ST STM32F101 series Reference Manual

General-purpose timers (TIM2 to TIM5) RM0008
375/1128 DocID13902 Rev 15
1. As no filter is needed in this example, write ETF[3:0]=0000 in the TIMx_SMCR register.
2. Set the prescaler by writing ETPS[1:0]=01 in the TIMx_SMCR register
3. Select rising edge detection on the ETR pin by writing ETP=0 in the TIMx_SMCR
register
4. Enable external clock mode 2 by writing ECE=1 in the TIMx_SMCR register.
5. Enable the counter by writing CEN=1 in the TIMx_CR1 register.
The counter counts once each 2 ETR rising edges.
The delay between the rising edge on ETR and the actual clock of the counter is due to the
resynchronization circuit on the ETRP signal.
Figure 124. Control circuit in external clock mode 2
15.3.4 Capture/compare channels
Each Capture/Compare channel is built around a capture/compare register (including a
shadow register), a input stage for capture (with digital filter, multiplexing and prescaler) and
an output stage (with comparator and output control).
The following figure gives an overview of one Capture/Compare channel.
The input stage samples the corresponding TIx input to generate a filtered signal TIxF.
Then, an edge detector with polarity selection generates a signal (TIxFPx) which can be
used as trigger input by the slave mode controller or as the capture command. It is
prescaled before the capture register (ICxPS).
Figure 125. Capture/compare channel (example: channel 1 input stage)
Counter clock = CK_CNT = CK_PSC
Counter register
35 3634
ETR
CNT_EN
CK_INT
ETRP
ETRF
TI1
0
1
TIMx_CCER
CC1P
divider
/1, /2, /4, /8
ICPS[1:0]
TI1F_ED
filter
ICF[3:0]
downcounter
TIMx_CCMR1
Edge
Detector
TI1F_Rising
TI1F_Falling
to the slave mode controller
TI1FP1
11
01
TIMx_CCMR1
CC1S[1:0]
IC1
TI2FP1
TRC
(from channel 2)
(from slave mode
controller)
10
f
DTS
TIMx_CCER
CC1E
IC1PS
TI1F
0
1
TI2F_rising
TI2F_falling
(from channel 2)

ST STM32F101 series Specifications

General

Brand	ST
Model	STM32F101 series
Category	Computer Hardware
Language	English