at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 88

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

Figure 14-4. General Reset State
88
AT91SAM9G20 Preliminary
Backup Supply
backup_nreset
periph_nreset
Main Supply
POR output
POR output
proc_nreset
(nrst_out)
RSTTYP
SLCK
NRST
MCK
device. The length of startup time is hardcoded to comply with the Slow Clock Oscillator startup
time.
After this time, the processor clock is released at Slow Clock and all the other signals remain
valid for 3 cycles for proper processor and logic reset. Then, all the reset signals are released
and the field RSTTYP in RSTC_SR reports a General Reset. As the RSTC_MR is reset, the
NRST line rises 2 cycles after the backup_nreset, as ERSTL defaults at value 0x0.
When VDDBU is detected low by the Backup Supply POR Cell, all resets signals are immedi-
ately asserted, even if the Main Supply POR Cell does not report a Main Supply shutdown.
VDDBU only activates the backup_nreset signal.
The backup_nreset must be released so that any other reset can be generated by VDDCORE
(Main Supply POR output).
Figure 14-4
Startup Time
shows how the General Reset affects the reset signals.
XXX
Processor Startup
EXTERNAL RESET LENGTH
= 3 cycles
= 2 cycles
BMS Sampling
0x0 = General Reset
Freq.
Any
6384B–ATARM–15-Dec-08
XXX