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Changing CPU Speed While Keeping Bus & Peripheral Speed Constant

Question asked by PETER TWISS on Feb 1, 2016
Latest reply on Feb 1, 2016 by Kerry Zhou

Hello,

 

I think I know the answer but I want to ask just to make sure.

 

I have a KL15 MCU where I run the CPU and bus as 5.99 MHz, and the I2C at 200 KHz. Sometimes I require to speed up the CPU to 48 MHz, but keep the bus and I2C exactly the same. But during this change  when going from 5.99MHz to 48 MHz, the FFL multiplier bumps up from 732x to1464x.

 

My question is...

 

Is it possible to change CPU speeds in the middle of I2C operations? I am not sure how good the clock gating is on these chips. Since the MCG clocks are 3 orders of magnitudes over the I2C clock, I was thinking it may be possible to do so.

 

If not, can we do it if the FFL,multiplier stays the same, and the speed is changes at the core clock prescalar?

 

Thanks,

-Peter

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