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DMA direction reconfigurations on-the-fly problem

Question asked by Nch on Aug 7, 2009
Latest reply on Aug 7, 2009 by WassimB

     I just designed ARM7+BF532 structure, and use SPI to connect ARM7(Master) and BF532(Slave). As long as ARM7 sent data to BF532 via SPI, BF532 return the result value to ARM7 via SPI. For there's frequent interrupt in BF532, SPI DMA has to be used to guarantee the realtime communication.

     So how to change the BF532 SPI DMA on-the-fly. I've tried as: Set SPI-->Set SPI receive DMA-->enable DMA-->enable SPI----->disable SPI-->disable DMA-->Set SPI--->Set SPI transmit DMA-->enable DMA-->enable SPI----->disable SPI.........

     But the data is not correct. I found that Sebastian had ever mentioned that handling DMA direction reconfigurations on-the-fly is something that must be done very carefully(, which means that it's difficult but feasible.   Could you give some details about this?