Virtuoso XL Layout Editor User Guide

Using the Virtuoso Custom Placer

The second value sets the maximum number of devices in a stack.

The example below sets all of the device chaining and stacking parameters to their default values.

layoutXL lxDeltaWidth float 0.0

layoutXL lxWidthTolerance string "(0.0 0.0)" layoutXL lxAllowPseudoParallelNets boolean nil layoutXL lxStackPartitionParameters string "(1 8)"

Defining the Boundary Layer (Placement Region)

The boundary shape defines the placement region. You specify the name of the boundary layer-purpose pair at several points in the placement and routing design flow. It is important that you identify this layer-purpose pair consistently. You identify the boundary layer in the boundary translation rules for the Virtuoso custom router, and you create the boundary shape either with the layout generation commands or by drawing a shape. When you draw the boundary layer shape, or when you define it during layout generation, be sure to use the same layer-purpose pair that you specified in the translation rules.

Important

If the iccLayers are not defined in the technology file you will receive the following error messages in the Placement Status window:

*ERROR* No boundary layers defined in placer rules, placement cannot continue.

The boundary layer shape must be a single rectangle or polygon. If the boundary layer consists of more than one shape, or a nonorthogonal shape, the translator exports the enclosing bounding box as the boundary.

Note: The default layer-purpose pair in the translation Rules Editor is

prBoundary drawing. The default layer-purpose pair during Virtuoso XL layout generation is also prBoundary drawing.

Abutting Standard Cells

Standard cells are typically defined with a component class type ofSTDCELL. During automatic placement, standard cells are treated somewhat differently than regular devices. Because of this, there are up front design considerations for proper standard cell abutment.

To achieve optimal placements quickly, standard cells are considered to be correct by construction. That is, all standard cells are designed to be abutted without creating design