19.4.4 Sleep Mode Operation

Each DMA channel can be configured to operate in any sleep mode. To enable operation in standby mode, the RUNSTDBY bit in Channel Control A (CHCTRLA.RUNSTDBY) register must be set. The DMAC can wake up the device using interrupts from any sleep mode or perform actions through the Event System.

For channels where CHCTRLA.RUNSTDBY is ‘0’, it is up to the software to stop DMA transfers on these channels and wait for completion before going into Standby sleep mode using the following sequence:

  1. Suspend the DMAC channels for which CHCTRLA.RUNSTDBY is ‘0’.
  2. Check the SYNCBUSY bits of the registers accessed by the DMAC channels being suspended.
  3. Enter sleep mode.
  4. When the device wakes up, resume the suspended channels.
Note:
  1. In Standby sleep mode, the DMAC can only access RAM when it is not back biased. Refer to the PM – Power Manager chapter for information on back biasing.