#ifdef RTCClockOutput_Enable
  /* Enable PWR and BKP clocks */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);
  /* Allow access to BKP Domain */
  PWR_BackupAccessCmd(ENABLE);
  /* Disable the Tamper Pin */
  BKP_TamperPinCmd(DISABLE); /* To output RTCCLK/64 on Tamper pin, the tamper
                                 functionality must be disabled */
  /* Enable RTC Clock Output on Tamper Pin */
  BKP_RTCOutputConfig(BKP_RTCOutputSource_CalibClock);
#endif 此帖出自小平头技术问答