Example Of Ping-Pong Μdma Transaction - Texas Instruments Concerto F28M35 Series Technical Reference Manual

Functional Description
Primary Structure
Alternate Structure
Primary Structure
Alternate Structure
16.3.6.5 Memory Scatter-Gather
Memory Scatter-Gather mode is a complex mode used when data must be transferred to or from varied
locations in memory instead of a set of contiguous locations in a memory buffer. For example, a gather
µDMA operation could be used to selectively read the payload of several stored packets of a
communication protocol and store them together in sequence in a memory buffer.
In Memory Scatter-Gather mode, the primary control structure is used to program the alternate control
structure from a table in memory. The table is set up by the processor software and contains a list of
control structures, each containing the source and destination end pointers, and the control word for a
specific transfer. The mode of each control word must be set to Scatter-Gather mode. Each entry in the
table is copied in turn to the alternate structure where it is then executed. The µDMA controller alternates
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M3 Micro Direct Memory Access ( µDMA)
Figure 16-2. Example of Ping-Pong µDMA Transaction
µDMA Controller
SOURCE
transfers using BUFFERA
DEST
CONTROL
Unused
SOURCE
transfers using BUFFERB
DEST
CONTROL
Unused
SOURCE
transfers using BUFFERA
DEST
CONTROL
Unused
SOURCE
transfers using BUFFERB
DEST
CONTROL
Unused
Copyright © 2012–2019, Texas Instruments Incorporated
Cortex-M3 Processor
BUFFER A
BUFFER B
·Process data in BUFFERA
·Reload primary structure
BUFFER A
·Process data in BUFFERB
·Reload alternate structure
BUFFER B
·Process data in BUFFERA
·Reload alternate structure
SPRUH22I – April 2012 – Revised November 2019
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