INT0: PUSH A
PUSH PSW
CLR EA
MOV TH0,#3CH
MOV TL0,#0B0H
DJNZ R5,EXIT
MOV R5,#14H
MOV A,24H
ADD A,#01H
DA A
MOV 24H,A
CJNE A,#60H,EXIT
MOV 24H,#00H
MOV A,23H
ADD A,#01H
DA A
MOV 23H,A
CJNE A,#60H,EXIT
MOV 23H,#00H
MOV A,22H
ADD A,#01H
DA A
MOV 22H,A
CJNE A,#24H,EXIT
MOV 22H,#00H
EXIT: POP PSW
POP A
SETB EA
SETB TR0
RETI