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S32K SAI request for DMA

Question asked by Jakub Mielczarek on Apr 4, 2019
Latest reply on May 8, 2019 by Jorge Antonio Alcala Vazquez

Hello,

 

Suppose that DMA is programmed to transfer 4 samples (4 bytes each) to SAI0 TX in one minor loop. There are two minor loops per major loop. SAI TX triggers the DMA transfer through request.

 

If watermark for SAI TX FIFO is set to 1 what will be the DMA transfer behavior:

 

opt. 1: SAI triggers request when FIFO level is less or equal 1, DMA performs 1 minor loop (transfers 4 samples), then DMA waits for next request from SAI (when FIFO level is again less or equal 1) to transfer the second minor loop

 

opt. 2: SAI triggers request when FIFO level is less or equal 1, DMA performs 1 minor loop (transfers 4 samples), then DMA peforms the second minor loop, not waiting for next request from SAI

 

Also a question: how does SAI<->DMA request handshaking work?

 

Thank you,

Jakub

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