47.5.12.4 LRC Error (Frame Error)

LRC (frame) errors produce different behavior in Audio mode than in Framed SPI mode. Though the FRMERR and FRMERREN behave the same, the check happens on every LRC edge that defines a channel start. An LRC error occurs when an LRC edge occurs before the correct number of bits (as defined by MODE[32:16] or AUDWD_MODE[1,0]) in a channel completes. Note that in DSP/PCM mode the check only occurs on the edge that defines the combined left/right channel start.

When an LRC error occurs, the SPI immediately set FRMERR. It pushes the data in the SPIxSR into the SPIxRXB and pops data from the SPIxTXB into the SPIxSR. Under this condition, the receive and transmit data is almost certainly corrupted, but the actions of the SPI preserve the audio mode.

The SPI provides detection of FRMERR for LRC for debugging. Since LRC is a free-running clock, its period is expected to be constant, so this error condition would not be automatically recoverable in a system.