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UM10601
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© NXP B.V. 2012. All rights reserved.
Preliminary user manual
Rev. 1.0 — 7 November 2012
50 of 313
NXP Semiconductors
UM10601
Chapter 5: LPC800 Reduced power modes and Power Management
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 itself and the
flash are powered down, decreasing power consumption compared to Deep-sleep mode.
Power-down 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. Wake-up times are longer
compared to the Deep-sleep mode.
5.7.6.1 Power configuration in Power-down mode
Power consumption in Power-down mode can be configured by the power configuration
setting in the PDSLEEPCFG (
) register in the same way as for Deep-sleep mode
):
•
The watchdog oscillator can be left running in Power-down mode if required for the
WWDT.
•
The BOD circuit can be left running in Power-down mode if required by the
application.
5.7.6.2 Programming Power-down mode
The following steps must be performed to enter Power-down mode:
1. The PD bits in the PCON register must be set to 0x2 (
2. Select the power configuration in Power-down mode in the PDSLEEPCFG (
)
register.
3. Select the power configuration after wake-up in the PDAWAKECFG (
register.
4. If any of the available wake-up interrupts are used for wake-up, enable the interrupts
in the interrupt wake-up registers (
) and in the NVIC.
5. Write one to the SLEEPDEEP bit in the ARM Cortex-M0 SCR register.
6. Use the ARM WFI instruction.
5.7.6.3 Wake-up from Power-down mode
The microcontroller can wake up from Power-down mode in the same way as from
Deep-sleep mode:
•
Signal on one of the eight pin interrupts selected in
. Each pin interrupt must
also be enabled in the STARTERP0 register (
) and in the NVIC.
•
BOD signal, if the BOD is enabled in the PDSLEEPCFG register:
–
BOD interrupt using the interrupt wake-up register 1 (
must be enabled in the NVIC. The BOD interrupt must be selected in the
BODCTRL register.
–
Reset from the BOD circuit. In this case, the BOD reset must be enabled in the
BODCTRL register (
•
WWDT signal, if the watchdog oscillator is enabled in the PDSLEEPCFG register: