STM32W108HB datasheet(166/278 Pages) STMICROELECTRONICS

166 / 278 page

General-purpose timers

STM32W108HB STM32W108CC STM32W108CB STM32W108CZ

166/278

Doc ID 16252 Rev 14

Figure 27.

TI2 external clock connection example

For example, to configure the up-counter to count in response to a rising edge on the TI2

input, use the following procedure:

Configure channel 2 to detect rising edges on the TI2 input by writing CC2S = 01 in the

TIMx_CCMR1 register.

Configure the input filter duration by writing the IC2F bits in the TIMx_CCMR1 register

(if no filter is needed, keep IC2F = 0000).

Note:

The capture prescaler is not used for triggering, so it does not need to be configured.

Select rising edge polarity by writing CC2P = 0 in the TIMx_CCER register.

Configure the timer in external clock mode 1 by writing SMS = 111 in the TIMx_SMCR

Select TI2 as the input source by writing TS = 110 in the TIMx_SMCR register.

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 TIE 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 the TI2 input.

Figure 28.

Control circuit in External Clock mode 1

CK_INT

Encoder

mode

External clock

mode 1

External clock

mode 2

Internal clock

mode

ETRF

TRGI

TI1F

TI2F

CK_PSC

TIMx_SMCR

SMS[2:0]

ITRx

TI1F_ED

TI1FP1

TI2FP2

ETRF

TIMx_SMCR

TS[2:0]

TI2

TIMx_CCER

CC2P

Filter

IC2F[3:0]

TIMx_CCMR1

Edge

detector

TI2F_rising

TI2F_falling

110

001

100

101

111

(Internal clock)

ECE

Counter clock = CK_CNT = CK_PSC

Counter register

TI2

CNT_EN

TIE

Write UIE=0

STM32W108HB Datasheet(PDF) 166 Page - STMicroelectronics

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