嵌入式系统中的ＩＯ口来模拟串口，需要一个定时器来作为波特率发生器，在嵌入式系统中串口资源比较紧张的系统比较有应用价值-Embedded System IO port to simulate the serial port, you need a timer as a baud rate generator, serial ports in embedded systems resources were more nervous systems have more value