schematic pcell implementation in virtuoso platform

October 5, 2004 1

Schematic pcell implementation in Virtuoso® platform

Presenter –Umesh SisodiaOn behalf of: Pranav Bhushan

Cadence Design System

September 2004

October 5, 2004 2

Content

• What are parameterized cells ?• Motivation • Creating a schematic pcell• Pcell architecure• Examples from Virtuoso® analogLib• Future work

October 5, 2004 3

What are parameterized cells ?

• Graphic, programmable, generic cell• Allows customized instances• Layout pcells are in use since many years• Schematic pcell is a relatively new concept• Required for changes in :

– Pins– Size– Structure/Shape

• Independent of underlying database• Open Simulation System (OSS) supports pcells

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Advantages

• Faster library development• Compact and efficient libraries• Less maintenance• Reduces chances of errors• Eliminates hierarchy explosion for small changes

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Creating a schematic pcell

•Steps to create a pcell

•Create and edit skill code

•Compile pcell

•Define CDF parameter(s)

•Test pcell

•Netlisting support

•Post processing support

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Defining a pcellskill code

pcDefnePcell (list( ddGetObj(“libName”) “cellName”

“viewName” “viewType”

)

( ( param1 “defaultValue” )( param2 10 ) ….

)

( ;; Create symbol shape & connectivity)

)

•Compiled skill function < 64 K

•You can call your own functions within pcells

•pcCellView is an internal variable automatically created

•Should be compiled in PD workbenches ( icfb, layoutPlus etc. )

Cell Identifier section

Formal Parameters

Body of pcell

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Specifying parameter values

The order in which system looks for value of parameters

1. On the instance2. In the CDF for cell3. In the CDF for library4. In the pcDefinePcell function ( default values )

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Pcell architecure

•You cannot descend into submaster from an instance of pcell.

•Edits to master does not reflect on instances unless you compile.

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Examples from Virtuoso®

analogLib

• ${CDS_INST_DIR}/tools/dfII/etc/cdslib/artist/analogLib• Some pcells in Virtuoso® analogLib:

– ibis_buffer– mtline– nport– scasubckt– vccsp– vcvsp

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Virtuoso® analogLib:ibis_buffer

• Formal Parameters:– Buffer Variant ( buffervariant )– Buffer Type ( bufferType )

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ibis_buffer cont…

Buffer Type

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Virtuoso® analogLib:mtline

• Formal Parameters:– Number of lines (n)– Use LMG subckt (uselmg )

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Setting Instance Parameters

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Setting Instance Parameters …

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Future work

• Virtuoso® AMS designer does not fully support pcells• Dynamic simInfo (Netlister support)• Dynamic termOrder, termMapping (Post-processing)• New components in Virtuoso® analogLib (on need basis)

schematic pcell implementation in virtuoso platform

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