Dear Champs,
I am asking this for our customer.
Is an external crystal required?
Without an external crystal, it seems DCO could not set internal oscillator freq. directly with FLLREF?
Would you please help clarify it?
Wayne
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Dear Champs,
I am asking this for our customer.
Is an external crystal required?
Without an external crystal, it seems DCO could not set internal oscillator freq. directly with FLLREF?
Would you please help clarify it?
Wayne
You can use the (internal) REFO clock to control the FLL [Ref User Guide (SLAU208Q) Sec 5.2.3]. The REFO is +/-3.5%, rather than (typ.) 20PPM for a 32kHz crystal [Ref data sheet (SLAS768E) Sec 5.18], and that will be reflected in the FLL output.
At Reset, UCSCTL3:SELREF=0, requesting XT1CLK (the crystal oscillator) so you have to explicitly set SELREF=2 to get the REFOCLK. I don't see an Example which does this.
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