I am going to use the term SCI as a short cut to mean the serial port on your Microcontroller. They do not, however, generate the proper voltages required for connecting to RS-232 devices.
Standards are a wonderful thing.
However, standards beget more standards, numbers, and classifications. Before you know it, people start talking in terms of standards and their revision numbers. Such is the case with RS-232. The RS-232 interface has been around for a very long time. It specifies the line voltages, connection considerations, baud rates, and a whole slew of other technical items.