Cadence Tutorial 4: Schematic of a parameterized Inverter

1. Open schematic window.
   File->New->Cellview
   In Create New File window,
• Library Name : Mylib
• Cell Name : inverter
• View Name : schematic
• Tool : Composer-Schematic

2. Place nmos transistor.
   sch:Add->Component (or "i")
   Add Component:click Browse
   In Library Browser window,
• Library : tsmc25Lib
• Cell : nfet3
• View : symbol

1. Place pmos, vdd, and gnd.

- Repeat above procedure for pfet3, vdd, and gnd placement. All components can be found at the same library (tsmc25Lib or basic).

2. Connect each component using wires.

Place mouse pointer on one of the node you want to connect
sch:Add->Wire(narrow) (or "w")
Click "mouse L", drag to other node to connect, and click "mouse L" to finish.
- Repeat above procedure to finish wiring.
- To make wire open node at one end (like input and output of inverter), double-click "mouse L"

3. Place pins.
   sch:Add->Pin (or "p")
   In Add Pin window,
• Pin Names : A X
• Direction : input

Move mouse to place A pin at input of inverter, then click "mouse L".
In Add Pin window, change direction to output.
Place X pin at output of inverter.

4. Add pmos parameters. (W/L)

Click pfet3
sch:Edit->Properties->Objects (or "q")
In Edit Object Properties window,

• Width : pPar("pw")
• Length : pPar("pl")
• Click OK or Apply
• Repeat for nfet3 with width pPar("nw") and length pPar("nl").

Comment: pPar means its parameter value is inherited from parent schematic. pPar(“pw”) can be interpreted as “set the width to the parameter pw of its parent schematic”. In this example, there are   four parameters (pw, pl, nw, nl) which can be individually controlled from the schematic that calls the symbol of this schematic.

Please refer to chapter8 Editing Properties -> Passing Parameters section in Cadence Virtuoso Schematic Composer User guide for more details.

Check and Save
sch:File->Check and Save

Inverter Symbol Create

1. Open symbol window.

icds:File->New->Cellview
In Create New File window,

• Library Name : MyLib
• Cell Name : inverter
• View Name : symbol
• Tool : Composer-Symbol
1. Draw outline for inverter symbol.

Click line icon on left toolbox of symbol window and draw outline of inverter.

3. Finish outline by adding circle.
   sym:Add->Shape->Circle
   Click "mouse L" on the center of circle, drag and click "mouse L" again.

4. Place pins.
   sym:Add->Pin (or "p")
   In Add Pin window,
• Pin Names : A X
• Direction : input
• Type : square

 Move mouse to place A pin at input of inverter, then click "mouse L".
In Add Pin window, change direction to output.
Place X pin at output of inverter.

5. Add labels.
   sym:Add->Label
   In Add Label window,
• Label : [@instanceName]

 Place label.

6.      Add NLPLabel for parameters.

<Symbol>Add->Label

<Add Symbol Label>

Label: [@pw:%:][@pl:/%:]

Label Type: NLPLabel

<Add Symbol Label>

Label: [@nw:%:][@nl:/%:]

Label Type: NLPLabel

Comment:  Putting NLPLabel for symbol will help you recognize the property of the instance in the schematic that uses this symbol.

7. Add CDF Parameters for the cellview.

<CIW>Tools->CDF->Edit

<Edit Component CDF>

CDF Type: Base

Library Name: MyLib

Cell Name: inverter

Component Parameters: Click Add

<Add CDF Parameter>

paramType: float

storeDefault: yes

name: nw(pw,nl,pl)

prompt: nw(pw,nl,pl)

defValue: 0.5u (or value of your choice, 0.24u for length)

Click Apply or OK

For more help please refer to Virtuoso Schematic Composer user guide using CDSDOC.

In case of any bug or comment please email to pgolani@usc.edu or pabeerel@usc.edu