Assura LVS output confusing value numbers

[RickK]

Hi can anyone help?
I'm fairly new and working my way through understanding error outputs
until today.
For example a gate size mismatch would simply output say, 5 versus 3.
okay simple.
In one schematic I have a multiple capacitors with a total value of
14000pF
Instead of seeing 14000 vs (some other number) i get weird numbers:

Assura LVS runs okay with a device match but I have a capacitor
paramater mismatch
It reads:
Schematic Instance: C1_0 Cap
Layout Instance: I3/I46/avD1446_1 Cap
VALUE 4.2e-08 vs 311.113e-08 differs by 25.8784%
Schematic instance is the merged result of C1 0 C1 2 C1 1
Layout instance is a merged result of I3/I46/avD1446_1

why doesn't it just give me a simple output difference?
Can someone tell me what this is?

Thanks from a newbie!!
Rick

 

[Bernd Fischer]

I assume in your Assura command rules is somewhere a command which
tells Assura to merge caps if they are in parallel.

Then your output is

Schematic instance is the merged result of C1 0 C1 2 C1 1
Layout instance is a merged result of I3/I46/avD1446_1

Sometimes this is wanted to reduce the devices in the netlists
which has to be compared.

Does this help?

Bernd

RickK wrote:

Hi can anyone help?
I'm fairly new and working my way through understanding error outputs
until today.
For example a gate size mismatch would simply output say, 5 versus 3.
okay simple.
In one schematic I have a multiple capacitors with a total value of
14000pF
Instead of seeing 14000 vs (some other number) i get weird numbers:

Assura LVS runs okay with a device match but I have a capacitor
paramater mismatch
It reads:
Schematic Instance: C1_0 Cap
Layout Instance: I3/I46/avD1446_1 Cap
VALUE 4.2e-08 vs 311.113e-08 differs by 25.8784%
Schematic instance is the merged result of C1 0 C1 2 C1 1
Layout instance is a merged result of I3/I46/avD1446_1

why doesn't it just give me a simple output difference?
Can someone tell me what this is?

Thanks from a newbie!!
Rick

 

[RickK]

On Mar 30, 5:12 am, Bernd Fischer <bernd.fisc...@nsc.NOSPAM> wrote:

I assume in your Assura command rules is somewhere a command which
tells Assura to merge caps if they are in parallel.

Then your output is
Schematic instance is the merged result of C1 0 C1 2 C1 1
Layout instance is a merged result of I3/I46/avD1446_1

Sometimes this is wanted to reduce the devices in the netlists
which has to be compared.

Does this help?

Bernd



RickK wrote:
Hi can anyone help?
I'm fairly new and working my way through understanding error outputs
until today.
For example a gate size mismatch would simply output say, 5 versus 3.
okay simple.
In one schematic I have a multiple capacitors with a total value of
14000pF
Instead of seeing 14000 vs (some other number) i get weird numbers:

Assura LVS runs okay with a device match but I have a capacitor
paramater mismatch
It reads:
Schematic Instance: C1_0 Cap
Layout Instance: I3/I46/avD1446_1 Cap
VALUE 4.2e-08 vs 311.113e-08 differs by 25.8784%
Schematic instance is the merged result of C1 0 C1 2 C1 1
Layout instance is a merged result of I3/I46/avD1446_1

why doesn't it just give me a simple output difference?
Can someone tell me what this is?

Thanks from a newbie!!
Rick- Hide quoted text -

- Show quoted text -

Hi thanks, but the merging of caps isn't the problem. it's the VALUE
output

My schematic cap is listed as 14000pF but the LVS value is listed as
4.2e-08 vs 311.113e-08 differs by 25.8784%

I reduced the size of my caps and was expecting to see an out put of
something like 14000 vs "some new smaller number".

How do I convert these machine? numbers?
Is there a reference manual to cross check the numbers output?
Hope someone can help.
Thanks

 

[S. Badel]

My schematic cap is listed as 14000pF but the LVS value is listed as
4.2e-08 vs 311.113e-08 differs by 25.8784%

Maybe your deck does not compare the capacitance but some other value such as area ?

I reduced the size of my caps and was expecting to see an out put of
something like 14000 vs "some new smaller number".

What happened ?

 

[RickK]

On Mar 30, 10:00 am, "S. Badel" <stephane.ba...@REMOVETHISepfl.ch>
wrote:

My schematic cap is listed as 14000pF but the LVS value is listed as
4.2e-08 vs 311.113e-08 differs by 25.8784%

Maybe your deck does not compare the capacitance but some other value such as area ?

I reduced the size of my caps and was expecting to see an out put of
something like 14000 vs "some new smaller number".

What happened ?

Hmm... Okay i did some googling on these numbers, It looks like
4.2e-08 is scientific notation for machine math because it cannot
write 4.2 to the minus 8.
If this is what I am interperting... then 4.2e-08 translates to
0.000000042.
But how do I translate that back to compare against 14000pF??

Thanks.

 

[S. Badel]

Hmm... Okay i did some googling on these numbers, It looks like
4.2e-08 is scientific notation for machine math because it cannot
write 4.2 to the minus 8.
If this is what I am interperting... then 4.2e-08 translates to
0.000000042.

Yes (of course !)

But how do I translate that back to compare against 14000pF??

14000p(F) is 1.4e-08.

Or, is you prefer, 4.2e-08 is 42000p(F ??)

That is exactly 3 times 14000p(F)

There must be a reason for this 3x factor, but it's either something wrong in your schematic, or it
is due to the way your rule decks are written.

Stéphane