Figure 110. Control Circuit In External Clock Mode 1; Figure 111. External Trigger Input Block - ST STM32F423 Reference Manual

Advanced-control timers (TIM1&TIM8)
External clock source mode 2
This mode is selected by writing ECE=1 in the TIMx_SMCR register.
The counter can count at each rising or falling edge on the external trigger input ETR.
Figure 111
For example, to configure the upcounter to count each 2 rising edges on ETR, use the
following procedure:
480/1324

Figure 110. Control circuit in external clock mode 1

gives an overview of the external trigger input block.

Figure 111. External trigger input block

RM0430 Rev 8
RM0430