The USART can be used in association with the DMAC in order to transfer data directly into/from the on- and off-chip memories without any processor intervention.
The DMAC uses the trigger flags, TXRDY and RXRDY, to write or read into the USART. The DMAC always writes in the Transmit Holding register (US_THR) and it always reads in the Receive Holding register (US_RHR). The size of the data written or read by the DMAC in the USART is always a byte.