Hi John,
maybe this would help..

<code>

tx_over bit 01h
rx_over bit 01h

org 0

ajmp main

org 0023h
acall ser
reti
ser:
jb ri,rxd
jb ti,txd
end_int:
ret
rxd:
setb rx_over
ajmp end_int

txd:
setb tx_over
ajmp end_int

org 0050h
main:
ORL SCON,#01110000B
ANL SCON,#01111100B
MOV PCON,#00000000B
MOV IE,#10010000B
MOV IP,#00010000B
MOV TH1,#0FDH
MOV TL1,#0FDH
MOV TMOD,#00100000B
MOV TCON,#00000000B

rece:
jnb rx_over,$
mov a,sbuf
; now there is a byte u received from HT
clr rx_over

trmit:
cpl a
mov sbuf,a
jnb tx_over,$
clr tx_over
...
...
</code>

Regards,
Harsha