After a hardware reset, P3.0 and P3.1 are initialised as normal I/O pins. If you want to use them for the serial transmission mode, you have to set up some registers.

As I see you have some questions about the 89C52, I recommend you to read following information:

From the tutorials of THIS site:
* Standard 8051 tutorial
(serial interface is handled in chapter 8)
* 8052 Tutorial

From Atmel:
http://www.atmel.com/atmel/products/prod20.htm
Where you can find datasheets, application notes, and reference material, also about your 89C52.

Have fun !

Henk