原创:10分频的VHDL实现,格雷码,50%占空比;欢迎拍砖.

hawkflyking

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity Divide_10 is   
      port(
        clk_in    : in        std_logic;
        clk_out   : out        std_logic
        );
end entity;

architecture rtl of Divide_10 is
signal cnt   :    std_logic_vector(3 downto 0);

begin

    process (clk_in)
    begin
    if (rising_edge(clk_in)) then
        case cnt is
        when "0000" =>clk_out <= '1';cnt <= "0001";
        when "0001" =>clk_out <= '1';cnt <= "0011";
        when "0011" =>clk_out <= '1';cnt <= "0111";
        when "0111" =>clk_out <= '1';cnt <= "0110";
        when "0110" =>clk_out <= '1';cnt <= "1110";
        when "1110" =>clk_out <= '0';cnt <= "1100";
        when "1100" =>clk_out <= '0';cnt <= "1101";
        when "1101" =>clk_out <= '0';cnt <= "1001";
        when "1001" =>clk_out <= '0';cnt <= "1000";
        when "1000" =>clk_out <= '0';cnt <= "0000";
        when others =>clk_out <= 'X';cnt <= "XXXX";
        end case;
    end if;
    end process;
            
end rtl;

40130064

修改麻烦。
分频系数大时更麻烦。

所以还是计数器的好。

hawkflyking

计数器有很大的时延，不够精确，4分，8分很容易，这个是拿来降频用的比如，48MHZ 3次十分频->48K 2次8分频->3K

你发个计数器的分频程序，给我看看示波器波形?

40130064

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity clk_div2 is
generic(countmax:integer :=5);
port(CLKIN:in std_logic;
      CLKOUT:BUFFER std_logic);     
end;
architecture EPM570 of clk_div2 is
begin
process(CLKIN)
variable count:integer range 1 to countmax;
begin
if CLKIN'event and CLKIN='1' then
  if count=count'high then
         CLKOUT<=NOT CLKOUT;
         count:=1;
  else
     count:=count+1;
  end if;
end if;
end process;
end ;


library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity clk_div is
generic(countmax:integer :=10);
port(CLKIN:in std_logic;
      CLKOUT:out std_logic);     
end;
architecture EPM570 of clk_div is
begin
process(CLKIN)
variable count:integer range 1 to countmax;
begin
if CLKIN'event and CLKIN='1' then
  if count=count'high then
         CLKOUT<='1';
         count:=1;
  else
     count:=count+1;
     CLKOUT<='0';
  end if;
end if;
end process;
end ;