UM10462
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User manual
Rev. 5.5 — 21 December 2016
49 of 523
NXP Semiconductors
UM10462
Chapter 3: LPC11U3x/2x/1x System control block
3. Use the ARM Cortex-M0 Wait-For-Interrupt (WFI) instruction.
3.9.3.3 Wake-up from Sleep mode
Sleep mode is exited automatically when an interrupt enabled by the NVIC arrives at the
processor or a reset occurs. After wake-up due to an interrupt, the microcontroller returns
to its original power configuration defined by the contents of the PDRUNCFG and the
SYSAHBCLKDIV registers. If a reset occurs, the microcontroller enters the default
configuration in Active mode.
3.9.4 Deep-sleep mode
In Deep-sleep mode, the system clock to the processor is disabled as in Sleep mode. All
analog blocks are powered down, except for the BOD circuit and the watchdog oscillator,
which must be selected or deselected during Deep-sleep mode in the PDSLEEPCFG
register. The main clock, and therefore all peripheral clocks, are disabled except for the
clock to the watchdog timer if the watchdog oscillator is selected. The IRC is running, but
its output is disabled. The flash is in stand-by mode.
Remark:
If the LOCK bit is set in the WWDT MOD register (
) and the IRC is
selected as a clock source for the WWDT, the IRC continues to clock the WWDT in
Deep-sleep mode.
Deep-sleep mode eliminates all power used by analog peripherals and all dynamic power
used by the processor itself, memory systems and related controllers, and internal buses.
The processor state and registers, peripheral registers, and internal SRAM values are
maintained, and the logic levels of the pins remain static.
3.9.4.1 Power configuration in Deep-sleep mode
Power consumption in Deep-sleep mode is determined by the Deep-sleep power
configuration setting in the PDSLEEPCFG (
) register:
•
The watchdog oscillator can be left running in Deep-sleep mode if required for the
WWDT.
•
If the IRC is locked as the WWDT clock source (see
), the IRC continues
to run and clock the WWDT in Deep-sleep mode independently of the setting in the
PDSLEEPCFG register.
•
The BOD circuit can be left running in Deep-sleep mode if required by the application.
3.9.4.2 Programming Deep-sleep mode
The following steps must be performed to enter Deep-sleep mode:
1. The PD bits in the PCON register must be set to 0x1 (
2. Select the power configuration in Deep-sleep mode in the PDSLEEPCFG (
)
register.
3. Determine if the WWDT clock source must be locked to override the power
configuration in case the IRC is selected as clock for the WWDT (see
4. If the main clock is not the IRC, power up the IRC in the PDRUNCFG register and
switch the clock source to IRC in the MAINCLKSEL register (
). This ensures
that the system clock is shut down glitch-free.