hex7.vhd

用VHDL编写的一个出租车计费器

library ieee;
use ieee.std_logic_1164.all;

entity hex7 is
	port(   clk : in  std_logic;
			hex : out std_logic_vector(3 downto 0));
end hex7;

architecture art of hex7 is
	signal cnt:integer range 0 to 9;
begin
  process(clk)
  begin
	if rising_edge(clk)then
		if cnt=9 then
			cnt<=0;
		else cnt<=cnt+1;
		end if;
	else null;
	end if;
	case cnt is
		when 0 =>hex<= "0000";
		when 1 =>hex<= "0001";
  		when 2 =>hex<= "0010";
  		when 3 =>hex<= "0011";
		when 4 =>hex<= "0100";
   		when 5 =>hex<= "0101";
   		when 6 =>hex<= "0110";
   		when 7 =>hex<= "0111";
   		when 8 =>hex<= "1000";
   		when 9 =>hex<= "1001";
		when others =>hex<= "0000";
	end case;
  end process;
end art;