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  3. Properly optimizing enable to clock gating enable

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Properly optimizing enable to clock gating enable

archive
archive over 19 years ago

Hi,

I am curious to know how you handle the path to clock gating enable  pin.

I have a design containing multiple level of clock gating on the clock network and when synthesizing using ideal clock all my patht o enable pins have a full  cycle but when My CTS will introduced the latency of the network will reduce the available time to reach those pins.

I understand I could perform post CTS optimization but I would prefer a more robust method to constraint those in ideal clock mode.

I'am thinking of the 2 following approach and would like to hear from you if you have use them or if you have used any others.

- max_delay to enable pins equal to (clock period - expected network latency post clock gating element)
- defining generated clock after each clock gating element with different latency

Those 2 methods have the inconvenience of requiring a lot of data management  :(

Thanks for your help,
Eric.


Originally posted in cdnusers.org by evenditti
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  • archive
    archive over 19 years ago

    RC has better command than set_max_delay. Use "path_adjust" command.

    I was thinking that using a max_delay would give a set of constraints for layout tools to use for opt pre-cts/post-place (rather than trying to do it post-cts) as well as for synthesis. For that, you need a command in the SDC that the layout tool understands and supports (max_delay seemed most obvious to me).

    CD


    Originally posted in cdnusers.org by crispy_duck
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  • archive
    archive over 19 years ago

    RC has better command than set_max_delay. Use "path_adjust" command.

    I was thinking that using a max_delay would give a set of constraints for layout tools to use for opt pre-cts/post-place (rather than trying to do it post-cts) as well as for synthesis. For that, you need a command in the SDC that the layout tool understands and supports (max_delay seemed most obvious to me).

    CD


    Originally posted in cdnusers.org by crispy_duck
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