- DBP bit (PWR_CR) is set to enable write access - RTC_WPR is written key-sequenze (by function itself) to enable write access - call of RTC_SmoothCalibConfig(...) does not change Register RTC->CALR - return of RTC_SmoothCalibConfig(...) is SUCSESS, nevetheless RTC->CALR remains always 0x0000 - I find no Remarks in Errata sheet about this problem