Question is still there why it not block further burst of "LLLL...."

Thanks JW & Erick,
I replace the JNB TI,$ with ACALL DELAY .It is working fine,it each the data back.every thing is working.

Erik Bible's reference serves very well......keep it up

CODE here
My opology, I am not addeding comment to this

ORG 0
			LJMP MAIN
			
			ORG 23H
			LJMP SERIAL
			
ORG 30H

MAIN:		MOV P1,#0FFH
			MOV TMOD,#20H
			MOV TH1,#0FAH
			MOV SCON,#50H
			MOV IE,#10010000B ;only serial 
			SETB TR1
			MOV R0,#'L'

BACK:		
			CPL P1.2
			MOV A,R0
			MOV SBUF,A
                      //JNB TI,$   
			ACALL DELAY 

AGN:		INC	R3
			ACALL DELAY
			ACALL DELAY
			ACALL DELAY 
			ACALL DELAY
			CJNE R3,#0FFH,AGN
			
			MOV R3,#00H
			SJMP BACK			
			
;;;;;;;;;;;;;;;;;;SERIAL ISR;;;;;;;;;;;;;;;;;;;;;;
SERIAL:		
			
			JNB RI,TRANS
			ACALL DELAY
			MOV A,SBUF
			CLR RI
			MOV R0,A
			JB TI,TRANS
			RETI	
			
			
TRANS:		CLR TI
			RETI


;;;;;;;;;;;;;;;;;;;DELAY;;;;;;;;;;;;;;;
DELAY:		MOV R1,#00H
AGAIN:		INC R1
			CJNE R1,#0FH,AGAIN
			RET
			
END