Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f1/STM32F101/CAN1/RF1R#0x0
receive FIFO 1 register
FMP1
FULL1
FOVR1
RFOM1
https://github.com/modm-io/cmsis-svd-stm32