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External crystal 32.768KHz ( msp430 )

selva kumar
Prodigy 40 points
Other Parts Discussed in Thread: MSP430F5659

Hi,

If external crystal(32.768kHz) is not there then what is the impact on the system. In our project we are using  MSP430F5659 controller for NFC.

Kindly provide me with your suggestions.

Thank you,

  • 0
    Guru 74080 points

    Selva,

    Have a look in the user's guide, chapter 5 Unified Clock System (page 158 and following).

    Dennis

  • 0 in reply to Dennis Eichmann
    Prodigy 40 points

    Hi Dennis,

    I gone through that document, but i'm not able to conclude for the above query.

    Regards,

    Selva 

  • 0 in reply to selva kumar
    Guru 292560 points

    What exaclty do you mean with "not there"? Does your hardware have a crystal, and you want to know what happens when it fails? Or do you want to build hardware that works both with and without a crystal?

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points
    i want to built a hardware that works both with and without a crystal, so i want to know whats the impact if external crystal is not there in the System.
  • 0 in reply to Dennis Eichmann
    Prodigy 40 points

    Hi Dennis,

    I have gone through that. 

    But I need to know that if  I use only internal clock(32.768khz) and don't use external clock, how will the Timers viz,..MCLK, ACLK and SMCLK work or will they not work as expected?

    Also, whether  current consumption changes if we have a system without external crystal(32.768khz)?

  • 0 in reply to selva kumar
    TI__Prodigy 735 points

    Hi Selva,


    if you don' have an external crystal present, you could use the REFO instead. That is a built in oscillator that is meant as a substitute in case you can't or don't want to use an external crystal.

    It is not as accurate as an external watch crystal and needs a bit more supply current but you can save the costs for the crystal.

    If you don't necessarily need the 32.768kHz, you could use a different internal clock as source for the ACLK, for example the VLO (typ. 9.4kHz) which is having a lower accuracy and higher spread but needs significantly less current.

     

    Thanks and best regards,

    Christoph

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