说明： 串口编程--接收PC发过来的字符串,回发字符串.发送期间中断控制LED灯闪烁
采用外部晶振22.1184MHz 使用定时器1,方式2产生波特率,SMOD = 0或者1
定时器初值X=256-SYSCLK*(SMOD+1)(BAUDRATE*384)
(Serial Programming-- receiving PC sent the string, the string back. During this interruption control LED lights external crystal 22.1184MHz use of a timer, two methods have baud rate, SMOD = 0 or a timer initial X = 256-SYSCLK* (SMOD a) (baudrate* 384))
