ten.vhd

出租车的计费系统

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity ten is
     port(reset,clk  :in std_logic;
          q       :out std_logic_vector(3 downto 0));
end ten;
architecture tenx of ten is
     signal qo:std_logic_vector(3 downto 0);
begin
     process(clk,reset,qo)
     begin
          if reset='0' then
                qo<="0000";
          else if(clk'event and clk='1') then
              if qo<"1001" then
                 qo<=qo+1;
              else 
                 qo<="0000"; 
                end if;
          end if;
         end if;
       q<=qo;
   end process;
end tenx;