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tip: to avoid xtalk on clock nets

archive

If you use 2x/3x spacing in your design.ctstch to get the extra spacing for xtalk prevention, you might not get what you want if your design is too congested.  Since those rule are soft constrain, Nanoroute will try it best to follow it if possible.  To be sure you are getting the 2x/3x spacing, you need to create a NONDEFAULT rule in your lef file and specify it in your design.ctstch before you run CTS.
 
  RouteTypeName 3xSpacRoute
  NonDefaultRule 3xSpacing
  TopPreferredLayer 6
  BottomPreferredLayer 5
  End

You also need to add the following before the clock routing.

  setNanoRouteMode routeStrictlyHonorNonDefaultRule true

li siang


Originally posted in cdnusers.org by lisiang

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