CIF (Caltech Intermediate Form) is a ASCII file format designed by Caltech (now California Institute of Technology) for IC-designs. It is even older than the GDSII format, but still in use. The newest and last published specification for the CIF file format was published on Februry 11, 1980 by the California Institue of Technology in Technical Report 2686. Some other EDA tools extend this specification by interpreting special comments inside the CIF file as additional design data. These extensions are far away from any standard and not used by the LayoutEditor with the only exception of text elements which are not natively supported by CIF.
The CIF file format can be loaded and saved like the GDSII or OASIS file format. There are some options specific for the CIF file format. All options can be set in the SetupDialog. These options are available:
The CIF file format only stores layer names. Layer number as used in GDSII or OASIS are not used. By opening a CIF file the LayoutEditor analyzed the used layer names. If a layer name already exist in the current setup, this layer number is used. Otherwise the first unused layer is renamed.
The CIF file format allows to handle circles. Circles are not supported by the LayoutEditor as basic elements nor in the GDSII file format, circles are stored as regular polygons. By activating this option any regular polygon with more than 8 points will be saved as a circle element and not as a polygon.
By default the CIF file format is a collection of individual cells without marking any cell as a top cell. But the CIF file format also allows to set a main cell. By activation this option a main cell is set and added to the CIF file during the save feature.
CIF file are stored in the ASCII text format. Each line start with a single or double character command. e.g. a P represents a polygon followed by the coordinates of the vertexes. Lines end with a semicolon.
DS 1 1 10; 9 cellname; L layername; P 340000,-90000 460000,-260000 490000,-260000 530000,-160000 420000,-100000; L layername; B 180000 260000 220000,-210000; DF; E