The FSI receiver has a 16-word buff

The FSI receiver has a 16-word buffer into which the data is copied to when it has been received. This buffer is implemented as a circular buffer, not a FIFO, so some care must be taken to properly interpret buffer overrunand underrun as well as the RX_BUF_PTR_STS register. These flags and pointers work under the assumption that the software or DMA is using the buffer as a circular buffer. If the receiver state machine enters into an erroneous state, there is no way for software to cleanly handle this because there is no guaranteed receive clock. For the receiver to detect a clean resynchronization, the state machine needs to be operational and not in the error state. The only way to recover from the error state is to reset the entire receiver module. For overrun and underrun, the receiver can no longer guarantee which values in the buffer are valid. As such, the best way to recover is to reset the FSI and resynchronize with the transmitter.