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标题: Cadence的Instance和Occurrences的区别---原厂说明 [打印本页]

作者: dreambird 时间: 2011-4-27 15:21
标题: Cadence的Instance和Occurrences的区别---原厂说明

这是从Orcad Help摘下来的原文，希望能够为大家提供帮助。

It is important to understand the concept of part instances and part occurrences when using Capture to create your schematic designs.
A part instance is a part you have placed on a schematic page. [url=mk

MSITStore

:\Tools\PPlive\tools\capture\Capture.chm::/Glossary/occurrence.htm]Part occurrences[/url] are created each time the part instance occurs in a schematic that is within the design hierarchy. So, for example, placing a part on a schematic page in your design creates both an instance and an occurrence. You can assign properties to the part instance, in which case the property (and its associated value) will "shine through" to each part occurrence unless the value is specifically replaced by a value on an individual part occurrence.
The [url=mk

MSITStore

:\Tools\PPlive\tools\capture\Capture.chm::/Standard%20topics/Using_the_property_editor.o.htm]property editor[/url] graphically illustrates the state of instance and occurrence properties. (The yellow lines are occurrences, while the white lines are instances.)

[img=32,32]mk

MSITStore

:\Tools\PPlive\tools\capture\Capture.chm::/Capture_Environment/Graphics/otisnote.gif[/img]

Logical and physical view properties from Capture v7.2 (and older) versions map logical view properties into instances, and physical view properties into occurrences.

The instance property values shines through to the occurrence as long as the occurrence property values have not been edited in any way. When you explicitly edit an occurrence property value or when Capture modifies it via one of its tools, the occurrence values overrides the instance value. Only the occurrence value will be placed in the netlist.

If you...	The result will be...
place a part on an unused page in your design	only instance properties on that part.
place one part in the root schematic	one set of instance properties and one set of occurrence properties on that part.
do not modify the occurrence properties on an object	instance properties will "shine through" on the occurrence. The instance properties themselves may be shining through from the library definition (or design cache if the two differ).
edit a part in a library	no affect on the part in any project. Use the Update Cache or Replace Cache command to bring library changes into a design.

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