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author | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-09 08:24:04 -0800 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-09 08:24:04 -0800 |
commit | 6026179519896e7d35b2564e7544487d1c8948e7 (patch) | |
tree | c78c7032abce24d846423572204f1cd4e97d8efc /Documentation/sound/alsa/soc/DAI.txt | |
parent | d27146dd5b72ab7d7e641f56f4bee1484dabd0b7 (diff) | |
parent | c2902c8ae06762d941fab64198467f78cab6f8cd (diff) |
Merge branch 'linus' of master.kernel.org:/pub/scm/linux/kernel/git/perex/alsa
* 'linus' of master.kernel.org:/pub/scm/linux/kernel/git/perex/alsa: (212 commits)
[PATCH] Fix breakage with CONFIG_SYSFS_DEPRECATED
[ALSA] version 1.0.14rc2
[ALSA] ASoC documentation updates
[ALSA] ca0106 - Add missing sysfs device assignment
[ALSA] aoa i2sbus: Stop Apple i2s DMA gracefully
[ALSA] hda-codec - Add support for Fujitsu PI1556 Realtek ALC880
[ALSA] aoa: remove suspend/resume printks
[ALSA] Fix possible deadlocks in sequencer at removal of ports
[ALSA] emu10k1 - Fix STAC9758 front channel
[ALSA] soc - Clean up with kmemdup()
[ALSA] snd-ak4114: Fix two array overflows
[ALSA] ac97_bus power management
[ALSA] usbaudio - Add support for Edirol UA-101
[ALSA] hda-codec - Add ALC861VD/ALC660VD support
[ALSA] soc - ASoC 0.13 Sharp poodle machine
[ALSA] soc - ASoC 0.13 Sharp tosa machine
[ALSA] soc - ASoC 0.13 spitz machine
[ALSA] soc - ASoC Sharp corgi machine
[ALSA] soc - ASoC 0.13 pxa2xx DMA
[ALSA] soc - ASoC 0.13 pxa2xx AC97 driver
...
Diffstat (limited to 'Documentation/sound/alsa/soc/DAI.txt')
-rw-r--r-- | Documentation/sound/alsa/soc/DAI.txt | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/Documentation/sound/alsa/soc/DAI.txt b/Documentation/sound/alsa/soc/DAI.txt new file mode 100644 index 00000000000..58cbfd01ea8 --- /dev/null +++ b/Documentation/sound/alsa/soc/DAI.txt @@ -0,0 +1,56 @@ +ASoC currently supports the three main Digital Audio Interfaces (DAI) found on +SoC controllers and portable audio CODECS today, namely AC97, I2S and PCM. + + +AC97 +==== + + AC97 is a five wire interface commonly found on many PC sound cards. It is +now also popular in many portable devices. This DAI has a reset line and time +multiplexes its data on its SDATA_OUT (playback) and SDATA_IN (capture) lines. +The bit clock (BCLK) is always driven by the CODEC (usually 12.288MHz) and the +frame (FRAME) (usually 48kHz) is always driven by the controller. Each AC97 +frame is 21uS long and is divided into 13 time slots. + +The AC97 specification can be found at :- +http://www.intel.com/design/chipsets/audio/ac97_r23.pdf + + +I2S +=== + + I2S is a common 4 wire DAI used in HiFi, STB and portable devices. The Tx and +Rx lines are used for audio transmision, whilst the bit clock (BCLK) and +left/right clock (LRC) synchronise the link. I2S is flexible in that either the +controller or CODEC can drive (master) the BCLK and LRC clock lines. Bit clock +usually varies depending on the sample rate and the master system clock +(SYSCLK). LRCLK is the same as the sample rate. A few devices support separate +ADC and DAC LRCLK's, this allows for similtanious capture and playback at +different sample rates. + +I2S has several different operating modes:- + + o I2S - MSB is transmitted on the falling edge of the first BCLK after LRC + transition. + + o Left Justified - MSB is transmitted on transition of LRC. + + o Right Justified - MSB is transmitted sample size BCLK's before LRC + transition. + +PCM +=== + +PCM is another 4 wire interface, very similar to I2S, that can support a more +flexible protocol. It has bit clock (BCLK) and sync (SYNC) lines that are used +to synchronise the link whilst the Tx and Rx lines are used to transmit and +receive the audio data. Bit clock usually varies depending on sample rate +whilst sync runs at the sample rate. PCM also supports Time Division +Multiplexing (TDM) in that several devices can use the bus similtaniuosly (This +is sometimes referred to as network mode). + +Common PCM operating modes:- + + o Mode A - MSB is transmitted on falling edge of first BCLK after FRAME/SYNC. + + o Mode B - MSB is transmitted on rising edge of FRAME/SYNC. |