Datasheet

487
SAM9G25 [DATASHEET]
11032D–ATARM–10-Mar-2014
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 31-4 on page 487 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 31-4. 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.
DMAC PIP transfers