Table 114. Lptim External Trigger Connection - ST STM32F413 Reference Manual

Low-power timer (LPTIM)
Bits 4:3 CKFLT: Configurable digital filter for external clock
The CKFLT value sets the number of consecutive equal samples that should be detected when a level
change occurs on an external clock signal before it is considered as a valid level transition. An internal
clock source must be present to use this feature
00: any external clock signal level change is considered as a valid transition
01: external clock signal level change must be stable for at least 2 clock periods before it is
considered as valid transition.
10: external clock signal level change must be stable for at least 4 clock periods before it is
considered as valid transition.
11: external clock signal level change must be stable for at least 8 clock periods before it is
considered as valid transition.
Bits 2:1 CKPOL: Clock Polarity
If LPTIM is clocked by an external clock source:
When the LPTIM is clocked by an external clock source, CKPOL bits is used to configure the active
edge or edges used by the counter:
00: the rising edge is the active edge used for counting
01: the falling edge is the active edge used for counting
10: both edges are active edges. When both external clock signal's edges are considered active
ones, the LPTIM must also be clocked by an internal clock source with a frequency equal to at
least four time the external clock frequency.
11: not allowed
If the LPTIM is configured in Encoder mode (ENC bit is set):
00: the encoder sub-mode 1 is active
01: the encoder sub-mode 2 is active
10: the encoder sub-mode 3 is active
Refer to Section 21.4.13: Encoder mode
Bit 0 CKSEL: Clock selector
The CKSEL bit selects which clock source the LPTIM will use:
0: LPTIM is clocked by internal clock source (APB clock or any of the embedded oscillators)
1: LPTIM is clocked by an external clock source through the LPTIM external Input1
Caution: The LPTIM_CFGR register must only be modified when the LPTIM is disabled (ENABLE bit
is reset to '0').
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Table 114. LPTIM external trigger connection

TRIGSEL
ext_trig0
ext_trig1
ext_trig2
ext_trig3
ext_trig4
ext_trig5
ext_trig6
ext_trig7
DocID029473 Rev 3
for more details about Encoder mode sub-modes.
External trigger
RTC_TAMP input detection
GPIO
RTC alarm A
RTC alarm B
TIM1
TIM5
Not connected
Not connected
RM0430