K60P100M100SF2RM Datasheet, PDF (353/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 15 Low-leakage wake-up unit (LLWU)
In the case of a wakeup due to external pin or internal module wakeup, the I/O states are
held until software clears the ACKISO bit (by writing a 1 to it). Recovery is always via a
system reset flow and the MC_SRS[WAKEUP] is set indicating the low leakage mode
was active prior to the last system reset flow.
An VLLS reset event due to RESET pin assertion causes an exit via a system reset. State
retention data is lost, the I/O states return to their reset state, and the ACKISO bit is not
set. The MC_SRS[WAKEUP] and MC_SRS[PIN] bits are set and the system executes a
reset flow before CPU operation begins with a reset vector fetch.
15.4.3 Initialization
Flags associated with external input pins (WUFx) are cleared upon entry into LLS or
VLLS modes.
For an enabled peripheral wakeup input, the peripheral flag should be cleared by the user
before entering LLS or VLLS to avoid an immediate exit from LLS or VLLS.
15.4.4 Low power mode recovery
Recovery from VLLSx is through the wake-up Reset event. The chip wake-ups from
VLLSx by means of reset, an enabled pin or enabled module. See the table "LLWU
inputs" in the LLWU configuration section for a list of the sources.
The wake-up flow from VLLS1,2 and 3 is through reset. The wakeup bit in the SRS
registers in the Mode Controller is set indicating that the chip is recovering from a low
power mode. Code execution begins; however, the I/O pins are held in their pre-low-
power mode entry states, and the oscillator is disabled (even if EREFSTEN had been set
before entering VLLSx). Software must clear this hold by writing a 1 to the ACKISO bit
in the Control and Status register in the LLWU module.
NOTE
To avoid unwanted transitions on the pins, software must re-
initialize the I/O pins to their pre-low-power mode entry states
before releasing the hold.
The oscillator cannot be re-enabled before the ACKISO bit is cleared and must be
reconfigured after the hold is released.
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
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