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clock tree quality

Rajesh Vembu

What are the metrics (physical and timing-related) that determine if the clock tree built is robust and of good quality?

If i want to compare the clock tree quality built using 2 different clock tree spec files, what would be the steps to follow?

It should be noted that the AutoCTSRootPin definitions in the 2 spec files could be different, hence a one-to-one comparison of the clock tree report (generated using reportClockTree) won't be helpful.

 - Rajesh

Parents

  •  Hi Gele,

    I guess it depends on the clock root definition.

    Case 1 : i have a place-holder buffer, connecting to input clock pin, inside the core and set that as AutoCTSRootPin and build a clock tree from there 

    Case 2 : Define the IO clock pin (driving the place-holder buffer) as the AutoCTSRootPin.

    If i try to load in the case 2 ctstch to report the metrics from clock tree db (done using case 1), the results would not be correct as the clock tree was not built from the IO pin.

    But the other case (loading case 1 ctstch in case 2 clock tree db) could provide the correct (?) results.

    - Rajesh

    Note : This is just one case mentioned for explanation purpose. As we go  through reconvergent-clock clock root definitions, it could get complicated.

Reply

  •  Hi Gele,

    I guess it depends on the clock root definition.

    Case 1 : i have a place-holder buffer, connecting to input clock pin, inside the core and set that as AutoCTSRootPin and build a clock tree from there 

    Case 2 : Define the IO clock pin (driving the place-holder buffer) as the AutoCTSRootPin.

    If i try to load in the case 2 ctstch to report the metrics from clock tree db (done using case 1), the results would not be correct as the clock tree was not built from the IO pin.

    But the other case (loading case 1 ctstch in case 2 clock tree db) could provide the correct (?) results.

    - Rajesh

    Note : This is just one case mentioned for explanation purpose. As we go  through reconvergent-clock clock root definitions, it could get complicated.

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