AT32UC3L064_1 ATMEL [ATMEL Corporation], AT32UC3L064_1 Datasheet - Page 198

• Manufacturer Part Number: AT32UC3L064_1
• Description: AVR32 32-bit Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

14.5.7
14.5.8
14.5.9
32099A–AVR32–06/09
Voltage Regulator (VREG)
System RC Oscillator (RCSYS)
3.3 V Supply Monitor (SM33)
It is not recommended to override default factory settings as it may prevent correct operation of
the Flash and BOD. To prevent unexpected writes due to software bugs, write access to this
register is protected by a locking mechanism, for details please refer to the UNLOCK register
description
The embedded voltage regulator can be used to provide the VDDCORE voltage from the
VDDIN. It is controlled by the VREGCR register. The voltage regulator is turned on by default at
startup but can be turned off by software if an external power is provided on the VDDCORE
The voltage regulator has its own voltage reference that is calibrated through the
VREGCR.CALIB field. This field is loaded after a Power On Reset with default values stored in
factory-programmed flash fuses.
Although it is not recommended to override default factory settings, it is still possible to override
these default values by writing to those registers. To prevent unexpected writes due to software
bugs, write access to this register is protected by a locking mechanism, for details please refer to
the UNLOCK register description.
The voltage regulator interface also includes control bits for the POR33 (Power-On Reset 3.3V)
detector that monitors the VDDIN voltage during power-up. The POR33 is on by default but can
be turned off by software to reduce power consumption. The 3.3V Supply Monitor can then be
used to monitor the VDDIN power supply (see
The RC32K oscillator must be turned on to disabled the POR33. Once the POR33 had ben dis-
abled, the RC32K oscillator can be turned off again. Note that if the POR33 is re-enabled later, it
will generate a reset.
The system RC oscillator (RCSYS) has a 3 cycles startup time, and is always available except in
Static mode. The system RC oscillator operates at a nominal frequency of 115 kHz, and is cali-
brated using the RCCR.CALIB Calibration field. After a Power On Reset, the RCCR.CALIB field
is loaded with a factory defined value stored in the Flash fuses.
Although it is not recommended to override default factory settings, it is still possible to override
these default values by writing to the RCCR.CALIB field. To prevent unexpected writes due to
software bugs, write access to this register is protected by a locking mechanism, for details
please refer to the UNLOCK register description.
The 3.3V supply monitor (SM33) is a specific voltage detector for the VDDIN voltage. It will indi-
cate if the VDDIN voltage is above the minimum required input voltage for the voltage regulator
(typically 1.75V). The user can choose to generate either a reset or an interrupt when the VDDIN
voltage drops below this limit.
In order to reduce power consumption, the SM33 can operate in “sampling mode”. In sampling
mode, the SM33 is periodically turned on for a small time (just enough for making the measure-
ment) then it is turned off for a longer time.
By default, the SM33 operates in “sampling” mode during DeepStop and Static mode and in
continuous mode for other sleep modes. Sampling mode can also be forced during sleep modes
other than DeepStop and Static and during normal operation.
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