NXP Semiconductors K22F series, Reference Manual, Page: 1371 / 1407

49.4.6 Word mask register
The SAI transmitter and receiver each contain a word mask register, namely TMR and
RMR, that can be used to mask any word in the frame. Because the word mask register is
double buffered, software can update it before the end of each frame to mask a particular
word in the next frame.
The TMR causes the Transmit Data pin to be tri-stated for the length of each selected
word and the transmit FIFO is not read for masked words.
The RMR causes the received data for each selected word to be discarded and not written
to the receive FIFO.
49.4.7 Interrupts and DMA requests
The SAI transmitter and receiver generate separate interrupts and separate DMA requests,
but support the same status flags. Asynchronous versions of the transmitter and receiver
interrupts are generated to wake up the CPU from stop mode.
49.4.7.1 FIFO request flag
The FIFO request flag is set based on the number of entries in the FIFO and the FIFO
watermark configuration.
The transmit FIFO request flag is set when the number of entries in any of the enabled
transmit FIFOs is less than or equal to the transmit FIFO watermark configuration and is
cleared when the number of entries in each enabled transmit FIFO is greater than the
transmit FIFO watermark configuration.
The receive FIFO request flag is set when the number of entries in any of the enabled
receive FIFOs is greater than the receive FIFO watermark configuration and is cleared
when the number of entries in each enabled receive FIFO is less than or equal to the
receive FIFO watermark configuration.
The FIFO request flag can generate an interrupt or a DMA request.
49.4.7.2 FIFO warning flag
The FIFO warning flag is set based on the number of entries in the FIFO.
Chapter 49 Integrated Interchip Sound (I2S) / Synchronous Audio Interface (SAI)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 1371