NXP Semiconductors KL25 Series - Functional Description

LLWU_FILT2 field descriptions (continued)
Field Description
0 Pin Filter 2 was not a wakeup source
1 Pin Filter 2 was a wakeup source
6–5
FILTE
Digital Filter On External Pin
Controls the digital filter options for the external pin detect.
00 Filter disabled
01 Filter posedge detect enabled
10 Filter negedge detect enabled
11 Filter any edge detect enabled
4
Reserved
This field is reserved.
This read-only field is reserved and always has the value 0.
3–0
FILTSEL
Filter Pin Select
Selects 1 out of the 16 wakeup pins to be muxed into the filter.
0000 Select LLWU_P0 for filter
... ...
1111 Select LLWU_P15 for filter
15.4 Functional description
This on-chip peripheral module is called a low-leakage wakeup unit (LLWU) module
because it allows internal peripherals and external input pins as a source of wakeup from
low-leakage modes. It is operational only in LLS and VLLSx modes.
The LLWU module contains pin enables for each external pin and internal module. For
each external pin, the user can disable or select the edge type for the wakeup. Type
options are:
• Falling-edge
• Rising-edge
• Either-edge
When an external pin is enabled as a wakeup source, the pin must be configured as an
input pin.
The LLWU implements optional 3-cycle glitch filters, based on the LPO clock. A
detected external pin is required to remain asserted until the enabled glitch filter times
out. Additional latency of up to 2 cycles is due to synchronization, which results in a total
of up to 5 cycles of delay before the detect circuit alerts the system to the wakeup or reset
event when the filter function is enabled. Two wakeup detect filters are available to
detect up to two external pins. Glitch filtering is not provided on the internal modules.
Functional description
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
262 Freescale Semiconductor, Inc.