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MSP430F6769: External crystal required?

Wayne Huang
Genius 17125 points

Part Number: MSP430F6769

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

  • 0
    Guru 43485 points

    No MSP430 "requires" a crystal. The proof of that is that the thing starts up and executes code before the clock system is even set up to use the crystal.

  • 0
    Guru 102705 points

    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.

  • 0
    TI__Mastermind 31205 points

    Hi Wayne,

    Refer to following UCS block diagram, without external crtystal, you can select VFOCLK or REFOCLK for the clock source. And, the REFOCLK can be the input of the FLL.

    B.R.

    Sal

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