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AD9528 Status Monitor PLL1

I have noticed a difference between the status monitor register 0x0505 and status register 0x0508 - PLL 1 status

We have a potential issue with PLL1 when running from a cpri reference.  I have noticed that the PLL1 status indicated in 0x0508 indicates PLL1 is out of lock whereas 0x505 indicates it is locked.  Which should I pay attention too?  

reg 0x0505 readback value 0x01 ( both PLL1 and PLL2 are locked)

reg 0x0508 readback value 0xea (PLL1 is not locked)

NB I can make PLL1 0x508 lock indication change to 0xef by changing which reference I run from - 0x0505 doesn't change from above

Based on the flow diagrams it would appear 0x0508 is the one to rely on but would like confirmation.

Cheers

Mark

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  • HI,

    I'm sorry for getting back to you so late.

    The register 0x505 is a register that controls the information that is provided at STATUS0 pin. Whenever you set a new value into it, you have to execute an IO Update instruction as well (write 1 to register 0xF). You also have to enable STATUS0 pin output by setting bit 2 in register 0x507. You also need an IO Update after this. You do not need to write IO Update after every writing to an AD9528 register, you can execute it only once after writing a group of registers.

    The register 0x508 is a readback register, which means the value in it changes in real time.

    I would have to test this on the evaluation board. If you can share your stp file, I can run it to see the difference between STATUS0 PLL1 lock indication and register 0x508 bit 0.

    Then, you switched the reference of PLL1 and the register 0x508 changed to 0xEF: bit 4 cleared to 0, both REFA/REFB are missing, but PLL1 bit 0 remained 1, meaning PLL1 was locked.

    I need to see this in the lab. The reference monitoring functions in this way: The reference clocks are monitored after the dividers. If there is no REFA and REFB clock toggling for 2 PFD cycles, the PLL1 switches to holdover because considers the references as missing. If one of them toggles, it is considered correct. 

    Please send me your stp file so I can take a look at the settings and I can play with it in the lab on the evaluation board.

    Petre

  • Hi,

    I went today in the lab and I played with the AD9528 trying to replicate the behavior you outlined.

    I did not see it. Everything behaved as expected. PDF

    See attached the document describing what I did. Please tell me what you did to trigger it.

    Petre

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