AN4031 datasheet(14/36 Pages) STMICROELECTRONICS

14 / 36 page

DMA controller description

AN4031

14/36

DocID022648 Rev 1

1.1.11

Double-buffer mode

A double-buffer stream works as a regular (single-buffer) stream, with the difference that it

has two memory pointers. When the Double-buffer mode is enabled, the Circular mode is

automatically enabled and at each end of transaction (DMA_SxNDTR register reach 0), the

memory pointers are swapped.

This allows the software to process one memory area while the second memory area is

being filled/used by the DMA transfer.

Figure 6. Double-buffer mode

Table 6. Possible burst configurations

MSIZE

FIFO level

MBURST = INCR4

MBURST = INCR8

MBURST = INCR16

Byte

1/4

1 burst of 4 bytes

forbidden

1/2

2 bursts of 4 bytes

1 burst of 8 bytes

3/4

3 bursts of 4 bytes

forbidden

Full

4 bursts of 4 bytes

2 bursts of 8 bytes

1 burst of 16 bytes

Half-word

1/4

forbidden

1/2

1 burst of 4 half-words

3/4

forbidden

Full

2 bursts of 4 half-words 1 burst of 8 Half-word

Word

1/4

forbidden

1/2

3/4

Full

1 burst of 4 words

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