Question

一段VHDL程序。。。。有些地方不太明白，麻烦高手指点指点

用该程序来控制LED灯的亮法及数码管的计数

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

entity led_control is

port (clk : in std_logic;
led_c : out std_logic_vector(3 downto 0);
led_l : out std_logic_vector(6 downto 0);
qout : out std_logic_vector( 7 downto 0));

end led_control;

architecture design of led_control is

signal cnt : integer range 0 to 9999999 :=0; ---这个的作用是？
signal clk_out : std_logic;
signal led_cnt : integer range 0 to 8 :=0;
signal con_q : std_logic_vector (7 downto 0);
signal lcnt : integer range 0 to 9 :=0;

begin
process(clk)----该进程的作用是？
begin
if clk'event and clk = '1' then
if cnt < 9999999 then
cnt <= cnt + 1 ;
else cnt <= 0;
clk_out <= not clk_out;
end if ;
end if;

if clk_out'event and clk_out= '1' then
if led_cnt < 8 then
led_cnt <= led_cnt + 1;
else led_cnt <= 0;
end if;
end if;
end process;

with led_cnt select

con_q <= "10010010" when 0,
"01001001" when 1,
"11100000" when 2,
"11110000" when 3,
"11111000" when 4,
"01010101" when 5,
"10101010" when 6,
"00110011" when 7,
"11001100" when 8;

qout <= con_q ;
led_c <= "1111";
process(clk_out)
begin
if clk_out'event and clk_out = '1' then
if led_cnt = 8 then
if lcnt < 9 then
lcnt <= lcnt + 1;
else lcnt <= 0;
end if;
end if ;
end if;
一次发不完。。。继续

---十进制－BCD码转换；----这个的作用是？好像并没有什么用啊

--- if lcnt>999 then
-- lcnt<=lcnt-1000;
-- d4<=d4+1;
---led_c <= "1111";
--- elsif lcnt>99 then
-- lcnt<=lcnt-100; d3<=d3+1; --led_c <= "1110" ;
-- elsif lcnt>9 then
--lcnt<=lcnt-10; d2<=d2+1; --led_c <= "1100" ;
-- elsif lcnt>0 then
-- lcnt<=lcnt-1; d1<=d1+1; -- led_c<= "1000";

--else led_c<= "1111";

Answer 1

每一个的作用就是定义一个信号，它的数据类似是整型，可以是0到9999999变化，并给他赋个初值 为0
第二进程作用就是一个分频器，它把你系统的时钟的频率缩小5000000倍，使得时钟周期由us为单位的放大到以s为单位，这样可以让人眼观察到LED的变化