Information

In Pulse Counter mode with the prescaler/glitch filter bypassed, the selected input source
directly clocks the CNR and no other clock source is required. To minimize power in this
case, configure the prescaler clock source for a clock that is not toggling.
NOTE
The clock source or pulse input source selected for the LPTMR
should not exceed the frequency f
LPTMR
defined in the device
datasheet.
37.4.3 LPTMR prescaler/glitch filter
The LPTMR prescaler and glitch filter share the same logic which operates as a prescaler
in Time Counter mode and as a glitch filter in Pulse Counter mode.
NOTE
The prescaler/glitch filter configuration must not be altered
when the LPTMR is enabled.
37.4.3.1 Prescaler enabled
In Time Counter mode, when the prescaler is enabled, the output of the prescaler directly
clocks the CNR. When the LPTMR is enabled, the CNR will increment every 2
2
to 2
16
prescaler clock cycles. After the LPTMR is enabled, the first increment of the CNR will
take an additional one or two prescaler clock cycles due to synchronization logic.
37.4.3.2 Prescaler bypassed
In Time Counter mode, when the prescaler is bypassed, the selected prescaler clock
increments the CNR on every clock cycle. When the LPTMR is enabled, the first
increment will take an additional one or two prescaler clock cycles due to
synchronization logic.
Functional description
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
836 Freescale Semiconductor, Inc.