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17.6.1.2 Power Down
When AUX is in power down mode, the domain receives a power-down clock, configured in
[AON_WUC:AUXCLK:PWR_DWN_SRC].
The options are:
Clock Source Description
NONE The AUX system receives no system clock. The sensor controller will not run, and any
accesses to AUX from the system CPU will return a bus fault. Any peripherals that can
run on an asynchronous clock (such as timers and the TDC) will continue to run.
SCLK_LF AUX runs on the low-frequency system clock (SCLK_LF). The sensor controller can run
on this clock as well as all peripherals. Any accesses to AUX from the system CPU will
take several SCLK_LF clock periods before returning.
SCLK_MF AUX runs on the medium-frequency system clock (SCLK_MF). Behavior is as for
SCLK_LF
NOTE: Using SCLK_MF as a power-down source for AUX is not recommended, as the high speed
oscillator will continue running, preventing a full-device power down. AUX must be switched
over to another power-down clock source before the device can power down.
NOTE: Accesses to the AUX domain from the system CPU while AUX is using a low-frequency
clock will be slow, as the system CPU stalls while waiting for a response from AUX.
17.6.2 Sensor Controller Clock
The sensor controller always runs at the same clock as the AUX system.
When switching between power modes, any code running on the device will have a non-deterministic run-
time as the clock source changes, which can be avoided either by not running code on the sensor
controller while switching power modes, or by requesting to always run on the low-frequency clock when
switching between power modes.
See the clock section in Section 17.5.2.1, Active Mode, for more details.
17.6.3 Peripheral Clocks
AUX can request a number of clocks for the peripherals in the AUX domain.
Enabling clocks for most peripherals is done using the [AUX_WUC:MODCLKEN0] registers. After enabling
the clock for a peripheral, it is ready to be accessed immediately.
17.7 Use Cases
17.7.1 RTC Calibration
17.7.2 Capacitive Sensing
17.7.3 Pulse Counting
17.8 AUX – Sensor Controller Registers
1211
SWCU117A–February 2015–Revised March 2015 AUX – Sensor Controller with Digital and Analog Peripherals
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