Blockage Halos

A blockage halo defines an area around an instance that cannot overlap the placement blockage.

• Placement halo: A placement halo is a type of blockage associated with an instance or a master, representing an area around the master’s PR boundary. The shape of the halo is determined from the shape of the PR boundary of the master and the given offsets, and it is automatically updated to reflect changes in the master’s PR boundary.
  The placement halo is most commonly used to prevent standard cells from being placed within a certain range of an instance. This is usually done to make sure there is enough space to properly route to the presumably large number of pins on the side of a block.
• Layer halo: A layer halo is a type of blockage associated with an instance or a master, representing an area on a given layer around the master's PR boundary. The shape of the halo is determined from the shape of the PR boundary of the master and the given offsets, and it is automatically updated to reflect changes in the master's PR boundary.
  The oaLayerHalo applies around the perimeter of an instance. It prohibits routing on the given layer parallel to the edge of the instance, but it allows routing perpendicular to the instance edge. This prevents long lines being routed parallel to the edge of the instance, which causes cross-coupling. However, it allows routing straight into the pins. Since power lines do not switch, they can be routed anywhere within the halo area.

You can create a blockage halo by using the Halo Editor form. You can access this form by clicking the Define Halo button in the Create Instance form or the Create P&R Boundary form.

Related Topics

Halo Editor Form

Create Instance Form

Create P&R Boundary Form

Creating a Blockage

Blockages