TRY THIS ONE....

ORG 000H
LCALL START
(YOUR PROGRAM ....)


START:
MOV TH1,#0FDH MOV TL1,#0FDH
MOV SP,#010H
MOV SCON,#050H
MOV TMOD,#021H
MOV TCON,#040H
RET

READ: JNB RI,READ
CLR RI
MOV A,SBUF
RET

WRITE: CLR TI
MOV SBUF,A
JNB TI,$
CLR TI ;
RET