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。-General textbook on the procedures provided by the UART transceivers often use a round robin (Polling) a simple manner to send and receive code. But for high-speed AVR speaking, this approach greatly reduces the efficiency of MUC. When using the AVR should be based on the characteristics of the chip itself (on-chip high-capacity data device RAM, more suitable for high-level language for writing system programs), the preparation of highly efficient and reliable UART transceiver interface (lower) program. The following is a typical USART interface program.