In the PCB editor, the connectivity between the nodes in a net is represented by a series of point-to-point connection lines, which are collectively referred to as the ratsnest.When the design is transferred from the schematic (Design » Update PCB), the components are placed on the PCB design space and the connection lines are displayed (as thin, solid lines).
Within an individual net, the connection lines join all of the nodes in that net. The pattern, or order they connect, is called the Net Topology, which is discussed below.
The nodes in the net are connected by connection lines in accordance with the applicable Routing Topology rule (the default is Shortest).
In this design, the GND and 5V nets use a different color for their connection lines.
As well as being a helpful guide during component placement, the connection lines are also a valuable guide during interactive routing and autorouting.
The PCB editor includes a net analyzer that constantly monitors the location of all objects in the design space and updates the connection lines when any net-type object is edited (including an object being moved). For example, when a component is moved, the far end of each connection from that component can jump from one target pad to another target pad, as they are updated to maintain the topology defined by the applicable design rule. An example of this is shown for the GND net in the video below;this net has a topology of shortest.
Note how the GND connection lines jump around as the resistor is moved, automatically being rearranged to keep the shortest overall connection length.
An un-routed board can appear intimidating - a mass of connection lines crisscrossing all over the board. A good approach to routing is to work from the schematic, where you can easily locate important components and critical nets. You can cross-select and cross-probe directly from the schematic components and nets, highlighting the equivalent item on the PCB. Learn more about Working Between the Schematic and the Board.
A valuable feature is the PCB editor's ability to mask or dim objects in the design space. This filtering feature will fade out everything, except the object(s) that pass through the filter. The image below shows a single net has been selected, with the filtering system set to Dim all objects that do not pass the filter.
To explore this, set the PCB panel to Nets mode, this will display a list of nets on the board. Use the dropdown to set the filter mode to Dim or Mask, then enable the Select and Zoom options, as shown in the image below.
As you click on a net name in the panel the design space display will change, zooming to show the nodes in the net, and fading out everything except the pads and connection lines in the net - effectively pulling that net out from the rest of the board. Note that even when you click in the workspace the filter remains, the chosen net remains clearly visible, making it easy to examine or route.
Use the filter feature to make it easier to find a net or net class.
Click the Clear button at the top of the PCB panel to clear the filter and restore the entire design space to normal brightness (or press the Shift+C shortcut).
Note that as well as an individual net, you can filter out a class of nets (if any classes are defined) in the Net Classes section of the panel, and also interactively select multiple nets (hold Ctrl as you click in the PCB panel to select a net name).
Connection line(s) of a specific net can be selected to display their properties in the Properties panel by using the IsConnection And InNet('<NetName>') query in PCB Filter panel.
For more information about working with the query language and the Filter panels, refer to the Working with the Query Language page.
In the PCB panel's Nets mode, its three main regions change to reflect the net hierarchy of the current PCB design (in order from the top):
In the top region of the panel (Net Classes), right-click on a net or net item entry then choose Properties from the subsequent menu (or double-click on the entry directly) to access the Edit Net Class dialog in which you can view or edit the net membership of the class, rename it, or add additional classes.
You can also manage net classes using the following commands of the Design » Netlist sub-menu of the main menus or the Net Actions sub-menu of the right-click menu of selected net object(s):
The Choose Net Class dialog
The easiest and quickest way to select nets (or rather the objects thereof) in the design space is to use the PCB panel configured in its Nets mode. Choose <All Nets> in the Net Classes region then select the required net(s) in the Nets region. Filtering is applied to the design workspace, leaving just those electrical objects associated with the chosen net(s) selected (make sure the Select option is enabled on the panel and also that the highlighting mode is either set to Mask or Dim). This makes it especially easier to distinguish the objects if using the right-click method of access.
The middle region of the panel displays nets from the Net Class(es) selected in the region above.
The following information is listed with each Net by default:
If there are Length design rules configured, the routed state of each net targeted by the rule is also colored, highlighted in yellow if the route length < rule minimum, clear if the net passes the rule, or red if the route length > rule maximum.
The following notes apply to Signal Length calculations:
A signal is a point-to-point entity; for this reason, only nets with two nodes will show a Signal Length in the Nets mode of the panel (nets with other Node counts will display 0). For nets with more than two nodes, define xSignals to calculate their signal length.
Right-click in the region then use the Columns sub-menu to add the following columns:
Vertical distance through a via - the vertical distance a signal travels through a via is the sum of all layer thicknesses (copper and dielectric) between the start and stop layers copper layers, plus half the thickness of the start layer and half the thickness of the stop layer.
The length and delay for a net that is part of a defined Supply Nets design rule
