1. Introduction
2. Setting up
the environment
3. Starting Cadence
4. Library Manager
5. Creating new library
6. Creating new cell
7. Schematic Composer
8. Creating Symbols
9. Logic Simulation with
Verilog-XL
10. Custom layout with
Virtuoso
11. Layout Extraction
12. Layout Vs. Schematic (LVS)
13. Abstract view
To create a two input NAND gate, we need two NMOS, two PMOS, ground net, vdd net and three I/O pins.
First, we want to place all the NMOS. Click Add -> Instance... in "Virtuosos Schematic Editing" window (or type i on the keyboard for shortcut).
Two windows will pop out: "Add Instance" and "Component Browser"
In "Component Browser" under Library, choose NCSU_Analog_Parts.
To get the NMOS, choose N_Transistors. In the same window, click nmos.
"Add Instance" window will now look like the following. You can change the property of this NMOS now, however, we will show how to change the properties of the instances later in this page.
You can now place your NMOS on your schematic by left clicking your mouse at a desired location on the schematic. Remember you need two of them for two input NAND gate.
To get PMOS, go back to "Component Browser" (you may need to click on (Go up 1 level) to go back up for P_Transistor) and click P_Transistor. Click on pmos and your "Add Instance" window will look like the following.
Again, place your PMOS where you want them to be in your schematic.
Now it is time to add Supply Nets to your schematic.
Go back up one level and click on Supply Nets.
click on vdd, place it on the schematic, and do the same thing for gnd. Your schematic should look something similar to this.
We also need pins for the schematic. We need two input pins and one output pin. To acquire pins, click on Add -> Pin... (or you can use the shortcut by typing p on your keyboard). An "Add Pin" window appears. For our input, we use pin A and B. For output, we use pin Z. Make sure the Direction of your pin is set correctly. Here is an example of our input.
This picture shows example of output pin. You can place the pins same way as placing instances.
Now it is time to add wires. To acquire wires, click on Add -> Wire (narrow) (or again, you can type w on your keyboard). Click on the red pins on your instances to connect the wires. Your schematic should look similar to the one below.
We are almost done with the schematic. Now
it is
time to change the properties of our instances.
First we need to highlight the instance we want to change. You can also hold
"Shift" key to select
multiple instances.
Click on Edit -> Properties -> Objects... (or simply type q)
If you want to change multiple instances at a time, you can select the option
all select to make your job easier.
In the next screen shot, we have changed two PMOS to have width equal 800n M.
You should now do the same thing to NMOS and change its width to 600n M.
After changing instance properties to a
desired one, you need to Check and Save your progress. Below is an
example of our final cell schematic.
Again, you can Check and Save by clicking on Design -> Check and Save
or you can just type f8 on your keyboard.
When everything is working fine, you should have no errors showing in your CIW window.
