如图13所示，利用AT89S51单片机的P0端口的P0.0－P0.7连接到一个共阴数码管的a－h的笔段上，数码管的公共端接地。在数码管上循环显示0－9数字，时间间隔0.2秒。 -Shown in Figure 13, using AT89S51 microcontroller ports P0.0-P0.7 P0 is connected to a common cathode tube in a-h digital pen section, the digital control of public grounded. Pipe loop in the digital display 0-9 numbers, the time interval 0.2 seconds.