使用DSP软件实现UART功能.一般教科书上提供的UART收发的程序往往是一段采用轮循（Polling）方式完成收发的简单代码。但对于高速的AVR来讲，采用这种方式大大降低了 MUC的效率。在使用AVR时，应根据芯片本身的特点（片内大容量数据存储器RAM，更适合采用高级语言编写系统程序），编写高效可靠的UART收发接口（低层）程序。下面是一个典型的USART的接口程序。-use DSP software UART functions. General textbooks UART transceivers provide the procedure is often used for Round Robin (Polling) transceiver accomplished a simple code. But for the AVR-speaking, the adoption of this approach greatly reduces the efficiency of MUC. The use of AVR, according to the characteristics of the chip itself (large-capacity on-chip data RAM memory, more suitable for the preparation of high-level language system procedures), the preparation of highly efficient and reliable UART interface transceiver (lower) process. Below is a typical USARTs interface procedures.