zhengshu.vhd

出租车的计费系统

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity zhengshu is
  port(clk,reset,stop     :in std_logic;
         enn             :out std_logic;
       shi_1,ge_0    :out std_logic_vector(3 downto 0));
end zhengshu;
architecture cnt_100_x of zhengshu is
     signal shi,ge:std_logic_vector(3 downto 0);
begin
    process(reset,clk,stop)
    begin
        if(reset='1') then
          shi<="0000";ge<="0000";
        else if(clk'event and clk='1') then
               ge<="0101";
             if(ge=9) then ge<="0000";
                if (shi=9) then shi<="0000";                         
                   else shi<=shi+1;
                end if;
               else ge<=ge+1;
              end if;
              if(shi>1) then
                 enn<='1';
               end if;
             if(stop='1') then
                 shi<=shi;
                 ge<=ge;
             end if;
          
      if(shi=9 and ge=9) then
         shi<="0000";
         ge<="0000"; 
      end if; 
     end if; 
   end if;
           shi_1<=shi;
          ge_0<=ge; 
end process;
end cnt_100_x;