Chapter 7
Autorouting and Autoplacement
©
National Instruments Corporation
7-13
Complete the following steps to set up cost factor parameters:
1.
Select the
Cost Factors
tab in the
Routing Options
dialog box.
2.
Edit one or more of the following fields in the
Routing and
Optimization
area:
•
Via Cost Factor
—A high via cost factor results in fewer vias than
a low via cost factor, but also results in relatively complex circuit
traces. A low via cost factor permits the router to place vias up to
the maximum number you specify with the
Maximum Via Count
per Trace
function.
•
Maximum Via Count per Trace
—This is the maximum number
of vias that the router can place between two connected pins.
•
Counter Direction Cost Factor
—a high counter direction cost
factor forces a strict adherence to the layer-specific preferred
routing directions, while a low factor permits deviations from the
preferred direction.
•
Off-Grid Routing Cost Factor
—Is considered only when you
activate the half-grid option. A high off-grid routing cost factor
limits the use router’s use of the sub-grid, while a low factor
permits frequent use of the sub-grid.
•
Trace Crossing Cost Factor
—Sets the trace transition cost
factor, which the router and optimizer use to control cleanup
pattern recognition during multi-net optimization. A high trace
crossing cost factor permits complex routing with many traces
crossing each other. This creates a relatively large number of vias.
A low factor leads to more intensive and time-consuming analysis
during cross-net optimization. Relatively few vias are produced.
•
Adjusted Width Cost Factor
—When
Auto Adjust Width
is
selected in the
General
tab, a high adjusted width cost factor
limits the router’s use of narrow trace widths.
3.
Edit one or more of the following fields in the
Routing
area:
•
Pin Channel Cost Factor
—A high pin channel cost factor results
in infrequent use of pin channels, the regions between adjacent
part pins. A low value allows frequent use of pin channels.
•
Packing Cost Factor
—A high packing cost factor instructs the
router to bundle circuit traces wherever possible. A low factor
results in a wider distribution of circuit traces across the board.
•
Dynamic Density Cost Factor
—Controls the global distribution
of traces. A high dynamic density cost factor explicitly tries to
create an even or wide distribution of traces across the board, rather
than letting the other costs determine how traces should be placed.
A low factor lets trace distribution be determined by routing cost.
