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11100B–ATARM–31-Jul-12
SAM4S Series [Preliminary]
Figure 13-3. General Reset State
13.4.4.2
Backup Reset
A Backup reset occurs when the chip returns from Backup Mode. The core_backup_reset signal
is asserted by the Supply Controller when a Backup reset occurs.
The field RSTTYP in RSTC_SR is updated to report a Backup Reset.
13.4.4.3
User Reset
The User Reset is entered when a low level is detected on the NRST pin and the bit URSTEN in
RSTC_MR is at 1. The NRST input signal is resynchronized with SLCK to insure proper behav-
ior of the system.
The User Reset is entered as soon as a low level is detected on NRST. The Processor Reset
and the Peripheral Reset are asserted.
The User Reset is left when NRST rises, after a two-cycle resynchronization time and a 3-cycle
processor startup. The processor clock is re-enabled as soon as NRST is confirmed high.
When the processor reset signal is released, the RSTTYP field of the Status Register
(RSTC_SR) is loaded with the value 0x4, indicating a User Reset.
T h e N R S T M a n a g e r g u a r a n t e e s t h a t t h e N R S T l i n e i s a s s e r t e d f o r
EXTERNAL_RESET_LENGTH Slow Clock cycles, as programmed in the field ERSTL. How-
ever, if NRST does not rise after EXTERNAL_RESET_LENGTH because it is driven low
externally, the internal reset lines remain asserted until NRST actually rises.
SLCK
periph_nreset
proc_nreset
NRST
(nrst_out)
EXTERNAL RESET LENGTH
= 2 cycles
MCK
Processor Startup
= 2 cycles
backup_nreset
Any
Freq.
RSTTYP
XXX
0x0 = General Reset
XXX
Summary of Contents for SAM4S Series
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