STM32W108B-SK STMicroelectronics, STM32W108B-SK Datasheet - Page 117

• Manufacturer Part Number: STM32W108B-SK
• Description: STARTER KIT FOR STM32W108
• Manufacturer: STMicroelectronics
• Series: STM32r
• Type: MCUr

Specifications of STM32W108B-SK

• Featured Product: STM32 Cortex-M3 Companion Products
• Contents: Board
• Silicon Manufacturer: ST Micro
• Core Architecture: ARM
• Core Sub-architecture: Cortex - M3
• Silicon Core Number: STM32
• Silicon Family Name: STM32W108xx
• Kit Contents: Board
• Features: IEEE
• Mfg Application Notes: STM32W108 Adjacent Channel Rejection Measurements
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: *
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

STM32W108CB, STM32W108HB
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 24.
Figure 28
Figure 28. External trigger input block
For example, to configure the up-counter to count each 2 rising edges on ETR, use the
following procedure:
●
●
●
●
●
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.
00
01
10
11
TIM_EXTRIGSEL bits
As no filter is needed in this example, write TIM_ETF = 0000 in the TIMx_SMCR
register.
Set the prescaler by writing TIM_ETPS = 01 in the TIMx_SMCR register.
Select rising edge detection on ETR by writing TIM_ETP = 0 in the TIMx_SMCR
register.
Enable external clock mode 2 by writing TIM_ECE = 1 in the TIMx_SMCR register.
Enable the counter by writing TIM_CEN = 1 in the TIMx_CR1 register.
Table
gives an overview of the external trigger input block.
TIM_EXTRIGSEL clock signal selection
24.
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.
Doc ID 16252 Rev 8
Clock signal selection
General-purpose timers
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