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Chapter 5
Setting up the board for routing
Push N’ Shove The push n’ shove routing pass is the most powerful routing pass
in SmartRoute. It pushes and shoves existing tracks out of the way in order to make
room for new tracks. It routes on a diagonal. It has no limits on how far it can push
other tracks, and can jump over vias and pads.
Ripup Upon completion of the push n’ shove routing pass, there may be spacing
violations, or contentions on the board (contentions appear as small yellow circles).
Generally, subsequent passes of the various routing passes remove the contentions.
In very dense boards, however, contentions may persist after all the previous passes
are completed. The ripup routing pass is then used to unroute the routed tracks
associated with the contentions and reroute them, eliminating the problem. The
number of contentions displays in the status bar interactively as routing progresses.
For more information about contentions, see Contention in this chapter.
Contention
The term contention is a relatively new term in autorouting vocabulary. All the
routing passes in SmartRoute are based on contention routing. That is, it is
permissible for the autorouter to place a track or via so that it creates a spacing
violation (contention) with other tracks, vias, and pads.
Some examples of routing contention include:
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A track segment crossing a track segment of a different net
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A track segment being placed on top of a track segment of another net
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A track segment that violates space requirements with an existing via or pad
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A via that violates space requirements with another via, pad, or track segment
When a contention is created, a small yellow circle approximately 0.1" in diameter
(hollow) is created at the point of contention. It remains until the contention is
cleared. Subsequent routing passes attempt to remove the contention by either
pushing or rerouting the track that caused the contention, or by pushing or rerouting
the existing track. If there is not enough room to push or reroute a track to eliminate
the contention, the contention remains and must be fixed by manual routing, or fixed
in Layout Plus.
The number of contentions displays in the status bar. During routing, the number of
yellow circles (contentions) on the board may differ from the number shown in the
status bar. This is due to the fact that the screen is updated instantly as a connection
is routed, whereas the data line is updated only after a major routing pass.
6 Tip
If there are still unrouted nets or contentions after routing, they may be
completed by another combination of push n’ shove and ripup passes.
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OrCAD Layout SmartRoute User’s Guide