Datasheet

SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
974
Multi-buffer DMAC transfer: A DMAC transfer may consist of multiple DMAC buffers. Multi-buffer DMAC transfers
are supported through buffer chaining (linked list pointers), auto-reloading of channel registers, and contiguous
buffers. The source and destination can independently select which method to use.
 Linked lists (buffer chaining) – A descriptor pointer (DSCR) points to the location in system memory
where the next linked list item (LLI) exists. The LLI is a set of registers that describe the next buffer
(buffer descriptor) and a descriptor pointer register. The DMAC fetches the LLI at the beginning of
every buffer when buffer chaining is enabled.
 Replay – The DMAC automatically reloads the channel registers at the end of each buffers to the
value when the channel was first enabled.
 Contiguous buffers – Where the address of the next buffer is selected to be a continuation from the
end of the previous buffer.
Picture-in-Picture Mode: DMAC contains a picture-in-picture mode support. When this mode is enabled,
addresses are automatically incremented by a programmable value when the DMAC channel transfer count
reaches a user defined boundary.
Figure 40-4 illustrates a memory mapped image 4:2:2 encoded located at image_base_address in memory. A user
defined start address is defined at Picture_start_address. The incremented value is set to memory_hole_size =
image_width - picture_width, and the boundary is set to picture_width.
Figure 40-4. Picture-In-Picture Mode Support
Channel locking: Software can program a channel to keep the AHB master interface by locking the arbitration for
the master bus interface for the duration of a DMAC transfer, buffer, or chunk.
Bus locking: Software can program a channel to maintain control of the AMBA bus by asserting hmastlock for the
duration of a DMAC transfer, buffer, or transaction (single or chunk). Channel locking is asserted for the duration of
bus locking at a minimum.