EVAL-AD1871EB Datasheet, PDF (18/28 Pages) Analog Devices – Stereo Audio, 24-Bit, 96 kHz, Multibit
- ADC

AD1871
I²S Mode
In I²S Mode, the data is left-justified, MSB first, with the MSB
placed in the second BCLK period following the transition of
the LRCLK. A high-to-low transition of the LRCLK signifies
the beginning of the left channel data transfer, while a low-to-
high transition on the LRCLK signifies the beginning of the
right channel data transfer (see Figure 12).
LRCLK
LEFT CHANNEL
RIGHT CHANNEL
BCLK
DOUT
MSB MSB–1 MSB–2
LSB+2 LSB+1 LSB
MSB MSB–1 MSB–2
LSB+2 LSB+1 LSB
MSB
Figure 12. I²S Mode
LJ Mode
In LJ Mode, the data is left-justified, MSB first, with the MSB
placed in the first BCLK period following the transition of the
LRCLK. A high-to-low transition of the LRCLK signifies the
beginning of the right channel data transfer, while a low-to-high
transition on the LRCLK signifies the beginning of the left
channel data transfer (see Figure 13).
LRCLK
LEFT CHANNEL
RIGHT CHANNEL
BCLK
DOUT
MSB MSB–1 MSB–2
LSB+2 LSB+1 LSB
MSB MSB–1 MSB–2
LSB+2 LSB+1 LSB
MSB MSB–1
Figure 13. Left-Justified Mode
RJ Mode
In RJ Mode, the data is right-justified, LSB last, with the
LSB placed in the last BCLK period preceding the transition
of the LRCLK. A high-to-low transition of the LRCLK signifies
the beginning of the right channel data transfer, while a low-to-
high transition on the LRCLK signifies the beginning of the left
channel data transfer (see Figure 14).
LRCLK
LEFT CHANNEL
RIGHT CHANNEL
BCLK
DOUT LSB
MSB MSB–1 MSB–2
LSB+2 LSB+1 LSB
MSB MSB–1 MSB–2
LSB+2 LSB+1 LSB
Figure 14. Right-Justified Mode
DSP Mode
In DSP Mode, the LRCLK signal becomes a frame sync signal
that pulses high for the BCLK period prior to the MSB (or in
the BCLK period of the previous LSB–32 bits). The data is left-
justified, MSB first, with the MSB placed in the BCLK period
following the LRCLK pulse (see Figure 15).
In I²S and LJ Modes, since the data is left-justified, differences in
data word-width between the AD1871 and the controller are not
catastrophic since the MSBs are guaranteed to be transferred.
There may, however, be a slight reduction in performance
depending on the scale of the mismatch. In RJ Mode, however,
differences in word-width between the AD1871 and controller
have a catastrophic effect on signal performance as the MSBs
of each sample may be lost due to the mismatch.
LRCLK
BCLK
DOUT
LEFT CHANNEL
RIGHT CHANNEL
MSB MSB–1
LSB+2 LSB+1 LSB
MSB MSB–1
Figure 15. DSP Mode
–18–
LSB+2 LSB+1 LSB
MSB MSB–1
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