at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 91

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

Figure 14-7. Software Reset
14.3.4.5
6384B–ATARM–15-Dec-08
SRCMP in RSTC_SR
Write RSTC_CR
Watchdog Reset
if PROCRST=1
periph_nreset
if PERRST=1
if EXTRST=1
proc_nreset
(nrst_out)
RSTTYP
NRST
SLCK
MCK
If EXTRST is set, the nrst_out signal is asserted depending on the programming of the field
ERSTL. However, the resulting falling edge on NRST does not lead to a User Reset.
If and only if the PROCRST bit is set, the Reset Controller reports the software status in the field
RSTTYP of the Status Register (RSTC_SR). Other Software Resets are not reported in
RSTTYP.
As soon as a software operation is detected, the bit SRCMP (Software Reset Command in
Progress) is set in the Status Register (RSTC_SR). It is cleared as soon as the software reset is
left. No other software reset can be performed while the SRCMP bit is set, and writing any value
in RSTC_CR has no effect.
The Watchdog Reset is entered when a watchdog fault occurs. This state lasts 3 Slow Clock
cycles.
When in Watchdog Reset, assertion of the reset signals depends on the WDRPROC bit in
WDT_MR:
The Watchdog Timer is reset by the proc_nreset signal. As the watchdog fault always causes a
processor reset if WDRSTEN is set, the Watchdog Timer is always reset after a Watchdog
Reset, and the Watchdog is enabled by default and with a period set to a maximum.
• If WDRPROC is 0, the Processor Reset and the Peripheral Reset are asserted. The NRST
• If WDRPROC = 1, only the processor reset is asserted.
line is also asserted, depending on the programming of the field ERSTL. However, the
resulting low level on NRST does not result in a User Reset state.
Freq.
Any
Any
Resynch.
1 cycle
Processor Startup
XXX
= 3 cycles
EXTERNAL RESET LENGTH
AT91SAM9G20 Preliminary
8 cycles (ERSTL=2)
0x3 = Software Reset
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