Controlling Autorouter

Use these parameters to control Autorouter.

• Design Rules
  • Minimum clearances (DRC commands for Clearance and Distance)
  • Via diameter (Annular ring setting) and the hole diameter of the vias (Sizes setting)
  • Minimum track width
• Net classes (if any are defined)
  • Special minimum clearances
  • Track widths and hole diameters for vias carrying particular signals
• Cost factors and control parameters in Autorouter menu. These affect the route given to tracks during automatic routing. Parameters are saved in the BRD file when the layout is saved. You can also save these values in an Autorouter control file (CTL). This enables you to use a particular set of parameters for different layouts. Neither Design Rules nor the data for various net classes are part of the control file.

Autorouter runs in four stages. All of these stages are optional.

Bus router (optional):

Normally the bus router starts first. It routes signals in the preferred X and Y directions while allowing only slight deviations. This is an optional step.

For Autorouter, buses are connections that can be laid as straight lines in the X or Y direction with only a few deviations. This is not the same as other electronic buses, such as address buses.

Routing pass:

Autorouter attempts a full routing. A large number of vias might be deliberately allowed to avoid paths becoming blocked.

TopRouter:

If you use a routing variant with upstream TopRouter, the traces will be laid out with another routing algorithm, which tends to use less vias.

Optimization:

After the main routing pass, a number of optimization passes can be made. Parameters determine whether to remove superfluous vias and smooth track paths. Tracks are removed and rerouted one at a time. This can lead to a higher degree of routing, since it is possible for new paths to be freed by the changed path of this track.

The number of optimization passes must be specified before starting Autorouter. It is not possible to optimize at a later stage. Once the routing job has been completed, all the tracks are considered to have been prerouted, and can no longer be changed.