Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

Overriding Bus Spacing

You can override the current spacing for gathered bus wires and make the spacing change take place immediately on the layer you are routing, or you can have the change take place when you add a via pattern and change routing layers.

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

The Route Options form appears.

2.Do one of the following:

If you want the new spacing to take effect immediately on the current routing layer, choose Use Override and type a new spacing value in the Override Value field.

If you want the new spacing to take effect on the next routing layer after you add a via pattern, choose Use Override On Next Via and type a new spacing value in the Override Value field.

3.Click OK.

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

Note: If you want to return to the default spacing value while routing the multiple paths, choose Ignore Override.

Rotating the Bus Cursor

When you gather wires, the bus cursor automatically orients perpendicular to the set of active wire segments.

To rotate the cursor, do the following:

While routing, press Control and click right.

The cursor will toggle back and forth between horizontal and vertical each time you press Control and click right.

After you rotate the bus cursor, the cursor orientation stays fixed for the current routes. If you want to change the orientation, you must use the command again.

Cycling the Control Wire

As you are routing multiple wires, your cursor will be pointing to a wire segment called the control wire. The control wire serves as a pivot point and allows you to control the position of via patterns by changing which wire segment the cursor attaches to as you route the set of wires. By default, the center wire is the control wire and is visually identified by a white outline on the end of the control path.

To cycle the control wire, do the following:

While routing, press Shift and click right.

Repeatedly using this command cycles the control wire between the two outermost wires and the center wire of the set.

Working with Insufficient Routing Space

If there is insufficient routing space for all the wires of a multiple wire set, you can drop wires and finish routing a portion of the wires or have no new wire segments added.

To drop wires and route a portion of the wire set, do the following:

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

As many wires as possible are routed and the rest are dropped. The dropped wires are replaced by guides drawn from the last digitized locations to pins on their respective nets

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

and you can continue routing a subset of wires. However, even with the option set on, no new segments are added if there is insufficient space to route at least one wire of the set.

If wires are dropped you can use the Picking Up Dropped Wires command to restart the set from a new location and reroute the dropped wires.

To have no new segments added, do the following:

From the Layout pop-up menu, choose Route Only If All Succeed.

No new segments are added if there is insufficient routing space for all the wires of the set.

Picking Up Dropped Wires

If you chose Route As Many As Possible from the Layout pop-up menu, wires that can cause violations are dropped as you route a multiple wire set. You can restart some or all of the dropped wires at the currently digitized location of the set. Only the wires that do not introduce violations are restarted, and guides are drawn from the new locations back to the locations from which these wires were dropped. You can then route the set of picked up wires from the new locations.

To route the dropped set of wires, follow these steps:

1.Click to digitize the locations of the undropped wires.

2.From the Layout pop-up menu, choose Pick Up Dropped Wires.

All the wires of the set that do not create violations restart at locations consistent with the currently digitized locations.

3.Continue routing the set of wires.

4.After you complete the routing of the dropped wires, you must route each dropped wire from the location where it was dropped to the location where it was restarted.

Allowing Redundant Wiring

Redundant wiring requires two steps. The first step is creating wire. The second step is editing the wire and creating a loop or crossing over the wire by adding an additional wire.

This is considered redundant wiring and by default is not allowed. You might need redundant wires on selected nets for increased current capacity or to create power rings. Redundant wiring is permitted on nets when Allow Redundant Wiring On Enabled Nets is turned on and the allow_redundant_wiring rule is attached to the net.

Virtuoso XL Layout Editor User Guide

Wire Editing in the Virtuoso XL Layout Editor

Note: Self intersecting wires are allowed by default. When you create a path and cross over the path in one step, this is considered a same-net violation and by default is not checked.

For more information about same net violations, refer to “SameNet Checking” on page 376.

To allow redundant wiring, follow these steps:

1. Create a .do file with the following syntax:

rule net netName (allow_redundant_wiring on)

You can also apply the allow_redundant_wiring rule to a class of nets. For example:

rule class className (allow_redundant_wiring on)

2.Load the .do file.

For more information about loading .do files, refer to,“Loading .do Files” on page 417.

3.From the Route Options form, turn Allow Redundant Wiring On Enabled Nets on. Wire loops will be allowed on nets with the attached allow redundant wiring rule.

Allowing Orthogonal Jogs

You can permit orthogonal jogs in existing paths when they are pushed with the Create Path,

Stretch, and Pull commands by selecting Allow Orthogonal Jogs. The Push Routing option must be on to enable path pushing. By default, Allow Orthogonal Jogs is turned on.

To permit orthogonal jogs, do the following:

From the Route Options form, turn Allow Orthogonal Jogs on.

To prevent orthogonal jogs, do the following:

From the Route Options form, turn Allow Orthogonal Jogs off.

Figure 11-1 Orthogonal Jogs