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Types of EDMA Transfers
6.8 Types of EDMA Transfers
6.8.1
Non-2Dimensional Transfers
6.8.1.1 R/WSYNC Non-2D Transfer (FS=0)
6-20
The EDMA provides for two types of data transfers, namely non-2-dimensional
(non-2D) and 2-dimensional (2D) transfers. This is selected by setting the 2DD
and 2DS bits in the event's options field. 2DD when set to 1 represents two-di-
mensional transfer on the destination. Similarly, a 2-D transfer on the source
is performed when 2DS is equal to1. Various combinations of 2DS and 2DD
are supported.
For non-2D transfers, a group of elements equal to element count constitute
a frame. Each element transfer in a frame can be driven by the R/WSYNC
event (FS=0). In addition, the elements can be contiguous or spaced by an ele-
ment index amount. Once a complete frame is transferred, the element count
reaches zero. Therefore for multi-frame transfers, the element count has to be
reloaded by the element count reload field in the transfer entry. Frame count
is the number of frames in a non-2D transfer. The start of a frame transfer can
be triggered by a frame sync (FS=1) wherein the channel-specific event is
used to synchronize the entire frame.
Figure 6–9 shows the concept of a non-2D EDMA transfer with 'n' elements
in each frame and frame count is 2, for a total of three frames. Each element
in a frame is transferred from its source to destination address upon receiving
the channel-specific sync event. After the channel receives a sync event, it
sends off a transfer request for DMA service. The EDMA controller then
decrements the element count (EC) by 1 in the parameter RAM. When a
channel sync event occurs and EC = 1 (indicating the last element in a frame),
the EDMA controller first sends off the transfer request triggered by the event.
Afterward, element count reload occurs and frame count (FC) decrements by
1. User-specified element index (EIX) is used to compute the address of the
next element in a frame. Similarly, frame index (FIX) is added to the last
element address in a frame to derive the next frame start address. The
address modification and count modification depends on the type of update
modes chosen. They are mentioned here only for an understanding of a
non-2D transfer. Specific updates are described in sections 6.11 and 6.12.
If linking is enabled (LINK=1, see section 6.9), the complete transfer parame-
ters get reloaded (from the parameter reload space in EDMA parameter RAM)
after sending the last transfer request to the address generation hardware.
This sets up a new set of parameters in advance for the next occurrence of the
event.
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