STM32W108CB datasheet(90/179 Pages) STMICROELECTRONICS

90 / 179 page

General-purpose timers

STM32W108CB, STM32W108HB

90/179

Doc ID 16252 Rev 2

Note:

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

Select rising edge polarity by writing TIM_CC2P = 0 in the TIMx_CCER register.

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

TIMx_SMCR register.

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

Enable the counter by writing TIM_CEN = 1 in the TIMx_CR1 register.

When a rising edge occurs on TI2, the counter counts once and the INT_TIMTIF 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 23.

Control Circuit in External Clock Mode 1

External clock source mode 2

This mode is selected by writing TIM_ECE = 1 in the TIMx_SMCR register. The counter can

count at each rising or falling edge on the external trigger input ETR.

The TIM_EXTRIGSEL bits in the TIMx_OR register select a clock signal that drives ETR, as

shown in Table 12.

Table 12.

TIM_EXTRIGSEL clock signal selection

TIM_EXTRIGSEL bits

Clock Signal Selection

PCLK (peripheral clock). When running from the 24 MHz crystal oscillator,

the PCLK frequency is 12 MHz. When the 12M Hz RC oscillator is in use,

the frequency is 6 MHz.

Calibrated 1 kHz internal RC oscillator

Optional 32 kHz clock

TIMxCLK pin. If the TIM_CLKMSKEN bit in the TIMx_OR register is set,

this signal is AND'ed with the TIMxMSK pin providing a gated clock input.

STM32W108CB Scheda tecnica(PDF) 90 Page - STMicroelectronics