Thanks Ron,

I found the fault.

Both the SBUF in code and serial channel refer to transmission buffer!? eventhough SBUF is on right hand side of a statement. uVision get receive data from serial window #1.
Both RI & TI in serial channel can trigger interrupt, but can only access the transmit buffer. The documentation of Keil is not clear and their solution in knowledge base is misleading.

Regards,
David