ST STM32L0x3 User Manual

RM0367 Rev 7 563/1043
RM0367 General-purpose timers (TIM21/22)
601
External clock source mode 1
This mode is selected when SMS=’111’ in the TIMx_SMCR register. The counter can count
at each rising or falling edge on a selected input.
Figure 172. TI2 external clock connection example
For example, to configure the upcounter to count in response to a rising edge on the TI2
input, use the following procedure:
1. Configure channel 2 to detect rising edges on the TI2 input by writing CC2S = ‘01’ in
the TIMx_CCMR1 register.
2. Configure the input filter duration by writing the IC2F[3:0] bits in the TIMx_CCMR1
register (if no filter is needed, keep IC2F=’0000’).
3. Select the rising edge polarity by writing CC2P=’0’ and CC2NP=’0’ in the TIMx_CCER
register.
4. Configure the timer in external clock mode 1 by writing SMS=’111’ in the TIMx_SMCR
register.
5. Select TI2 as the trigger input source by writing TS=’110’ in the TIMx_SMCR register.
6. Enable the counter by writing CEN=’1’ in the TIMx_CR1 register.
For code example, refer to A.11.1: Upcounter on TI2 rising edge code example.
Note: The capture prescaler is not used for triggering, so it does not need to be configured.
When a rising edge occurs on TI2, the counter counts once and the TIF 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 TI2 input.
External clock
mode 1
Internal clock
mode
TRGI
CK_INT
CK_PSC
TIMx_SMCR
SMS[2:0]
ITRx
TI1_ED
TI1FP1
TI2FP2
TIMx_SMCR
TS[2:0]
TI2
0
1
TIMx_CCER
CC2P
Filter
ICF[3:0]
TIMx_CCMR1
Edge
detector
TI2F_Rising
TI2F_Falling
110
0xx
100
101
MS31196V1
(internal clock)
TI1F or
TI2F or
or
Encoder
mode
ETRF
111
External clock
mode 2
ETRF
ECE

ST STM32L0x3 Specifications

General

Brand	ST
Model	STM32L0x3
Category	Microcontrollers
Language	English