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49.4.5.2 FIFO pointers
When writing to a TDR, the WFP of the corresponding TFR increments after each valid
write. The SAI supports 8-bit, 16-bit and 32-bit writes to the TDR and the FIFO pointer
will increment after each individual write. Note that 8-bit writes should only be used
when transmitting up to 8-bit data and 16-bit writes should only be used when
transmitting up to 16-bit data.
Writes to a TDR are ignored if the corresponding bit of TCR3[TCE] is clear or if the
FIFO is full. If the Transmit FIFO is empty, the TDR must be written at least three bit
clocks before the start of the next unmasked word to avoid a FIFO underrun.
When reading an RDR, the RFP of the corresponding RFR increments after each valid
read. The SAI supports 8-bit, 16-bit and 32-bit reads from the RDR and the FIFO pointer
will increment after each individual read. Note that 8-bit reads should only be used when
receiving up to 8-bit data and 16-bit reads should only be used when receiving up to 16-
bit data.
Reads from an RDR are ignored if the corresponding bit of RCR3[RCE] is clear or if the
FIFO is empty. If the Receive FIFO is full, the RDR must be read at least three bit clocks
before the end of an unmasked word to avoid a FIFO overrun.
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.
Chapter 49 Integrated Interchip Sound (I2S) / Synchronous Audio Interface (SAI)
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
Freescale Semiconductor, Inc.
Preliminary
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