说明：  这是我才开始学习飞思卡尔MC9S12XEP100的学习记录，里面包含了引脚的使用、系统时钟配置、ECT的使用、PWM的配置、CAN的使用，对于飞思卡尔的入门者很有用
(This is the records I made when I began to learn the microcontroller,freescale MC9S12XEP100,including the pin configurrtion,system clock configuration,the usage of ECT,and the methods of application for PWM and CAN.It must be beneficial to get start learning MC9S12XEP100 microcontroller )