Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series0/EZR32WG/EZR32WG230F64R60/USART1/RXDOUBLE#0x0
RX FIFO Double Data Register
RX Data 0
RX Data 1
https://github.com/cmsis-svd/cmsis-svd-data