Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG11B/EFM32GG11B510F2048IQ64/USART1/RXDATA#0x0
RX Buffer Data Register
RX Data
https://github.com/cmsis-svd/cmsis-svd-data