Cadence Tutorial

Schematic Entry with Composer

Authors:  Jeannette Djigbenou, Carrie Aust and Meenatchi Jagasivamani


This tutorial explains how to copy gate & switch symbols into MOSIS library and a procedure for gate-level and switch-level schematic entry. At this point, you should have set up the environment. Otherwise, refer to Setting UP Your Unix Environment. You are assumed to know how to use schematic editor, Composer. If you don't know the schematic editor, follow the on-line tutorial in the cdsdoc. The tutorial for Composer can be opened by typing "cdsdoc" in the command line within your Cadence environment.
Select Docs by ICS 1.415 -> Cadence Platform -> Custom IC design -> Virtuoso Schematic Editor User Guide
If you get an error message concerning the Viewer, start mozilla in your command line first, then attempt to re-open the tutorial. 

  1. Creating a New Library (if necessary)
    • Use a library to store related cell views.  For example, use a library to hold all the cell views for a single project.
      • If you are using the NCSU design kit, you can create a new library from the CIW window (use the Help button to get instructions on creating a new library).
    • To create library from the CIW window (for NCSU kit):

a)  Select File -> New -> Library.
b)  Enter a library name.
c)  Enter the absolute path name if you want the library created somewhere other than the working directory.
d)  Choose the Attach to an existing techfile option.
e)  Choose your library; for instance, for 0.25um in MOSIS DEEP rule, choose NCSU_Techlib_tsmc03d.
f)  Click OK.

  1. Creating a New Schematic Cell View
    • In the CIW window:

a)  Select File -> New -> Cellview.
b)  Choose the library under which you would like to create the new cell view.
c)  Enter a cell view name.
d)  Choose Composer - Schematic as the Tool.  View name should be schematic.
e)  Click OK.
A blank composer - schematic window should open.

  1. Creating Logic Using Gate-Level or Switch-Level Logic
    • Gate-Level

a)  Create an instance of a logic gate from the technology library.

        1. Select Add -> Instance or use the toolbar.
        2. Choose logic gates from the NCSU_Digital_Parts library for NCSU kit. Use the Browse button in the Add Instance Form to choose a symbol view of a logic gate.

b)  Add pins for inputs and outputs.

        1. Select Add -> Pin or use the toolbar.
        2. Enter pin name(s) (You can enter several names at once).
        3. Choose appropriate direction: Input or Output or InputOutput (bidirectional).
        4. Place pin in the schematic.
        5. Click Cancel when done placing pin(s).
        6. Add wires to connect gates and pins: Add -> Wire or use the toolbar.
    • Switch-Level

a)  Create instance of nmos or pmos from the analogLib library.

        1. Select Add -> Instance or use the toolbar.
        2. Choose devices from NCSU_Analog_Parts for the NCSU kit.  Use the Browse button in the Add Instance Form to choose a symbol view of a CMOS device.
        3. Enter values for device parameters in the Add Instance Form.
          • Model Namefrom NCSU_Analog_Parts for the NCSU kit,  N_Transistors (or P_Transistors) -> nmos4 (or pmos4) in the component browser; note that for NCSU kit, single-click (not double-click) in the component browser window chooses the device, and also, VDD and ground connections are also available under "supply nets" category in the component browser.
          • Bulk Node Connection: vss! for nmos device or vdd! for pmos device.
          • Width: Your chosen width (example: 600nm, 2.4um, or as necessary)
          • Length:  Your chosen length.

b)  Add wire to source of nmos/pmos and type "l" to add wire name as VDD! and VSS!.
c)  Add pins for inputs and outputs.

        1. Select Add -> Pin or use the toolbar.
        2. Enter pin name(s) (You can enter several names at once).
        3. Choose appropriate direction: Input or Output or InputOutput (bidirectional).
        4. Place pin in the schematic.
        5. Click Cancel when done placing pin(s).

d)  Add wires to connect gates and pins:  Add -> Wire or use the toolbar.

  1. Use Check and Save to save design.  Select Design -> Check and Save or use the toolbar.  Errors will be displayed in the CIW.  Correct any errors.
  2. Further instruction is available in cdsdoc.  To view Composer tutorial:

a)  At the UNIX command line, type:  cdsdoc
b)  After the cdsdoc window has appeared, select Design Entry -> Composer Tutorial.  Scroll through the contents to find the subjects of interest.

Have fun!