SAM3U Datasheet, PDF (23/59 Pages) ATMEL Corporation – AT91SAM ARM-based Flash MCU

SAM3U Series
5.7 Fast Start-Up
The SAM3U allows the processor to restart in a few microseconds while the processor is in wait
mode. A fast start up can occur upon detection of a low level on one of the 19 wake-up inputs.
The fast restart circuitry, as shown in Figure 5-5, is fully asynchronous and provides a fast start-
up signal to the Power Management Controller. As soon as the fast start-up signal is asserted,
the PMC automatically restarts the embedded 4/8/12 MHz fast RC oscillator, switches the mas-
ter clock on this 4/8/12 MHz clock and reenables the processor clock.
Figure 5-5. Fast Start-Up Sources
USBEN
usb_wakeup
rtc_alarm
RTCEN
rtt_alarm
RTTEN
WKUP0
WKUP1
High/Low
Level
Detector
High/Low
Level
Detector
FSTT0
FSTT1
fast_restart
WKUP15
High/Low
Level
Detector
FSTT15
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6430ES–ATARM–22-Aug-11