sel_7.vhd

出租车的计费系统

library ieee;
use ieee.std_logic_1164.all;
entity sel_7 is
       port(d  :in std_logic_vector(6 downto 0);
            y  :out std_logic);
end sel_7;
architecture sel_7x of sel_7 is
begin
         process(d)
         variable temp:integer;
         begin
             temp:=0;
            for i in 0 to 6 loop
                   if(d(i)='1') then
                       temp:=temp+1;
                   end if;
            end loop;
                if(temp>3) then 
                     y<='1';
                else
                    y<='0';
                end if;
         end process;
end sel_7x;