SAM3S8B Atmel Corporation, SAM3S8B Datasheet - Page 451

• Manufacturer Part Number: SAM3S8B
• Manufacturer: Atmel Corporation

25.1.11
451
451
SAM3S8/SD8
SAM3S8/SD8
Fast Startup
As the Programmable Clock Controller does not manage with glitch prevention when switching
clocks, it is strongly recommended to disable the Programmable Clock before any configuration
change and to re-enable it after the change is actually performed.
The device allows the processor to restart in less than 10 microseconds while the device is in
Wait mode. The system enters Wait mode by executing the WaitForEvent (WFE) instruction of
the processor while the LPM bit is at 1 in the PMC Fast Startup Mode Register (PMC_FSMR).
Important: Prior to asserting any WFE instruction to the processor, the internal sources of
wakeup provided by RTT, RTC and USB must be cleared and verified too, that none of the
enabled external wakeup inputs (WKUP) hold an active polarity.
A Fast Startup is enabled upon the detection of a programmed level on one of the 16 wake-up
inputs (WKUP) or upon an active alarm from the RTC, RTT and USB Controller. The polarity of
the 16 wake-up inputs is programmable by writing the PMC Fast Startup Polarity Register
(PMC_FSPR).
The Fast Restart circuitry, as shown in
startup signal to the Power Management Controller. As soon as the fast startup signal is
asserted, the embedded 4/8/12 MHz Fast RC oscillator restarts automatically.
Figure 25-9. Fast Startup Circuitry
Each wake-up input pin and alarm can be enabled to generate a Fast Startup event by writing 1
to the corresponding bit in the Fast Startup Mode Register PMC_FSMR.
WKUP15
WKUP0
WKUP1
RTC Alarm
USB Alarm
RTT Alarm
FSTP15
FSTP0
FSTP1
FSTT15
RTCAL
USBAL
FSTT0
FSTT1
RTTAL
Figure
25-9, is fully asynchronous and provides a fast
11090A–ATARM–10-Feb-12
11090A–ATARM–10-Feb-12
fast_restart