ORG  0000H
		   LJMP START
		   ORG  000BH;
		   LJMP INT0X
		   ORG  0030H
START:   
T1S        EQU  30H
           MOV  P1,#0FFH
		   MOV  TMOD,#01H
		   MOV  TH0,#(5536-50000)/256
		   MOV  TL0,#(65536-50000) MOD 256
		   MOV  T1S,#00H
		   SETB EA
		   SETB ET0
		   SETB TR0
		   SJMP $
INT0X:      PUSH ACC
           PUSH PSW
		   INC  T1S
		   MOV  A,T1S
		   CJNE A,#20,NEXT
		   CPL  P1.0
		   MOV  T1S,#00H
NEXT:      MOV  TH0,#(65536-50000)/256
		   MOV  TL0,#(65536-50000) MOD 256
		   POP  PSW
		   POP  ACC
		   RETI

           END