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Altera_Forum
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16 years ago

How to find all clock domain crossings?

I've been charged with taking over an fpga design from another engineer. This design has 17 clock domains with numerous crossings among its 43 rtl modules spread over 5 levels of hierarchy. I am concerned that some of the clock crossings are not being handled properly, and because the design is full of code evolved from prior designs, I'm facing a daunting challenge to discover and analyze all the crossing points.

Is there way to get TQ to report every source/destination register pair that doesn't lie in a single domain? I'm thinking of a report that has something like: from node, to node, launch clock, and latch clock. I could then scan the list and quickly see where to go in the design to check the logic. If there isn't a ready-made means to generate that report, does anyone know a way to "coerce" that information out of TQ?

Any guidance is much appreciated.

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    --- Quote Start ---

    I've been charged with taking over an fpga design from another engineer. This design has 17 clock domains with numerous crossings among its 43 rtl modules spread over 5 levels of hierarchy. I am concerned that some of the clock crossings are not being handled properly, and because the design is full of code evolved from prior designs, I'm facing a daunting challenge to discover and analyze all the crossing points.

    Is there way to get TQ to report every source/destination register pair that doesn't lie in a single domain? I'm thinking of a report that has something like: from node, to node, launch clock, and latch clock. I could then scan the list and quickly see where to go in the design to check the logic. If there isn't a ready-made means to generate that report, does anyone know a way to "coerce" that information out of TQ?

    Any guidance is much appreciated.

    --- Quote End ---

    Hi,

    which Timing Analyzer do use ? TimeQuest ?

    Kind regards

    GPK
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    Hi pletz. I use TimeQuest. I probably should have added that I'm familiar with the Report Clock Transfers report, which suggests TQ has intimate knowledge of which signals are crossing which domains. I just need it to go one step further and list them. Maybe I need to go through a two- or three-step process to get what I want, and maybe it's possible to at least semi-automate via TCL, but I'm hoping TQ has something built in that will get me there or that someone will suggest the steps I need go through. I am by no means a TimeQuest expert! Yet!!