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Original question:

LMK04803 Questions

LMK04803: LMK04803B Mode switch issue

Xiao Zhu2
Expert 3215 points

Part Number: LMK04803

Hello Team

When change one mode to another mode, how to setup the register?  For example, First used PLL2 internal VCO mode,  all the register are set to the right value, then change to the clock distribution, and then change to PLL2 internal VCO mode back, during this change only change  r0 -r5 register value. Following the up operation, the pll will not lock. only set all the registers value twice, the PLL will lock.

it seem, when change one mode to other mode, all the register be write, the device will work well.

  • 0
    TI__Genius 9920 points
    Hi Xiao Zhu,
    1, If you used R0 RESET bit, then all registers should be programmed as your application.
    2, If you didn't use RESET, and still like to keep current register settings with less changes, it is possible.
    When an internal VCO mode is used, programming Register 30 triggers the frequency calibration routine. Before this VCO calibration, we should make sure other register settings are correct. So if we want to make PLL2 lock again, we should write R30 again.

    Anyway, R0 Reset to get device default settings, then program all registers need be changed, as datasheet "8.5.2 Recommended Programming Sequence" showed. This method always works.

    Noticed you mentioned "only set all the registers value twice, the PLL will lock.", it is possible there is abnormal on MICROWIRE Timing. Please refer to datasheet "8.3.1 Serial MICROWIRE Timing Diagram" and "8.3.2 Advanced MICROWIRE Timing Diagrams".
    After programming is complete the CLKuWire, DATAuWire, and LEuWire signals should be returned to a low state.

    Hope you find a proper method to set LMK0480x device.

    Regards,
    Shawn