at91cap7e ATMEL Corporation, at91cap7e Datasheet - Page 70

• Manufacturer Part Number: at91cap7e
• Description: Customizable Microcontroller
• Manufacturer: ATMEL Corporation

14.3.3.2
Figure 14-4. Wake-up State
14.3.3.3
70
AT91CAP7E
Wake-up Reset
User Reset
backup_nreset
periph_nreset
Main Supply
POR output
proc_nreset
(nrst_out)
RSTTYP
SLCK
NRST
MCK
The Wake-up Reset occurs when the Main Supply is down. When the Main Supply POR output
is active, all the reset signals are asserted except backup_nreset. When the Main Supply pow-
ers up, the POR output is resynchronized on Slow Clock. The processor clock is then re-enabled
during 2 Slow Clock cycles, depending on the requirements of the ARM processor.
At the end of this delay, the processor and other reset signals rise. The field RSTTYP in
RSTC_SR is updated to report a Wake-up Reset.
The “nrst_out” remains asserted for EXTERNAL_RESET_LENGTH cycles. As RSTC_MR is
backed-up, the programmed number of cycles is applicable.
When the Main Supply is detected falling, the reset signals are immediately asserted. This tran-
sition is synchronous with the output of the Main Supply POR.
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 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.
Resynch.
2 cycles
XXX
Processor Startup
EXTERNAL RESET LENGTH
= 3 cycles
= 4 cycles (ERSTL = 1)
0x1 = WakeUp Reset
Freq.
Any
XXX
8549A–CAP–10/08