23.5.1 Receiver Data Register Low Byte

This register contains the eight LSbs of the data received by the USART receiver. The USART receiver is double-buffered, and this register always represents the data for the oldest received frame. If the data for only one frame is present in the receive buffer, this register contains that data.

The buffer shifts out the data either when RXDATAL or RXDATAH is read, depending on the configuration. The register, which does not lead to data being shifted, must be read first to be able to read both bytes before shifting.

When the Character Size (CHSIZE) bit field in the Control C (USARTn.CTRLC) register is configured to 9-bit (low byte first), a read of RXDATAH shifts the receive buffer, or else, RXDATAL shifts the buffer.