Datasheet

level. Writing a one to the BOD12 Hysteresis bit (BOD12.HYST) in the BOD12 register will add hysteresis
to the BOD12 threshold level.
17.6.10 Voltage Reference System Operation
The Voltage Reference System (VREF) consists of a Bandgap Reference Voltage Generator and a
temperature sensor.
The Bandgap Reference Voltage Generator is factory-calibrated under typical voltage and temperature
conditions.
At reset, the VREF.CAL register value is loaded from Flash Factory Calibration.
The temperature sensor can be used to get an absolute temperature in the temperature range of CMIN to
CMAX degrees Celsius. The sensor will output a linear voltage proportional to the temperature. The
output voltage and temperature range are located in the Electrical Characteristics. To calculate the
temperature from a measured voltage, the following formula can be used:

MIN
+ Vmes+  Vou
MAX
temperature
voltage
Related Links
37. Electrical Characteristics
17.6.10.1 User Control of the Voltage Reference System
To enable the temperature sensor, write a one the Temperature Sensor Enable bit (VREF.TSEN) in the
VREF register.
The temperature sensor can be redirected to the ADC for conversion.
The Bandgap Reference Voltage Generator output can also be routed to the ADC if the Bandgap Output
Enable bit (VREF.BGOUTEN) in the VREF register is set.
The Bandgap Reference Voltage Generator output level is determined by the CALIB bit group
(VREF.CALIB) value in the VREF register.The default calibration value can be overridden by the user by
writing to the CALIB bit group.
17.6.11 Voltage Regulator System Operation
The embedded Voltage Regulator (VREG) is an internal voltage regulator that provides the core logic
supply (VDDCORE).
17.6.12 DMA Operation
Not applicable.
17.6.13 Interrupts
The SYSCTRL has the following interrupt sources:
• XOSCRDY - Multipurpose Crystal Oscillator Ready: A “0-to-1” transition on the
PCLKSR.XOSCRDY bit is detected
• XOSC32KRDY - 32kHz Crystal Oscillator Ready: A “0-to-1” transition on the
PCLKSR.XOSC32KRDY bit is detected
• OSC32KRDY - 32kHz Internal Oscillator Ready: A “0-to-1” transition on the PCLKSR.OSC32KRDY
bit is detected
• OSC8MRDY - 8MHz Internal Oscillator Ready: A “0-to-1” transition on the PCLKSR.OSC8MRDY
bit is detected
SAM D21 Family
SYSCTRL – System Controller
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 189