how to simulate UART program in Keilc51

Sir,
Here is my UART program...
$
org 000h
ljmp begin
org 23h
ljmp serial_IT
;/**
; * FUNCTION_PURPOSE: This file set up uart in mode 1 (8 bits uart) with
; * timer 1 in mode 2 (8 bits auto reload timer).
; * FUNCTION_INPUTS: void
; * FUNCTION_OUTPUTS: void
; */
org 0100h
begin:
MOV SCON, #50h; /* uart in mode 1 (8 bit), REN=1 */
ORL TMOD, #20h; /* Timer 1 in mode 2 */
MOV TH1, #0FDh; /* 9600 Bds at 11.059MHz */
MOV TL1, #0FDh; /* 9600 Bds at 11.059MHz */
SETB ES; /* Enable serial interrupt*/
SETB EA; /* Enable global interrupt */
SETB TR1; /* Timer 1 run */
JMP $; /* endless */
;/**
; * FUNCTION_PURPOSE: serial interrupt, echo received data.
; * FUNCTION_INPUTS: P3.0(RXD) serial input
; * FUNCTION_OUTPUTS: P3.1(TXD) serial output
; */
serial_IT:
JNB RI,EMIT_IT ; test if it is a reception
CLR RI ; clear reception flag for next reception
MOV A,SBUF ; read data from uart
MOV SBUF,A ; write same data to uart
LJMP END_IT
EMIT_IT:
CLR TI ; clear transmition flag for next transmition
END_IT:
RETI
end

This program is taken from ATMEL SITe..

when i simulate it....during simulation how do i give serial input?
When u just run it,setting RI manually...check out SBUF value...no value in it???

How to give serial input??

Since port 3 (P3.0 (RXD) and P3.1 (TXD) ) is used for serial communication..
how to set p3.1 as output pin and p3.0 as input pin??

Thank you.
Tushar