Chapter 7
Autorouting and Autoplacement
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unless you achieve poorer routing results than you expect. When changing
cost factors, even slight adjustments can have large effects on routing
success, either improving or worsening the results.
Optimization
The optimizer is usually applied after the autorouter achieves 100%
completion. It eliminates unnecessary vias and smooths wire bends to
reduce manufacturing costs. It also routes any remaining open connections.
You can prevent Ultiboard from calling the optimizer by unchecking
Optimization Pass
in the
General
tab of the
Routing Options
dialog box.
The optimizer can also be run separately by selecting
Autoroute»Start
Optimization
. This also optimizes user-placed traces and vias, provided
that
Trace can be Moved
is selected in the
General
tab of the trace’s
properties dialog box. For vias,
Via can be Moved
must be selected in the
Via
tab of the
Via Properties
dialog box.
Routing Selected Parts and Nets
Complete the following to place traces on a selection of parts:
1.
Select the desired parts and select
Autoroute»Autoroute Selected
Parts
.
Complete the following to route selected nets:
1.
Select the desired nets and select
Autoroute»Autoroute Selected
Nets
.
Note
You can also pre-place traces and vias before running the autorouter. Refer to the
Working with Traces and Copper
, for more
information. Once a trace is placed, lock it by selecting
Trace is Fixed
in its properties
dialog in Ultiboard. Lock vias with
Via is Fixed
. Any traces set this way are treated as
locked when you run the autorouter. The autorouter can also be stopped during placement
to allow you to place some fixed traces, and then be restarted.
Running the Autorouter
The full autorouter runs an end-to-end autorouting process that includes all
four routing functions, applied in the following order:
1.
Preprocessing.
2.
Initial routing.
3.
Rip-up and retry passes.
4.
Optimization.
