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iMX6D/Q uSDHC read/write methods

Question asked by cagatay ozdemir on Apr 6, 2016
Latest reply on Apr 7, 2016 by Yuri Muhin

Hi all,


In iMx6Q uSDHC module, there are three options to read from / write to SD Card:

1-> Internal DMA, Over AHB Bus

2-> External DMA, Over IP Bus

3-> PIO, reading a register


What are the advantages/disadvantages or considerations about these methods? In my opinion:


a-) Reading a file via PIO is the slowest one and also makes CPU busy. This is not an efficient way. Then in which circumstances should we think to use this way?


b-) Internal DMA is special to uSDHC. It provides us not to occupy external DMA, so it seems an efficient way to use resources of the chip. However I am not sure about comparison of internal/external DMA speeds.


What are your experiences/thoughts?