;利用8051串行口，和并行输出串行移位寄存器74LS164，
                           ;扩展一位数码显示在数码显示器上循环显示0-9这10个数字。
                           ;晶振频率为11.0592MHZ
                           ;4C00为50ms定时常数
                             ORG                       0000H
                             LJMP START
                             ORG                       000BH                             ;定时器0中断程序入口地址
                             AJMP INTT0
                             ORG                       0040H
START:
                             MOV                       SP,#60H
                             MOV                       TMOD,#01H                         ;定时器0方式 1
                             MOV                       TL0,#00H                          ;延时 50mS 的常数
                             MOV                       TH0,#4CH
                             MOV                       R0,#0
                             MOV                       R1,#20
                             MOV                       SCON,#00H                         ;置串口工作方式 0
                             CLR                       TI
                             CLR                       RI
                             SETB TR0                               ;开中断
                             SETB ET0
                             SETB EA
                             SJMP $
INTT0:                                        ;定时器0中断子程序
                             PUSH ACC                               ;保护现场
                             PUSH PSW
                             CLR                       ET0                                ;关定时器0中断
                             CLR                       TR0
                             MOV                       TL0,#00H                          ;延时 50mS 的常数
                             MOV                       TH0,#4CH        
                             DJNZ R1,EXIT
                             MOV                       R1,#20                         ;延时一秒的常数
                             MOV                       DPTR,#DATAb                        ;置表格基址
                             MOV                       A,R0                              ;置表格偏移量
                             MOVC A,@A+DPTR                         ;读表格数据
                             CLR                       TI
                             MOV                       SBUF,A                            ;串行发送数据
                             INC                       R0
                             CJNE R0,#0AH,EXIT ;判断是否到表尾
                             MOV                       R0,#00H                           ;调整表格偏移量
EXIT:
                             SETB TR0
                             SETB ET0                                ;开定时器0中断
                             POP                       PSW
                             POP                       ACC                               ;恢复现场
                             RETI
DATAb:                                          ;数码管显示常数表
                             DB 03H,9FH,25H,0DH,99H,49H,41H,1FH,01H,09H                        ;0 1 2 3 4 5 6 7 8 9
                             END 关键字：8051  单片机  串行口  串并转换