On F446RC, sysreset does not put bit 19 into default setting of 0, its stuck on 1 if 1 is written previously.
Procedure to set and clear bit:
RTC->CR = (0<<19); //Clear bit19, 512hz modeRTC->CR = (1<<19); //Set bit19, 1hz mode
This is the correct behaviour, as RCC_CR is in the backup domain - read 6.1.3 Backup domain reset and the RCC_CR description in RCC registers chapter.
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