我要设计一个基于单片机的非接触式人体红外测温系统，系统包括STC89C52单片机，MLX90614红外测温模块，LCD1602显示模块等装置，请写一段代码，实现测量人体温度并将温度值显示在LCD1602上的功能

好的，以下是一个简单的代码示例，可以实现你所描述的功能：

#include <reg52.h>
#include <intrins.h>

#define FOSC 11059200L
#define BAUD 9600

typedef unsigned char uchar;
typedef unsigned int uint;

sbit SCL=P2^1;
sbit SDA=P2^0;
sbit E=P1^7;
sbit RW=P1^6;
sbit RS=P1^5;

// I2C总线相关操作
void delay5us() _naked
{
    _asm
        nop
        nop
        nop
        nop
    _endasm;
}

void i2c_start()
{
    SDA = 1;
    delay5us();
    SCL = 1;
    delay5us();
    SDA = 0;
    delay5us();
    SCL = 0;
    delay5us();
}

void i2c_stop()
{
    SDA = 0;
    delay5us();
    SCL = 1;
    delay5us();
    SDA = 1;
    delay5us();
}

void i2c_ack()
{
    SDA = 0;
    delay5us();
    SCL = 1;
    delay5us();
    SCL = 0;
    delay5us();
    SDA = 1;
    delay5us();
}

void i2c_nack()
{
    SDA = 1;
    delay5us();
    SCL = 1;
    delay5us();
    SCL = 0;
    delay5us();
    SDA = 1;
    delay5us();
}

uchar i2c_write_byte(uchar dat)
{
    uchar i, ack_bit;
    for(i=0; i<8; i++)
    {
        SDA = (dat & 0x80) >> 7;
        dat <<= 1;
        delay5us();
        SCL = 1;
        delay5us();
        SCL = 0;
        delay5us();
    }
    SDA = 1;
    delay5us();
    SCL = 1;
    delay5us();
    ack_bit = SDA;
    SCL = 0;
    delay5us();
    return ack_bit;
}

uchar i2c_read_byte()
{
    uchar i, dat = 0;
    SDA = 1;
    delay5us();
    for(i=0; i<8; i++)
    {
        dat <<= 1;
        SCL = 1;
        delay5us();
        dat |= SDA;
        SCL = 0;
        delay5us();
    }
    return dat;
}

// MLX90614红外测温模块相关操作
void mlx90614_init()
{
    i2c_start();
    i2c_write_byte(0xB4);
    i2c_write_byte(0x01);
    i2c_write_byte(0x60);
    i2c_stop();
}

float mlx90614_get_temp()
{
    uchar i, temp_h, temp_l;
    float temp;
    i2c_start();
    i2c_write_byte(0xB4);
    i2c_write_byte(0x07);
    i2c_stop();
    i2c_start();
    i2c_write_byte(0xB5);
    temp_h = i2c_read_byte();
    temp_l = i2c_read_byte();
    i2c_nack();
    i2c_stop();
    temp = (temp_h << 8) | temp_l;
    temp *= 0.02;
    temp -= 273.15;
    return temp;
}

// LCD1602显示模块相关操作
void lcd_write_cmd(uchar cmd)
{
    RS = 0;
    RW = 0;
    P0 = cmd;
    E = 1;
    _nop_();
    _nop_();
    E = 0;
}

void lcd_write_data(uchar dat)
{
    RS = 1;
    RW = 0;
    P0 = dat;
    E = 1;
    _nop_();
    _nop_();
    E = 0;
}

void lcd_init()
{
    lcd_write_cmd(0x38);
    lcd_write_cmd(0x0C);
    lcd_write_cmd(0x06);
    lcd_write_cmd(0x01);
}

void lcd_display_temp(float temp)
{
    uchar i, temp_int, temp_dec;
    temp_int = (uchar)temp;
    temp_dec = (uchar)((temp - temp_int) * 100);
    lcd_write_cmd(0x80);
    lcd_write_data('T');
    lcd_write_data('e');
    lcd_write_data('m');
    lcd_write_data('p');
    lcd_write_data(':');
    lcd_write_data(' ');
    lcd_write_data(temp_int / 10 + '0');
    lcd_write_data(temp_int % 10 + '0');
    lcd_write_data('.');
    lcd_write_data(temp_dec / 10 + '0');
    lcd_write_data(temp_dec % 10 + '0');
    lcd_write_data('C');
}

// 主函数
void main()
{
    float temp;
    TMOD = 0x20;
    TH1 = TL1 = -(FOSC/12/32/BAUD);
    TR1 = 1;
    SCON = 0x50;
    ES = 1;
    EA = 1;
    lcd_init();
    mlx90614_init();
    while(1)
    {
        temp = mlx90614_get_temp();
        lcd_display_temp(temp);
        delay_ms(500);
    }
}

// 串口中断服务函数
void uart_isr() interrupt 4
{
    RI = 0;
    TI = 0;
}

这段代码使用了STC89C52单片机，通过I2C总线与MLX90614红外测温模块进行通信，读取人体温度值，然后通过LCD1602显示模块将温度值显示出来。

注意，这段代码中串口通信部分还没有实现，如果需要使用串口通信功能，需要自己添加相关代码。