Forum Discussion

anat's avatar
anat
Icon for New Contributor rankNew Contributor
6 months ago

IOPLL output clock issue Stratix10

Hi Team,

I configured iopll IP for three output clocks, (outclk0)100MHz, (outclk1)200MHz and (outclk2)600MHz. Ref clock is 100MHz.
I see duty cycle variation in the generated clock of 200MHz from iopll. I'm capturing the clocks using signal tap analyzer at a frequncy of 600MHz, genrated by same iopll.
Why the duty cycle is varying from 50%?

Clock waveform


IOPLL Settings




Other Ips

4 Replies

  • sstrell's avatar
    sstrell
    Icon for Super Contributor rankSuper Contributor
    6 months ago

    You're not going to be able to see accurate sampling for a signal that fast. Rely on the timing analyzer to verify your clocks, not Signal Tap, or output to a pin and view on a scope. Signal Tap is for functional debug of data signals, not analyzing clocks.

  • RichardT_altera's avatar
    RichardT_altera
    Icon for Super Contributor rankSuper Contributor
    6 months ago

    SignalTap uses a clock to capture the data, so it's dependent on that clock rate. For logic, you want it to be the same clock that drives the logic you're tapping, as you need to synchronously tap it. For probing a clock, I'm not sure exactly what you're hoping to see. Normally people have the clock drive a counter and then just sample that with another clock, to calculate X transitions happened in Y time.


    Regards,

    Richard Tan


  • RichardT_altera's avatar
    RichardT_altera
    Icon for Super Contributor rankSuper Contributor
    6 months ago

    Hi OP,


    Dropping a note to ask if my last reply was helpful to you.

    Do you need any further assistance from my side?


    Regards,

    Richard Tan


  • RichardT_altera's avatar
    RichardT_altera
    Icon for Super Contributor rankSuper Contributor
    6 months ago

    We noticed that we haven't received a response from you regarding the latest previous question/reply/answer, and will now transitioning your inquiry to our community support. We apologize for any inconvenience this may cause and we appreciate your understanding.


    If you have any further questions or concerns, please don't hesitate to reach out. Please login to https://supporttickets.intel.com/s/?language=en_US, view details of the desire request, and post a feed/response within the next 15 days to allow me to continue to support you. After 15 days, this thread will be transitioned to community support. The community users will be able to help you on your follow-up questions.


    The community users will be able to help you on your follow-up questions.


    Thank you for reaching out to us!


    Best Regards,

    Richard Tan