Arbiter; Dma Streams; Source, Destination And Transfer Modes; Table 32. Source And Destination Address - ST STM32F412 Reference Manual

Direct memory access controller (DMA)
9.3.5

Arbiter

An arbiter manages the 8 DMA stream requests based on their priority for each of the two
AHB master ports (memory and peripheral ports) and launches the peripheral/memory
access sequences.
Priorities are managed in two stages:
•
Software: each stream priority can be configured in the DMA_SxCR register. There are
four levels:
–
–
–
–
• Hardware: If two requests have the same software priority level, the stream with the
lower number takes priority over the stream with the higher number. For example,
stream 2 takes priority over stream 4.
9.3.6

DMA streams

Each of the eight DMA controller streams provides a unidirectional transfer link between a
source and a destination.
Each stream can be configured to perform:
•
Regular type transactions: memory-to-peripherals, peripherals-to-memory or memory-
to-memory transfers
•
Double-buffer type transactions: double buffer transfers using two memory pointers for
the memory (while the DMA is reading/writing from/to a buffer, the application can
write/read to/from the other buffer).
The amount of data to be transferred (up to 65535) is programmable and related to the
source width of the peripheral that requests the DMA transfer connected to the peripheral
AHB port. The register that contains the amount of data items to be transferred is
decremented after each transaction.
9.3.7

Source, destination and transfer modes

Both source and destination transfers can address peripherals and memories in the entire
4-Gbyte area, at addresses comprised between 0x0000 0000 and 0xFFFF FFFF.
The direction is configured using the DIR[1:0] bits in the DMA_SxCR register and offers
three possibilities: memory-to-peripheral, peripheral-to-memory or memory-to-memory
transfers.
The table below describes the corresponding source and destination addresses.
Bits DIR[1:0] of the
DMA_SxCR register
200/1163
Very high priority
High priority
Medium priority
Low priority

Table 32. Source and destination address

Direction
00 Peripheral-to-memory
01 Memory-to-peripheral
Source address
DMA_SxPAR
DMA_SxM0AR
RM0402 Rev 6
RM0402
Destination address
DMA_SxM0AR
DMA_SxPAR