Virtuoso Schematic Composer User Guide

Creating Schematics

Getting Started with Schematics

One of the best ways to begin a schematic in an empty window is by adding objects in a certain order, as indicated below:

Adding Instances

You can add instances to your design using several methods with different options.

■What Is an Instance? on page 130

■Methods of Adding an Instance to Your Design on page 130

■Adding Instances One by One on page 131

■Adding Instances by Rows and Columns (an Array) on page 133

Virtuoso Schematic Composer User Guide

Creating Schematics

■Adding Instances Using an Iterative Expression on page 136

■Changing the Default Instance Name Prefix on page 138

■Editing Instance Masters on page 138

■Specifying the View to Use While Placing the Instance on page 139

■Changing the View after an Instance Is Already Placed on page 139

■Renumbering Instances on page 139

Virtuoso Schematic Composer User Guide

Creating Schematics

What Is an Instance?

An instance is a database object that represents a master symbol cellview. When you add an instance to your design, you actually create a reference of the master symbol from a reference library.

Instance name

You can have several instances of the same master symbol cellview in a design, but the instance name must be different. For example, the nand3 gate is a master symbol stored in the Cadence® sample library. Each time you add a nand3 gate to your design, you add an instance of the nand3 master. The instance names can be I1, I2, I3, and so forth.

Related topic: patchcords

Methods of Adding an Instance to Your Design

Plan to place instances

■One by one

■By rows and columns (an array)

Virtuoso Schematic Composer User Guide

Creating Schematics

■By using iterative expressions

Adding Instances One by One

The Add – Instance command lets you place multiple copies of a single instance in a schematic, based on a single lib/cell/view name.

To add instances singly in your design window, do the following:

1. Choose Add – Instance.

Virtuoso Schematic Composer User Guide

Creating Schematics

The Add Instance form appears.

2.In the Library, Cell, and View fields, specify the cellview of the instance.

You can also click on the Browse button to assist you in finding the cellview you want to add.

You can designate the Browse button to open either the Component Browser or the Library Browser. If the cell you want does not exist, you need to create it using the symbol editor.

If you do not add instance names in the Names field, the system generates default instance names prefixed with the letterI.

3.Move the pointer into your cellview.

The instance appears attached to the pointer.

4.Click in your cellview to place the instance.

The Add – Instance command is modal (if modal mode is turned on) and continues to prompt you to add another instance. To stop generating instances, press the Esc key, press Control-c, or choose another command.