SAM3U Datasheet, PDF (20/59 Pages) ATMEL Corporation – AT91SAM ARM-based Flash MCU

Entering Wait Mode:
• Select the 4/8/12 MHz Fast RC Oscillator as Main Clock
• Set the LPM bit in the PMC Fast Startup Mode Register (PMC_FSMR)
• Execute the Wait-For-Event (WFE) instruction of the processor
5.5.3
Note:
Internal Main clock resynchronization cycles are necessary between the writing of MOSCRCEN
bit and the effective entry in Wait mode. Depending on the user application, Waiting for
MOSCRCEN bit to be cleared is recommended to ensure that the core will not execute undesired
instructions.
Sleep Mode
The purpose of sleep mode is to optimize power consumption of the device versus response
time. In this mode, only the core clock is stopped. The peripheral clocks can be enabled. This
mode is entered via Wait for Interrupt (WFI) or Wait for Event (WFE) instructions with LPM = 0 in
PMC_FSMR.
The processor can be awakened from an interrupt if WFI instruction of the Cortex M3 is used, or
from an event if the WFE instruction is used to enter this mode.
20 SAM3U Series
6430ES–ATARM–22-Aug-11