SAM4L Datasheet, PDF (921/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
ger one acquisition per event. The peripheral-event-triggered operation is enabled by writing a
one to the Event Triggered Operation bit in the Control Register (CR.ETRIG). In this mode, the
CATB will start the required clocks for performing an acquisition, and can thereby operate in all
sleep modes where the peripheral event generator is running.
Using the peripheral-event-triggered mode allows the CATB to be used as a low-power wake-up
source for the CPU, as interrupts can be generated on in-touch or out-of-touch events. It is not
possible to use multiple sensors in sleep modes where the Peripheral DMA Controller is
disabled.
Writing a one to the Event Triggered Operation bit in the Control Register (CR.ETRIG) will dis-
able the continuous sampling and only sample when the CATB receives a peripheral event. The
number of samples per peripheral event can be configured by writing to the Number of Event
Samples field in the Control Register (CR.ESAMPLES). One peripheral event causes CR.ESA-
MPLES+1 samples to be acquired. If a monitored threshold is passed, the CATB can wake the
device from sleep.
When the CATB receives a peripheral event during sleep mode, it automatically requests both
the CLK_CATB and the CLK_ACQ clock. Note that it is not possible to use the peripheral-event-
triggered operation with the GCLK as a source for CLK_ACQ in sleep modes where the GCLK is
disabled. Refer to Section 10. ”Power Manager (PM)” on page 102 for details. If no touch is
detected after an acquisition, CLK_CATB and CLK_ACQ will be stopped, returning the device to
low power mode.
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