NXP Semiconductors MKW01Z128, Reference Manual, Page: 236 / 884

4.2.2.1.1 RESET pin filter
The RESET pin filter supports filtering from both the 1 kHz LPO clock and the bus
clock. RCM_RPFC[RSTFLTSS], RCM_RPFC[RSTFLTSRW], and
RCM_RPFW[RSTFLTSEL] control this functionality; see the
RCM chapter. The filters
are asynchronously reset by Chip POR. The reset value for each filter assumes the
RESET pin is negated.
For all stop modes where LPO clock is still active (Stop, VLPS, LLS, VLLS3, and
VLLS1), the only filtering option is the LPO-based digital filter. The filtering logic either
switches to bypass operation or has continued filtering operation depending on the
filtering mode selected. When entering VLLS0, the RESET pin filter is disabled and
bypassed.
The LPO filter has a fixed filter value of 3. Due to a synchronizer on the input data, there
is also some associated latency (2 cycles). As a result, 5 cycles are required to complete a
transition from low to high or high to low.
4.2.2.2 Low-voltage detect (LVD)
The chip includes a system for managing low-voltage conditions to protect memory
contents and control MCU system states during supply voltage variations. The system
consists of a power-on reset (POR) circuit and an LVD circuit with a user-selectable trip
voltage. The LVD system is always enabled in Normal Run, Wait, or Stop mode. The
LVD system is disabled when entering VLPx, LLS, or VLLSx modes.
The LVD can be configured to generate a reset upon detection of a low-voltage condition
by setting PMC_LVDSC1[LVDRE] to 1. The low-voltage detection threshold is
determined by PMC_LVDSC1[LVDV]. After an LVD reset has occurred, the LVD
system holds the MCU in reset until the supply voltage has risen above the low voltage
detection threshold. RCM_SRS0[LVD] is set following either an LVD reset or POR.
4.2.2.3 Computer operating properly (COP) watchdog timer
The computer operating properly (COP) watchdog timer (WDOG) monitors the operation
of the system by expecting periodic communication from the software. This
communication is generally known as servicing (or refreshing) the COP watchdog. If this
periodic refreshing does not occur, the watchdog issues a system reset. The COP reset
causes RCM_SRS0[WDOG] to set.
Chapter 4 Reset and Boot
MKW01Z128 MCU Reference Manual, Rev. 3, 04/2016
Freescale Semiconductor, Inc. 105