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K60  EXTAL0  EXTAL1 operation question

Question asked by pk2 on Jul 23, 2013
Latest reply on Aug 7, 2013 by pk2

I am using a MK60FN1M0VLQ12 in a project and using the RMII Ethernet interface.  This interface requires a RMII_REFCLK from the PHY which connects to the EXTAL0 pin of the K60.  I am planning on running the K60 with this clock.  I also generate a RESET signal to the PHY using a GPIO pin. 

 

However, when the PHY is reset, the REFCLK pin of the PHY is tri-stated which will kill the clock to the K60.

 

The MK60FN1M0VLQ12 has a second external oscillator pin, EXTAL1 which I would like to use to run the K60 using a clock that is always present.  How do I power up the K60 and configure it to use the clock on EXTAL1?  I understand there are some restrictions when using EXTAL1.

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