Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B310F1024GQ100/USART3/RXDATAXP#0x0
RX Buffer Data Extended Peek Register
RX Data Peek
Data Parity Error Peek
Data Framing Error Peek
https://github.com/cmsis-svd/cmsis-svd-data