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System DMA
Example 1.
Packing Enabled
54
Direct Memory Access (DMA) Support
Another sort of packing groups bytes or word16 accesses within an element.
This is always done if the LCh is configured as such. Packing within an element
is done if the access types are smaller than the element sizes (data_type). For
instance, if the data_type is set to s32 but the source target port only supports
16 bits, then two consecutive word16 source accesses are packed to build the
word32 element. This element is then sent to the destination port. This is done
independently of the source and destination packing bits.
Packing within an element is supported even if the constant addressing mode
is used or if EI is different from 1.
Example 1 shows an example of packing enabled.
A detailed example (see Table 22 and Table 23) of packing 2 x s16 => 32 is:
A logical channel is set up for a transfer with the following parameters for
-
its source:
Number of frames in the block: FN = 2 elements
J
Number of elements per frame: EN = 5 elements
J
Type of data:
J
Frame index in bytes:
J
Element index in bytes:
J
Source start address:
J
Source addressing mode:
J
The source port is a 32-bit port with byte/word16/word32 access
J
capability.
Packing is enabled but burst is disabled.
J
Memory block to transfer is: element i, j (where j is the element number
J
of frame i).
i and j start with the highest number and decreases, so the first
J
element written is element 2,5.
s16
FI = 13 bytes
EI = 1 byte
SA = 2 bytes
Double-indexed addressing mode
SPRU755B
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