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PPI DMA on BF548

Question asked by Tao.Cheng on Jun 13, 2010
Latest reply on Jul 19, 2010 by rkarthik

Hi,Guys,

   Here I used PPI1(external SCLK and FS) DMA(DMA13, stop mode, 16bit length) to receive external data, and store the data onto on-chip L2 SRAM. Before DMA13 is enabled each time, I will read the same L2 SRAM block. Then I found that the DMA13 will lose about 10~16 words(16bit) at the beginning.  

  I just did some experiments:

1. If remove the read operation before DMA is enabled, the DMA works correctly.

2. If use write operation to replace read operation before DMA is enabled, the DMA works correctly.

3. add huge number of "NOP" between read operation and DMA enabling, the issue is still there.

4. add "async" between read operation and DMA enabling, the issue is still there.

It seems that the read operation will not release L2 block bus grand, so that DMA could not access the same block. 

 

 

Need your suggest about this issue.

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