5744P system clock select

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5744P system clock select

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shidongxing
Contributor II

Hi. I would like to config the system clock source in case of XOSC failure. But I don't know how to select system clock source. Can anybody help me?

I my opinion, If I want to switch XOSC to IRCOSC, I only need to config AUX Clock Selector 4 and system clock selector,is that right?

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davidtosenovjan
NXP TechSupport
NXP TechSupport

For this it is needed to use Mode Entry module. For instance you have configured RUN0 mode to have system clock driven by IRCOSC and RUN1 mode to have system clock driven by XOSC. Changing is being done by transition between user modes.

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However as you specifically mentioned XOSC failure, it is recommended to be followed by reset:

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Also pay attention to following appnote, specifically to description NCF[24]-NCF[31]:

https://www.nxp.com/docs/en/application-note/AN5259.pdf 

And here using of FCCU and it is related to this topic as well:

https://www.nxp.com/docs/en/application-note/AN5284.pdf

For mode entry module I could recommend to see for instance my example wrriten for MPC5643L but ME module principle is the same. Pay attention to ModesAndClks_init function in main.c file where you can several transitions between user modes:

https://community.nxp.com/docs/DOC-101713 

Hope it helps