Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B530F512GQ100/USART3/CTRLX#0x0
Control Register Extended
Debug Halt
CTS Pin Inversion
CTS Function Enabled
RTS Pin Inversion
https://github.com/cmsis-svd/cmsis-svd-data