Net does not cross match error

[psitham]

Hello Everybody,

I'm relatively new to working with cadence and I'm actually working on
laying out a 8x256 decoder using 2 4x16 decoders. I have a "Net does
not cross match, it has 1 connections" error which is one of a host of
other "Net does not cross match" errors when I do an LVS for schematic
Vs extracted view for this decoder. I checked the schematic and also
the layout and things look ok to me. The net that it points out in the
schematic is connected exactly in the same configuration in the layout
as well, so I don't understand how to approach this problem and where
to look to solve it. I would be glad and very very appreciative if
anyone could help me out in this issue.

Thank you once again and have a nice day.

Regards,
~Prassanna

[G Vandevalk]

Which LVS tool? Assura? DIVA? Which kit and coding?

Node count LVS (diva) always has a problem with single count nets when any
device is unmatched!
The problem has nothing to do with the net. The device is not unambiguously
defined. (According to the tool!)

A trick in symmetric circuits on node - count - only circuits is to make
them non-symmetric artificially.

One brutal but effective method is to add (many) terminals to the device in
ways that identify the parallel
circuits an make them unique.

Make sure you turn pin matching on or this will not work.

(LVS tools are not smart w.r.t. symmetric circuits. )

But make sure that this is the real problem first.

First make sure the names of the devices match !!!!
Make sure the terminal names match !!!

Fix the devices on the "edge" of where LVS gets lost
and soon as you have "fixed" a few, run it again!!!

Good Luck, LVS is detective work at best.

-- Gerry






"psitham" <prassanna@gmail.com> wrote in message
news:497fa390.0411120836.1591a0d8@posting.google.c om...

Hello Everybody,

I'm relatively new to working with cadence and I'm actually working on
laying out a 8x256 decoder using 2 4x16 decoders. I have a "Net does
not cross match, it has 1 connections" error which is one of a host of
other "Net does not cross match" errors when I do an LVS for schematic
Vs extracted view for this decoder. I checked the schematic and also
the layout and things look ok to me. The net that it points out in the
schematic is connected exactly in the same configuration in the layout
as well, so I don't understand how to approach this problem and where
to look to solve it. I would be glad and very very appreciative if
anyone could help me out in this issue.

Thank you once again and have a nice day.

Regards,
~Prassanna