Virtuoso Schematic Composer User Guide

Creating Symbols

Adding a Selection Box

A symbol selection box defines the area of the symbol that you can use when selecting an instance of that symbol from the schematic editor.

To create a selection box, using the symbol editor, do the following:

1.Choose Add – Selection Box.

The Add Selection Box dialog box appears.

2.Draw a selection box manually, or click Automatic.

To draw the selection box manually, click the first corner of the rectangle, then move the cursor to the opposite corner and click.

1st point

[@instanceName]

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inv

2nd point

To draw the box automatically, click Automatic. The software generates a selection box that encloses all symbol pins and symbol shapes.

Note: You can use the Stretch command to adjust the box shape.

Adding Labels

Symbol labels display assorted textual information. You can add one of three types of labels to your symbol:

Virtuoso Schematic Composer User Guide

Creating Symbols

■Normal labels, which have fixed text

This type of label is generally used to identify the device and pins.

■NLP labels, which have expressions that the editor evaluates to determine the value

When you place an instance in your schematic, the system evaluates the NLP expression and displays the resulting value. For example, the system displays the NLP label [@instanceName] in the symbol editor but displays a value—for example, I3— in the schematic editor.

■IL labels, which have expressions that are evaluated by the SKILL language to determine the value

When you place an instance in your schematic, the system evaluates the SKILL expression and displays the resulting value. For example, the system displays the IL label ilInst~>name in the symbol editor, but displays a value—for example, I3—in the schematic editor.

Symbol editor Schematic editor

Adding a Normal Label

To add a normal label, using the symbol editor, do the following:

1. Choose Add – Label.

Virtuoso Schematic Composer User Guide

Creating Symbols

The Add Symbol Label form appears.

2.In the Label field, type the name of your symbol.

3.In the Label Choice cyclic field, chooselogical label.

4.In the Label Type field, clicknormalLabel.

5.Move the pointer into your design window.

The normalLabel expression is attached to the pointer.

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6.Click to place the label.

When you place an instance of the symbol in your design, the schematic editor displays the label text. To force an evaluation of the SKILL expression or function and display the results, use the Window – Redraw command.

Virtuoso Schematic Composer User Guide

Creating Symbols

Adding an NLP Label

To add an NLP label, using the symbol editor, do the following:

1.Choose Add – Label.

The Add Symbol Label form appears.

2.In the Label field, do one of the following:

Accept the default, [@instanceName]

Type your own expression

3.In the Label Type field, clickNLPLabel. The label choice affects the color of the label.

4.Move the pointer into your design window.

The NLPLabel expression is attached to the pointer.

[@instanceName] Example of an NLP label

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Virtuoso Schematic Composer User Guide

Creating Symbols

5.Click to place the label next to the symbol.

When you place an instance of a symbol in a schematic cellview, the schematic editor interprets the [@instanceName] label and displays the current value of the property.

To force an evaluation of the SKILL expression or function and display the results, use the Window – Redraw command.

The schematic editor evaluates NLP labels using netlisting rules.

Example – Syntax for an NLP Label Expression Containing One Property

[@propertyName : displayFormat1 [: displayFormat2]]

In the example, displayFormat1 is used when a specified property exists, and displayFormat2 (optional) is used when a specified property cannot be located.

If displayFormat2 is not defined and the property does not exist, the editor does not display the NLP label.

The rules table below and the examples that follow the table show how NLP label expressions are interpreted.

Virtuoso Schematic Composer User Guide

Creating Symbols

Examples – Evaluating NLP Label Expressions

If the current value of a named property is defined, the schematic editor substitutes the defined value for the percent character (%) in theNLPLabel expression when you place the instance in the design.

If the schematic editor does not find a value for a property when you place an instance of a symbol, the schematic editor uses displayFormat2.

A label expression represents the current value of a property.

■Example 1 – Basic expressions

[@w:%]

or

[@w]

If you reference only one property in the NLPLabel expression, you specify only the name of the property. When evaluated, the schematic editor returns the value of the property. In Example 1, when w has a value of 8, the editor generates the following label:

8

■Example 2 – Simple expressions

[@w:w=%]

The editor considers any nonreserved characters after the separator (:) to be a text string. When evaluated, the schematic editor returns the string. If there is a special character in the expression, the editor evaluates it also. In Example 2, when w has a value of 8, the editor generates the following label:

w=8

■Example 3 – Compound expressions

[@w:w=%;][@l:l=%;]

In Example 3, if w is not defined andl has a defined value of8, the editor generates the following label:

l=8;

In Example 3, if w has a value of 4 and l has a value of 8, the editor generates the following label:

w=4;l=8;

If you specify a value for w and l after you place the instance, or if you change the value after you place the instance, the schematic editor updates the label to display the current value.

■Example 4 – Combined label expressions