#include "reg51.h" #include "intrins.h" #define FOSC 11059200UL #define BRT (65536 - FOSC / 115200 / 4) sfr AUXR = 0x8e; sfr T2H = 0xd6; sfr T2L = 0xd7; sfr S2CON = 0x9a; sfr S2BUF = 0x9b; sfr IE2 = 0xaf; sfr P0M1 = 0x93; sfr P0M0 = 0x94; sfr P1M1 = 0x91; sfr P1M0 = 0x92; sfr P2M1 = 0x95; sfr P2M0 = 0x96; sfr P3M1 = 0xb1; sfr P3M0 = 0xb2; sfr P4M1 = 0xb3; sfr P4M0 = 0xb4; sfr P5M1 = 0xc9; sfr P5M0 = 0xca; bit busy; char wptr; char rptr; char buffer[16]; void Uart2Isr() interrupt 8 { if (S2CON & 0x02) { S2CON &= ~0x02; busy = 0; } if (S2CON & 0x01) { S2CON &= ~0x01; buffer[wptr++] = S2BUF; wptr &= 0x0f; } } void Uart2Init() { S2CON = 0x10; T2L = BRT; T2H = BRT >> 8; AUXR = 0x14; wptr = 0x00; rptr = 0x00; busy = 0; } void Uart2Send(char dat) { while (busy); busy = 1; S2BUF = dat; } void Uart2SendStr(char *p) { while (*p) { Uart2Send(*p++); } } void main() { P0M0 = 0x00; P0M1 = 0x00; P1M0 = 0x00; P1M1 = 0x00; P2M0 = 0x00; P2M1 = 0x00; P3M0 = 0x00; P3M1 = 0x00; P4M0 = 0x00; P4M1 = 0x00; P5M0 = 0x00; P5M1 = 0x00; Uart2Init(); IE2 = 0x01; EA = 1; Uart2SendStr("Uart Test !\r\n"); while (1) { if (rptr != wptr) { Uart2Send(buffer[rptr++]); rptr &= 0x0f; } } } 修改此程序使发送者发送字母o接收者连接的板子中端口P2.5灯开始亮其余灯灭

修改后的程序如下：

#include "reg51.h"
#include "intrins.h"

#define FOSC 11059200UL
#define BRT (65536 - FOSC / 115200 / 4)

sfr AUXR = 0x8e;
sfr T2H = 0xd6;
sfr T2L = 0xd7;
sfr S2CON = 0x9a;
sfr S2BUF = 0x9b;
sfr IE2 = 0xaf;
sfr P0M1 = 0x93;
sfr P0M0 = 0x94;
sfr P1M1 = 0x91;
sfr P1M0 = 0x92;
sfr P2M1 = 0x95;
sfr P2M0 = 0x96;
sfr P3M1 = 0xb1;
sfr P3M0 = 0xb2;
sfr P4M1 = 0xb3;
sfr P4M0 = 0xb4;
sfr P5M1 = 0xc9;
sfr P5M0 = 0xca;

bit busy;
char wptr;
char rptr;
char buffer[16];

void Uart2Isr() interrupt 8 {
    if (S2CON & 0x02) {
        S2CON &= ~0x02;
        busy = 0;
    }
    if (S2CON & 0x01) {
        S2CON &= ~0x01;
        buffer[wptr++] = S2BUF;
        wptr &= 0x0f;
    }
}

void Uart2Init() {
    S2CON = 0x10;
    T2L = BRT;
    T2H = BRT >> 8;
    AUXR = 0x14;
    wptr = 0x00;
    rptr = 0x00;
    busy = 0;
}

void Uart2Send(char dat) {
    while (busy);
    busy = 1;
    S2BUF = dat;
}

void Uart2SendStr(char *p) {
    while (*p) {
        Uart2Send(*p++);
    }
}

void main() {
    P0M0 = 0x00;
    P0M1 = 0x00;
    P1M0 = 0x00;
    P1M1 = 0x00;
    P2M0 = 0x00;
    P2M1 = 0x00;
    P3M0 = 0x00;
    P3M1 = 0x00;
    P4M0 = 0x00;
    P4M1 = 0x00;
    P5M0 = 0x00;
    P5M1 = 0x00;

    Uart2Init();
    IE2 = 0x01;
    EA = 1;

    Uart2SendStr("Uart Test !\r\n");

    while (1) {
        if (rptr != wptr) {
            char received = buffer[rptr++];
            rptr &= 0x0f;

            if (received == 'o') {
                P2 = 0x20;
            } else {
                P2 = 0x00;
            }

            Uart2Send(received);
        }
    }
}

其中，修改的部分为：

if (received == 'o') {
    P2 = 0x20;
} else {
    P2 = 0x00;
}

该部分代码会检测接收到的字符是否为字母'o'，如果是，则点亮P2.5灯（二进制为0010 0000），否则将P2口置为0（灭灯）。