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Exports and Imports in EDWinXP
is equipped with several export and output routines. Through export, certain categories of data in project database may be extracted and stored in formats that are readable by other CAM/CAD software or directly by machinery used in manufacturing and testing of printed circuit board. Imports are intended for transferring projects from other, similar to EDWinXP software packages, reverse engineering or as source for creating simulation models.
Basic set of documentation necessary for fabrication of PCBs include artworks of boards layers output in Gerber RS -274-D or RS-274-X ASCII formats. Characteristic feature of EDWinXP output is that we use mixed polarity capabilities of RS-274-X and polygon area fill to plot artwork containing copper pour areas. Other packages usually apply less efficient stroke fill method. Our approach shortens processing time with generation, plotting time on the photo-plotter and produces files that are more compact. The feature for automatic generation of coupons and targets is included as an option.
Drill data with or without optimization of tool movement are extracted in Excellon Format 2. Optional drill template may be obtained in printed form or plotted with highest precision on the photo-plotter Format used to output automatic assembly data is as defined by IPC-D-355 standard. As an option so called “generic format” defined by Visionics may be used instead. This is a simple ASCII format there the user have a possibility to select the contents. It is intended for post-processing by other software to format readable by users’ machinery.
Similarly, IPC-D-356A standard is used to output data used for bare board testing. Here we have optional “generic format” too. Manufactures often use bare board test output to double check integrity of layer artworks in Gerber ASCII format files.
Certain manufacturers would rather extract data necessary for each fabrication step themselves. For this purpose, EDWinXP may export fabrication data in two formats. GenCAM format allows exporting complete project – all circuits with respective multi-page schematics and PCB layouts. Newly introduced ODB++ format export contains only PCB part of the project. This format unfortunately does not support export of schematics.
IDF V3.0 format export is provided to create simplified 3-dimensional image of the PCB for farther processing in software packages that use this format. Other way to output 3-dimensional image of PCB from EDWinXP is to do export in DXF format.
EDWin XP net list export and import
There are two simple net list ASCII formats defined by Visionics –PCB Wire List and Schematic Net List. The latter is used mainly as source code for creating simulation models. On the other hand, PCB Wire List format is provided for importing basic project data – list of components on the PCB layout and list of connection between pins. It can be used for various tasks.
First section in the file contains list of components with corresponding parts. It is assumed that required parts are stored in the system library. This information allows creating layout components and equivalent schematic components. Connections are processed next and the common net list is created. Therefore, – due to integrated structure of EDWinXP project database – it is possible to build a base for the whole design – its schematic and layout part, even if data in imported file apply to layout part only. What is left to do at this stage is placing components at desired positions and routing connection, which may be done manually or with the help of auto-placers and autorouters. This feature may be very useful when someone wishes to recreate complete project from old schematics in printed form. It may take less time to edit complete net list fil e in text editor, with all components and connections and importing it instead of creating components and connecting them interactively in Schematic Diagram or Layout editor. This practice is often applied by PCB design houses that use EDWinXP.
The same capabilities are provided for export and import of OrCAD PCB II Wire List format. Here a problem may arise with part names that in OrCAD library may be different from equivalents in EDWinXP library. The solution for that is through optional dictionary file that contain list of “foreign names” and “EDWinXP library names”.
Other net list exports and imports
EDWinXP may also export schematic net list in variety of formats that are readable by software packages used for design of programmable logic devices. These are CUPL, JEDEC, Xilinx, ALTERA and EDIF 2.0. EDIF format net list generated by ALTERA may be imported. EDWinXP may also compile and import circuits defined in VHDL. These categories of import and export are provided for special purposes and are not intended for transferring of whole projects between other CAD packages and EDWinXP.
ODB++ Job Import
Most comprehensive method for transferring project from other CAD packages is ODB++ Job Import. Since this format supports layout part of the project only – as seen by EDWinXP – only this part will be imported. Schematic part can be easily reconstructed afterwards by changing references of imported layout components to parts in system library. Condition for successful import of ODB++ Job is that it must have been e xported from the source package without suppressing EDA information and at least one layer of component type is defined in the job matrix. Compressed ODB++ Jobs have to be decompressed prior to import.
This feature allows for partial or complete reconstruction of a project database from “unintelligent” graphic data like Gerber ASCII files or Autocad DXF format. In other words, it could be understood as a form of reverse engineering. DXF input was meant as provision to import geometrically complicated board outlines and cutouts rather than a way to recreate whole PCB layout. Gerber ASCII files are better suited for this purpose. In both cases, the first stage is conversion of source files to common intermediary format that in EDWinXP terminology are called artwork files.
From these files user may extract groups of graphics elements and store them as separate data type categories – pad masters, traces masters, outlines. This may be achieved through applying filters limiting import to selected t ypes of elements or selected sizes of elements to given category. There is usually impossible to recognize automatically with 100 % accuracy whether a line in Gerber file is a track or part of pad or part of the board outline. Once graphics are imported, elements in each category may be edited or transferred individually or in groups between categories, since the filters cannot always solve ambiguities. It is also possible to add additional elements to categories.
As long as the purpose of import is just lesser revision of artworks like changing size of tracks and pads, adding or removing track or pads, the job is finished at this stage. Results of import and changes are enough to re-generate new sets of Gerber ASCII files and even drilling data. However, this is still a “dumb”, purely graphic database, without proper components and net list.
Reconstruction phase that may optionally follow afterwards uses imported data as templates.From elements stored in category “board outlines” user may recreate board outline automatically or use their geometrical properties to add vertexes to existing outline in proper coordinates. Elements stored in categories “silkscreen”, “pad positions” and “pad stacks” serve two purposes – either as placement template for components created in Layout Editor or parts and packages and finally layout components may be recreated from them. This is manual and partially automatic function since users has to select those elements that should be included in the package. Recreation of layout components is the most laborious part of the whole reconstruction process. Once it is don e recreating traces and net list may be executed in fully automatic mode.
Graphic Imports and Reconstruct From Graphics are powerful if somewhat complicated tools.. We shall therefore dedicate a special article to issue connected with reconstruction. That may be made even more effective by combining with other forms of import.
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