p0口接8个发光二极管，共阴极接法，要求：如果外部中断0维持接低电平，则8个二极管保持全灭状态；如果外部中断1维持接低电平，则8个二极管保持全亮状态；如果两个外部中断端口同时接为低电平，则二极管全亮；如果两个中断源都接高电平，则8个二极管中，高4位亮，低4位灭；-Port P0 is connected to 8 light-emitting diodes, commoncathode, requirements: if the external interrupt 0 maintain the low level, the 8 diode maintain Quanmie state　if the external interrupt 1 maintain the low level, the 8 diodes keep bright　if the two external interrupt port and connected to a low level, is diode full bright　if two interrupt sources are connected to a high level, 8 diodes, 4 high light, low 4 out