13.2.4.1.2 FIFO Overflow Condition
If the channel attempts to write into a receive FIFO which is already full, a receive overflow error (RXOVERFLOW) is generated. This can be conditionally used to generate an interrupt. In this case, the transmission continues but the data is now corrupted because the data frame is missing. It is assumed that the software clears the interrupt and recover; possibly by reading from the receive FIFO to clear the source of the interrupt, allowing more data to be received, or even by halting the transmission and resetting the SPI controller.