Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

Routing Paths

When wire editing is enabled you can route design-rule-correct single or multiple paths between connectivity objects. While routing, you can insert vias to change the routing layer and push aside routes and components, depending on the options you have set.

You can use the middle button Layout pop-up menu to access routing options. For details about setting up the routing environment and controlling the routing style, refer to “Routing Options and Styles” on page 379.

Routing a Single Path

To create a single path, follow these steps:

1.From the layout window, choose Create – Path.

When routing paths, you can use the middle button to open the Layout pop-up menu and change the width of a path or Matching Path Width and Pin Widths to the path you are editing.

2.Click or area select a connectivity object (pin, via, or an existing path).

Flight lines appear showing the connectivity of the selected net, and the status bar shows the name of the selected net.

When starting a path from a pin or an existing path, the routing layer is changed to the same layer as the pin or path. When starting a path at a coordinate where there are overlapping layers or from an object with more than one layer, such as the source or drain

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

of a MOS device, a dialog box appears showing you the selectable layers and prompts you to choose one.

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

Paths and vias are prevented from creating violations and will push aside other paths and vias if Push Routing is on. By default, Push Routing is on.

Components will be pushed aside by paths and vias when there is insufficient routing space if Push Components is on. By default, Push Components is off.

For information about changing layers, refer to “Changing Layers and Adding Vias” on page 394.

For information about checking for violations, refer to “Preventing and Checking Design Rule Violations” on page 375.

4.Finish the path by doing one of the following:

From the Layout pop-up menu, choose Finish Routing.

The connection will be finished from the last digitized point. An area for the path must lie within the routing search area or the automatic operation is terminated. Some connections may require layer changes and vias to be added in order to finish the connection.

Continue digitizing points to complete one or more connections.

Double click or press the Return key.

The path is terminated where the cursor is positioned.

Note: To erase the segments you draw, press the Back Space key. Each time you press Back Space, the last digitized segment is deleted.

Routing Multiple Paths

You can route arbitrary path sets, buses, differential pairs, and bundles. All multiple path routing is considered bus routing. Differential pairs and bundles retain their association after

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

routing is completed. In general, only connections that use the same layers and vias can be routed together. The exception is tandem layer routing.

For details about setting up the routing environment and controlling the routing style for buses, refer to “Routing Options and Styles” on page 379.

When routing multiple paths, follow these steps:

1.From the layout window, choose Create – Path.

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

2.Select adjacent pins, vias, or existing paths.

You can Shift-click to add additional objects to your selection set.

Flight lines appear showing the connectivity of the selected nets, and the status banner shows the names of the selected nets.

Note: Enable Bus Routing must be turned on in the Routing Options form – Bus tab.

The default setting for Enable Bus Routing is on.

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

Paths starting from pins that are not at minimum spacing will be gathered to the minimum separation at the first digitized point. To gather bus wires before the first digitized point, you can turn gathering bus wires on and also specifying the spacing of wires.

When routing multiple paths, the pointer attaches to a control wire. Cycling the control wire can help you when you are changing the routing direction to avoid obstacles.

For more information about change layers, refer to “Using Vias atternsP on Multiple Paths” on page 395.

4.Finish the paths by doing one of the following:

From the Layout pop-up menu, choose Finish Routing.

The connections will be finished from the last digitized point. Some connections may require layer changes and vias to be added in order to finish the connection. An area for the path must lie within the routing search area or the automatic operation is terminated.

From the Layout pop-up menu, choose Route As Many As Possible

If routing space is limited to fewer than all the path segments of the set, you can choose to automatically drop the paths that cannot be routed, or have no new segments added. For more information, refer to “Working with Insufficient Routing Space” on page 384.