SAM4L Datasheet, PDF (161/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
• RCSYS: This oscillator is always enabled when selected as clock source. Refer to Section
10. ”Power Manager (PM)” on page 102 for details about RCSYS and the Power Save
Modes. Refer to the Section 42.6 ”Oscillator Characteristics” on page 1125 chapter for the
oscillator’s frequency characteristics.
• OSC32K or RC32K: This oscillator has to be enabled in the BSCIF Interface before using it
as clock source for the BOD18/33. The BOD18/33 will not be able to detect if this clock is
stopped.
It is recommended to disable the BOD18/33 before disabling the clock, to avoid freezing the
BOD18/33 in an undefined state.
12.6.3.6
Changing Clock Source
The BOD18/33SAMPLING.CEN bit should always be disabled before changing the sampling
clock source. To change the clock for the BOD18/33 the following steps need to be taken:
1. Write a zero to the CEN bit, leaving the other bits unchanged, to stop the clock.
2. Wait until CEN reads as zero, giving the clock time to stop.
3. Select a new clock source by writing to the BOD18/33SAMPLING.CSSEL bit.
4. Write a one to the CEN bit, leaving the other bits unchanged, to enable the clock.
5. Wait until CEN reads as one, giving the clock time to start.
12.6.3.7
Changing the Prescaler
To change the Prescaler value for the BOD18/33 during sampling mode the following steps
need to be taken:
1.Wait until the PCLKSR.BOD18/33SYNRDY bit is one.
2.Write the selected value to the PSEL field.
12.6.3.8
BOD18/33 Interrupts/Reset
The BOD18/33 can generate either an interrupt or a reset based on the ACTION field in the
BOD18/33CTRL register. The Interrupt/Reset is triggered when there is a voltage
(VDDIO/VDDCORE) failure. Before enabling the BOD18/33 reset mode the ACTION field must
first be initialized to zero in order to avoid any false BOD18/33 detection when the BOD18/33 is
not ready.
12.6.3.9
Hysteresis
The hysteresis functionality may be used in both continuous and sampling mode. Writing a one
to the HYST bit in BOD18/33CTRL can add hysteresis to the BOD18/33 trigger level.
12.6.3.10
BOD18 Threshold Ranges
The BOD18 has two threshold voltage ranges. There is a Standard Threshold Range, for opera-
tion in Power Scaling 0 and 2 Mode (PS0 andPS2), and a Low Threshold Range for operation at
lower supply voltage values, such as Power Scaling 1 Mode or deep Power Save Mode. The
user must take care of using the right threshold settings according to the different Modes. Refer
to Section 42.8 ”Analog Characteristics” on page 1133 for regulator minimal values in the differ-
ent modes
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