Calibre LVS" Warning: Ambiguity points were found and r

[fanshuo]

calibre lvs

I got a warning after the Calibre LVS
" Warning: Ambiguity points were found and resolved arbitrarily."
Should I try to get rid of this warning or not?
Thanks!

 

[erikl]

Re: Calibre LVS question

" Warning: Ambiguity points were found and resolved arbitrarily."
Should I try to get rid of this warning or not?
Thanks!

Ambiguity points are nodes with high symmetry, i.e. similar nodes within similar parallel paths. It could be a pb., as you can't allocate a certain delay to the appropriate path. If prop. delay differences in these paths do not matter (e.g. because you synchronise the signals anyway), you may neglect this warning.

 

[fanshuo]

Calibre LVS question

is there a way to get rid of the warning?

 

[erikl]

Re: Calibre LVS question

is there a way to get rid of the warning?

Sure. Without additional info, LVS cannot differentiate between similar parallel paths, so allocates them arbitrarily. In order to allow for unambiguous mapping (concerning the position in layout), it is necessary to assign node labels to the schematic wires as well as to the corresponding layout routes. The names of the corresponding node labels are to be written into a correspond_file:
layout_node_name_1 schematic_node_name_1
layout_node_name_2 schematic_node_name_2
...
Usually, just a single node in each parallel path has to be labeled; for (e.g.) 8 paths, 7 node labels are enough (of course).
Diva LVS uses a correspond_file with a fixed name, if it exists. See your Calibre doc how it is handled there.