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can LEC provide cdc check?

zhiweiwu0318

Who can kindly tell me which rule is cdc(cross domain check) in LEC? i can't find any clue in the document.

by the way, i used IFV for cdc, but it can't provide all un-synchronizer singals, oops!

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  • timmynolan

    Hi,

    I agree that the easiest way to get clocks in is to read an SDC file. That is what I have been using. otherwise you need to manually add them yourself using the 'ADD CLOCK' command I believe. Again the ref/user manuals should help you with that.

    What do you not understand about the synchronization rules? I found the whole two flows things a bit confusing at first and only after talking to Cadence people did I understand it. I assume if you have read the documentation (or part of it :) then you know that Lec has 2 CDC flows. The 'normal validation' flow and the 'categorization' flow. If you do NOT use the 'ADD SYNCHRONIZER RULE' command Lec goes into the categorization flow where it will try to group your CDC paths into a predefined rule. (e.g. a flop synchronizer where the logic inbetween is only allowed to be buffers or nothing). Each of the rules is different combinations of flop and mux synchronizers. You can also define custom rules. The categorization flow is aimed to give you an idea of the synchronizers in your design. To actually run the checks you need to be in the normal validation flow - that is to add synchornization rules for the allowed CDC 'types' in your design. e.g. a 2 flop synchronizer with nothing allowed between the flops. You then add the structural checks and check those before adding functional ones.

     I hope this makes sense :)

    Tim 

Reply
  • timmynolan

    Hi,

    I agree that the easiest way to get clocks in is to read an SDC file. That is what I have been using. otherwise you need to manually add them yourself using the 'ADD CLOCK' command I believe. Again the ref/user manuals should help you with that.

    What do you not understand about the synchronization rules? I found the whole two flows things a bit confusing at first and only after talking to Cadence people did I understand it. I assume if you have read the documentation (or part of it :) then you know that Lec has 2 CDC flows. The 'normal validation' flow and the 'categorization' flow. If you do NOT use the 'ADD SYNCHRONIZER RULE' command Lec goes into the categorization flow where it will try to group your CDC paths into a predefined rule. (e.g. a flop synchronizer where the logic inbetween is only allowed to be buffers or nothing). Each of the rules is different combinations of flop and mux synchronizers. You can also define custom rules. The categorization flow is aimed to give you an idea of the synchronizers in your design. To actually run the checks you need to be in the normal validation flow - that is to add synchornization rules for the allowed CDC 'types' in your design. e.g. a 2 flop synchronizer with nothing allowed between the flops. You then add the structural checks and check those before adding functional ones.

     I hope this makes sense :)

    Tim 

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