Gerber (RS-274X)
A Gerber File is a standard file format used by printed circuit board (PCB) fabrication houses that contains data necessary for computer controlled machines to draw exact patterns for circuit boards. These patterns are typically used to electrically connect components in electronics assemblies. The patterns usually contain features such as land patterns, signal traces, drilled holes, milling and cutting information. The Gerber Format was originally a subset of EIA RS-274-D. Later the format was then extended by the so called "Mass Parameters" and was then also called RS-274-X. The LayoutEditor supports this new RS-274-X standard. The newer Gerber format RS-274X, also known as X-Gerber or Extended Gerber, includes the aperture information into the file headers. With embedded apertures, this makes every X-Gerber file complete as to how each PCB layer should look. However, there are still problems with the interpretation of these files, such as on polygons, or the question of which file to use for which layer. Gerber file extensions are often .GBR, .GBX. Sometimes extensions such as .TOP and .BOT are used instead.
Using Gerber in the LayoutEditor
A Gerber File stores only a single layer of a design. For this reason they are handled in a different way than all other supported file formats. With the open function a new cell is opened and the file data is added to the active layer. With the import function the file data is added to the current cell on the active layer. An update will replace all elements on the active layer in the current cell with the file data. Gerber files may also use a "layer polarity", which contains elements that had to be clear. These elements will be added on a one higher than the active layer. A Gerber File can not handle any hierarchy. If a file is saved to the gerber file format, the current cell is flatten to remove any cell references and all used layers are saved in independent file. They are named like filename-layername.gbx. Additionally a macro is created which loads all created gerber files.
