SAM4L Datasheet, PDF (51/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
6.1.4 Wakeup Time
6.1.4.1
Wakeup Time From SLEEP Mode
The latency depends on the clock sources wake up time. If the clock sources are not stopped,
there is no latency to wake the clocks up.
6.1.4.2
Wakeup Time From WAIT or RETENTION Mode
The wake up latency consists of:
• the switching time from the low power configuration to the RUN mode power configuration.
By default, the switching time is completed when all the voltage regulation system is ready.
To speed-up the startup time, the user can set the Fast Wakeup bit in BPM.PMCON register.
• the wake up time of the RC oscillator used to start the system up. By default, the RCSYS
oscillator is used to startup the system. The user can use another clock source (RCFAST for
example) to speed up the startup time by configuring the PM.FASTWKUP register. Refer to
Section 10. ”Power Manager (PM)” on page 102.
• the Flash memory wake up time.
6.1.4.3
To have the shortest wakeup time, the user should:
- set the BPM.PMCON.FASTWKUP bit.
- configure the PM.FASTSLEEP.FASTRCOSC field to use the RCFAST main clock.
- enter the WAIT or RETENTION mode
Upon a wakeup, this is required to keep the main clock connected to RCFAST until the voltage
regulation system is fully ready (when BPM.ISR.PSOK bit is one). During this wakeup period,
the FLASHCALW module is automatically configured to operate in “1 wait state mode”.
Wake time from BACKUP mode
It is equal to the Core domain logic reset latency (similar to the reset latency caused by an exter-
nal reset in RESET_N pin) added to the time required for the voltage regulation system to be
stabilized.
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