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Clocking the KL03 from the external crystal (FRDM-KL03Z)

Question asked by Mark Butcher on Nov 17, 2014
Latest reply on Nov 11, 2015 by Mark Butcher

Hi All


I wonder whether anyone has tried clocking the KL03 from its 32kHz oscillator?


According to the user's manual it should be quite simple:

The device starts up in the 8MHz mode and may move directly to the EXT mode.

That means:

1. set 0x04 in MCG_C2

2. Modify MSCG_C1 from its default value of 0x40 (running from the 8MHz internal clock) to 0x80 (EXT mode)


If this is performed the processor loses its clock and the debugger stops working. Also the 32kHz oscillator is not yet running.


If an initial step of enabling the OSC (writing 0xa0 to OSC_CR) is performed the 32kHz is measurable on the crystal after step 1 and MCG_S shows that the oscillator has been initialised.

However again, when trying to mode the the EXT mode (step 2), the same thing happens - processor/debugger die.


Any ideas what is wrong?