On SAMD21, is seems I can't read the DMAC->CRCCHKSUM.reg with a DMA channel. The CRC module is enabled, the DMA descriptor->SRCADDR.reg is set to &DMAC->CRCCHKSUM.reg.
Once the DMAC channel is enabled, the processor hangs.
There is no problem if the descriptor source address is set to any other memory buffer.
BTW, the same approach is not a problem on the SAMD51, where I have a descriptor with a SRCADDR pointing to &DMAC->CRCCHKSUM.reg, and I can send over SPI directly a generated CRC16 checksum.
Is possible that the SAMD21 is not capable of reading the DMAC->CRCCHKSUM.reg address at all?
Thanks for the help,