RS-232 VDD. The RS-232 output signals (Pin 1 ~ Pin 3) are
designed for 5V, 3.3V or 3V operation. VDD_232 should be
connected to the same power level of the RS-232 interface.
(The RS-232 input signals are always 5V~3V tolerant.)
Note: This document version only provides 5V DC characteristic
information. Refer to future revisions for updates.