Applied Parameters: Action=Start
Summary
This command is used to route the entire board, using the Situs Autorouter. Situs 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 Auto Route » All command, from the main menus.
Use
After launching the command, the Situs Routing Strategies dialog will appear. 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 you are working with. A new routing strategy can be added from the dialog by clicking the Add button - giving access to 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 2 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.
With a clean pre-routing analysis, and the chosen routing strategy selected, proceed to start the Autorouter by clicking the Route All button.
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.
- Differential pair nets cannot be autorouted and must be manually routed and locked before using the Autorouter. If differential pairs are not locked prior to auto routing, it is very likely that they will be altered by the Autorouter and signal integrity of the differential pair could be adversely effected.
- Don’t be afraid to experiment. If the results of running the Autorouter are not acceptable, do something to change the router's approach. Add intermediate cleanup and straighten passes, make more room around dense areas or change layer directions. Experiment with the router by creating new strategies to control the order of passes, changing the number of vias that can be dropped by the Autorouter, changing the routing layer directions, constraining the router to orthogonal routes only, and so on. Keep notes of the combinations that have been tried use this information to identify and reuse which configurations work best on particular designs.
- All Autorouter event and routing information will appear as messages in the Messages panel.
Altium Designer Documentation
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Command Reference
PCB Commands