Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32n6/STM32N645/FDCAN1/FDCAN_TXEFS#0x0
EFF=B_0x0
FDCAN Tx event FIFO status register
Event FIFO fill level
Event FIFO get index
Event FIFO put index
Event FIFO full
0 (B_0x0): Tx event FIFO not full
1 (B_0x1): Tx event FIFO full
Tx event FIFO element lost
https://github.com/modm-io/cmsis-svd-stm32