22.6.6.1 Dynamic SleepWalking based on Event

To enable SleepWalking with dynamic power domain gating, the Dynamic Power Gating for Power Domain SW bit in the Standby Configuration register (STDBYCFG.DPGPDSW) has to be written to '1'.

When in retention state, a power domain can be automatically set to active state by the PM if an event is directed to this power domain. In this device, this concerns the event users located in power domain PDSW.

  • When PDSW is in retention state, dynamic SleepWalking can be triggered by:
    • AC output event
    • RTC output event
    • EIC output event (if using the CLK_ULP32K clock and debouncing is enabled)

Refer also to 22.6.1.2 Power Domains.

Dynamic SleepWalking based on event is illustrated in the following example:

Figure 22-8. Dynamic SleepWalking based on Event: AC Periodic Comparison

The Analog Comparator (AC) peripheral is used in single shot mode to monitor voltage levels on input pins. A comparator interrupt, based on the AC peripheral configuration, is generated to wake up the device. In the GCLK module, the AC generic clock (GCLK_AC) source is routed a 32.768kHz oscillator (for low power applications, OSC32KULP is recommended). RTC and EVSYS modules are configured to generate periodic events to the AC. To make the comparator continue to run in standby sleep mode, the RUNSTDBY bit is written to '1'. To enable the dynamic SleepWalking for PDSW power domain, STDBYCFG.PDSW must be written to '1'.

Entering standby mode: The Power Manager sets the PDSW power domain in retention state. The AC comparators, COMPx, are OFF. The GCLK_AC clock is stopped. The VDDCORE is supplied by the low power regulator.

Dynamic SleepWalking: The RTC event (RTC_PERX) is routed by the Event System to the Analog Comparator to trigger a single-shot measurement. This event is detected by the Power Manager, which sets the PDSW power domain to active state and starts the main voltage regulator.

After enabling the AC comparator and starting the GCLK_AC, the single-shot measurement can be performed during Sleep mode (sleepwalking task), refer to 42.6.14.2 Single-Shot Measurement during Sleep for details. At the end of the conversion, if conditions to generate an interrupt are not met, the GCLK_AC clock is stopped again, as well as the AC comparator.

The low-power regulator starts again and the PDSW power domain is set back to retention state by the PM. During this dynamic SleepWalking period, the CPU is still sleeping.

Exiting standby mode: during the dynamic SleepWalking sequence, if conditions are met, the AC module generates an interrupt to wake up the device.