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Figure 8.9. 2D copy
Source buffer
WIDTH
So u r c e
end
pointer
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Destination buffer
WIDTH
Dest in at ion
end pointer
SRCSTRIDE
DSTSTRIDE
When doing a rectangle copy, the source and destination address of the channel descriptor will be
incremented line for line as the DMA works its way through the rectangle. The operation is done when
the number of lines specified by HEIGHT in DMA_RECT0 has been copied. The source and destination
addresses in the channel descriptor will then point at the last element of the source and destination
rectangles.
On completion, the DONE interrupt flag of channel 0 is set. Looping is not supported for rectangle copy.
In some cases, e.g. when performing graphics operations, it is desirable to create a list of copy operations
and have them executed automatically. This can be done using 2D copy together with the scatter gather
mode of the DMA controller. Set DESCRECT in DMA_CTRL to override SCRSTRIDE and HEIGHT
in DMA_RECT0 and WIDTH in DMA_LOOP0 by the values in the user part of the DMA descriptor as
shown in Table 8.12 (p. 70) . In this way every copy command in the list can specify these parameters
individually.
Table 8.12. User data assignments when DESCRECT is set
Bit
[30:20]
[19:10]
Field
SRCSTRIDE
HEIGHT
Description
Stride in source buffer
Height - 1 of data to be copied
[9:0]
WIDTH
Width - 1 of data to be copied
With regular 2D copy, the DMA descriptor will be updated as the copy operation proceeds. To be able to
reuse 2D copy scatter gather list without rewriting source and destination end addresses, set PRDU in
DMA_CTRL. This will prevent the address in the descriptor from being updated. In this case RDSCH0
in DMA_RDS must be set and all other bits in DMA_RDS must be cleared. The bits in DMA_RDS make
individual DMA channels remember the source and destination end pointers while active, speeding up
their transfers.
8.4.6 Interaction with the EMU
The DMA interacts with the Energy Management Unit (EMU) to allow transfers from , e.g., the LEUART
to occur in EM2. The EMU can wake up the DMA sufficiently long to allow data transfers to occur. See
section "DMA Support" in the LEUART documentation.
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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