Specifying Cover Obstructions

You use the Cover Obstruction tab to create cover obstructions in your soft block. Cover obstructions are defined at the layer level. When you create a cover obstruction, the selected layer and all lower layers are automatically obstructed. For example, in the following diagram, Metal 1 is the lowest layer and Metal 6 is the top most layer. Adding a cover obstruction on Metal 3 will generate obstructions on layers Metal 3, Metal 2, and Metal 1. As a result, routing cannot be done on these layers.

This type of obstruction is typically generated for layers where you want to prevent over-the-cell routing to improve performance or to avoid electrical effects between tracks.

A soft block can be associated with only one cover obstruction. So, any new cover obstruction that is created on a soft block replaces the existing cover obstruction (if any) on it.

Use LayerHalo obstructions to block routing at the child-level. These obstructions are effective at the parent-level.

Following are the steps to create a Cover Obstruction:

1. Click the Cover Obstruction tab in the Attributes pane.
   
   
2. Select the layer on which you want to create an obstruction in the Select a Top Layer pane and click the Create button.
   
   
   The selected layer and lower layers are automatically populated in the Obstruction Applied on Layers pane.
   
   
3. To allow power and ground nets, check the Allow PGNet box.
4. Click Save Soft Block.

SKILL Functions

Alternatively you can use the following SKILL functions:

• cphSbDefineCovObstruction: To define cover obstructions
• cphSbDelCovObstruction: To delete cover obstructions
• cphSbDisplayCovObstructionInfo: To display information about cover obstructions
• cphSbHasCovObstruction: To check for the presence of cover obstructions in a soft block

Related Topics

Comparison between LayerHalo and Cover Obstructions

Soft Block Mode in the CPH Window

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