请问《单片机C程序设计100例》中4.13的1602液晶显示的DS1302实时时钟如何分析？

13 1602液晶显示的DS1302实时时钟
/***************   writer:shopping.w   ******************/
#include <reg52.h>
#include <intrins.h>
#include <string.h>
#define uint unsigned int
#define uchar unsigned char

sbit IO = P1^0;   //DS1302数据线
sbit SCLK = P1^1;  //DS1302时钟线
sbit RST = P1^2;//DS1302复位线
sbit RS = P2^0; //LCD寄存器选择
sbit RW = P2^1; //LCD读写控制器
sbit EN = P2^2; //LCD启用
//0,2,3,4,5,6,7分别对应周日，周一至周六
uchar *WEEK[]=
{
  "SUN","***","MON","TUS","WEN","THU","FRI","SAT"
};
uchar LCD_DSY_BUFFER1[]={"DATE 00-00-00    "}; //LCD显示缓冲
uchar LCD_DSY_BUFFER2[]={"TIME 00:00:00    "};
uchar DateTime[7];//所读取的日期时间
//延时
void DelayMS(uint ms)
{
  uchar i;
 while(ms--)
 {
   for(i=0;i<120;i++);
 }
}
//向DS1302写入一字节
void Write_A_Byte_TO_DS1302(uchar x)
{
  uchar i;
 for(i=0;i<8;i++)
 {
   IO=x&0x01;SCLK=1;SCLK=0;x>>=1;
 }
}
//向DS1302读取一字节
uchar Get_A_Byte_FROM_DS1302()
{
  uchar i,b=0x00;
 for(i=0;i<8;i++)
 {
   b |= _crol_((uchar)IO,i);
  SCLK=1;SCLK=0;
 }
 return b/16*10+b%16;  、、//返回BCD码
}
//向DS1302指定位置读数据
uchar Read_Data(uchar addr)
{
  uchar dat;
 RST = 0;SCLK=0;RST=1;
    Write_A_Byte_TO_DS1302(addr);
 dat = Get_A_Byte_FROM_DS1302();
    SCLK=1;RST=0;
 return dat;
}
//读取当前日期时间
void GetTime()
{
  uchar i,addr = 0x81;
 for(i=0;i<7;i++)
 {
   DateTime=Read_Data(addr);addr+=2;
 }
}
//读LCD状态
uchar Read_LCD_State()
{
  uchar state;
 RS=0;RW=1;EN=1;DelayMS(1);
 state=P0;
 EN = 0;DelayMS(1);
 return state;
}

//忙等待
void LCD_Busy_Wait()
{
  while((Read_LCD_State()&0x80)==0x80);
 DelayMS(5);
}
//向LCD写数据
void Write_LCD_Data(uchar dat)
{
  LCD_Busy_Wait();
 RS=1;RW=0;EN=0;P0=dat;EN=1;DelayMS(1);EN=0; 
}
//写LCD指令
void Write_LCD_Command(uchar cmd)
{
  LCD_Busy_Wait();
 RS=0;RW=0;EN=0;P0=cmd;EN=1;DelayMS(1);EN=0; 
}
//LCD初始化
void Init_LCD()
{
  Write_LCD_Command(0x38);
 DelayMS(1); 
 Write_LCD_Command(0x01);
 DelayMS(1); 
 Write_LCD_Command(0x06);
 DelayMS(1); 
 Write_LCD_Command(0x0c);
 DelayMS(1); 
}
//设置液晶显示位置
void Set_LCD_POS(uchar p)
{
  Write_LCD_Command(p|0x80); 
}
//在LCD是显示字符串
void Display_LCD_String(uchar p,uchar *s)
{
  uchar i;
 Set_LCD_POS(p);
 for(i=0;i<16;i++)
 {
  Write_LCD_Data(s);
  DelayMS(1);  
 }
}
//日期与时间值转换为数字字符
void Format_DateTime(uchar d,uchar *a)
{
  a[0]=d/10+'0';
 a[1]=d%10+'0';
}
//主程序
void main()
{
  Init_LCD();
 while(1)
 {
   GetTime();
   //年月日
  Format_DateTime(DateTime[6],LCD_DSY_BUFFER1+5);
  Format_DateTime(DateTime[4],LCD_DSY_BUFFER1+8);
  Format_DateTime(DateTime[3],LCD_DSY_BUFFER1+11);
  //星期
  strcpy(LCD_DSY_BUFFER1+13,WEEK[DateTime[5]]);
  //时分秒
  Format_DateTime(DateTime[2],LCD_DSY_BUFFER1+5);
  Format_DateTime(DateTime[1],LCD_DSY_BUFFER1+8);
  Format_DateTime(DateTime[0],LCD_DSY_BUFFER1+11);
  //显示年月日时分秒
  Display_LCD_String(0x00,LCD_DSY_BUFFER1);
  Display_LCD_String(0x40,LCD_DSY_BUFFER2);
 }
}

谁能帮我分析一下！！！感谢！