Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

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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 = 1.8V at 25°C).
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:

1. Write a 1 to the VROFF bit of SUPC_CR.

To enter backup mode using the WFE instruction:

1. Write a 1 to the SLEEPDEEP bit of the Cortex-M4 processor.
2. 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.
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 by setting the WAITMODE bit to 1 in the  CKGR_MOR register in conjunction with FLPM = 0 

or FLPM = 1 bits of the PMC_FSMR register or by the WFE instruction.
The Cortex-M4 is able to handle external or internal events in order to wake-up the core. This is done by 

configuring the external lines WUP0-15 as fast startup wake-up pins (refer to 

). RTC or 

RTT Alarm and USB wake-up events can be used to wake up the CPU.
To enter wait mode with WAITMODE bit:

1. Select the 4/8/12 MHz fast RC oscillator as Main Clock.
2. Set the FLPM field in the PMC Fast Startup Mode Register (PMC_FSMR). 
3. Set Flash wait state to 0.
4. Set the WAITMODE bit = 1 in PMC Main Oscillator Register (CKGR_MOR).
5. Wait for Master Clock Ready MCKRDY = 1 in the PMC Status Register (PMC_SR).

To enter wait mode with WFE:

1. Select the 4/8/12 MHz fast RC oscillator as Main Clock.
2. Set the FLPM field in the PMC Fast Startup Mode Register (PMC_FSMR).