1 ==================================
2 ASoC Digital Audio Interface (DAI)
3 ==================================
4
5 ASoC currently supports the three main Digital
6 SoC controllers and portable audio CODECs toda
7
8
9 AC97
10 ====
11
12 AC97 is a five wire interface commonly found o
13 now also popular in many portable devices. Thi
14 multiplexes its data on its SDATA_OUT (playbac
15 The bit clock (BCLK) is always driven by the C
16 frame (FRAME) (usually 48kHz) is always driven
17 frame is 21uS long and is divided into 13 time
18
19 The AC97 specification can be found at :
20 https://www.intel.com/p/en_US/business/design
21
22
23 I2S
24 ===
25
26 I2S is a common 4 wire DAI used in HiFi, STB a
27 Rx lines are used for audio transmission, whil
28 left/right clock (LRC) synchronise the link. I
29 controller or CODEC can drive (master) the BCL
30 usually varies depending on the sample rate an
31 (SYSCLK). LRCLK is the same as the sample rate
32 ADC and DAC LRCLKs, this allows for simultaneo
33 different sample rates.
34
35 I2S has several different operating modes:-
36
37 I2S
38 MSB is transmitted on the falling edge of th
39 transition.
40
41 Left Justified
42 MSB is transmitted on transition of LRC.
43
44 Right Justified
45 MSB is transmitted sample size BCLKs before
46
47 PCM
48 ===
49
50 PCM is another 4 wire interface, very similar
51 flexible protocol. It has bit clock (BCLK) and
52 to synchronise the link while the Tx and Rx li
53 receive the audio data. Bit clock usually vari
54 while sync runs at the sample rate. PCM also s
55 Multiplexing (TDM) in that several devices can
56 is sometimes referred to as network mode).
57
58 Common PCM operating modes:-
59
60 Mode A
61 MSB is transmitted on falling edge of first
62
63 Mode B
64 MSB is transmitted on rising edge of FRAME/S
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