当外部中断没有发生时，接在PD口的8个发光二极管一起不停的闪烁，当外部中断发生时，即开关S0被按一次后，接在PD0口的D0二极管不停的闪烁。-When the external interrupt did not occur, then 8 in the PD population with non-stop blinking light-emitting diode, when the external interrupt occurs, the switch S0 is pressed once, then the mouth of D0 in PD0 stop the flashing LED.