stm8无法读取亚秒SubSecond

调用库函数读出的数据为零。后来发现，是因为我用的是stm8l052c6t6。stm8l052c6 没有ss_rx寄存器不能读亚秒.

uint16_t RTC_GetSubSecond(void)//stm8l052c6 没有ss_rx寄存器不能读亚秒
{
  uint8_t ssrhreg = 0, ssrlreg = 0;
  uint16_t ssrreg = 0;

  /* Get subseconds values from the correspondent registers*/
  ssrhreg = RTC->SSRH;
  ssrlreg = RTC->SSRL;

  /*read DR3 register to unfroze calender registers */
  (void) (RTC->DR3);

  /* Clear RSF flag by writing 0 in RSF bit通过在RSF位中写入0来清除RSF标志 */
  RTC->ISR1 &= (uint8_t)~(RTC_ISR1_RSF);

  ssrreg = (uint16_t)((uint16_t)((uint16_t)ssrhreg << 8) | (uint16_t)(ssrlreg));
  return (uint16_t)(ssrreg);

}