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Occasional ContributorGenerated visible in "Report Clocks" but the same generated clock not found during timing analysis
Hi,
In my design when I report clocks, I see that the the clock in question is generated and the generated clocks are set to be asynchronous by "set_clock_groups -asynchronous ...." in the top level .sdc but during the timing analyzer cannot find those clocks and gives critical warning that the clocks could not be matched with a existing clock which leads to timing violations to be reported.
The relevant snippets are attached.
The .sdc has additional derive_pll_clocks at the beginning of the file but that command is ignored.
Please suggest ways that the timing analyzer can detect the clock and apply the set_clock_group constraint.
Thanks
BB
5 Replies
sstrellSuper Contributor
Have the .sdc files generated by these IP been added to the project? EMIF usually has its own .sdc that gets added automatically. Have you tried running report_sdc in the timing analyzer to see the actual constraints that are being applied to the design?
BKBThe SDC's for PLLs and other IPs are also automatically added. As per the "Report SDC File List" the sdc for the clock_control_blocki is added and shown in the list with other sdc file.
But in the list generated by "Report SDC" there is no constraint from the clock_control_block_i and hence the constraint which is trying setting the clock groups asynchronous is ignored.
- sstrell
So in your top-level .sdc (you have one, right?) you should have a create_clock for the reference clock input to the device.
- BKB
Yes, I do have a top-level .sdc. I didn't have create_clock at that level as the IP generating that clocks was already having that in its sdc and the clocks were also visible in the "report clocks" list.
I added the create_clock reference and the messages went away. Thanks for your help SStrell.
Best,
BB
AdzimZM_AlteraRegular Contributor
I’m glad that your question has been addressed, I now transition this thread to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.
