（1）二个外部中断EINTB（KEY1）、EINTC(KEY2)，三个任务A、B、C，优先级由低到高。

（2）A任务每运行一次使得第一组数码管的值增加1，调用延时函数为1s

（3）B任务等待信号量bsem（初始值为0），中断INTB触发信号量bsem的发送。该任务每运行一次使得第二组数码管的值增加1，调用延时函数为0.5s

（4）C任务等待信号量csem（初始值为0），中断INTC触发信号量csem的发送，该任务每运行一次使得某个发光二级管闪烁，调用延时函数为0.1s

-(A) two external interrupt EINTB (KEY1), EINTC (KEY2), three tasks A, B, C, from low to high priority. (2) A task runs once every digital tube such that the first group increases the value of one, call the delay function 1s (3) B task waiting for the semaphore bsem (initial value is 0), the interrupt INTB amount bsem trigger signal transmission. Each time you run the task so that the second group increases the value of a digital control, call the delay function is 0.5s (4) C task waiting for the semaphore csem (initial value is 0), the interrupt is triggered semaphore csem INTC transmission, the task Each time you run such a light-emitting diode flashes, call the delay function is 0.1s