Look at the schematic on this purple web site page. Near the upper corner it shows a very simple minded RS232 interface circuit for an 8051/8052 board. This can be used when the length of the cable to/from the host PC computer or other equipment is kept short and you keep the baud rate to lower rates. (I doubt the shown circuit would be reliable at 115200 baud for instance).

I don't know why you would try to avoid the choice of using a MAX232 but if the reason to is that you cannot procure them or you are trying to build a one-up interface using scrap parts from your junk box then maybe the referenced transistor circuit be just what you need.

Michael Karas