Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Keil/AT32F405xx_v2/CAN1/RFDTL0#0x0
Receive FIFO 0 low byte data register
Receive FIFO data byte 0
Receive FIFO data byte 1
Receive FIFO data byte 2
Receive FIFO data byte 3
https://github.com/cmsis-svd/cmsis-svd-data