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ymiler's avatar
ymiler
Icon for Contributor rankContributor
1 year ago

clock gated conversion

Hello,

I'm running Quartus 22.3 building for an S10 FPGA.

Since my FPGA is prototype, the project includes several clock gated

to solve it I added the following command to the QSF :

set_global_assignment -name SYNTH_GATED_CLOCK_CONVERSION ON -

(replace all the clock gated to clock enable)

After the synthesis and P & R the *.syn.rpt file show list of gated clocks which found and converted to use as clock enable

but at least 1 clock gated doesn't convert and I get hold violation on this path.

I expected to see any information about this clock gated on the report like as list of unconverted gated clocks(and reason why its not converted) , but there is no list at all in this file .

please advice

Fpga Devkit

13 Replies

  • sstrell's avatar
    sstrell
    Icon for Super Contributor rankSuper Contributor
    1 year ago

    It would help to see some code and understand why you have so many gated clocks to begin with. It would be much better to use clock enables instead of gated clocks.

    • ymiler's avatar
      ymiler
      Icon for Contributor rankContributor
      1 year ago

      Hi

      Original code is ASIC RTL who use clock gate to decrease power supply.

      Here the clock gated code:

      // Gated Clock Latch
      module gcw__ckltchand (
      TE,
      E,
      CP,
      Q
      );
      input TE;
      input E;
      input CP;
      output Q;

      wire EN_TE;
      reg CPEN;

      or or1 (EN_TE,E,TE);


      always @(EN_TE or CP)
      if(~CP) CPEN <= EN_TE;

      and an1 (Q,CPEN,CP);

      endmodule //gcw__ckltchand

      • RichardT_altera's avatar
        RichardT_altera
        Icon for Super Contributor rankSuper Contributor
        1 year ago

        By adding the top.v file with attached code. The tool able to recognize the gated clock and converted to use clock enables.

        Info(19019): Convert gated clock gcw__ckltchand_1|Q

        module top (
        input i_rst_n,
        input i_en,
        input i_clk,
        input i_data,
        output reg o_data
        );

        wire gclk;

        gcw__ckltchand gcw__ckltchand_1 (
        .CP(i_clk),
        .E(i_en),
        .TE(),
        .Q(gclk)
        );

        always @(posedge gclk or negedge i_rst_n) begin
        if (!i_rst_n) begin
        o_data <= 1'b0;
        end else begin
        o_data <= i_data;
        end
        end

        endmodule

        Perhaps you could check your design hierarchy to see what might be going wrong.

        You could also share a simple testcase .qar file (Project > Archive Project) that you expect the tool to convert the gated clock but it does not.


        Regards,
        Richard Tan

  • RichardT_altera's avatar
    RichardT_altera
    Icon for Super Contributor rankSuper Contributor
    1 year ago

    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
    1 year 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 let us know.

    Thank you for reaching out to us!

    Best Regards,

    Richard Tan


    • ymiler's avatar
      ymiler
      Icon for Contributor rankContributor
      1 year ago

      Hi

      Following to you answer you use:

      gcw__ckltchand gcw__ckltchand_1 (
      .CP(i_clk),
      .E(i_en),
      .TE(),
      .Q(gclk)
      );

      Is it Altera primitive code ?

      • RichardT_altera's avatar
        RichardT_altera
        Icon for Super Contributor rankSuper Contributor
        1 year ago

        No, "gcw__ckltchand" is the module instantiation that you provided in your previous post. Posted on 18th April.

        // Gated Clock Latch
        module gcw__ckltchand (
        TE,
        E,
        CP,
        Q
        );
        input TE;
        input E;
        input CP;
        output Q;

        wire EN_TE;
        reg CPEN;

        or or1 (EN_TE,E,TE);


        always @(EN_TE or CP)
        if(~CP) CPEN <= EN_TE;

        and an1 (Q,CPEN,CP);

        endmodule //gcw__ckltchand
    • ymiler's avatar
      ymiler
      Icon for Contributor rankContributor
      1 year ago

      I replaced my clock gate instance to:

      gcw__ckltchand gcw__ckltchand_1 (
      .CP(i_clk),
      .E(i_en),
      .TE(),
      .Q(gclk)
      );

      then I re-run synthesis and get the message:

      Gated clock:

      top|cnvr|cnvr_tlgc_inst|cnvr_scu_ins|cnvr_scu_dig_cgu_ins|scu_top_cg_aux_clk_ins|cell__clk_enable_nlt_reg|gcw__ckltchand|an1

      Base clock :

      top|cnvr_pll1_inst|iopll_0|stratix10_altera_iopll_i|outclk[0]

      Converted to Clock enable :

      No

      Reason not converted :

      Found unsupported gate top|cnvr|cnvr_tlgc_inst|cnvr_scu_ins|cnvr_scu_seq_ins|block_gated_clk_seq_ins|stdc__clk_enable_nlt_reg|gcw__ckltchand|CPEN in the gated clock tree

      Could you explain why Quartus did not succeed to converted?

  • Adrien_Lacroix's avatar
    Adrien_Lacroix
    Icon for New Contributor rankNew Contributor
    9 months ago

    Hello,
    I am facing the same issue trying to synthetize my design into a Stratix 10 (1SG280H).
    I am using this FPGA for ASIC prototyping and I also have several (and cascaded) gated clocks.
    Do you have a solution to correctly convert those gated clock into clock enable ?
    I have tried so far:

    1. using "set_global_assignment -name SYNTH_GATED_CLOCK_CONVERSION ON". It does not work as several clocks are not correctly converted.
    2. using a module "stratix10_clk_ctrl" but it does not work as it seems that this module does not accept to receive a gated clock in input (so it does not work for cascaded gated clock)

    I am using Quartus Prime Pro 24.2.0

    Thank you,

    Adrien

    • ymiler's avatar
      ymiler
      Icon for Contributor rankContributor
      9 months ago

      Hi Adrien

      I still haven't received a solution to my issue.

      However, I have opened a case on the Altera support website.

      As far as I know, they are working on finding a solution in their next release.

  • Adrien_Lacroix's avatar
    Adrien_Lacroix
    Icon for New Contributor rankNew Contributor
    9 months ago

    Hello,
    Thank you for your answer.
    It could be really helpful if you notified me in this channel whenever you get an answer for your case.