SI4736-B20 Datasheet, PDF (20/38 Pages) Silicon Laboratories – BROADCAST WEATHER BAND RADIO RECEIVER

Si4736/37/38/39-B20
4.6. Digital Audio Interface (Si4737/39
Only)
The digital audio interface operates in slave mode and
supports three different audio data formats:
 I²S
 Left-Justified
 DSP Mode
4.6.1. Audio Data Formats
In I²S mode, by default 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, by default 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
1DCLK 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. In addition, if
preferred, the user can configure the MSB to be
captured on the falling edge of DCLK via properties.
The number of audio bits can be configured for 8, 16,
20, or 24 bits.
4.6.2. Audio Sample Rates
The device supports a number of industry-standard
sampling rates including 32, 40, 44.1, and 48 kHz. The
digital audio interface enables low-power operation by
eliminating the need for redundant DACs on the audio
baseband processor.
(OFALL = 1)
INVERTED
DCLK
(OFALL = 0)
DCLK
I²S
(OMODE = 0000)
DFS
DOUT
1 DCLK
1
MSB
LEFT CHANNEL
1 DCLK
2
3
n-2
n-1
n
1
2
LSB
MSB
Figure 10. I²S Digital Audio Format
RIGHT CHANNEL
3
n-2
n-1
n
LSB
(OFALL = 1)
INVERTED
DCLK
(OFALL = 0)
DCLK
Left-Justified
(OMODE = 0110)
DFS
DOUT
LEFT CHANNEL
RIGHT CHANNEL
1
2
3
MSB
n-2
n-1
n
LSB
1
2
3
MSB
Figure 11. Left-Justified Digital Audio Format
n-2
n-1
n
LSB
(OFALL = 0)
DCLK
DFS
(OMODE = 1100)
DOUT
(MSB at 1^st rising edge)
DOUT
(OMODE = 1000) (MSB at 2^nd rising edge)
1 DCLK
1
MSB
LEFT CHANNEL
RIGHT CHANNEL
2
3
n-2
n-1
n
1
2
3
LEFT CHANNEL
LSB
MSB
n-2
n-1
RIGHT CHANNEL
1
2
3
n-2
n-1
n
1
2
3
n-2
MSB
LSB
MSB
Figure 12. DSP Digital Audio Format
n
LSB
n-1
n
LSB
20
Rev. 1.0