> So my question is does anyone have any
> idea as to how I could set this up so that it routes for a double sided
> board but with a very constrained ste of options for the "top" side. So for
> instance it would only allow straight traces on the top side and would not
> allow traces to pass under a component, it would give a very high priority
> to the bottom side of the board. Then I could just use the upper set of
> traces as a set of links on a single sided board. I've taken a quick look at
> the spectra manuals and you seem to be able to set just about every
> parameter under the sun, but it seems like you could spend a good part of
> your life working out what they all mean. So any experts out there?

I've had reasonable success with just setting the top layer costing
very high and the top direction one way and the bottom, anyway.
What I used to do with older autorouters was to make the board
several times bigger than it was going to be and spread all the parts
out to match. Run the autorouter and then move the tracks and parts
back into the real size and layout. Usually there were only one or
two areas that were dense and spreading the parts out allowed it do
the rest without choking.

You are right about the command syntax being huge but that is what
makes it such a good product. If you have a dense 12 layer board,
spending a few days making up a .do file is worth the effort. That's
not so apparent with a single sided board.

Anyway, I saved this little gem from the Specctra mailing list:

Steve.

=================================================



 Yes, Specctra has a concept of jumper layers. I assume that most Cad
 systems
can't handle the design language syntax so here is a example of what
you will need to add to your design file to make this work.

You will need to add a jumper layer (this must be added on top or
bottom) and you will need to specify the jumper lengths. Specctra
automaticaly forces jumpers outside of components and jumpers are
added at a very high cost.

Example of design file syntax:

(PCB Jumper_test
  ...
 (structure
  (layer jumper (type jumper)(direction vert))    <---- Add jumper
  layer (layer top (type signal) (direction hori)) (layer bottom (type
  signal) (direction vert))
 )
 (placement
    ...
 )
 (library
  ....
  (jumper (length 50))     <--- Add jumpers for routing
  (jumper (length 100))
  (jumper (length 150))
  (jumper (length 200))
 )
 (network
  ...
 )
 (wiring
  ...
 )
)


For more info... See jumpers in the Design language Reference
guide....

======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680, New Lynn      http://www.tla.co.nz
Auckland, New Zealand        ph  +64 9 820-2221
email: steveb@tla.co.nz      fax +64 9 820-1929
======================================================

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