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Simulators >> Circuit Simulators >> Error:Hierarchy Flattening in Cadence
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Message started by madan on Apr 23^rd, 2008, 5:13pm

Title: Error:Hierarchy Flattening in Cadence
Post by madan on Apr 23^rd, 2008, 5:13pm

HI,
i am getting the following message when i am trying to netlist and run the inverter:

Error found by spectre in 'Inv22' : 'I6', During hierarchy flattening.
I6.PM0: Instance (of type mos2) requires the use of a model.

I have created a test bench for the inverter and instantiated Inverter made as cell named 'Inv22' in it. I6 is the instance name of the inverter. I am using the CMOSP35 library. This error message is not coming constantly. Sometimes it does not come and the simulation runs successfully. I have been using Cadence for last 1 year but this error started coming only recently.

what i understand from the error message is that netlist is not being created properly. There is an error in the netlist line containing all MOSFETs.
The MOSFET line in the netlist reads something like this:

m5 (list of nodes) mos2 w=1u l= 0.35u ........

Instead of mos2 it should be nch or pch.

If anyone knows the way to solve this problem then please help me. Thanks in advance

Title: Re: Error:Hierarchy Flattening in Cadence
Post by Geoffrey_Coram on Apr 24^th, 2008, 6:37am

Do you have a schematic or symbol in your library named "mos2" ?

Title: Re: Error:Hierarchy Flattening in Cadence
Post by madan on Apr 24^th, 2008, 8:45am

Geoffrey_Coram wrote on Apr 24^th, 2008, 6:37am:

Do you have a schematic or symbol in your library named "mos2" ?

No i don't have schematic or symbol in my library named "mos2".

I have gone through the spectre manual and found that mos2 means BSIM level2 model. From that what i understand is that the netlister is instantiating a BSIM level2 model for the mosfets ( nfet and pfet from cmosp35), where is should create a nch or pch model in the netlist.

The problem started only when i started using the Virtuoso layout editor. I have been using schematic editor for quite some time now but never experienced the problem. When I use "extracted" before "schematic" in the switch view list in the the environment setup dialogue, then the netlist is sometimes created correctly(for extracted shell view). But this doe not happen consistently. Again, when I remove extracted from the switch view list and redo the netlisting, then netlist SOMETIMES gets created correctly (even for the schematic view). But there is no consistency in all this.

Also, exiting the icfb does not help consistently.

Title: Re: Error:Hierarchy Flattening in Cadence
Post by Geoffrey_Coram on Apr 25^th, 2008, 5:22am

From the error message, I knew mos2 was some sort of built-in model (it's mos level=2; this is not the same as "bsim2" which is BSIM 2, or mos level=5).

I can't imagine why the netlister would pick "mos2"; it was a wild guess that it might be a cell in your library. I suppose it might be hard-coded into some netlisting function, but I don't have any suggestions where to start looking for that, nor why it would be inconsistent.

Title: Re: Error:Hierarchy Flattening in Cadence
Post by BWhite on May 1^st, 2008, 4:29pm

Try

setenv CDS_Netlisting_Mode Analog

before you run the tool.