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Max tran violations

diablo

Pls suggest on improving max tran violations in SocEncounterafter after routing. After postCTS, there are no violations on setup, hold, max_tran, max_fanout. However, after post route, I can see around 100 of max_tran violations but there is still no setup and hold violations. After iteratively running  optDesign -postRoute -drv, i still get those violations. I was wondering why the tool is not using buffers to fix it. 

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  • I just wanted to add that it's common practice to have a tighter transition constraint on the clock trees than the rest of the design. For example, maybe the max tran for the design is 900 ps, but for my clocks I want 400 ps. This is specified in the clock spec file:

    SinkMaxTran     400ps
    BufMaxTran      400ps

    The report generated after CTS will show if these transition limits were met. Even if they violate slightly, we usually move on because we know the transition is tight in the first place. I don't think violations of the 400ps clock spec would show up in the general transition violation report, so you wouldn't have to filter them out.

    - Kari

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  • I just wanted to add that it's common practice to have a tighter transition constraint on the clock trees than the rest of the design. For example, maybe the max tran for the design is 900 ps, but for my clocks I want 400 ps. This is specified in the clock spec file:

    SinkMaxTran     400ps
    BufMaxTran      400ps

    The report generated after CTS will show if these transition limits were met. Even if they violate slightly, we usually move on because we know the transition is tight in the first place. I don't think violations of the 400ps clock spec would show up in the general transition violation report, so you wouldn't have to filter them out.

    - Kari

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