Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32g4/STM32G431/FMAC/X1BUFCFG#0x0
FMAC X1 Buffer Configuration register
X1_BASE
X1_BUF_SIZE
FULL_WM
https://github.com/modm-io/cmsis-svd-stm32