Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32F7x/OTG_FS_HOST/OTG_FS_HCTSIZ9#0x0
OTG_FS host channel-9 transfer size register
Transfer size
Packet count
Data PID
https://github.com/cmsis-svd/cmsis-svd-data