45.6.6.2 Sending Data with FIFO Enabled
When the Transmit FIFO is enabled, write access to TWIHS_THR loads the Transmit FIFO.
The Transmit FIFO level is provided in TWIHS_FLR.TXFL. If the FIFO can accept the number of data to be transmitted, there is no need to monitor TWIHS_SR.TXRDY and the data can be successively written in TWIHS_THR.
If the FIFO cannot accept the data due to insufficient space, wait for the TXRDY flag to be set before writing the data in TWIHS_THR.
When the space in the FIFO allows only a portion of the data to be written, the TXRDY flag must be monitored before writing the remaining data.
See the figure below and the figure Sending/Receiving Data with FIFO Enabled in Client Mode.