ATSAM3U datasheet(19/62 Pages) ATMEL

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6430CS–ATARM–09-Apr-10

SAM3U Series

5.4

Active Mode

Active mode is the normal running mode with the core clock running from the fast RC oscillator,

the main crystal oscillator or the PLLA. The power management controller can be used to adapt

the frequency and to disable the peripheral clocks.

5.5

Low Power Modes

The various low power modes of the SAM3U are described below:

5.5.1

Backup Mode

The purpose of backup mode is to achieve the lowest power consumption possible in a system

which is performing periodic wake-ups to perform tasks but not requiring fast startup time

(<0.5ms).

The Supply Controller, zero-power power-on reset, RTT, RTC, Backup registers and 32 kHz

Oscillator (RC or crystal oscillator selected by software in the Supply Controller) are running.

The regulator and the core supply are off.

Backup Mode is based on the Cortex-M3 deep-sleep mode with the voltage regulator disabled.

The SAM3U Series can be awakened from this mode through the Force Wake-Up pin (FWUP),

and Wake-Up input pins WKUP0 to WKUP15, Supply Monitor, RTT or RTC wake-up event. Cur-

rent Consumption is 2.5 µA typical on VDDBU.

Backup mode is entered by using WFE instructions with the SLEEPDEEP bit in the System Con-

trol Register of the Cortex-M3 set to 1. (See the “Power Management” description in The “ARM

Cortex M3 Processor” section of the product datasheet).

Exit from Backup mode happens if one of the following enable wake up events occurs:

• FWUP pin (low level, configurable debouncing)

• WKUPEN0-15 pins (level transition, configurable debouncing)

•SM alarm

•RTC alarm

• RTT alarm

5.5.2

Wait Mode

The purpose of the wait mode is to achieve very low power consumption while maintaining the

whole device in a powered state for a startup time of less than 10 µs.

In this mode, the clocks of the core, peripherals and memories are stopped. However, the core,

peripherals and memories power supplies are still powered. From this mode, a fast start up is

available.

This mode is entered via Wait for Event (WFE) instructions with LPM = 1 (Low Power Mode bit in

PMC_FSMR). The Cortex-M3 is able to handle external events or internal events in order to

wake-up the core (WFE). By configuring the external lines WKUP0-15 as fast startup wake-up

pins (refer to Section 5.7 “Fast Start-Up”). RTC or RTT Alarm and USB wake-up events can be

used to wake up the CPU (exit from WFE).

Current Consumption in Wait mode is typically 15 µA on VDDIN if the internal voltage regulator

is used or 8 µA on VDDCORE if an external regulator is used.

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