After you have finshed your design in VHDL you'll need a driver RS-232 that is, it translate 3.3v or 5v or else logic level you have to a ±5V ÷ ±12V (the standard allow large voltage interval). Every converter, transmitter or receiver inverts the signal, then if you send a logic high (1) it is inverted by your transmitter (driver) and the receiver (driver in your computer) inverts the signal again.
Then for sure, a Start bit is allways '0' and Stop bit(s) always '1'.
This converters (drivers) are available from Linear Technology, Analog devices, Maxim, Texas Instruments .... and much more.
I hope this helps