MKW30Z/MKW40Z driven from external 32 MHz TCXO

[giovanni]

Were trying to drive the MKW30Z with an external TCXO at 32 MHz.  We cannot find any documentation on driving the RF Oscillator circuit with an external 32 MHz source, not a 32 MHz crystal.  How do we setup the device to do this?

[jorge_a_vazquez]

Hi Gary

As you mentioned there is not much information on how to do this, but I have found this configuration:

RF_OSC_BYPASS_EN

This bit, that is defined in the RSIM_CONTROL register is described in the Reference manual as:

RF Ref Osc Bypass Enable
This bit engages the RF Ref Osc analog bypass circuit if the RF Ref Osc is enabled. When the RF Ref Osc is in bypass mode it passes the EXTAL clock as the RF Ref Osc clock.
Note that the RF Ref Osc Ready signal is always asserted in RF Ref Osc Bypass mode, unless overridden with the RF_OSC_READY_OVRD_EN bit

So, I think this is the configuration that you need. in the connectivity software there is a XcvrInit that initialized the radio, here you can a line code like:

RSIM->CONTROL |= RSIM_CONTROL_RF_OSC_BYPASS_EN_MASK;

and it should use the external clock from 32 Mhz as a oscillator instead of a crystal.

Best Regards

Jorge Alcala