User Manual

Apollo3 Blue Datasheet

DS-A3-0p9p1 Page 177 of 909 2019 Ambiq Micro, Inc.

5.1.2 Auto Power Down

The DMA-capable peripherals can be configured to automatically power down the respective peripheral

device once the total DMA transaction is complete. This feature is particularly useful in cases where a

device transaction can be queued up allowing the CPU to go into deep sleep while the transaction

completes which could take a long time depending on the data rate of the device and/or the trigger

conditions for sending/receiving data.

The auto power down mode is fully autonomous where not only is the peripheral device powered down but

any associated memory is also replaced back into its lowest power state as applicable. The auto power

down mode is enabled in the DMA_CFG register of the respective peripheral device register space.

5.1.3 Priority

Each DMA agent can be assigned a high priority or a “best effort” priority. This allows software to ensure a

certain quality of service as required for the particular peripheral depending on the use case requirements.

The peripheral also has safeguards to auto promote priority if its corresponding trigger levels are

approaching critical levels. This is to ensure the respective peripheral does not overflow/underflow.

The priority settings as well as the auto promote feature are enabled in the DMA_CFG register of the

respective peripheral device register space.

5.1.4 Hardware Handshake / Hardware Triggering

The IOM, BLE and MSPI peripherals include handshaking to allow coordination of data flow between the

peripherals and system memory without CPU involvement by using the command queuing support in the

peripheral. See the respective peripheral sections for details regarding command queuing and hardware

triggering.