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calibre pex warnings: The ground net "VSS/VSSO" defined in PEX NETLIST

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sanjaysharmaiitk

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I compared LAYOUT vs CLD netlist of UART design by RTL code and gds exported into Virtuoso.
There are no error but following warning is coming during PEX in calibre .

"The ground net "VSS/VSSO" defined in PEX NETLIST statement is not a valid GND net in the design."

what is the cause of this warning ,How to remove this warning.

In LAYOUT VSS,VSSO VDD ,VDDO dc supply are used for PADs and VDD ,VSS are common to both for PADs and Chip.
VSS, VDD are supplied to both Core-Ring and to PAD-ring by PADs defined in PDK for supply to both PAD-RING and CORE-RING.
scl pdk is used for design.
 

Depending on your process (PDK) you might need an extra connection between VSS(O) and GND, either a direct connection or via a SUBSTR-SUBTAP symbol (or similar name).
 
Re: calibre antenna drc rule check warnings:

these warning are coming during antenna rule check in calibre.
these warning are harmful or not.
how to remove these warnings.
warnings
ACUTE angle on layer M2 at location (64.11,0.99) in cell subil_pngatebuff_ESD122.
ACUTE angle on layer M2 at location (64.11,0.99) in cell subil_pngatebuff_ESD1.
ACUTE angle on layer M2 at location (64.11,0.99) in cell subil_pngatebuff.
ACUTE angle on layer AA at location (28.73,325.56) in cell subil_midconer2.
ACUTE angle on layer AA at location (34.43,317.94) in cell subil_midconer2.
ACUTE angle on layer AA at location (36.86,315.64) in cell subil_midconer2.
 

Re: calibre antenna drc rule check warnings:

... these warning are harmful or not.
They are undesired and possibly could provoke a rejection of your design.

how to remove these warnings.
Usually such warnings (angle < 90° , even just a tiny bit less, invisible) result from usage of an incorrect grid.

Set the correct grid and re-grid your design. If there aren't too many acute angle warnings, you could do the re-gridding manually.
 

"The ground net "VSS/VSSO" defined in PEX NETLIST statement is not a valid GND net in the design."

It looks like you defined two ground nets but put no spaces or commas etween the names, but the slash - so PEX thinks this is one net name, and says it's invalid (I think ground net names should not contain slashes - slashes are usually used as hierarchy separators).
Leave only one net as ground (such as VSS), see what happens - to check my theory.
 

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