org    2030h
          DW     TI
          org    2032h
          DW     RI
          org    2080h
          ld     dx, #0a000h
          ldb    ah, #0ffh
          stb    ah, [dx]
          ld     sp, #0100h         ;設置堆棧
          orb    IOC1, #20h         ;設定P2.1為RXD
          ldb    baud_rate, #4Dh    ;設波特率為2400
          ldb    baud_rate, #80h
          ldb    sp_con, #09h       ;允許接收，方式1
          stb    sbuf,40h           ;清緩沖器
          di                        ;關中斷
          orb    int_mask, #40h     ;開中斷
          andb   INT_PEND, #10111111B        ;清中斷掛號
loop1:
          ldb    al, #01h
          ldb    ah, #8
loop:
          stb    al, sbuf
          ldb    bl, sbuf
          not    bl
          stb    bl, [dx]
          call   delay
          shlb   al, #1
          djnz   ah, loop
          sjmp   loop1
delay:
          ld     cx, #0ffffh
dloop:
          djnz   cl, dloop
          djnz   ch, dloop
          ret
TI:
          ret
RI:
          ret
          end