Working with Properties

Capture uses properties to describe objects. Imagine a brown, ceramic capacitor that measures 6 millimeters in height. Type, color, and height are properties, while ceramic, brown, and 6 millimeters are property values. Every Capture object is made up of such name-and-value pairs.

Inherent and user-defined properties

Some properties, called inherent properties, are an essential part of an object; others, called user-defined properties, are not used by Capture, but may be used by another tool. For example, if you want to include the supplier and the price per hundred for the objects on your schematic pages, you create two user-defined properties for the objects. You can add as many user-defined properties to objects as you like, and you can remove user-defined properties when you find that you do not need them. Graphic objects such as lines, ellipses, and rectangles do not support user-defined properties.

Creating and adding properties

When you create a user-defined property with the Edit Part Properties dialog box, you can make the property name visible and specify the font and location of the property value text, even before you specify the property value. The property name acts as a placeholder until you supply the property value.
When you add a user property to an existing object using the property editor, you can assign the property value at the time you create the new property or later. The additional benefit to using the property editor is the flexibility with which you can edit all properties on an object or group of objects on a schematic page.
Once you have added properties to a part on a schematic page, its properties no longer match the properties of the same part residing in the library. This part on the schematic page is unique, in that it has properties assigned specifically to it that are not inherited from the library part definition.
The property editor window shows you all available properties in the new single view. You can use the tabs to edit properties of all selected objects from the property editor. The property editor also displays all library definitions, instance properties, and occurrence properties for an object.

Properties in the design cache

When a part is first placed on a schematic page, a copy of the part and its library properties is put into the design cache from the library. A few of the library properties, such as PCB Footprint and Value, are also copied as instance properties onto the placed part. The rest of the library properties “shine through” from the cache to the instance and occurrence of the part property.
“Shine through” is indicated by hash marks in the cell. In the property editor, you can assign an instance or occurrence value, creating an instance or occurrence property. This instance or occurrence property then will override the shine-through definition.

Instance property

An instance property is a user property applied to the placed instance of a part or symbol in the design. This includes PCB Footprint, Value, and Name properties of each placed part or symbol in a design. This is the same as the user properties displayed and editable from the Capture Logical view.
An instance property will "shine through" to all occurrences of that instance unless it is overridden by occurrence properties that you have edited. A change using any of the tools, like Annotate, also may update the instance property.

Occurrence property

An occurrence property is a user property applied to a particular occurrence of a placed instance of a part or symbol in a design. This is the same as the user properties displayed and editable from the Capture v7.2 Physical view.
The spreadsheet will expand to display occurrence properties if values are different from the instance shine through value; otherwise, the rows are hidden from view. To quickly hide or display all the occurrence properties, press and hold the CTRL key while clicking on one of the plus (+) symbols in the property editor.

Push Occurrence Properties into Instance Utility

Suppose that you copied a circuit or part of a circuit from design A and pasted it in design B. You might see occurrence and instance level properties with different values on the pasted parts in design B. In previous releases of Capture, you had to invoke the property editor on each part, copy and paste the occurrence property values of the Part Reference, PCB Footprint property and any other property as instance property values, and remove occurrence properties.
The Push Occurrence Properties into Instance Utility allows you to automatically do this. It automatically:

• transfers occurrence property values of the part reference and PCB footprint properties as instance level property values
  
  • removes all occurrence properties from the design and sets the preferred mode of the design to instance (if you select the Remove occurrence level properties check box).
• transfer occurrence property values of flat nets to schematic nets.
  To run this utility, from the Accessories menu in Capture, choose Push Occ. Prop into Instance, then choose Transfer Occ. Prop. to Instance.
  See Push Occ. properties to instance dialog box for more information.

Combined property strings

With many of the tools in Capture, such as Create Netlist and Annotate, you use combined property strings to convey information to the tool or to limit the tool's action.
A combined property string consists of one or more property names, enclosed in braces, and can also contain literal text. Capture combines the values of the named properties with any literal text to create a string. An example is:

{Value}{Reference}

where "Value" and "Reference" are property names. Using this combined property string and a part with a part value of 74LS32 and a part reference of U?A, Capture creates the string:

74LS32U?A

You can include spaces and other characters in the combined property string, as in this example:

Part: {Value} ({Reference})

Using this combined property string and the same part, Capture creates the string:

Part: 74LS32 (U?A)

Different tools use combined property strings in different ways. For example, Annotate uses one to compare parts---if one part's combined property string matches another part's combined property string, it packages the parts together.

Bill of Materials and other commands on the Tools menu that generate an output file based on a combined property string may produce errors if you include extra curly braces.

You can include tabs in combined property strings, so that the output file can be manipulated in a spreadsheet or database application. Tabs also help format report files, such as those created by the Bill of Materials command.

Wherever you want to have a tab in the output file, insert the characters \t (a backslash and a lowercase "t") in the combined property string.

Certain properties can be edited, but not removed. These are called inherent properties, and are listed in the table below.

In this section:

• Defining Properties
• Editing Properties
• Importing Part and Pin Properties
• Exporting Part and Pin Properties