Figure 202. Control Circuit In Trigger Mode - ST STM32G0 1 Series Reference Manual

General-purpose timers (TIM2/TIM3/TIM4)
CC2P=1 and CC2NP=0 in TIMx_CCER register to validate the polarity (and detect low
level only).
2. Configure the timer in trigger mode by writing SMS=110 in TIMx_SMCR register. Select
TI2 as the input source by writing TS=00110 in TIMx_SMCR register.
When a rising edge occurs on TI2, the counter starts counting on the internal clock and the
TIF flag is set.
The delay between the rising edge on TI2 and the actual start of the counter is due to the
resynchronization circuit on TI2 input.
Counter clock = ck_cnt = ck_psc
Slave mode: External Clock mode 2 + trigger mode
The external clock mode 2 can be used in addition to another slave mode (except external
clock mode 1 and encoder mode). In this case, the ETR signal is used as external clock
input, and another input can be selected as trigger input when operating in reset mode,
gated mode or trigger mode. It is recommended not to select ETR as TRGI through the TS
bits of TIMx_SMCR register.
In the following example, the upcounter is incremented at each rising edge of the ETR
signal as soon as a rising edge of TI1 occurs:
1. Configure the external trigger input circuit by programming the TIMx_SMCR register as
follows:
–
–
–
2. Configure the channel 1 as follows, to detect rising edges on TI:
–
–
–
–
3. Configure the timer in trigger mode by writing SMS=110 in TIMx_SMCR register. Select
TI1 as the input source by writing TS=00101 in TIMx_SMCR register.
662/1390

Figure 202. Control circuit in trigger mode

TI2
cnt_en
Counter register
TIF
ETF = 0000: no filter
ETPS=00: prescaler disabled
ETP=0: detection of rising edges on ETR and ECE=1 to enable the external clock
mode 2.
IC1F=0000: no filter.
The capture prescaler is not used for triggering and does not need to be
configured.
CC1S=01in TIMx_CCMR1 register to select only the input capture source
CC1P=0 and CC1NP=0 in TIMx_CCER register to validate the polarity (and detect
rising edge only).
RM0444 Rev 5
34 35 36
RM0444
37 38
MS31403V1