Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

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SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

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.

The SAM4S has the following low-power modes: backup mode, wait mode and sleep mode. 

Note:

The Wait For Event instruction (WFE) of the Cortex-M4 core can be used to enter any of the low-power modes, how-
ever, this may add complexity in the design of application state machines. This is due to the fact that the WFE
instruction goes along with an event flag of the Cortex core (cannot be managed by the software application). The
event flag can be set by interrupts, a debug event or an event signal from another processor. Since it is possible for an
interrupt to occur just before the execution of WFE, WFE takes into account events that happened in the past. As a
result, WFE prevents the device from entering wait mode if an interrupt event has occurred.
Atmel has made provision to avoid using the WFE instruction. The workarounds to ease application design are as fol-
lows:
- For backup mode, switch off the voltage regulator and configure the VROFF bit in the Supply Controller Control Reg-
ister (SUPC_CR).
- For wait mode, configure the WAITMODE bit in the PMC Clock Generator Main Oscillator Register of the Power Man-
agement Controller (PMC)
- For sleep mode, use the Wait for Interrupt (WFI) instruction.

Complete information is available in 

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. Total current consumption is 1 

μA typical (VDDIO

= 1.8 V to 25°).

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.

The SAM4S can be awakened from this mode using the WKUP0-15 pins, the supply monitor (SM), the RTT or RTC
wake-up event. 

Backup mode is entered by writing a 1 to the VROFF bit of the Supply Controller Control Register (SUPC_CR) (A key is
needed to write the VROFF bit, refer to the Supply Controller SUPC section of the product datasheet) and with the
SLEEPDEEP bit in the Cortex-M4 System Control Register set to 1. (See the power management description in the ARM
Cortex-M4 Processor section of the product datasheet).

To enter backup mode using the VROFF bit:



Write a 1 to the VROFF bit of SUPC_CR.

To enter backup mode using the WFE instruction:



Write a 1 to the SLEEPDEEP bit of the Cortex-M4 processor.



Execute the WFE instruction of the processor.

In both cases, exit from backup mode happens if one of the following enable wake up events occurs:



WKUPEN0-15 pins (level transition, configurable debouncing)



Supply Monitor alarm



RTC alarm



RTT alarm

The purpose of 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. Current consumption in wait mode is typically 32 μA (total current

consumption) if the internal voltage regulator is used.