Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFR32MG13P/EFR32MG13P731F512GM48/RTCC/SYNCBUSY#0x0
Synchronization Busy Register
CMD Register Busy
https://github.com/cmsis-svd/cmsis-svd-data