51单片机串口通信(相关例程), 单片机串行口发送/接收程序，每接收到字节(即发送出去)和微机相接后键入的字符回显示在屏幕上. -51 single-chip serial communication (related routines) microcontroller serial port to send/receive program, each received byte is sent and the computer after connecting back to displa