Layer Transitions

Lets you select a layer on which you want to create a via stack

Rotate Via(s) Cut Pattern

Rotates the via cuts and swaps the rows and columns, if any, while rotating the via shape by 90 degree as you place or drag the via. You can also rotate pending vias by clicking the middle mouse button. However, the top and bottom via shapes are not rotated.  This option is  available both in Create Stranded Wire Form and Create Bus Context-Sensitive Menu.

Via Alignment

Enables you to align vias as they are digitized during wire or bus creation. You can choose to align a via either automatically or by selecting a custom alignment option. Vias are aligned between the edges of via enclosure shapes and the edges of the connecting wires on the same layer. For example, for a Metal1 to Metal2 via, the via location is adjusted in a way that the Metal1 wire edge is aligned with the Metal1 via enclosure and the Metal2 wire edge is aligned with the Metal2 via enclosure. The alignment offsets the via origin to maintain it at the intersection of the wire end points. If you are adding and aligning a via stack, the same via alignment is applied to all the vias in the stack.

You can also access the via alignment options from the Create Stranded Wire Form.

Automatic

Automatically aligns the digitized via with respect to both the existing and the new pathSeg. By default, this check box is not selected. After you select the check box, it remains selected for the remaining session while you digitize more vias.

When the check box is selected, the default alignment of the next via is calculated automatically. When the check box is not selected, the default alignment of the next via is Center Center (see Override option setting).

Automatic via alignment is not supported while routing a bus.

The following figures illustrate the automatic via alignment in three different scenarios based on the directions in which the next pathSeg of the wire is added.

For orthogonal transitions

Controls alignment behavior for orthogonal transitions.

• align to incoming and outgoing layers aligns to the edges of both incoming and outgoing layers. This is the default option.
• align to incoming layers aligns to the edge of the incoming layer only.
• align to outgoing layers aligns to the edge of the outgoing layer only.
• do not perform automatic alignment, if selected no alignment is done for a via.

Environment variable: autoViaAlignmentOrthoTransitionBehavior

For collinear transitions

Controls alignment behavior for colinear transitions.

• align to incoming and outgoing layers aligns to the edges of both incoming and outgoing layers. This is the default option.
• do not perform automatic alignment, if selected no alignment is done for a via.

Environment variable: autoViaAlignmentColinearTransitionBehavior

Override

Enables you to specify a custom via alignment option that overrides the automatic alignment. The Override buttons are available only if you click a target layer button.

Each Override button carries the image of two pathSegs—blue and red—and a rectangular via. The two pathSeg colors indicate two layers. You move the wire you are creating from one layer to the other after digitizing a via. The image on the button represents the alignment of the via with respect to the two layers. Clicking a button displays a check mark on the button; the check mark is cleared when you digitize a via with the selected alignment setting. The Center button is available only if the Automatic check box is selected.

Environment variable: viaAlignment

Clear

Removes the check mark displayed on the selected Override button.

Via Pattern

Helps you specify a pre-defined manner in which multiple vias can be added simultaneously when routing multiple wires.

Environment variable: viaPattern

Mode

• Auto No Crossing: Automatically places the vias in a diagonal pattern in such a way that bus wires do not cross when making orthogonal transitions. This pattern retains the bus bit order and might prevent the wire editor from creating jogs if Via Alignment is on.
• Auto Crossing: Automatically places the vias in a diagonal pattern in such a way that bus wires do cross when making orthogonal transitions. This pattern reverses the bus bit, which might be useful if the starting and targets pins are reversed.
• Perpendicular: Vias are created along a line perpendicular to the incoming direction of the wires.
  
  
• Diagonal Down: The right-most or top bus is the longest segment to drop via. This pattern is most appropriate for right-hand turns.
  
  

• Diagonal Up: The left-most and bottom bus is the longest segment to drop via. This pattern is most appropriate for left-hand turns.
  
  
• Stagger
  
  
• In Taper
  
  
• Out Taper
  
  

Via patterns and Fan Out to Vias support both orthogonal and diagonal wire directions.