DocID018909 Rev 11
595/1731
RM0090
General-purpose timers (TIM2 to TIM5)
640
Note:
The capture prescaler is not used for triggering, so you don’t need to configure it.
3. Select rising edge polarity by writing CC2P=0 and CC2NP=0 in the TIMx_CCER
register.
4. Configure the timer in external clock mode 1 by writing SMS=111 in the TIMx_SMCR
register.
5. Select TI2 as the input source by writing TS=110 in the TIMx_SMCR register.
6. Enable the counter by writing CEN=1 in the TIMx_CR1 register.
When a rising edge occurs on TI2, the counter counts once and the TIF flag is set.
The delay between the rising edge on TI2 and the actual clock of the counter is due to the
resynchronization circuit on TI2 input.
Figure 156. Control circuit in external clock mode 1
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.
gives an overview of the external trigger input block.
Figure 157. External trigger input block
Counter clock = CK_CNT = CK_PSC
Counter register
35
36
34
TI2
CNT_EN
TIF
Write TIF=0
ETR
0
1
TIMx_SMCR
ETP
divider
/1, /2, /4, /8
ETPS[1:0]
ETRP
filter
ETF[3:0]
downcounter
CK_INT
TIMx_SMCR
TIMx_SMCR
ETR pin
CK_INT
encoder
mode
external clock
mode 1
external clock
mode 2
internal clock
mode
ETRF
TRGI
TI1F
TI2F
or
or
or
(internal clock)
CK_PSC
ECE
TIMx_SMCR
SMS[2:0]