Setting net properties

This section explains how to set net properties for routing. Net properties affect manual routing, autorouting, and autoplacement. Most of the net data used in Layout is established at the schematic level using net properties. However, these rules can be enhanced or modified at any time during the design process. Net data can be viewed and accessed in the Nets spreadsheet.

To open the Nets spreadsheet

1 Choose the spreadsheet toolbar button, then choose Nets. The Nets spreadsheet appears.

To edit net properties

1 In the Nets spreadsheet, double-click on a net. The Edit Net dialog box appears.

2 Edit the options in the dialog box as desired, then choose the OK button.

The Edit Net dialog box

Net Name

Gives the name of the selected net.

Routing Enabled

Indicates that the net is enabled for routing. If this option is not selected for a net, you cannot route that net.

Retry Enabled

Gives the router the option to reroute a net to create room for another track. Usually you select or deselect Retry Enabled in tandem with Shove Enabled. If the net is completely routed, deselecting both options is similar to using Lock (from the pop-up menu), except that using Lock affects only previously routed segments.

Share Enabled

Tells Layout that an existing track within a net is considered a legal connection point for any new tracks within the net, allowing T-routing to be used on the board. Deselecting this option forces nets to go to pads only, and no connections can be made to any existing track. Share Enabled is generally deselected when routing ECL nets (to force daisy-chaining) or high-speed lines.

Shove Enabled

Allows the selected net to be moved to create space for other tracks. You would not normally deselect Shove Enabled without also deselecting Retry Enabled, for an existing piece of track, because the router could still use Retry Enabled to rip up the track, if necessary. Therefore, if you want to completely lock a net, you should deselect both Shove Enabled and Retry Enabled. If the net is completely routed, deselecting both options is similar to using Lock (from the pop-up menu), except that using Lock affects only previously routed segments.

Highlight

Displays critical connections in the highlight color, to make them easier to see. The default color for highlighted nets on all layers is white. You can change the highlight color on a layer-by-layer basis.

Test Point

Lets you assign test points to the nets you select manually. Or (in Layout and Layout Plus only), the nets are assigned test points when you choose Place and then Test Points from the Auto menu. To define a via as a test point, open the Padstacks spreadsheet and double-click on a via. In the Edit Padstack dialog box, select the Use For Test Point option, then choose the OK button.

Group

The number you assigned to a group of nets in the schematic design. The ratsnests of grouped nets are displayed in a distinct color. All nets not assigned to a group at the schematic level are assigned to group zero, whose default color is yellow. You can edit a net’s group number only at the schematic level. Net groups are displayed in the following default colors.

Weight

The priority a net is given for routing. The higher the weight, the sooner the net will be routed. The range is zeroto 100, with 50 as the default. A higher weight overrides all other ordering criteria.

Min Width

The minimum width of routed tracks. You can override this value for individual tracks using the Track Width dialog box.

Conn Width

The router creates new tracks using the value set for Conn Width. For nets with variable widths, set Conn Width to the preferred width. Then, you can override the width as desired using the Track Width dialog box.

Max Width

The maximum width of routed tracks. You can override this value for individual tracks using the Track Width dialog box.