电路是：P0口接数码管的字型码笔段，P2口接数码管的数位选择端.

下面是汇编语言源程序：

SECOND EQU 30H

TCOUNT EQU 31H

ORG 00H

LJMP START

ORG 0BH

LJMP INT0X

START: MOV SECOND ,#00H

MOV A,SECOND

MOV B,#10

DIV AB

MOV DPTR,#TABLE

MOVC A,@A+DPTR

MOV P0,A

MOV A,B

MOVC A,@A+DPTR

MOV P2,A

MOV TCOUNT,#00H

MOV TMOD,#01H

MOV TH0,#(65536-50000)/256

MOV TL0,#(65536-50000) MOD 256

SETB TR0

SETB ET0

SETB EA

SJMP $

INT0X: MOV TH0,#(65536-5000)/256

MOV TL0,#(65536-5000) MOD 256

INC TCOUNT

MOV A,TCOUNT

CJNE A,#20,NEXT

MOV TCOUNT,#00H

INC SECOND

MOV A,SECOND

CJNE A,#60,NEX

MOV SECOND,#00H

NEX: MOV A,SECOND

MOV B,#10

DIV AB

MOV DPTR,#TABLE

MOVC A,@A+DPTR

MOV P0,A

MOV A,B

MOVC A,@A+DPTR

MOV P2,A

NEXT: RETI

TABLE: DB 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH

END

T0工作在方式1，计时50ms，共20个循环，总计时1秒。

P0口显示低位，P2口显示高位，满60清零