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DMA transfer procedure
1. Start data transfer by following the procedure shown in Section 6.2.1, "Initialization." In Step 2 of
the initialization procedure, set Task A and Task B to the primary data structure and the
alternate data structure, respectively.
2. Set Task C to the primary data structure after a DMA transfer completion interrupt has occurred
by Task A.
3. Set Task D to the alternate data structure when a DMA transfer completion interrupt has occurred
by Task B.
4. Repeat Steps 2 and 3.
5. Set cycle_ctrl to 0x0 after a DMA transfer completion interrupt has occurred by the next to last
task.
6. The DMA transfer is completed when a DMA transfer completion interrupt occurs by the last task.
6.5.4. Memory Scatter-Gather Transfer
In scatter-gather transfer mode, first the DMAC, using the primary data structure, copies a data
structure from the data structure table, which has been prepared with multiple data structures
included in advance, to the alternate data structure, and then it performs DMA transfer using the
alternate data structure. The DMAC performs this operation repeatedly. By programming the transfer
mode of the data structure located at the end of the table as a basic transfer, the DMA transfer can be
terminated with a transfer completion interrupt. This mode requires a DMA transfer request only for
starting the first data transfer. Subsequent data transfers are performed by auto-requests.
Transfer destination end pointer
Transfer source end pointer
Transfer destination end pointer
Transfer source end pointer
Transfer destination end pointer
Transfer source end pointer
Transfer destination end pointer
Transfer source end pointer
Figure 6.5.4.1 Example of Data Structure Table for Scatter-Gather Transfer
6-8
Reserved
Control data
Reserved
Control data
Reserved
Control data
Reserved
Control data
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Data structure for Task D
Data structure for Task C
Data structure for Task B
Data structure for Task A
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
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