辛辛苦苦编了一个10s循环计时的程序，原理图和程序如下：

ORG 0000H

AJMP MAIN

ORG 000BH

AJMP INTT0

ORG 0030H

MAIN:CLR P2.7

CLR P2.6

MOV DPTR,#TAB

CLR A

MOV R2,#0H

MOV R3,#0H

MOV TMOD,#01H

MOV TH0,#4CH

MOV TL0,#00H

SETB EA

SETB ET0

SETB TR0

HERE: CJNE R2,#14H,HERE

MOV R2,#0H

PUSH ACC

MOVC A,@A+DPTR

MOV P0,A

POP ACC

INC A

INC R3

CJNE R3,#0AH,HERE

MOV R3，#00H ;此处用DJNZ 更方便，只不过R3的初始值要设置为0AH,同时取消INC R3指令(此行上面第二行)

CLR A

AJMP HERE

ORG 80H

INTT0:MOV TH0,#4CH

MOV TL0,#00H

INC R2

RETI

TAB: DB 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,90H

END