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TIP OF THE MONTH: How can I compare unreachable logic? Conformal LEC doesn't map nor compare it.

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How can I compare unreachable logic? Conformal LEC doesn't map nor compare it.

Important note: the settings discussed below make Conformal more picky than it really needs to be for regular EC. Do not employ them as default settings but, only when absolutely needed.

Unreachable logic is logic that doesn't affect the functionality of the design. Unreachable FF's and latches will appear in the mapping manager as yellow dots with a "U" inside. Since these compare points don't change the functionality they are not mapped nor compared by Conformal LEC. Typical unreachables: disabled logic (constraints), spare gates, or unconnected logic in the RTL (which synthesis will blow away).

There are times when you may want to compare unreachable logic. For example, if you are checking an IP block, have little knowledge of its functionality, and don't know if the unreachable logic should be unreachable. Also, it may also make it easier to debug the design with unreachables mapped and compared.

To preserve, map, and compare unreachable logic, do the following: When reading in your design, use the "-keep_unreach" option: 

read design rtl.v  -golden  -keep_unreach 
read design gate.v -revised -keep_unreach
After you've read in the designs but before mapping, issue the following command: 
set mapping method -unreach
The unreachable logic should now get mapped and compared.


Originally posted in cdnusers.org by darylk
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    Hello Ali,

    I don't think this module has any problem.  The result of the comparison for this module is equivalent.

    ==================================================
    Compared points    PO    DFF    BBOX    Total
    --------------------------------------------------------------------------------
    Equivalent                28    49         1        78
    =========================================
     
    To be able to map all the unreachable, the keypoints must be existing on both sides.  Just like default flow. In your case, the unreachable key points are only in the revised.  There are nothing to map with from the Golden.

    Hope this helps. 

    Regards,
    Jess


    Originally posted in cdnusers.org by jessican
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  • archive

    Hello Ali,

    I don't think this module has any problem.  The result of the comparison for this module is equivalent.

    ==================================================
    Compared points    PO    DFF    BBOX    Total
    --------------------------------------------------------------------------------
    Equivalent                28    49         1        78
    =========================================
     
    To be able to map all the unreachable, the keypoints must be existing on both sides.  Just like default flow. In your case, the unreachable key points are only in the revised.  There are nothing to map with from the Golden.

    Hope this helps. 

    Regards,
    Jess


    Originally posted in cdnusers.org by jessican
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