57.9.6.9 Transmit FIFO Lock

If a frame is terminated early due to a not-acknowledge error (NACK flag), SMBus timeout error (TOUT flag) or host code acknowledge error (MACK flag), a lock is set on the Transmit FIFO preventing any new frame from being sent until it is cleared. This allows clearing the FIFO if needed, resetting DMA channels, etc., without any risk.

FLEX_TWI_SR.LOCK is used to check the state of the Transmit FIFO lock.

The Transmit FIFO lock can be cleared by setting FLEX_TWI_CR.TXFLCLR to ‘1’.