Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32n6/STM32N645/ETH/ETH_MTLTXQ1ECR#0x0
SLC=B_0x0
Tx queue 1 ETS control Register
AV Algorithm
Credit Control
Slot Count
0 (B_0x0): 1 Slot
1 (B_0x1): 2 Slots
2 (B_0x2): 4 Slots
3 (B_0x3): 8 Slots
4 (B_0x4): 16 Slots
https://github.com/modm-io/cmsis-svd-stm32