ORG    0000H
        SJMP   START
        
        ORG    0003H
        CPL    F0
        RETI
        
        ORG    0040H
START:  CLR    F0
        SETB   IT0
        SETB   EX0
        SETB   EA       

;power LED flash  
        CLR    P1.0
        LCALL  DELAY2
        SETB   P1.0
        LCALL  DELAY2
        CLR    P1.0
        LCALL  DELAY2
        SETB   P1.0
        LCALL  DELAY2
        
;8 LED  all light,then all down
        MOV    DPTR,#0BFFFH
        MOV    A,#0FFH
        MOVX   @DPTR,A
        LCALL  DELAY2
        LCALL  DELAY2
        MOV    A,#00H
        MOVX   @DPTR,A
        LCALL  DELAY2
        
;wait for INT0
LOOP:   JNB   F0,$

;8 LED flow light 
        MOV    A,#01H
FLOW:   MOVX   @DPTR,A
        LCALL  DELAY2
        RL     A
        JNB    F0,NEXT
        SJMP   FLOW
        
NEXT:   MOV    A,#00H
        MOVX   @DPTR,A
        
        SJMP   LOOP        
        

;250ms delay
DELAY2: MOV    R3,#0FAH
DL3:    ACALL  DELAY1
        DJNZ   R3,DL3
        RET

;1ms delay
DELAY1: MOV  R1,#0AH
DL2:    MOV  R2,#18H
DL1:    NOP
        NOP
        DJNZ R2,DL1
        DJNZ R1,DL2
        RET

        END