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?