331
SAM4CP [DATASHEET]
43051E–ATPL–08/14
20.4.8 System Reset
The Supply Controller manages the system reset signal (vddcore_nreset) to the Reset Controller, as described in
Section 20.4.7 ”Backup Power Supply Reset”
. The system reset signal is normally asserted before shutting down the
core power supply and released as soon as the core power supply is correctly regulated.
There are two additional sources which can be programmed to activate the system reset signal:
a supply monitor detection
a brownout detection
20.4.8.1 Supply Monitor Reset
The supply monitor is capable of generating a reset of the system. This can be enabled by setting the SMRSTEN bit in
SUPC_SMMR.
If SMRSTEN is set and if a supply monitor detection occurs, the system reset signal is immediately activated for a
minimum of 1 slow clock cycle.
20.4.8.2 Brownout Detector Reset
The brownout detector provides the core voltage status signal (BODCORE_out) to the SUPC which indicates that the
voltage regulation is operating as programmed. If this signal is lost for longer than 1 slow clock period while the voltage
regulator is enabled, the Supply Controller can assert system reset signal. This feature is enabled by writing
BODRSTEN (Brownout Detector Reset Enable) to 1 in SUPC_MR.
If BODRSTEN is set and the voltage regulation is lost (output voltage of the regulator too low), the system reset signal is
asserted for a minimum of 1 slow clock cycle and then released if the core voltage status has been reactivated. The
BODRSTS bit is set in SUPC_SR so that the user knows the source of the last reset.
The system reset signal remains active as long as the core voltage status signal (BODCORE_out) indicates a powerfail
condition.
20.4.8.3 Power-on-Reset on VDDBU_SW
The power-on-reset monitors VDDBU_SW. It is active by default and monitors voltage at start up but also during power
down. It can be deactivated by software through SUPC_MR. If VDDBU_SW goes below the threshold voltage, the entire
chip is reset. Note that due to the automatic power switch, VDDBU_SW can be either VDDIO or VDDBU.