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Functional description
To reenter Normal Run mode, clear PMCTRL[RUNM]. PMSTAT is a read-only status
register that can be used to determine when the system has completed an exit to RUN
mode. When PMSTAT=RUN, the system is in run regulation and the MCU can run at
full speed in any clock mode. If a higher execution frequency is desired, poll PMSTAT
until it is set to RUN when returning from VLPR mode.
Any reset always causes an exit from VLPR and returns the device to RUN mode after
the MCU exits its reset flow.
14.5.4 Wait modes
This device contains two different wait modes which are listed here.
• Wait
• Very-Low Power Wait (VLPW)
14.5.4.1 WAIT mode
WAIT mode is entered when the ARM core enters the Sleep-Now or Sleep-On-Exit
modes while SLEEPDEEP is cleared. The ARM CPU enters a low-power state in which
it is not clocked, but peripherals continue to be clocked provided they are enabled. Clock
gating to the peripheral is enabled via the SIM module.
When an interrupt request occurs, the CPU exits WAIT mode and resumes processing in
RUN mode, beginning with the stacking operations leading to the interrupt service
routine.
A system reset will cause an exit from WAIT mode, returning the device to normal RUN
mode.
14.5.4.2 Very-Low-Power Wait (VLPW) mode
VLPW is entered by the entering the Sleep-Now or Sleep-On-Exit mode while
SLEEPDEEP is cleared and the MCU is in VLPR mode.
In VLPW, the on-chip voltage regulator remains in its stop regulation state. In this state,
the regulator is designed to supply enough current to the MCU over a reduced frequency.
To further reduce power in this mode, disable the clocks to unused modules by clearing
the peripherals' corresponding clock gating control bits in the SIM (or PCC).
VLPR mode restrictions also apply to VLPW.
236
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
Freescale Semiconductor, Inc.
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