C8051F020单片机用UART0实现RS-232通信，运行前将TX0和P0.0短接，将RXD和P0.1短接，当接收到一个数据后，再将接收到的数据送出。-C8051F020 single-chip implementation using UART0 communication RS-232, run before TX0 and shorted P0.0, P0.1 to RXD and shorted, when the rece