Digital Audio Interface - Silicon Laboratories Si4704 Series Programming Manual

9. Digital Audio Interface

The digital audio interface operates in slave mode and supports 3 different audio data formats:
2
I S
Left-Justified
DSP Mode
2
In I S mode, the MSB is captured on the second rising edge of DCLK following each DFS transition. The remaining
bits of the word are sent in order down to the LSB. The Left Channel is transferred first when the DFS is low, and
the Right Channel is transferred when the DFS is high.
In Left-Justified mode, the MSB is captured on the first rising edge of DCLK following each DFS transition. The
remaining bits of the word are sent in order down to the LSB. The Left Channel is transferred first when the DFS is
high, and the Right Channel is transferred when the DFS is low.
In DSP mode, the DFS becomes a pulse with a width of 1 DCLK period. The Left Channel is transferred first,
followed right away by the Right Channel. There are two options in transferring the digital audio data in DSP mode:
the MSB of the left channel can be transferred on the first rising edge of DCLK following the DFS pulse or on the
second rising edge.
In all audio formats, depending on the word size, DCLK frequency and sample rates, there may be unused DCLK
cycles after the LSB of each word before the next DFS transition and MSB of the next word.
The number of audio bits can be configured for 8, 16, 20, or 24 bits.
INVERTED
(IFALL = 1)
DCLK
(IFALL = 0) DCLK
DFS
I2S
(IMODE = 0000)
DIN/DOUT
INVERTED
(IFALL = 1)
DCLK
(IFALL = 0)
DCLK
DFS
Left-Justified
(IMODE = 0110)
DIN/DOUT
(IFALL = 0)
DCLK
DFS
DIN/DOUT
(IMODE = 1100)
st
(MSB at 1 rising edge)
DIN/DOUT
(IMODE = 1000) nd
(MSB at 2 rising edge)
LEFT CHANNEL
1 DCLK
1 2 3 n-2
MSB
2
Figure 13. I
LEFT CHANNEL
1 2 3 n-2
MSB
Figure 14. Left-Justified Digital Audio Format
LEFT CHANNEL
1 2 3
MSB
LEFT CHANNEL
1 DCLK
1 2 3
MSB
Figure 15. DSP Digital Audio Format
Confidential Rev. 0.2
1 DCLK
n-1 n
1
MSB
LSB
S Digital Audio Format
n-1 n
1 2
MSB
LSB
n-2 n-1 n
1 2
MSB
LSB
n-2 n-1 n
1
MSB
LSB
AN332
RIGHT CHANNEL
n-2 n-1
2 3
RIGHT CHANNEL
3 n-2 n-1 n
LSB
RIGHT CHANNEL
3 n-2 n-1 n
LSB
RIGHT CHANNEL
2 3 n-2 n-1
LSB
n
LSB
n
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