entity LED_DRIVER is
  port ( D : in bit_vector (1 downto 0);
         S : out bit_vector (6 downto 0));
end entity LED_DRIVER;

architecture CONCURRENT of LED_DRIVER is
begin
  S <= "1111011" when D = "00" else
       "0001010" when D = "01" else
       "0110111" when D = "10" else
       "0011111" when D = "11";
end CONCURRENT;