architecture RTL_IF of DECODER is
begin architecture
  process(KEYPAD)
  begin process
    if KEYPAD(0) = '1' then KEY <= … ;
    elsif KEYPAD(1) = '1' then KEY <= … ;
    elsif KEYPAD(2) = '1' then KEY <= … ;
    elsif KEYPAD(3) = '1' then KEY <= … ;
    elsif KEYPAD(4) = '1' then KEY <= … ;
    …
    elsif KEYPAD(9) = '1' then KEY <= … ;
    else KEY <= … ;
    end if;
  end process;
end RTL_IF;