Datasheet

111
SAM9263 [DATASHEET]
Atmel-6249N-ATARM-SAM9263-Datasheet_14-Mar-16
13.3.4.3 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 behavior 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 three-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.
The NRST Manager guarantees that the NRST line is asserted for EXTERNAL_RESET_LENGTH Slow Clock
cycles, as programmed in the field ERSTL. However, 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.
Figure 13-6. User Reset State
13.3.4.4 Software Reset
The Reset Controller offers several commands used to assert the different reset signals. These commands are
performed by writing the Control Register (RSTC_CR) with the following bits at 1:
 PROCRST: Writing PROCRST at 1 resets the processor and the watchdog timer.
 PERRST: Writing PERRST at 1 resets all the embedded peripherals, including the memory system, and, in
particular, the Remap Command. The Peripheral Reset is generally used for debug purposes.
Except for Debug purposes, PERRST must always be used in conjunction with PROCRST (PERRST and
PROCRST set both at 1 simultaneously.)
 EXTRST: Writing EXTRST at 1 asserts low the NRST pin during a time defined by the field ERSTL in the
Mode Register (RSTC_MR).
The software reset is entered if at least one of these bits is set by the software. All these commands can be
performed independently or simultaneously. The software reset lasts three Slow Clock cycles.
SLCK
periph_nreset
proc_nreset
NRST
NRST
(nrst_out)
>= EXTERNAL RESET LENGTH
MCK
Processor Startup
= 2 cycles
Any
Freq.
Resynch.
2 cycles
RSTTYP
Any XXX
Resynch.
2 cycles
0x4 = User Reset