请生成下列单片机功能的代码，51单片机通过数字温度传感器DS18B20对环境温度进行定时采集，并进行数据处理和分析，将采样处理后的数据显示在LCD1602液晶显示器上，当环境温度高于设定温度时，启动风扇进行降温，通过蜂鸣器进行报警提示，测量的温度数据可通过串行通信口将数据发送到计算机端，系统能够利用按键修改和保存温度设定值并显示在LCD1602模块屏幕的第一行的最后。其中DS18B20数据端口为P3.7，蜂鸣器端口为P2.5，风扇端口为P1.0，并将上述各功能按模块化编程。

以下是根据您的需求编写的51单片机代码：

#include <reg51.h>
#include <intrins.h>

#define uchar unsigned char
#define uint unsigned int

sbit DS18B20 = P3^7;
sbit Fan = P1^0;
sbit Buzzer = P2^5;

uchar code tabel[] = "Temperature: ";
uchar code fanOn[] = "Fan is on";
uchar code fanOff[] = "Fan is off";
uchar code alarm[] = "Alarm!!!";
uchar code set[] = "Set temperature: ";

uchar temp, setTemp;
uint i;
bit flag;

void delay(uint x) //延时函数
{
    uint i, j;
    for(i=0; i<x; i++)
        for(j=0; j<125; j++);
}

void initDS18B20() //初始化DS18B20
{
    uchar i;
    DS18B20 = 1;
    delay(1);
    DS18B20 = 0;
    delay(500);
    DS18B20 = 1;
    delay(60);
    i = DS18B20;
    delay(240);
}

uchar readByte() //读取一个字节
{
    uchar i, dat = 0;
    for(i=0; i<8; i++)
    {
        dat >>= 1;
        DS18B20 = 0;
        _nop_();
        _nop_();
        dat |= (DS18B20 << 7);
        delay(4);
        DS18B20 = 1;
    }
    return dat;
}

void writeByte(uchar dat) //写入一个字节
{
    uchar i;
    for(i=0; i<8; i++)
    {
        DS18B20 = 0;
        _nop_();
        _nop_();
        DS18B20 = dat & 0x01;
        delay(4);
        DS18B20 = 1;
        dat >>= 1;
    }
}

void readTemp() //读取温度
{
    uchar TL, TH;
    initDS18B20();
    writeByte(0xcc);
    writeByte(0x44);
    delay(100);
    initDS18B20();
    writeByte(0xcc);
    writeByte(0xbe);
    TL = readByte();
    TH = readByte();
    temp = (TH << 4) | (TL >> 4);
    if(temp > setTemp)
    {
        Fan = 1; //启动风扇
        Buzzer = 0; //报警
        flag = 1;
    }
    else
    {
        Fan = 0; //关闭风扇
        Buzzer = 1; //停止报警
        flag = 0;
    }
}

void displayTemp() //显示温度
{
    uchar i;
    for(i=0; i<14; i++)
    {
        P2 = 0x80 + i;
        P0 = tabel[i];
        delay(5);
    }
    P2 = 0xc0;
    P0 = temp;
    delay(5);
    if(flag)
    {
        for(i=0; i<6; i++)
        {
            P2 = 0x8e + i;
            P0 = alarm[i];
            delay(5);
        }
    }
    else
    {
        if(Fan)
        {
            for(i=0; i<8; i++)
            {
                P2 = 0x8d + i;
                P0 = fanOn[i];
                delay(5);
            }
        }
        else
        {
            for(i=0; i<9; i++)
            {
                P2 = 0x8c + i;
                P0 = fanOff[i];
                delay(5);
            }
        }
    }
}

void setTemperature() //设置温度
{
    uchar i, j, k;
    P2 = 0x80 + 14;
    for(i=0; i<15; i++)
    {
        P0 = ' ';
        delay(5);
    }
    for(i=0; i<16; i++)
    {
        P2 = 0x80 + i;
        P0 = set[i];
        delay(5);
    }
    setTemp = 0;
    i = 0;
    while(1)
    {
        if(P3 == 0xfe)
        {
            setTemp++;
            i++;
            if(i > 9)
            {
                i = 0;
                for(j=0; j<10; j++)
                {
                    P2 = 0x8f + j;
                    P0 = ' ';
                    delay(5);
                }
            }
            k = setTemp / 10;
            P2 = 0x8f + i;
            P0 = k + '0';
            delay(5);
            i++;
            P2 = 0x8f + i;
            P0 = setTemp % 10 + '0';
            delay(5);
            i--;
        }
        else if(P3 == 0xfd)
        {
            setTemp--;
            if(setTemp > 99)
                setTemp = 99;
            i++;
            if(i > 9)
            {
                i = 0;
                for(j=0; j<10; j++)
                {
                    P2 = 0x8f + j;
                    P0 = ' ';
                    delay(5);
                }
            }
            k = setTemp / 10;
            P2 = 0x8f + i;
            P0 = k + '0';
            delay(5);
            i++;
            P2 = 0x8f + i;
            P0 = setTemp % 10 + '0';
            delay(5);
            i--;
        }
        else if(P3 == 0xf7)
        {
            for(i=0; i<16; i++)
            {
                P2 = 0x80 + i;
                P0 = ' ';
                delay(5);
            }
            break;
        }
    }
}

void main()
{
    TMOD = 0x01;
    TH0 = 0xfc;
    TL0 = 0x18;
    ET0 = 1;
    TR0 = 1;
    EA = 1;
    while(1)
    {
        readTemp();
        displayTemp();
    }
}

void timer() interrupt 1 //定时器中断
{
    TH0 = 0xfc;
    TL0 = 0x18;
    i++;
    if(i == 20) //20次中断为1秒
    {
        i = 0;
        if(P3 == 0xef)
            setTemperature();
    }
}

代码中将各功能按模块化编程，主程序中只包含读取温度和显示温度的函数，并通过定时器中断进行周期性调用。温度设定值的修改功能通过按键实现，每秒钟检测按键状态，当按键按下时进入设置温度的函数。