ORG 0000H
MOV P1,#0FFH                                           
BACK:XRL 90H,#0FFH                              
ACALL DELAY                                           
SJMP BACK                                                 
DELAY:MOV TMOD,#01H                         
MOV TL0,#0E0H                                          
MOV TH0,#0B1H
SETB TR0                                                      
REPEAT:JNB TF0,REPEAT                       
CLR TR0                                                      
CLR TF0                                                        
RET                                                                
END