89C51单片机全双工串行通信代码

以下是89C51单片机全双工串行通信的代码示例：

#include <reg51.h>

#define BAUD_RATE 9600
#define FREQ_OSC 11059200
#define PRESCALER 12

void init_serial() {
    TMOD = 0x20; // set timer 1 in mode 2
    TH1 = 256 - (FREQ_OSC / (BAUD_RATE * PRESCALER * 2));
    TL1 = TH1;
    TR1 = 1; // start timer 1
    SM0 = 0;
    SM1 = 1; // set serial mode as 8-bit UART
    REN = 1; // enable receiver
    TI = 0;  // clear transmit flag
    RI = 0;  // clear receive flag
}

void send_serial(char c) {
    SBUF = c; // transmit character
    while (!TI); // wait until transmit flag is set
    TI = 0; // clear transmit flag
}

char receive_serial() {
    while (!RI); // wait until receive flag is set
    RI = 0; // clear receive flag
    return SBUF; // return received character
}

void main() {
    char c;
    init_serial();
    while (1) {
        c = receive_serial(); // receive character
        send_serial(c); // send character back
    }
}

该代码初始化了串行通信，设置了波特率、时钟频率和预分频器，并实现了发送和接收字符的函数。主函数不断接收字符，并将其发送回去，实现了全双工通信。需要注意的是，该代码仅供参考，具体实现可能需要根据硬件和需求进行调整。