how to detect external clock's frequency

hey there,

I'm working on an audio interface which should be capable of synchronizing to an external word clock signal (sample rate). I'm just wondering how that's done, because: everything I get from outside, is the word clock signal. the master clock frequency for the ICs is of course many times (256fs @ 44.1) higher. where do I get the master clock signal from? maybe by synchronizing an internal clock generator with the external signal? I think about using the CS2000 by cirrus, but I can't find a way, how to synchronize to an external word clock signal with this IC. maybe there's a better way/IC?

so, in master mode everything's fine. I can produce the 11.2896 as well as the 12.288 MHz with the CS2000 and divide down to the needed frequencies for I2C and of course the sample rate itself, but what if I want to use an external word clock signal (44.1, 48, 96 and 192)? that's basically the question.

thanks a lot in advance.

best regards
tommy