22.6.6.2 Dynamic SleepWalking Based on Peripheral DMA Trigger

To enable this advanced feature, the Dynamic Power Gating for Power Domain SW bit in the Standby Configuration register (STDBYCFG.DPGPDSW) have to be written to '1'.

When in retention state, the power domain PDSW (containing the DMAC) can be automatically set to active state if the PM detects a valid DMA trigger that is coming from a peripheral located in PDAO. A peripheral DMA trigger is valid if the corresponding DMA channel is enabled and its Run in Standby bit (RUNSTDBY) is written to '1'.

This is illustrated in the following example:

The DMAC is configured to operate in standby sleep mode by using its respective RUNSTDBY bit. A DMAC channel is configured to set the DMA destination. The Run in Standby bit of this DMAC channel is written to '1' to allow it running in Standby Sleep mode.

Entering Standby mode: The Power Manager peripheral sets PDSW to retention state. The VDDCORE is supplied by the low-power regulator.

Dynamic SleepWalking: based on RTC conditions, an RTC output signal (DMA request for timestamp) triggers DMAC to put timestamp value at configured DMA destination.

This event is detected by the Power Manager which sets the PDSW power domain to active state and starts the main voltage regulator.

This DMA transfer request is detected by the PM, which sets PDSW (containing the DMAC) to active state. The DMAC requests the CLK_DMAC_AHB clock and transfer the timestamp value to the memory. When the DMA beat transfer is completed, the CLK_DMAC_AHB clock is stopped again.

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

Exiting Standby mode: during SleepWalking with Dynamic Power Gating sequence, if conditions are met, the DMAC generates an interrupt to wake up the device.