Applied Parameters: Action=Setup
Summary
This command is used to run the Situs Routing Strategies dialog, from where you can interrogate a pre-routing analysis report for the design and choose the strategy to be used when routing. The routing strategy is the intelligence of the Router, defining which of the various routing algorithms to use and when in order to turn the 'virtual' routing paths identified in the topological map into high-quality, highly efficient, real routing on the board.
The Situs Autorouter is a Topological Autorouter. A topological autorouter uses a different method of mapping the routing space - one that is not geometrically constrained. Rather than using workspace coordinate information as a frame of reference (dividing it into a grid), a topological autorouter builds a map using only the relative positions of the obstacles in the space without reference to their coordinates. It does this by triangulating the space between adjacent obstacles. This triangulated map is then used by the routing algorithms to "weave" between the obstacle pairs from the start route point to the end route point. The greatest strengths of this approach are that the map is shape independent (the obstacles and routing paths can be any shape) and the space can be traversed at any angle - the routing algorithms are not restricted to purely vertical or horizontal paths as with a rectilinear expansion routers.
Access
This command is accessed from the PCB Editor by choosing the Route » Auto Route » Setup command from the main menus.
Use
After launching the command, the Situs Routing Strategies dialog will open. The Autorouter conducts its own pre-routing analysis and presents the results as a report in the dialog. The report provides information including:
- Design rules currently defined for the design that will be adhered to by the Autorouter (and the number of design objects - nets, components, pads - affected by each rule).
- Routing directions defined for all signal routing layers.
- Drill layer pair definitions.
The report lists potential problems that could affect router performance. Where possible, hints are provided in order to advise how the design could be better prepared prior to autorouting. Any errors/warnings/hints that are listed should be scrutinized and, if needed, the corresponding routing rules adjusted before proceeding to route the design.
It is essential that any routing-related rule violations are resolved before starting the Autorouter. Not only can violations prevent routing at the location of the violation, they can also greatly slow the router as it continually attempts to route an unrouteable area.
The Autorouter comes pre-configured with a number of Routing Strategies that have been found to be useful for different applications, but you can create your own strategies based on experimentation and the sorts of boards with which you are working. A new routing strategy can be added from the dialog by clicking the Add button, which opens the Situs Strategy Editor dialog. Use this latter dialog to define the strategy as required by including the routing passes you need.
In general, the default routing strategies for two layer and multi-layer boards are fine for most routing situations. It is important, however, to ensure that any relevant routing design rules are set up prior to running the Autorouter.
After the required routing strategy has been chosen/defined and any warnings investigated/resolved, click the OK button. The chosen strategy will be selected the next time you use the Autorouter to route the entire board.
Tips
- Pre-route critical nets and, if it is essential that they are not changed by the routing process, lock them by enabling the Lock All Pre-routes option in the Situs Routing Strategies dialog. Avoid unnecessary locking though; a large number of locked objects can make the routing problem much more difficult.
