Channel Selection; Table 22. Dma1 Request Mapping; Figure 23. Channel Selection - ST STM32F207 Series Reference Manual

Advanced arm-based 32-bit mcus

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DMA controller (DMA)

After an event, the peripheral sends a request signal to the DMA controller. The DMA

controller serves the request depending on the channel priorities. As soon as the DMA

controller accesses the peripheral, an Acknowledge signal is sent to the peripheral by the

DMA controller. The peripheral releases its request as soon as it gets the Acknowledge

signal from the DMA controller. Once the request has been deasserted by the peripheral,

the DMA controller releases the Acknowledge signal. If there are more requests, the

peripheral can initiate the next transaction.

Channel selection

Each stream is associated with a DMA request that can be selected out of 8 possible

channel requests. The selection is controlled by the CHSEL[2:0] bits in the DMA_SxCR

The 8 requests from the peripherals (TIM, ADC, SPI, I2C, etc.) are independently connected

to each channel and their connection depends on the product implementation.

See the following table(s) for examples of DMA request mappings.

REQ_STRx_CH7

REQ_STRx_CH6

REQ_STRx_CH5

REQ_STRx_CH4

REQ_STRx_CH3

REQ_STRx_CH2

REQ_STRx_CH1

REQ_STRx_CH0

I2S3_ext_RX TIM4_CH2

RM0033 Rev 9

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