Question about Assura LVS filter function

In my design I have a dummy resistor with its two terminals connected
together and tied to the VDD line. When I run Assura LVS, a mismatch
was found, namely, the dummy resistor was found in the layout, but not
in the schematic.

I checked the "compare.rul" and I see that the resistors with two
terminals short are set to be filtered. I don't understand why Assura
doesn't filter my resistor in the layout.

I know that if the resistor can be filtered if the compare.rul is
modified properly, or if the "avCompareRules" is setup from the Assura
GUI. But I don't know the format. Can anyone give me an example of
these files? Thanks.

 

Hi Allen,

If you add the following into your compare rule file :

filter(“X”)

Then it Filters out any device (MOS, BJT, RES, CAP, DIODE, IND, or
generic) where all terminals are tied together.
This is a kind of global shorted-devices filtering.

If you want to set filters for a certain type of devices, you can use
one or more of the following commands:

filter(res "X" )
filter(cap "X" )
filter(mos "X" )
filter(ldd "X" )
filter(bjt "X" )
filter(ind "X" )
filter(generic "X" )

There are plenty of other options, please give a look at the following
document in your ASSURA stream:
Assura Physical Verification Command Reference (assuracommandref.pdf)

Cheers,
Riad.

 

Hi Riad,

Thanks for your prompt answer. I checked my compare.rul file, The
command "filter(res "X" )" is already there.
I guess this command doesn't work for my case. In order to test it, I
keep the two terminals of the resistor connected,
but I disconnected them from the VDD line. I also changed the layout
accordingly. Guess what? the schematic and layout matches.
So it seems like the command "filter(res "X" )" only works if the
devices' terminals short and not connected to other wires.
Do you have an idea how to solve this problem?
I tried to let LVS filter the resistor by giving the resistor name,
but didn't succeed, I guess my syntax was not right.
Do you know if it's possible to do it this way?

Thanks.

Best,
Allen

 

I think the simplest way is that add the dummy resistors in your
schematic if the number of them is not huge.

 

In fact, all the dummy resistors were added in the schmatic. Somehow
Assura knows to filter out them but don't know to filter out the
according ones in the layout. Thanks.