主函数里面
 while (1)
  {
   RTC_GetTime(RTC_Format_BIN, &RTC_TimeStructure);
 RTC_GetDate(RTC_Format_BIN, &RTC_DateStructure);
   if(Rtctmp != RTC_TimeStructure.RTC_Seconds)
 {
  printf("The Date :  Y:20%0.2d - M:%0.2d - D:%0.2d - W:%0.2d ", RTC_DateStructure.RTC_Year,RTC_DateStructure.RTC_Month, RTC_DateStructure.RTC_Date,RTC_DateStructure.RTC_WeekDay); 
  printf("The Time :  %0.2d:%0.2d:%0.2d ", RTC_TimeStructure.RTC_Hours, RTC_TimeStructure.RTC_Minutes, RTC_TimeStructure.RTC_Seconds); 
  (void)RTC->DR;
 }
 Rtctmp = RTC_TimeStructure.RTC_Seconds;
  }         
 之前定义Rtctmp =0，不明白  if(Rtctmp != RTC_TimeStructure.RTC_Seconds)是有什么作用，还有(void)RTC->DR是什么意思呢