Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f0/STM32F0x0/TIM3/SMCR#0x0
slave mode control register
Slave mode selection
Trigger selection
Master/Slave mode
External trigger filter
External trigger prescaler
External clock enable
External trigger polarity
https://github.com/modm-io/cmsis-svd-stm32