Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual page 381

Reference Manual
RTCC - Real Time Counter and Calendar
13.3.1.3 RTCC Initialization
The counters of the RTCC, RTCC_CNT (RTCC_TIME and RTCC_DATE in calendar mode) and RTCC_PRECNT, can at any time be
written by software, as long as the registers are not locked using RTCC_LOCKKEY. All RTCC registers use the immediate synchroniza-
tion scheme, described in 4.3.1 Writing.
Note: Writing to the RTCC_PRECNT register may alter the frequency of the ticks for the RTCC_CNT register.
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