Figure 42-2. Continuous Measurement Example
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
COMPCTRLx.ENABLE
t
STARTUP
Write ‘1’
2-3 cycles
For low-power operation, comparisons can be performed during sleep modes without a clock. The
comparator is enabled continuously, and changes of the comparator state are detected asynchronously.
When a toggle occurs, the Power Manager will start GCLK_AC to register the appropriate peripheral
events and interrupts. The GCLK_AC clock is then disabled again automatically, unless configured to
wake up the system from sleep.
Related Links
on page 1147
Single-Shot
Single-shot operation is selected by writing COMPCTRLx.SINGLE to '1'. During single-shot operation, the
comparator is normally idle. The user starts a single comparison by writing '1' to the respective Start
Comparison bit in the write-only Control B register (CTRLB.STARTx). The comparator is enabled, and
after the start-up time has passed, a single comparison is done and STATUSA is updated. Appropriate
peripheral events and interrupts are also generated. No new comparisons will be performed.
Writing '1' to CTRLB.STARTx also clears the Comparator x Ready bit in the Status B register
(STATUSB.READYx). STATUSB.READYx is set automatically by hardware when the single comparison
has completed.
A single-shot measurement can also be triggered by the Event System. Setting the Comparator x Event
Input bit in the Event Control Register (EVCTRL.COMPEIx) enables triggering on incoming peripheral
events. Each comparator can be triggered independently by separate events. Event-triggered operation is
similar to user-triggered operation; the difference is that a peripheral event from another hardware module
causes the hardware to automatically start the comparison and clear STATUSB.READYx.
To detect an edge of the comparator output in single-shot operation for the purpose of interrupts, the
result of the current measurement is compared with the result of the previous measurement (one
sampling period earlier). An example of single-shot operation is shown in
.
Figure 42-3. Single-Shot Example
GCLK_AC
STATUSB.READYx
Sampled
Comparator Output
CTRLB.STARTx
t
STARTUP
Write ‘1’
t
STARTUP
Write ‘1’
2-3 cycles
2-3 cycles
For low-power operation, event-triggered measurements can be performed during sleep modes. When
the event occurs, the Power Manager will start GCLK_AC. The comparator is enabled, and after the
startup time has passed, a comparison is done and appropriate peripheral events and interrupts are also
generated. The comparator and GCLK_AC are then disabled again automatically, unless configured to
wake up the system from sleep.
Related Links
on page 1147
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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