NXP Semiconductors K22F series, Reference Manual, Page: 173 / 1407

NOTE
To prevent unexpected loss of clock reset events, all clock
monitors should be disabled before entering any low power
modes, including VLPR and VLPW.
6.2.2.6 MCG loss-of-lock (LOL) reset
The MCG includes a PLL loss-of-lock detector. The detector is enabled when configured
for PEE and lock has been achieved. If the MCG_C8[LOLRE] bit in the MCG module is
set and the PLL lock status bit (MCG_S[LOLS0]) becomes set, the MCU resets. The
RCM_SRS0[LOL] bit is set to indicate this reset source.
NOTE
This reset source does not cause a reset if the chip is in any stop
mode.
6.2.2.7 Stop mode acknowledge error (SACKERR)
This reset is generated if the core attempts to enter stop mode, but not all modules
acknowledge stop mode within 1025 cycles of the 1 kHz LPO clock.
A module might not acknowledge the entry to stop mode if an error condition occurs. The
error can be caused by a failure of an external clock input to a module.
6.2.2.8 Software reset (SW)
The SYSRESETREQ bit in the NVIC application interrupt and reset control register can
be set to force a software reset on the device. (See ARM's NVIC documentation for the
full description of the register fields, especially the VECTKEY field requirements.)
Setting SYSRESETREQ generates a software reset request. This reset forces a system
reset of all major components except for the debug module. A software reset causes the
RCM's SRS1[SW] bit to set.
6.2.2.9 Lockup reset (LOCKUP)
The LOCKUP gives immediate indication of seriously errant kernel software. This is the
result of the core being locked because of an unrecoverable exception following the
activation of the processor’s built in system state protection hardware.
Chapter 6 Reset and Boot
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 173