speakera.vhd

来自「用VHDL演示MUSIC的程序」· VHDL 代码 · 共 52 行

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity speakera is
port ( clk : in std_logic;
       tone : in std_logic_vector ( 10 downto 0 );
       spks : out std_logic );
end entity speakera;

architecture behave_speakera of speakera is
    signal preclk, fullspks : std_logic;
begin
divdeclk: process ( clk )
    variable count4 : std_logic_vector ( 3 downto 0 );
begin
    preclk <= '0';
    if count4 > 11 then 
       preclk <= '1'; count4 := "0000";
      elsif clk'event and clk = '1' then
            count4 := count4 + 1;
      end if;
    end process divdeclk;

genspks : process ( preclk, tone )
     variable count11 : std_logic_vector ( 10 downto 0 );
begin
   if preclk'event and preclk = '1' then
      if count11 = 16#7ff# then 
         count11 := tone; fullspks <= '1';
         else count11 := count11 + 1; fullspks <= '0';
      end if;
    end if;
end process genspks;

delayspks: process ( fullspks )
      variable count2 : std_logic;
           begin
           if fullspks'event and fullspks = '1' then
              count2 := not count2;
            if count2 = '1' then spks <= '1';
             else spks <= '0';
            end if;
           end if;
       end process delayspks;
end  behave_speakera;