大家帮忙看下这个程序里的CNT2变量是干什么用的
这是一个控制蜂鸣器发出友谊天长地久音乐的一个乐谱
用Q来表示的 另外再接一个控制部分就可以控制蜂鸣器演奏了
时钟频率4M
其中的CNT2变量是干什么用的呢？
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
entity yindiao is
port
(clk : in std_logic;
q : out integer range 0 to 10204
);
end yindiao;
architecture behave of yindiao is
begin
process(clk)
variable cnt1:integer range 0 to 1500000;
variable cnt2:integer range 0 to 8;
variable n :integer range 0 to 45;
begin
if clk'event and clk='1' then
if cnt1<1500000 then --此数值控制每一个音的长短
cnt1:=cnt1+1;
else
cnt1:=0;
case n is
when 0 =>q<=10204;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=1;
end if;
when 1 =>q<=7364;
if cnt2<6 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=2;
end if;
when 2 =>q<=6061;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=3;
end if;
when 3 =>q<=6803;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=4;
end if;
when 4 =>q<=7634;
n:=5;
when 5 =>q<=6803;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=6;
end if;
when 6 =>q<=6061;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=7;
end if;
when 7 =>q<=7634;
if cnt2<4 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=8;
end if;
when 8 =>q<=6061;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=9;
end if;
when 9 =>q<=5089;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=10;
end if;
when 10 =>q<=4535;
if cnt2<9 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=11;
end if;
when 11 =>q<=5089;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=12;
end if;
when 12 =>q<=6061;
if cnt2<2 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=13;
end if;
when 13 =>q<=7634;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=14;
end if;
when 14 =>q<=6803;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=15;
end if;
when 15 =>q<=7634;
n:=16;
when 16 =>q<=6803;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=17;
end if;
when 17 =>q<=6061;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=18;
end if;
when 18 =>q<=7634;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=19;
end if;
when 19 =>q<=9050;
if cnt2<2 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=20;
end if;
when 20 =>q<=10204;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=21;
end if;
when 21 =>q<=7634;
if cnt2<7 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=22;
end if;
when 22 =>q<=4535;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=23;
end if;
when 23 =>q<=5089;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=24;
end if;
when 24 =>q<=6061;
if cnt2<2 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=25;
end if;
when 25 =>q<=7634;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=26;
end if;
when 26 =>q<=6803;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=27;
end if;
when 27 =>q<=7634;
n:=28;
when 28 =>q<=6803;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=29;
end if;
when 29 =>q<=4535;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=30;
end if;
when 30 =>q<=5089;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=31;
end if;
when 31 =>q<=6061;
if cnt2<2 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=32;
end if;
when 32 =>q<=5089;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=33;
end if;
when 33 =>q<=4535;
if cnt2<7 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=34;
end if;
when 34 =>q<=3809;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=35;
end if;
when 35 =>q<=5089;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=36;
end if;
when 36 =>q<=6061;
if cnt2<2 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=37;
end if;
when 37 =>q<=7634;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=38;
end if;
when 38 =>q<=6803;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=39;
end if;
when 39 =>q<=7634;
n:=40;
when 40 =>q<=6803;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=41;
end if;
when 41 =>q<=6061;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=42;
end if;
when 42 =>q<=7634;
if cnt2<3 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=43;
end if;
when 43 =>q<=9050;
if cnt2<2 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=44;
end if;
when 44 =>q<=10204;
if cnt2<1 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=45;
end if;
when 45 =>q<=7634;
if cnt2<7 then
cnt2:=cnt2+1;
else
cnt2:=0;
n:=0;
end if;
end case;
end if;
end if;
end process;
end behave;
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