SAM4L Datasheet, PDF (972/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
37.6.7
Power Dissipation and Speed Trade-off
ACIFC is able to control whether an AC operates in fast or low-power mode, allowing a trade-off
between its active power dissipation and speed. The desired mode is selected by writing to the
FAST bit in the CONFx register (CONFx.FAST). When CONFx.FAST is zero (default), the corre-
sponding AC operates in low-power mode. When CONFx.FAST is one, it operates in fast mode.
In low-power mode, the AC dissipates significantly less active power than when it is in fast
mode, but has a longer start-up time and propagation delay. Refer to Section 42. ”Electrical
Characteristics” on page 1106 for details.
37.6.8
Wake Up from Sleep Modes by Interrupt
An AC is able to wake up the system from a sleep mode by its interrupt, including sleep modes
where CLK_ACIFC is stopped. For an AC to wake up the system, the user must follow this pro-
cedure before the system enters a sleep mode:
• Set AC in the Continuous Measurement mode (CONFx.MODE).
• Set the AC’s interrupt setting (CONFx.IS =2) so that it generates an interrupt on the toggling
of the corresponding AC output.
• Wait for AC to be ready (SR.ACRDYx = 1).
Once ACIFC detects a transition on the relevant AC output, it sends a request to Power Man-
ager for CLK_ACIFC to restart (the corresponding bit in the Power Manager Peripheral Power
Control Register (PPCR) must be set) and sets the corresponding interrupt status bit in ISR after
CLK_ACIFC has restarted. Note that in order for the interrupt from ACIFC to wake up the sys-
tem, the ACIFC bit in the Power Manager Asynchronous Wake Up Enable Register (AWEN)
must be set.
37.7
Peripheral Event Triggers
Peripheral events from other modules can trigger comparisons in the ACIFC. All ACs that are
configured in peripheral event triggered single measurement mode will be started simultane-
ously when a peripheral event is received. ACs operating in continuous measurement mode or
user triggered single measurement mode are unaffected by the received peripheral event. Soft-
ware can still operate these ACs independently of ACs in peripheral event triggered single
measurement mode.
A peripheral event will trigger one or more comparisons, in normal or window mode.
37.8
AC Test mode
By writing a one to the Analog Comparator Test Mode bit (CR.ACTEST), the outputs from the
ACs are overridden by the value in the Test Register (TR), see Figure 37-1. This can be useful
for software tests.
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