What is Kinetis K60's bus speed?

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What is Kinetis K60's bus speed?

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broccolee
Contributor III

I'm working through the accelerometer interface with I2C example. I'm trying to understand how the I2C baud rate is set, which according to K60 Sub-Family Reference Manual, I2C baud rate = bus speed (Hz)/(mul × SCL divider). So what is the K60's bus speed in this case? Is it the clock frequency? Or it's something else that I missed in the documentation...

Thanks,

Dao.

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Jorge_Gonzalez
NXP Employee
NXP Employee

Hello Dao Yan Lim:

Please always mention full part number, since there are different K60 devices.

About the bus speed, as you can see in the attached picture (for a K60_100 MHz part), this bus clock depends on the MCG clock module and SIM module divider.

The MCG module is very flexible, so at the same time it is complex to understand. It would be better if you start with Processor Expert, which tells you the core and bus frequencies without you having to worry about MCG configuration registers.

However if you want to make a quick I2C test, out of reset without configuring MCG module, default SIM dividers and slow internal oscillator trimmed to 32.768 kHz as it comes from factory; then the K60 should be in FEI clock mode, with core and bus clocks both at 20.971 MHz. With this frequency you can calculate I2C baud rate.

I hope this helps.


Regards!,
Jorge Gonzalez

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Jorge_Gonzalez
NXP Employee
NXP Employee

Hello Dao Yan Lim:

Please always mention full part number, since there are different K60 devices.

About the bus speed, as you can see in the attached picture (for a K60_100 MHz part), this bus clock depends on the MCG clock module and SIM module divider.

The MCG module is very flexible, so at the same time it is complex to understand. It would be better if you start with Processor Expert, which tells you the core and bus frequencies without you having to worry about MCG configuration registers.

However if you want to make a quick I2C test, out of reset without configuring MCG module, default SIM dividers and slow internal oscillator trimmed to 32.768 kHz as it comes from factory; then the K60 should be in FEI clock mode, with core and bus clocks both at 20.971 MHz. With this frequency you can calculate I2C baud rate.

I hope this helps.


Regards!,
Jorge Gonzalez

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------

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305 Views
broccolee
Contributor III

Thanks Jorge! That clarified a lot for me.

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