101110111";   
   SIGNAL out_bit_tmp :std_logic; 

BEGIN