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CC2340R5: What is effect of choosing LF-XOSC in sysConfig

Vaibhav Patil
Prodigy 191 points
Part Number: CC2340R5
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi Forum,

  We are trying to explore the "Low Frequency External Clock Source" options for CC2340R5. As we can see in sysConfig by default the option is "LF XOSC" which means module is expecting clock from external source BUT in our current module we don't have this external crystal populated and module is still working fine. So, Does this configuration in sysConfig is even taking effect? 

My other query is, If i  were to use external low frequency clock source, then what should be the configuration in sysConfig.

Regards

Vaibhav

  • 0
    TI__Genius 12351 points

    Hello Vaibhav,

    I hope you are doing well. I wound recommend checking the register LFCLKSEL in debug mode, as this is what controls the LF clock source here, this can tell us if its selecting the right clock source. 

    Thanks,
    Alex F

  • 0 in reply to Alex Fager
    Prodigy 191 points

    Hi Alex,

    May i know how to access this register? I could not find base address this register in Technical Reference Manual ?

    Regards

    Vaibhav

  • 0 in reply to Vaibhav Patil
    TI__Genius 12351 points

    Hello Vaibhav Patil,

    Looking in the SDK I think we can access it like: 

    HWREG(CKMD_BASE + CKMD_O_LFCLKSEL)
     
    #define CKMD_BASE               0x40001000 // CKMD
    // Low frequency clock selection
    #define CKMD_O_LFCLKSEL                                             0x000000C0U
     
    Thanks,
    Alex F
  • 0 in reply to Alex Fager
    Prodigy 191 points

    Hi Alex,

    As per the datasheet when we select "LF Frequency Clock Source" as LFXOSC, we should register value 02H. Then why in this case i am getting 00H? Please let me know am i understanding this correctly?

    Regards

    Vaibhav

  • 0 in reply to Vaibhav Patil
    TI__Genius 12351 points

    Hello Vaibhav,

    To give context I imported the example rfPacketTx project (leaving it unmodified) and build and debugged the project, and once the main starts I see the 2h (Low frequency crystal oscillator) is selected:

    Note that the registers did not fully update it seems until after board init/main was started. 

    Thanks,
    Alex F

  • 0 in reply to Alex Fager
    Prodigy 191 points

    Hi Alex,

    To give you context of how i did  is, i took basic_ble project, added break point in app_main-> appMain(). I believe app_main is called after board_init, so i was expecting register to be initialized.

    Regards

    Vaibhav

  • 0 in reply to Vaibhav Patil
    TI__Genius 12351 points

    Hello Vaibhav,

    I imported the basic_ble project as well (9_10 F3 SDK) and while the LFCLKSEL was initially "00" after board init, it then was configured to "10" (after pressing play then pause). 

    Thanks,
    Alex F