Datasheet

469
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
Channel: Read/write datapath between a source peripheral on one configured AMBA layer and a destination
peripheral on the same or different AMBA layer that occurs through the channel FIFO. If the source peripheral is
not memory, then a source handshaking interface is assigned to the channel. If the destination peripheral is not
memory, then a destination handshaking interface is assigned to the channel. Source and destination
handshaking interfaces can be assigned dynamically by programming the channel registers.
Master interface: DMAC is a master on the AHB bus reading data from the source and writing it to the destination
over the AHB bus.
Slave interface: The APB interface over which the DMAC is programmed. The slave interface in practice could be
on the same layer as any of the master interfaces or on a separate layer.
Handshaking interface: A set of signal registers that conform to a protocol and handshake between the DMAC
and source or destination peripheral to control the transfer of a single or chunk transfer between them. This
interface is used to request, acknowledge, and control a DMAC transaction. A channel can receive a request
through one of two types of handshaking interface: hardware or software.
Hardware handshaking interface: Uses hardware signals to control the transfer of a single or chunk transfer
between the DMAC and the source or destination peripheral.
Software handshaking interface: Uses software registers to control the transfer of a single or chunk transfer
between the DMAC and the source or destination peripheral. No special DMAC handshaking signals are needed
on the I/O of the peripheral. This mode is useful for interfacing an existing peripheral to the DMAC without
modifying it.
Transfer hierarchy: Figure 26-2 on page 469 illustrates the hierarchy between DMAC transfers, buffer transfers,
chunk or single, and AMBA transfers (single or burst) for non-memory peripherals. Figure 26-3 on page 470 shows
the transfer hierarchy for memory.
Figure 26-2. DMAC Transfer Hierarchy for Non-Memory Peripheral
DMAC 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