说明：  P1口扩展实验 P1口既做输入口又做输出口，KEY1做为左转弯开关，KEY2做为右转弯开关。LED5、LED6做为左转弯灯，LED7、LED8做为右转弯灯（如图2-2）。 编程实现汽车转向灯功能，即：KEY1接高电平KEY2接低电平时，右转弯灯灭，左转弯灯以一定频率闪烁（注意：KEY拨向上方为0）；KEY2接高电平KEY1接低电平时，左转弯灯灭，右转弯灯以一定频率闪烁；KEY1、KEY2同时接低电平时，发光二极管全灭；KEY1、KEY2同时接高电平时，发光二极管全亮。
(P1 I extended not only to do experiments P1 I also do input output, KEY1 switch as a left turn, KEY2 as switches and turn right. LED5, LED6 as a left turn lights, LED7, LED8 as lights and turn right (Figure 2-2). Programming car turn signal function, namely: KEY1 high key2 access low-level access, the right turn lights out, left turn to a certain frequency of flashing lights (Note: KEY allocated to the top to 0) KEY2 access high Key1 low-level access, the left turn lights out, turn right to a certain frequency of flashing lights KEY1, KEY2 low at the same time, the light-emitting diode body KEY1, KEY2 high at the same time, the light-emitting diode light-wide.)