STM32W108HB datasheet(104/179 Pages) STMICROELECTRONICS

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General-purpose timers

STM32W108CB, STM32W108HB

104/179

Doc ID 16252 Rev 2

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Configure the timer in gated mode by writing TIM_SMS = 101 in the TIMx_SMCR

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Enable the counter by writing TIM_CEN = 1 in the TIMx_CR1 register. In gated mode,

the counter does not start if TIM_CEN = 0, regardless of the trigger input level.

The counter starts counting on the internal clock as long as TI1 is low and stops as soon as

TI1 becomes high. The INT_TIMTIF flag in the INT_TIMxFLAG register is set when the

counter starts and when it stops.

The delay between the rising edge on TI1 and the actual stop of the counter is due to the

resynchronization circuit on the TI1 input.

Figure 37.

Control circuit in gated mode

Slave mode: trigger mode

In trigger mode the counter starts in response to an event on a selected input.

In the following example, the up-counter starts in response to a rising edge on the TI2 input:

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Configure channel 2 to detect rising edges on TI2 Configure the input filter duration. In

this example, no filter is required so TIM_IC2F = 0000. The capture prescaler is not

used for triggering, so it is not configured. The TIM_CC2S bits select the input capture

source only, TIM_CC2S = 01 in the TIMx_CCMR1 register. Write TIM_CC2P = 0 in the

TIMx_CCER register to validate the polarity and detect high level only.

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Configure the timer in trigger mode by writing TIM_SMS = 110 in the TIMx_SMCR

When a rising edge occurs on TI2, the counter starts counting on the internal clock and the

INT_TIMTIF 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 the TI2 input.

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