how i can find the Internal trigger connection of 446r neucleo board (ITR with TIMx) and in which reference i can find this?

[waclawek.jan]

Look just after the TIMx_SMCR description in individual timer chapters in R0390, in "TIMx internal trigger connections" tables.

It should be the same as in 'F407, which I have in a single table here. However, RM takes precedence, as usually.

AN4640 is what "Interconnections" is in other STM32 RMs; but sadly, it won't go to sufficient detail (as those chapters won't either).

JW