9.2.6.6 Peripheral Scatter-Gather
Peripheral Scatter-Gather mode is very similar to Memory Scatter-Gather, except that the transfers
are controlled by a peripheral making a μDMA request. Upon detecting a request from the peripheral,
the μDMA controller uses the primary control structure to copy one entry from the list to the alternate
control structure and then performs the transfer. At the end of this transfer, the primary control
structure will copy the next task to the alternate control structure . If the next task is a
memory-to-memory transfer, execution will start immediately and run to completion; if the next task
is a peripheral-type transfer, the μDMA will wait for a peripheral request to begin.
By using this method, the μDMA controller can transfer data to or from a peripheral from a set of
arbitrary locations whenever the peripheral is ready to transfer data.
Refer to Figure 9-5 on page 691 and Figure 9-6 on page 692, which show an example of operation
in Peripheral Scatter-Gather mode. This example shows a gather operation, where data from three
separate buffers in memory is copied to a single peripheral data register. Figure 9-5 on page 691
shows how the application sets up a µDMA task list in memory that is used by the controller to
perform three sets of copy operations from different locations in memory. The primary control
structure for the channel that is used for the operation is configured to copy from the task list to the
alternate control structure.
Figure 9-6 on page 692 shows the sequence as the µDMA controller performs the three sets of copy
operations. First, using the primary control structure, the µDMA controller loads the alternate control
structure with task A. It then performs the copy operation specified by task A, copying the data from
the source buffer A to the peripheral data register. Next, the µDMA controller again uses the primary
control structure to load task B into the alternate control structure, and then performs the B operation
with the alternate control structure. The process is repeated for task C.
June 18, 2014690
Texas Instruments-Production Data
Micro Direct Memory Access (μDMA)
To Next Page
Loading...
Need help?
General
