Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32F3x8/CAN/RF0R#0x0
receive FIFO 0 register
FMP0
FULL0
FOVR0
RFOM0
https://github.com/cmsis-svd/cmsis-svd-data