Lptmr Prescaler/Glitch Filter - NXP Semiconductors MKL27Z128VFM4 Reference Manual

31.5.3 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.
The prescaler/glitch filter configuration must not be altered
when the LPTMR is enabled.
31.5.3.1 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
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.
31.5.3.2 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.
31.5.3.3 Glitch filter
In Pulse Counter mode, when the glitch filter is enabled, the output of the glitch filter
directly clocks the CNR. When the LPTMR is first enabled, the output of the glitch filter
is asserted, that is, logic 1 for active-high and logic 0 for active-low. The following table
shows the change in glitch filter output with the selected input source.
The selected input source remains deasserted for at least 2
15
to 2 consecutive prescaler clock rising edges
The selected input source remains asserted for at least 2
15
2 consecutive prescaler clock rising-edges
The input is only sampled on the rising clock edge.
Freescale Semiconductor, Inc.
NOTE
If
1
to
NOTE
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Chapter 31 Low-Power Timer (LPTMR)
1
The glitch filter output will also deassert.
The glitch filter output will also assert.
2 16
to 2
Then
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