WORKING WITH SYMBOLS

If you want to use your design in other schematics, you need to create a symbol for it.
This is equivalent to the use of subcircuits in HSPICE. It gives a hierarchy to your project, making it easier to organize.

Creating a new symbol

First, in your schematic, remove any superfluous components that you have used in the previous example for the simulation (vdc for the power supply and for the input signal). Also remove the capacitor. These components will be defined again later.

Assign input and output pins:

Create->Pins
Type the pin name, such as Vin, select the direction as "input", and place it in the schematic. Do the same for Vout, selecting the direction as "output".

The schematic will look like this:

Figure 1: Inverter schematic with pins.

As a side comment, note that the net names changed and have now the same name as the pins.

Next, create the symbol:

File->Check and Save
Create->Create cellview->From cellview, click OK.

A new window will open with the symbol view. By default, the symbol shape is a rectangle, but we can change it. Since this design is an inverter, we will draw a triangle and put a small circle at the output. To do this, use:

Create->Shape
There are several shapes available: line, rectangle, circle, etc.

You will want to delete the green rectangle, draw the new shape, and move the terminals to new positions. The editing commands are similar to what you had for the schematic window.

You will also need to change the Selection box (the red rectangle), which defines the limits of the symbol. This can be done automatically by:

Create->Selection box
A window appears with only one button: "Automatic". Click it and the selection box will automatically adjust to the limits of your symbol.

Don't forget to check and save. The symbol may now look like this:

Figure 2: Inverter symbol.

You can now close the Symbol Editing window. It wont be necessary anymore.

Using the symbol in other schematics

Create a new schematic, using the instructions described in Create a new cell. Give a name such as test_inverter.
You place this symbol in the new schematic in the same way that you placed any other components, with:

Create->Component
This time changing the Library to your library and clicking on Uncategorized. Your symbol should be here.

Now, you can define power supplies in the new schematic. If you place new vdd and gnd components, they will be implicitly connected to the correspondent vdd and gnd components that are inside the inverter.
For simulation, you can connect a 'vdc' to the input terminal of the inverter, and a capacitor at the output terminal.
Here is an example of a possible setup:

Figure 3: Using the inverter symbol in a new schematic.

To move in the hierarchy, select the inverter, and then:

Edit->Hierarchy->Descend Edit
You can choose the schematic or the symbol for editing.

To return to the previous schematic, use:

Edit->Hierarchy->Return

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