29.1.2.6 Receiving 9-Bit Characters
The EUSART supports 9-bit character reception. When the RX9 bit of the RCxSTA register is set the EUSART will shift nine bits into the RSR for each character received. The RX9D bit of the RCxSTA register is the ninth and Most Significant data bit of the top unread character in the receive FIFO. When reading 9-bit data from the receive FIFO buffer, the RX9D data bit must be read before reading the eight Least Significant bits from the RCxREG.