Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

The layout window prompts you to enter a point or select an area to start the path.

2.From the Layout pop-up menu, choose Set up.

3.Click the Bus tab.

4.Turn on Enable Tandem Pair.

5.Click or area select the adjacent connectivity objects of the layer pairs you want to route.

The Choose which layer to use form appears.

6.Choose a layer and click OK. Paths are routed on both layers.

7.Digitize points where you want to route the path.

The paths are gathered and overlaid at the first digitized point.

Using Vias

You can change layers and add vias while routing individual paths or you can change via patterns while routing multiple paths.

This section describes

■Changing Layers and Adding Vias

■Using Vias Patterns on Multiple Paths

■Legal Via Sites

■Rotating Vias

Changing Layers and Adding Vias

To change layers and add a via while routing, do one of the following:

■From the Layout pop-up menu, choose Add Via.

The Add Via form appears and all available vias and routing layers that can be reached from the current routing layer are displayed. Choose the applicable layer you want to switch to or choose a via type on the layer.

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

Inaccessible layers are grayed out.

Vias will be added to the last digitized point.

■Press the space bar.

If only one layer and one via are available for selection, vias are placed and the layer is changed to the only available layer. If the current routing layer has more than one layer available for selection, the Add Via form is opened for you to choose a layer or via type.

If you try to add vias to locations that violate design clearance rules, you can use Via Assistance to display Legal Via Sites.

Using Vias Patterns on Multiple Paths

The procedure for adding a set of vias when routing multiple paths is the same as the procedure for adding individual vias, but the result is that multiple vias are added simultaneously in a predefined pattern. You can choose from several predefined via patterns:

Perpendicular, Diagonal 1, Diagonal 2, Stagger, Out Taper, and In Taper.

To add vias and choose via patterns while routing multiple paths, follow these steps:

1. From the Layout pop-up menu, choose Via Pattern.

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

The Via Pattern pop-up appears.

2.Click the icon of the via pattern you want to use.

Diagonal 1 is the default via pattern. The display indicates how the pattern would be placed for the current routing direction.

If the selected via pattern cannot be placed, single circles are displayed indicating the via site are not legal. Use the Fit Via Pattern option to search for nearby available via sites for those vias that have clearance conflicts. For more information, refer toLegal Via Sites.

Adding Vias to Gathered Bus Wires

The following are guidelines for adding vias to gathered buses.

When the bus wire spacing is set to the following:

■wire-via

Use any via pattern except the perpendicular pattern to keep the wires from spreading.

■via-via

Use all patterns without spreading the wires.

■wire-wire

All via patterns are likely to spread the wires (if the wire-wire clearance rules specify the smallest spacing possible).

After the vias are added, the wires will gather back to minimum wire spacing.

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

Note: For non-gathered bus wires, if the required via spacing differs from the minimum wire spacing, the wires are spread to accommodate the via spacing and the new via pitch is used as the new wire spacing.

Legal Via Sites

A legal via site is a location where you can add a via during routing and not violate design clearance rules.

When the add via operation fails, you can use Via Assistance to display legal via sites.

When vias are placed using Via Assistance, via pattern resembles the original pattern but with some via positions modified. IfSnap or Display are turned on, legal via sites are displayed as concentric circles. Single circles are via sites that are not reachable from the current digitized location.

■If Via Assistance is off, no via sites are displayed when you try to add a via to an illegal site.

■If Snap is on and the digitized point is within one via radius of a legal site, the tool routes to the legal via site and adds a via. If it is not within one via radius, legal via sites are displayed and no via is added.

■If Display is on and the last digitized point is a legal site, a via is added. If it is not a legal via site, nearby legal via sites are displayed and no via is added.

Rotating Vias

Use the Rotate button on the Add Via form to rotate vias 90 degrees as you place them. If the last digitized point is on or within one via radius of a legal site, a rotated via (or via pattern for multiple paths) is added automatically. Otherwise, the legal via sites in the area are displayed (when Via Assistance is on), and you can click one of them to add the rotated via or via pattern.