[alsa-devel] Question: PCM short and long sync formats

Omair Mohammed Abdullah omair.m.abdullah at linux.intel.com
Mon Mar 26 14:07:15 CEST 2012

On Monday 26 March 2012 03:56 PM, Mark Brown wrote:
> On Mon, Mar 26, 2012 at 02:36:53PM +0530, Omair Mohammed Abdullah wrote:
>> On Wednesday 21 March 2012 05:21 PM, Mark Brown wrote:
>>> What do you mean when you say "PCM short frame sync" and "PCM long
>>> frame sync"?
>> Sorry for the late reply, I was away.
>> What I mean by short/long frame sync is: the frame sync lasts for 1
>> bit/1 word wide.
>> Eg.: For short frame sync, we get a frame sync signal for 1 clock
>> before the first bit on the RX/TX.
>> It is different from I2S mode where the frame sync is inverted and
>> the transition starts 1 clock before the bits and lasts till bit 1.
> I'm sorry but I still have no idea what you're talking about.  You've
> described PCM mode but not explained what "short frame sync" and "long
> frame sync" mode are.

This diagram may explain things better:

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