8255的A口作为输入口，与逻辑电平开关K7～K8相连。8255的B口作为输出口，与发光二极管LED7～LED8相连。编写程序，使得逻辑电平开关的变化在发光二极管上显示出来。即当开关k7（或K8）置于L时,对应发光二极管LED7（或LED8）点亮；置于H时熄灭(The 8255 A port is used as the input port and is connected with the logic level switch K7 - K8. The 8255 B port is used as the output port and is connected with the light emitting diode LED7 ~ LED8. The program is programmed to display the change of the logic level switch on the light emitting diode. That is, when the switch K7 (or K8) is placed at L, the corresponding light emitting diode LED7 (or LED8) is lighted; when H is put out, the lamp is extinguished)