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zener's avatar
zener
Icon for Occasional Contributor rankOccasional Contributor
2 days ago

Agilex5: How to use a GTS refclk to clock the FPGA fabric?

I tried to use the GTS System PLL configured with FABRIC_USE_CASE and ref clock frequency to 156.25MHz, C1 enable and selected 101.768092 MHz from the C1 output frequency menu but this results in the following error:

Error (14566): The Fitter cannot place 1 periphery component(s) due to conflicts with existing constraints (1 I/O pad(s)). Fix the errors described in the submessages, and then rerun the Fitter. The Intel FPGA Knowledge Database may also contain articles with information on how to resolve this periphery placement failure. Review the errors and then visit the Knowledge Database at https://www.intel.com/content/www/us/en/support/programmable/kdb-filter.html and search for this specific error message number.
    Error (175019): Illegal constraint of I/O pad to the location PIN_AT120
        Info (14596): Information about the failing component(s):
            Info (175028): The I/O pad name(s): pad_spf_refclk_p
        Error (16234): No legal location could be found out of 1 considered location(s).  Reasons why each location could not be used are summarized below:
            Error (175006): There is no routing connectivity between the I/O pad and destination I/O input buffer
                Info (175027): Destination: I/O input buffer pad_spf_refclk_p~input
                Error (175022): The I/O pad could not be placed in any location to satisfy its connectivity requirements
                Error (175022): The destination I/O input buffer could not be placed in any location to satisfy its connectivity requirements
                Info (175029): 1 location affected
                    Info (175029): PIN_AT120



PIN_AT120 is REFCLK_GTSL1C_RX_P on the Arrow AXE5-Eagle board.

I also tried to use the regular IOPLL but it results in the same error.

How can I use the GTS refclk to clock the FPGA fabric?

5 Replies

  • zener's avatar
    zener
    Icon for Occasional Contributor rankOccasional Contributor

    I left the C0 port unconnected in my last test and only connected C1 as the documentation states: "Only available when Use case of system PLL is set to FABRIC_USE_CASE. When On, there is an output port C1 for FPGA core fabric use.". However, earlier I tried to use the C0 for the fabric (i.e. just clock a simple counter), but it resulted in the same error.

  • FvM's avatar
    FvM
    Icon for Super Contributor rankSuper Contributor

    Hi,

    I did a test with c0 output clock. How do you connect c0 in your test?

    I see that c0=322.265625, c1=101.768092 is accepted. But I neither get the reported error when using c1 clock in FPGA fabric.

  • zener's avatar
    zener
    Icon for Occasional Contributor rankOccasional Contributor

    Thank you for the feedback. I'm not able to manually enter any frequency in the field, only select from the dialog box as shown below:

     

  • FvM's avatar
    FvM
    Icon for Super Contributor rankSuper Contributor

    Hi,
    FABRIC_USE_CASE compiles for me with 100 or 101.875 MHz output frequency. Chosen 101.768092 MHz can't be implemented with 156.25 MHz reference frequency.

    Regards
    Frank

  • zener's avatar
    zener
    Icon for Occasional Contributor rankOccasional Contributor

    BTW This is using Quartus version  26.1.0 Build 110 03/26/2026 SC Pro Edition.