The signal levels output by uP are not the same as RS232 (which are much higher), you need a converter.
Search this site for "MAX232" and "Reset circuit"
Go to the Maxim or Dallas web site and get the data sheet for the MAX232 it has the circuit you need.
Erik always suggest a supervisor chip, but there are many things that don't really need one. I've never used one and haven't had any problems thus far.

Jon