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What's Good About Allegro PCB Editor Generic Cross-Section Files? See for Yourself in 16.6!

Comments(2)Filed under: PCB Layout and routing, PCB design, SPB, Allegro PCB Editor, Constraint Manager, PCB Editor, PCB, layout, "PCB design", design, Constraint-driven PCB Design flow, ECSets, electrical constraints, Allegro GUI, Grzenia, Allegro 16.6, 16.6, constraint databases, constraint difference, constraints

Beginning with the Allegro PCB Editor 16.6 release, you are provided a methodology to export a technology (.tcf) or constraints (.dcf) file which is a generic cross-section. A generic-cross-section file (GCSF) captures constraints for specific layer types. Currently, a GCSF supports four types of layers: TOP, INTERNAL (internal signal), PLANE, and BOTTOM.

Importing a GCSF will not update the design’s cross-section, but will update the design’s constraint information (electrical, physical, and spacing) based upon the current import modes (overwrite, merge, and replace).

When a GCSF is imported into a board, constraints from that techfile will be mapped as follows -
1.    TOP - TOP (topmost etch layer)
2.    INTERNAL - signal layers between TOP and BOTTOM
3.    PLANE - all plane layers
4.    BOTTOM - BOTTOM (bottommost etch layer)

Generating a GCSF

1. Open an existing board or create a new one and edit constraints.
2. In Constraint Manager, use File > Export > (Technology file or Constraints file):

3. Select  the “Generic” radio button  in the “Export cross-section” section.

The “Generic” radio button is enabled only if the “Physical & spacing constraints” box is checked.
The “Configure” button is enabled only when the “Generic” radio button is selected.
The “None” radio button is enabled only if “Physical & spacing constraints” box is not checked – otherwise cross-section data is necessary.

4. Click the “Configure” button if you want to select the layers you would like to use as TOP, BOTTOM, INTERNAL, and PLANE (layer mapping):

This step is optional. If generic cross-section is not configured, the default mapping will be used.
User selections are remembered only for the current dialog form – when you invoke the export dialog again, the default mapping will be used.

Default mapping:

    TOP:            first etch layer

    INTERNAL:   first signal layer after TOP

    PLANE:        first plane layer

    BOTTOM:     last etch layer

To exclude a generic layer from the techfile, select <IGNORE>:

In the situation shown in the screenshot above, the resulting generic techfile will have only three generic layers – TOP, PLANE, and BOTTOM.

Importing GCSF

Open Constraint Manager and select File > Import > (Technology file or Constraints file).
Select the GCSF that you have exported from a different database and choose an Import Mode (overwrite, merge, or replace).

If in the imported GCSF some of the generic layers are ignored, then layers matching the ignored layer will not be changed. This is what the report will look like:


Note: When a GCSF is imported, the cross-section of the original board stays intact (i.e. the number of layers, their names, and characteristics remain as before importing; only the Csets are imported).

The GCSF techfile units will behave the same way as any other techfile units. A suggested approach would be to have the same units used in both the original and the target board.

I look forward to your feedback!

Jerry “GenPart” Grzenia


By Ulf Kylenfall on April 19, 2013
As in the past, a lot of the often very useful features of the Alegro suite are well kept secrets. I am amazed to learn that these features are rarely described in major release documentations but instead are "leaked" on user forums and using bulletins. But maybe it's just me that almost never visits the release events...

By Jerry GenPart on April 19, 2013
Thanks for the comments Ulf! Almost all of the features I present in these Blogs are available from Cadence Online Support (http://support.cadence.com) in each product section's "What's New" area for a given release.

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