Extraction Stop Level

The extractStopLevel environment variable controls the Extract connectivity to level option in the Connectivity form, increasing the visibility of the extractor into the design hierarchy.

For example, an overlap between a top-level shape and a hierarchical shape at level “N” is processed by the extractor only if the extraction stop level is equal to or greater than “N”. However, if the hierarchical shape is a pin figure, it is visible from the top level even if the extraction stop level is “N-1”.

Likewise, an overlap between a hierarchical shape at level “N” and a hierarchical shape at level “M” in the hierarchies of two different top-level instances is processed by the extractor only if the extractStopLevel is equal to or greater than the greater of the two levels, “N” and “M”.

In the context of top-level extraction, the connectivity of a hierarchical shape is the net attached to the corresponding top-level instance terminal (if any). This top-level connectivity is established by recursively iterating in a bottom-up series from terminal to instance terminal, starting from the net attached to the hierarchical shape.

The greater the extractStopLevel, the more accurate is the extraction. For example:

• Top-level nets that are incomplete with extractStopLevel=0 may become complete with extractStopLevel>0. For example, a top-level shape on a given net overlaps a hierarchical shape that has its top-level connectivity defined by an instance terminal on the same net. The resolution of the open violation, in this case, happens only if the hierarchical shape is visible, implying that the extraction stop level is sufficient, which is achieved at an extraction stop level greater than 0.
• There is a better detection of shorts between top-level and hierarchical shapes.
• There is a better detection of shorts between different instances.
• Trim shapes have the same visibility as regular shapes. They are visible down to extractStopLevel.
  Trim shapes on a pin are visible down to extractStopLevel+1. There is an exception for a pinFig at extractStopLevel+1. Here, the trim shapes in the same master are seen as stopping the pinFig even when the trim shapes are actually at extractStopLevel+1.

The extractor attempts to bind the instances that are in the hierarchical depth defined by the extract stop level. By default, the extract stop level is 0. Therefore, the extractor tries to bind all the top-level instances to their corresponding master.

Whatever the extractStopLevel, the extractor only ever extracts the current top level; that is, it only changes the connectivity of objects or creates markers at the top level of the design.

Related Topics

extractStopLevel

Connectivity

Extracting Hierarchical Cellviews

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