串行口工作在方式1时，数据为8位，从RXD端输入，从TXD端输出，其波特率固定。在CPU将数据写入发送SBUF寄存器后立即启动发送，待8位数据输完后，硬件自动将TI置为1，TI必须用软件清零。8位数据接收完时，接收SBUF寄存器满，则硬件自动将RI置为1，RI必须用软件清零。-8-bit data transmission is complete, the hardware will automatically TI is set to 1, TI must be cleared by software. 8 bits of data have been received, the receiving SBUF register is full, the hardware will automatically be set to RI 1, RI must be cleared by software.