dclk.vhd

本源码用VHDL语言实现了用键盘控制米字管显示十进制

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity dclk is 
	port(clk:in std_logic;
		 divclk:out std_logic);
end dclk;
architecture dclk_arch of dclk is 
begin
	process(clk)
	variable cnt:std_logic_vector(1 downto 0);
	variable a:std_logic;
		begin
	if clk'event and clk='1' then
	 if a='0' then
	 if cnt="11" then
	  a:='1';
	else
          cnt:=cnt+1;
	end if;
        elsif a='1' then
	if cnt="00" then
          a:='0';
        else
	 cnt:=cnt-1;
	end if;
	end if;
	end if;
   divclk<=a;
end process;
end dclk_arch;