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MSP430FR6005: PLL_LOCK function inquiry

Joyce Gao
Expert 3190 points
Part Number: MSP430FR6005


Hi expert,

An abnormal situation has occurred with the PLL_LOCK function of the MSP430FR6005 microcontroller. In products reporting abnormal errors, measuring the crystal oscillator waveform with an oscilloscope shows no significant frequency shift. However, the amplitude of some individual crystals is lower than normal, but the system can still function normally (this situation indicates a problem with the crystal itself).
Questions as below:
1) What is the working mechanism of this function? The manual does not describe this function in detail. The diagram below only describes it as not working or not locked. 
2) What does "not locked" mean?
3) What situations would cause it to be locked?
4) Does "not working" mean the crystal oscillator is not oscillating, or that the PLL is not working? 
 
 
Joyce
  • 0
    TI__Expert 5340 points

    Hi Joyce,

    1. PLL("Phase-Locked Loop"), which means lock represents work fine. About this PLL_LOCK bit working mechanism please refer to a more detailed description in the TRM as shown below. About the PLL working mechanism please refer to the Wiki or website. 

    2. "Not Lock" means PLL module failed to lock the frequency to your desired one on the clock bus.

    3. Please refer to the above figure, locked means PLL output frequency reach the desired one and become stable.

    4. I believe both situation of crystal failed and PLL module failed will cause the bit of PLL_LOCK to be 0.

    Best Regards,
    Peter

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