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Sources which generate SAI_CK_A on STM32F7?

Question asked by bsder on Sep 12, 2016
Latest reply on Sep 12, 2016 by bsder
The problem is that I have an *external* 24.576 MHz MCLK.  In master mode, how do I get that from outside the chip onto the SAI_CK_A or SAI_CK_B clock?

I was going through section 36.3.1 "SAI block diagram" and figuring out how to wire everything up.

If the STM32F7 is a slave, things mostly make sense: SCK maps to BCLK, FS maps to FCLK or LRCLK, SD maps to data.  Presumably, MCLK is ignored--that's a little scary but I guess it could work given that the audio block has FIFOs.

If the STM32F7 is a master *AND* generates the clock, then things are perfectly straightforward: MCLK is generated and maps to MCLK, SCK maps to BCLK, FS maps to FCLK or LRCLK, SD maps to data. 

The reference manual mumbles in section 36.3.7:

The clock source for the clock generator comes from the product clock controller. 

Okaaaay.  I don't see anything in the manual about an SAI product clock controller.  Nothing is listed which directly drives SAI_CK_x in Figure 429.

Any help would be appreciated.