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KE06 using 18.432MHz XTAL not working in FEE

Question asked by Ted Kuhn on Jul 11, 2018
Latest reply on Jul 20, 2018 by Mark Butcher

We built a custom board based around the MKE06Z128VLK4, with an external crystal with a nominal frequency of 18.432MHz.  We are using MCUXpresso v10.2.0, and using the built-in Clock-config-tool. When we set up the clock module to have the ICS Mode set to FEE (FLL Engaged External), and tell the tool we're using an 18.432MHz external crystal, the part doesn't run.  If we use the same clock frequency, and set ICS Mode to FBE the part works.


I started experimenting with a FRDM-KE06Z eval board, replaced the 8MHz crystal that comes with the board with an 18.432MHz crystal from same ABM3B crystal family.  When I tell the Clock-config-tool that my crystal frequency is 18.432MHz, the part doesn't run.  When I tell the Clock-config-tool that my crystal frequency is 18.0MHz, the part runs fine.  The only setting I'm changing in the clock-config-tool is the crystal frequency; everything else is staying the same: RDIV=512, BDIV = /2, DIV1 and DIV3 = /1, and DIV2 = /2.


When I tell the tool I'm using 18.0, 18.1, or 18.2MHz it works, but as soon as I get to 18.3MHz, it stops working.  I'm not sure what I'm missing here...changing this one value in such a small amount, without changing any other settings, and without changing the physical hardware, results in the part not running?


To tell if the part is running, I'm simply using the frdmke06z_gpio_1_led_output program to toggle an LED.


Many thanks to anyone who made it to this point in my description.