RM0440 Rev 4 1483/2126
RM0440 Low-power timer (LPTIM)
1487
Caution: The LPTIM_CFGR register must only be modified when the LPTIM is disabled (ENABLE bit
reset to ‘0’).
32.7.5 LPTIM control register (LPTIM_CR)
Address offset: 0x010
Reset value: 0x0000 0000
Bits 4:3 CKFLT[1:0]: 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[1:0]: 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.
If the LPTIM is configured in Encoder mode (ENC bit is set), the encoder sub-mode 1 is active.
01:the falling edge is the active edge used for counting
If the LPTIM is configured in Encoder mode (ENC bit is set), the encoder sub-mode 2 is active.
10:both edges are active edges. When both external clock signal edges are considered active ones,
the LPTIM must also be clocked by an internal clock source with a frequency equal to at least
four times the external clock frequency.
If the LPTIM is configured in Encoder mode (ENC bit is set), the encoder sub-mode 3 is active.
11: not allowed
Refer to Section 32.4.14: Encoder mode for more details about Encoder mode sub-modes.
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
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RST
ARE
COUN
TRST
CNT
STRT
SNG
STRT
ENA
BLE
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