利用51的两个输入输出引脚如P1.0和P1.1，置1或0分别代表高低电 平，也就是串口通信中所说的位，如起始位用低电平，则将其置0，停止位为高电平，则将其置 1，各种数据位和校验位则根据情况置1或置0。-Using 51 as the two input and output pins P1.0 and P1.1, set to 1 or 0 representing the high and low, that is said in the bit serial communicati