Datasheet

973
SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
Figure 40-2. DMAC Transfer Hierarchy for Non-Memory Peripheral
Figure 40-3. DMAC Transfer Hierarchy for Memory
Buffer: A buffer of DMAC data. The amount of data (length) is determined by the flow controller. For transfers
between the DMAC and memory, a buffer is broken directly into a sequence of AMBA bursts and AMBA single
transfers.
For transfers between the DMAC and a non-memory peripheral, a buffer is broken into a sequence of DMAC
transactions (single and chunks). These are in turn broken into a sequence of AMBA transfers.
Transaction: A basic unit of a DMAC transfer as determined by either the hardware or software handshaking
interface. A transaction is only relevant for transfers between the DMAC and a source or destination peripheral if
the source or destination peripheral is a non-memory device. There are two types of transactions: single transfer
and chunk transfer.
 Single transfer: The length of a single transaction is always 1 and is converted to a single AMBA
access.
 Chunk transfer: The length of a chunk is programmed into the DMAC. The chunk is then converted
into a sequence of AHB access.DMAC executes each AMBA burst transfer by performing incremental
bursts that are no longer than 16 beats.
DMAC transfer: Software controls the number of buffers in a DMAC transfer. Once the DMAC transfer has
completed, then hardware within the DMAC disables the channel and can generate an interrupt to signal the
completion of the DMAC transfer. You can then re-program the channel for a new DMAC transfer.
Single-buffer DMAC transfer: Consists of a single buffer.
HDMA Transfer
DMA Transfer
Level
Buffer
Buffer Buffer
Buffer Transfer
Level
Chunk
Transfer
Chunk
Transfer
Chunk
Transfer
Single
Transfer
DMA Transaction
Level
Burst
Transfer
AMBA
Burst
Transfer
AMBA
Burst
Transfer
AMBA
Single
Transfer
AMBA
AMBA Transfer
Level
Single
Transfer
AMBA
HDMA Transfer
DMA Transfer
Level
Buffer
Buffer Buffer
Buffer Transfer
Level
Burst
Transfer
AMBA
Burst
Transfer
AMBA
Burst
Transfer
AMBA
Single
Transfer
AMBA
AMBA Transfer
Level