
Digital Audio Data Formats
LRCLK (note reversed phase)
SCLK
2-Channel I S (Philips Format) Stereo Input
2
Left Channel
Right Channel
LSB
MSB
LSB
32 clks
24-Bit Mode
20-Bit Mode
16-Bit Mode
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SLES235 – JULY 2008 ....................................................................................................................................................................................................... www.ti.com
MCLKOUT, SCLKOUT, and LRCLKOUT are passed through from the clock inputs MCLKIN, SCLKIN, and
LCLKIN.
MCLKIN 256 Fs is supplied externally
SCLKIN 64 Fs is supplied externally
LRCLKIN Fs is supplied externally
NOTE:
In slave mode all incoming serial audio data must be synchronous to an incoming
LRCLKIN of 32, 44.1 or 48 kHz. The TAS3218 does not support the use of an
external (i.e., 24 MHz) clock input through into XTALI
Serial data is input on pins SDIN1-3 on the TAS3218, allowing up to 6 channels of digital audio input. The
TAS3218 supports 16-, 20-, or 24-bit data in left, right, or I2S serial data format. By default, all TAS3218 serial
digital inputs are configured in the 24-bit I2S format. The serial data input format is configurable via the
SAP/Clock Settings Register.
Serial data is output on pins SDOUT1-2, allowing up to 4 channels of digital audio output. By default, the SDOUT
data format is 24-bit, I2S format at the same data rate as the input. The SDOUT1-2 output uses the SCLKOUT
and LRCLKOUT signals to provide synchronization. SDOUT2 is multiplexed with an SPDIF output.
NOTE:
To avoid audio artifacts, I2C commands to reconfigure the serial audio port (SAP)
should not be issued as standalone commands, rather should be accompanied by
mute and unmute commands.
The TAS3218 uses the SCLK as a reference for both input and output samples. The negative edge of SCLK is
used to output a new data bit, where as the positive edge of SCLK is used to sample incoming serial data.
Discrete I2S Timing
I2S timing uses an LRCLK to define when the data being transmitted is for the left channel and when it is for the
right channel. The LRCLK is LOW for the left channel and HIGH for the right channel. A bit clock running at 64
Fs is used to clock in the data. There is a delay of one bit clock from the time the LRCLK signal changes state to
the first bit of data on the data lines. The data is written MSB first and is valid on the rising edge of bit clock. The
TAS3218 will mask unused trailing data bit positions.
A.
All data are presented in 2's complement form with MSB first.
Figure 5. SAP I2S Format 64 Fs Format
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Copyright 2008, Texas Instruments Incorporated