Deep Sleep Mode; Power-Down Mode - NXP Semiconductors LPC1768 User Manual

NXP Semiconductors
mode, but may not access the flash memory, which is disabled in order to save power.
Sleep mode eliminates dynamic power used by the processor itself, memory systems and
related controllers, and internal buses.
Wake-up from Sleep mode will occur whenever any enabled interrupt occurs.

8.2 Deep Sleep mode

Note: Deep Sleep mode on the LPC17xx corresponds to the Sleep mode on LPC23xx
and LPC24xx series devices. The name is changed because ARM has incorporated
portions of reduced power mode control into the Cortex-M3. LPC17xx documentation
uses the Cortex-M3 terminology where applicable.
When the chip enters the Deep Sleep mode, the main oscillator is powered down, nearly
all clocks are stopped, and the DSFLAG bit in PCON is set, see
remains running and can be configured to drive the Watchdog Timer, allowing the
Watchdog to wake up the CPU. The 32 kHz RTC oscillator is not stopped and RTC
interrupts may be used as a wake-up source. The flash is left in the standby mode
allowing a quick wake-up. The PLLs are automatically turned off and disconnected. The
CCLK and USBCLK clock dividers automatically get reset to zero.
The processor state and registers, peripheral registers, and internal SRAM values are
preserved throughout Deep Sleep mode and the logic levels of chip pins remain static.
The Deep Sleep mode can be terminated and normal operation resumed by either a
Reset or certain specific interrupts that are able to function without clocks. Since all
dynamic operation of the chip is suspended, Deep Sleep mode reduces chip power
consumption to a very low value.
On the wake-up of Deep Sleep mode, if the IRC was used before entering Deep Sleep
mode, a 2-bit IRC timer starts counting and the code execution and peripherals activities
will resume after the timer expires (4 cycles). If the main external oscillator was used, the
12-bit main oscillator timer starts counting and the code execution will resume when the
timer expires (4096 cycles). The user must remember to re-configure any required PLLs
and clock dividers after the wake-up.
Wake-up from Deep Sleep mode can be brought about by NMI, External Interrupts EINT0
through EINT3, GPIO interrupts, the Ethernet Wake-on-LAN interrupt, Brownout Detect,
an RTC Alarm interrupt, a Watchdog Timer timeout, a USB input pin transition (USB
activity interrupt), or a CAN input pin transition, when the related interrupt is enabled.
Wake-up will occur whenever any enabled interrupt occurs.

8.3 Power-down mode

Power-down mode does everything that Deep Sleep mode does, but also turns off the
flash memory. Entry to Power-down mode causes the PDFLAG bit in PCON to be set, see
Table
before execution of code or data access in the flash memory can be accomplished.
When the chip enters Power-down mode, the IRC, the main oscillator, and all clocks are
stopped. The RTC remains running if it has been enabled and RTC interrupts may be
used to wake up the CPU. The flash is forced into Power-down mode. The PLLs are
automatically turned off and disconnected. The CCLK and USBCLK clock dividers
automatically get reset to zero.
UM10360_0
User manual
4–44. This saves more power, but requires waiting for resumption of flash operation
Rev. 00.06 — 5 June 2009
Chapter 4: LPC17xx Clocking and power control
UM10360
Table 4–44. The IRC
© NXP B.V. 2009. All rights reserved.
51 of 808