The mXT143E Xplained has a SPI Mode switch which can be used for the XMEGA based Xplained MCU boards, where the XMEGA has the option to use the USART in Master SPI mode. This enables the user to use the USART in SPI mode in combination with DMA, as the normal SPI module does not support DMA transfers.
For all non XMEGA based Xplained base boards the switch should be set to Normal SPI mode.