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Access of the USB FS DMA on MK22FN512VLH12 device

Question asked by Bruno Paillard on Dec 15, 2014
Latest reply on Dec 16, 2014 by Kan_Li



I am trying to access various memory-map regions of the MK22FN512 device using the USB-FS module. That is, trying to read and write various regions of the memory map through USB.


I find that reading the SRAM region is not a problem.

Reading peripherals or Flash however always returns zeros.


For instance, I am trying to read address 0x00000000, which the TRM indicates should be accessible from all bus masters. I tried also at other aliased addresses, to no avail.


Is there a limitation (or protection) that precludes the DMA of the USB-FS module from accessing peripherals or Flash?