SDHC with simple DMA?

[lizhenq]

      hi,I use the simple DMA mode of the SDHC' internal DMA with Vybrid Tower.The OS is MQX 4.0.2.When I select "DDR debug" with IAR,the file in the SD card was not written or readed correctly.But,when I select "Int Ram debug",the file was written or readed correctly.On the datasheet <vybrid Reference manual> page 2742,it say "the SDHC internal DMA does support  a virtual memory system".I want to know ,how to use simple DMA in DDR mode with Vybrid Tower system?

[lizhenq · Accepted solution]

  I find the reason.The function  fopen(ptr,flags)  in MFS,.The "flags" is only suport "r" "r+" "w" "w+",so when use "rb+",it will not write data to file.