ORG 0000H
LJMP MAIN
ORG 001BH
LJMP T1ISR
ORG 0030H
MAIN:
MOV TMOD,#20H
MOV TH1,#06H
MOV TL1,#06H
SETB ET1
SETB TR1
SETB EA
CLR 00H
CLR 01H
SETB P1.0
MOV R2,#0
SJMP $
T1ISR:
INC R2
MOV A,R2
CJNE A,#4,T1LOW1
MOV R2,#0
JB 00H,T1LOW
CLR P1.0
SETB 00H
RETI
T1LOW:
CPL 01H
JB 01H,T1LOW1
CLR 00H
SETB P1.0
T1LOW1:
RETI
END