div_clk_25mhz.vhd

这个是国外大学的项目代码

------------------------------------------------------------------------
--  div_clk_25Mhz.vhd -- 
------------------------------------------------------------------------
--  Authors : Albert Zemba & Mihai Cucicea
------------------------------------------------------------------------
-- Software version: Xilinx ISE 7.1i 
--                   WebPack
------------------------------------------------------------------------
-- This source file contains the div_clk_25Mhz component
------------------------------------------------------------------------
--  Behavioral description
-- Divides the input clock in half
-- The output is required for the vga input clock 
------------------------------------------------------------------------
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity div_clk_25Mhz is
	port(clock_50Mhz:in std_logic;
			clk25:out std_logic);
end div_clk_25Mhz;

architecture Behavioral of div_clk_25Mhz is
signal clk : std_logic:= '0';
begin

	 process (clock_50Mhz)
	 	begin
			if clock_50Mhz = '1' and clock_50Mhz'event then 
				clk <= not clk;
			end if;
	 clk25 <= clk;
	 end process;

end Behavioral;