用c语言对单片机89c51的实时钟写一个代码

好的，下面是一个简单的C语言代码示例，用于设置单片机89c51的实时时钟：

#include <reg51.h>

#define DS1302_PORT P1
sbit DS1302_SCL = P3^6;
sbit DS1302_DAT = P3^5;
sbit DS1302_RST = P3^4;

void ds1302_writebyte(unsigned char dat)
{
    unsigned char i;
    for (i=0; i<8; i++)
    {
        DS1302_SCL = 0;
        DS1302_DAT = dat & 0x01;
        dat >>= 1;
        DS1302_SCL = 1;
    }
}

unsigned char ds1302_readbyte()
{
    unsigned char i, dat = 0;
    for (i=0; i<8; i++)
    {
        DS1302_SCL = 0;
        dat >>= 1;
        if (DS1302_DAT)
            dat |= 0x80;
        DS1302_SCL = 1;
    }
    return dat;
}

void ds1302_init()
{
    DS1302_RST = 1;
    DS1302_SCL = 0;
    ds1302_writebyte(0x8e);
    ds1302_writebyte(0x00);
    DS1302_RST = 0;
    DS1302_RST = 1;
}

void ds1302_settime(unsigned char year, unsigned char month, unsigned char day, unsigned char week, unsigned char hour, unsigned char minute, unsigned char second)
{
    ds1302_writebyte(0x80);
    ds1302_writebyte(second);
    ds1302_writebyte(minute);
    ds1302_writebyte(hour);
    ds1302_writebyte(week);
    ds1302_writebyte(day);
    ds1302_writebyte(month);
    ds1302_writebyte(year);
    ds1302_writebyte(0x00);
}

void ds1302_gettime(unsigned char *year, unsigned char *month, unsigned char *day, unsigned char *week, unsigned char *hour, unsigned char *minute, unsigned char *second)
{
    ds1302_writebyte(0x81);
    *second = ds1302_readbyte();
    *minute = ds1302_readbyte();
    *hour = ds1302_readbyte();
    *week = ds1302_readbyte();
    *day = ds1302_readbyte();
    *month = ds1302_readbyte();
    *year = ds1302_readbyte();
}

void main()
{
    unsigned char year, month, day, week, hour, minute, second;
    ds1302_init();
    ds1302_settime(21, 8, 29, 1, 12, 30, 0); // 设置时间
    while (1)
    {
        ds1302_gettime(&year, &month, &day, &week, &hour, &minute, &second); // 读取时间
        // 进行其他操作
    }
}

这个代码示例使用了 DS1302 时钟芯片，通过 P1 端口连接单片机。具体的实现过程请根据实际情况进行调整。