clock15.vhd

eda 开发数字钟的设计具体编程代码和开发流程与设计图

--*************************************************************************************--
--Colour Sort Machine/Fifteen dividing clock module V1.0/01.11.30
--EIST Department,Nankai University
--Function part/clockall/15-dividing clock
--Src file:clock15.vhd
--Serial number:005
--2001----2002
--*************************************************************************************--
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity clock15 is
  port(clk:in std_logic;     
       clkout:out std_logic  
       );
end entity;

architecture arc of clock15 is
begin
 process(clk) 
  variable count:std_logic_vector(3 downto 0);
  begin
    if (clk'event and clk='1') then
       case count is
          when "0000"=>count:="0001";    --Gray coding counter
          when "0001"=>count:="0011";
          when "0011"=>count:="0010";
          when "0010"=>count:="0110";
          when "0110"=>count:="0111";
          when "0111"=>count:="0101";
          when "0101"=>count:="0100";
          when "0100"=>count:="1100";
          when "1100"=>count:="1101";
          when "1101"=>count:="1111";
          when "1111"=>count:="1110";
          when "1110"=>count:="1010";
          when "1010"=>count:="1011";
          when "1011"=>count:="1001";
          when "1001"=>count:="0000";   --if 1001 change 1000 or 0001, count is always  0.
          when others=>count:="0000";
        end case;
    end if;

       case count is
          when "0000"=>clkout<='0';
          when "0001"=>clkout<='0';
          when "0011"=>clkout<='0';
          when "0010"=>clkout<='0';
          when "0110"=>clkout<='0';
          when "0111"=>clkout<='0';
          when "0101"=>clkout<='0';
          when "0100"=>clkout<='1';
          when "1100"=>clkout<='1';
          when "1101"=>clkout<='1';
          when "1111"=>clkout<='1';
          when "1110"=>clkout<='1';
          when "1010"=>clkout<='1';
          when "1011"=>clkout<='1';
          when "1001"=>clkout<='1';   --if 1001 change 1000 or 0001, count is always  0.
          when others=>clkout<='0';
        end case;
  end process;
end arc;