Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B530F512GQ64/USART1/RXDOUBLEX#0x0
RX Buffer Double Data Extended Register
RX Data 0
Data Parity Error 0
Data Framing Error 0
RX Data 1
Data Parity Error 1
Data Framing Error 1
https://github.com/cmsis-svd/cmsis-svd-data