46.6.6.3 Receiving Data with FIFO Enabled
When the Receive FIFO is enabled, TWIHS_RHR access reads the FIFO.
When data are present in the Receive FIFO (RXRDY flag set to ‘1’), the exact number of data can be checked with TWIHS_FLR.RXFL. All the data can be read successively in TWIHS_RHR without checking the TWIHS_SR.RXRDY flag between each access.
See the figure below and the figure Sending/Receiving Data with FIFO Enabled in Client Mode.