AutoPlacer_Cmd-RunAutoPlacerRunAutoPlacer_AD

Applied Parameters: None

Summary

This command is used to set up, and run, one of the PCB Editor's two auto-placement tools.

Access

This command is accessed from the PCB Editor by choosing the Tools » Component Placement » Auto Placer command, from the main menus.

Use

After launching the command, the Auto Place dialog will appear. Use this dialog to select, set up, and launch, either the Cluster Placer or the Statistical Placer.

Using the Cluster Placer

This Auto Placer groups components into clusters based on their connectivity and then places these clusters geometrically. The algorithms in this Auto Placer are more suited to designs with a lower component count (less than 100).

To run the Cluster Placer, from the Auto Place dialog click on the Cluster Placer option, then click OK to start the autoplacement process.

Enable the Quick Component Placement option to give a quick geometric placement with no optimizations.

Using the Statistical Placer

This Auto Placer uses a statistical algorithm to place the components in an attempt to minimize the connection lengths. As it uses a statistical algorithm it is best suited to designs with more than 100 components.

To run the Statistical Placer, from the Auto Place dialog click on the Statistical Placer option, set the options as required, then click OK to start the autoplacement process.

Both Cluster and Statistical Placers can be stopped at any time during the autoplacement process. To stop the Cluster Placer, use the Stop Auto Placer command (available from the Auto Placement sub-menu). To stop the Statistical Placer, close the autoplacement window.

Tips for achieving optimal PCB autoplacement

The following are some important tips to ensure optimum autoplacement results from both the Statistical and Cluster Placers:

Pre-placing components

You can pre-place any component before running one of the Placers. Enable the Locked option in the Component Properties section of the Component dialog to prevent these components from being moved.

Apart from those components which have to be placed in certain locations on the board, such as edge connectors, heat sinks, or a group of analog components, it can be useful to pre-place components which need no restriction on their placement. For example, it might be desirable to pre-place the memory chips. This could facilitate the placement of the other components.

Use of Keepout zones

To keep certain regions of the board free of components, create keepout zones. These could be placed next to connectors, or in regions which must be kept clear for mechanical reasons. Place keepout arcs, tracks and fills to create these keepout zones.

Excluding larger nets

Large nets can affect the speed and quality of the Auto Placers. The reason for this is that the computation involved with rearranging a net is exponentially proportional to the net size. An interesting observation is that large nets, such as power and ground, can play an insignificant role in the overall placement process. Therefore, it can help the placement process by instructing the Placer to ignore these large nets.

• To do this for the Cluster Placer - define a Nets to Ignore design rule (under the Placement category in the PCB Rules and Constraints Editor dialog).
• To do this for the Statistical Placer - specify the nets in the Power Nets and Ground Nets fields of the Auto Place dialog.

Tips

1. Before performing autoplacement, ensure you have fully defined the electrical boundaries of the board, as wall as any "keep out" areas. Also, set the current origin back to the absolute origin. This can be important because the autoplacement routines use the absolute origin as a reference point and may place components off grid relative to the current (relative) origin you created.
2. For optimum autoplacement performance, first set up any relevant placement design rules before starting either Auto Placer.
3. When using the Statistical Placer, the temporary autoplacement document (DesignName.PLC) is only available for viewing the progress of the autoplacement.
4. Both Cluster and Statistical Placers can be stopped at any time during the autoplacement process. To stop the Cluster Placer, use the Stop Auto Placer command. To stop the Statistical Placer, close the autoplacement window.