Information

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.
VLPR mode restrictions also apply to VLPW.
VLPW mode provides the option to return to fully-regulated normal RUN mode if any
enabled interrupt occurs. This is done by setting PMCTRL[LPWUI]. Wait for the
PMSTAT register to set to RUN before increasing the frequency.
If the LPWUI bit is clear, when an interrupt from VLPW occurs, the device returns to
VLPR mode to execute the interrupt service routine.
A system reset will cause an exit from WAIT mode, returning the device to normal RUN
mode.
14.4.5 Stop modes
This device contains a variety of stop modes to meet your application needs. The stop
modes range from:
• a stopped CPU, with all I/O, logic, and memory states retained, and certain
asynchronous mode peripherals operating
to:
• a powered down CPU, with only I/O and a small register file retained, very few
asynchronous mode peripherals operating, while the remainder of the MCU is
powered down.
The choice of stop mode depends upon the user's application, and how power usage and
state retention versus functional needs may be traded off.
The various stop modes are selected by setting the appropriate fields in PMPROT and
PMCTRL. The selected stop mode mode is entered during the sleep-now or sleep-on-exit
entry with the SLEEPDEEP bit set in the System Control Register in the ARM core.
The available stop modes are:
• Normal Stop (STOP)
• Very-Low Power Stop (VLPS)
• Low-Leakage Stop (LLS)
• Very-Low-Leakage Stop (VLLSx)
Functional Description
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
276 Freescale Semiconductor, Inc.