Some time ago I had this issue in a project with STM32L433CCU6:
// Calibration clock output
#if 0
// Warning! PC13 is switched to output mode even with OSEL = 00b
RTC->OR = RTC_OR_OUT_RMP; // Remap RTC_CALIB from PC13 to PB2
RTC->CR |= RTC_CR_COE | RTC_CR_COSEL; // Enable 1 Hz
#endif
The code used the following configuration from RTC_OR register description, but the PC13 pin was still switched to output mode:
RTC_OUT_RMP = ‘1’:
If OSEL = ‘00’ and COE = ‘1’: RTC_CALIB is output on PB2
If I'm not mistaken, this issue is present at least on all L43x devices. The current errata versions have two issues related to pin PC13, but not this one.
