LPC1788FBD144 NXP Semiconductors, LPC1788FBD144 Datasheet - Page 64

• Manufacturer Part Number: LPC1788FBD144
• Description: The LPC1788 is a Cortex-M3 microcontroller for embedded applications featuring a high level of integration and low power consumption at frequencies of 120 MHz
• Manufacturer: NXP Semiconductors

NXP Semiconductors
LPC178X_7X
Objective data sheet
7.33.4.2 Deep-sleep mode
7.33.4.3 Power-down mode
The DMA controller can continue to work in Sleep mode and has access to the peripheral
RAMs and all peripheral registers. The flash memory and the main SRAM are not
available in Sleep mode, they are disabled in order to save power.
Wake-up from Sleep mode will occur whenever any enabled interrupt occurs.
In Deep-sleep mode, the oscillator is shut down and the chip receives no internal clocks.
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 output of the IRC is disabled but the IRC is not powered down to allow fast wake-up.
The RTC oscillator is not stopped because the RTC interrupts may be used as the
wake-up source. The PLL is automatically turned off and disconnected. The clock divider
registers are automatically reset to zero.
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. Power to the flash memory is left on in Deep-sleep
mode, allowing a very quick wake-up.
Wake-up from Deep-sleep mode can initiated by the NMI, External Interrupts EINT0
through EINT3, GPIO interrupts, the Ethernet Wake-on-LAN interrupt, Brownout Detect,
an RTC Alarm interrupt, a USB input pin transition (USB activity interrupt), a CAN input
pin transition, or a Watchdog Timer time-out, when the related interrupt is enabled.
Wake-up will occur whenever any enabled interrupt occurs.
On wake-up from Deep-sleep mode, the code execution and peripherals activities will
resume after four cycles expire if the IRC was used before entering Deep-sleep mode. If
the main external oscillator was used, the code execution will resume when 4096 cycles
expire. PLL and clock dividers need to be reconfigured accordingly.
Power-down mode does everything that Deep-sleep mode does but also turns off the
power to the IRC oscillator and the flash memory. This saves more power but requires
waiting for resumption of flash operation 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 the clock selection multiplexers are set to use the system
clock sysclk (the reset state). The clock divider control registers are automatically reset to
zero. If the Watchdog timer is running, it will continue running in Power-down mode.
On the wake-up of Power-down mode, if the IRC was used before entering Power-down
mode, it will take IRC 60 s to start-up. After this four IRC cycles will expire before the
code execution can then be resumed if the code was running from SRAM. In the
meantime, the flash wake-up timer then counts 12 MHz IRC clock cycles to make the
100 s flash start-up time. When it times out, access to the flash will be allowed. Users
need to reconfigure the PLL and clock dividers accordingly.
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 27 December 2011
32-bit ARM Cortex-M3 microcontroller
LPC178x/7x
© NXP B.V. 2011. All rights reserved.
64 of 120