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Creating a Schematic



This step may be trivial if you have experience with designing circuits in Cadence. If you wish to skip this step, make sure you use a schematic that uses only cells from the standard cell library you will be routing with. In the case of this tutorial, the OSU_diglib_ami06 library created at The Ohio State University will be used.

Create Design Library
  1. First, a design library will be created to contain all your design files. After starting icfb & in your Cadence working directory, the Library Manager should appear. In the Library Manager window, select File -> New -> Library.
  2. When the Create Library windows opens, enter the Name: of the design and select the option Attach to existing tech library. Select the tech library AMI 0.6u C5N from the menu. The window should look something like this:



    Click "OK" when done.
  3. Now, create a schematic in the new library by clicking on the new library in the Library Manager and selecting File -> New -> CellView.
  4. Name the cell in the Cell Name box and make sure the Composer-Schematic tool is selected and the View Name is set to "schematic." Click "OK" when done. The Virtuoso Schematic Editor should start.
  5. To add standard cells to the schematic, type "i" in the Virtuoso window to create an Instance. The Component Browser should open. Under the Library option select OSU_diglibimport_ami06. The cells available under that library should now be listed. This library is chosen, rather than the regular OSU_diglib_ami06, because of the special abstract cells contained in this library that will be used later in this tutorial.



  6. Selecting one of the cells and then clicking on the schematic window will place the cells into the window. Type "i" again to change the type of cells you wish to place on the schematic.



  7. To add wires to the schematic, press the "w" key and left-click on each point you wish to connect. Hit "escape" to stop placing that wire.
  8. To add input and output pins to the design, type "p" and fill out the form by adding the pin name and specifying whether it is an input or output in the Direction field. Place the pin by left-clicking where you want the pin to go on the schematic.







  9. Be sure to periodically check and save the schematic by selecting Design -> Check and Save in the Virtuoso Schematic window.
  10. This schematic can be tested using Analog Artist, however simulating this schematic is outside the scope of this particular tutorial.


For this example, a simple First In/ First Out string of D flip flops are put together using DFF_S cells as shown below.



The next steps will take this design and create an automatically generated silicon layout that can be fabricated.
Main Next: Automatic Placement

2003 James Copus