Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32u5/STM32U535/TIM15/SMCR#0x0
slave mode control register
Slave mode selection
Trigger selection
Master/slave mode
Capture/Compare 1 DMA request enable
https://github.com/modm-io/cmsis-svd-stm32