Array BCNT
Array 2
Array 1
Frame 0
ACNT bytes in
Array/1st dimension
Array 1
Frame 1
Array BCNT
Array 2
Array 1
Frame CCNT
Array BCNT
Array 2
CCNT frames in
Block/3rd dimmension
BCNT arrays in Frame/2nd dimmension
Architecture
584
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Enhanced Direct Memory Access (EDMA3) Controller
The DSTREGDEPTH parameter (fixed for a given transfer controller) determines the number of entries in
the Dst FIFO register set. The number of entries determines the amount of TR pipelining possible for a
given TC. The write controller can manage the write context for the number of entries in the Dst FIFO
register set. This allows the read controller to go ahead and issue read commands for the subsequent TRs
while the Dst FIFO register set manages the write commands and data for the previous TR. In summary, if
the DSTREGDEPTH is
n
, the read controller is able to process up to
n
TRs ahead of the write controller.
However, the overall TR pipelining is also subject to the amount of free space in the data FIFO.
17.2.2 Types of EDMA3 Transfers
An EDMA3 transfer is always defined in terms of three dimensions.
shows the three
dimensions used by EDMA3 transfers. These three dimensions are defined as:
•
1st Dimension or Array (A): The 1st dimension in a transfer consists of ACNT contiguous bytes.
•
2nd Dimension or Frame (B): The 2nd dimension in a transfer consists of BCNT arrays of ACNT bytes.
Each array transfer in the 2nd dimension is separated from each other by an index programmed using
SRCBIDX or DSTBIDX.
•
3rd Dimension or Block (C): The 3rd dimension in a transfer consists of CCNT frames of BCNT arrays
of ACNT bytes. Each transfer in the 3rd dimension is separated from the previous by an index
programmed using SRCCIDX or DSTCIDX.
Note that the reference point for the index depends on the synchronization type. The amount of data
transferred upon receipt of a trigger/synchronization event is controlled by the synchronization types
(SYNCDIM bit in OPT). Of the three dimensions, only two synchronization types are supported: A-
synchronized transfers and AB-synchronized transfers.
Figure 17-4. Definition of ACNT, BCNT, and CCNT