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The FastCap/FastHenry Interface

Xic contains an interface to the FastCap capacitance and FastHenry resistance/inductance extraction programs. The generated input files can be used with other programs that recognize the file format.

Updated versions of these programs are available on the Whiteley Research web site. The original versions of FastCap and FastHenry were developed at MIT, and are publicly available in source code form on the internet.

FastCap
The modified version (fastcap-2.0wr) allows all input to be supplied as a single file. The MIT version requires input from multiple input files, which seems inconvenient for our purpose. By default, Xic will generate unified files of this type, however by setting a check box in the interface panel or setting the FcOldFormat variable, Xic will use the original (multi-file) format.

FastHenry
The modified version (fasthenry-3.0wr) handles superconducting conductors, otherwise it is functionally identical to the MIT version.

Distributions of both programs provide detailed user manuals.

The interface allows extraction from planar structures likely to be encountered in integrated circuits. It is not a general purpose interface, though it can perhaps be used as a starting point when addressing general problems. It is best suited to extracting from a small collection of conducting objects. The user should be aware that both FastCap and FastHenry can become monsters with regard to memory use and execution time.

The interface is controlled from the RLC Extraction panel which is brought up by the Extract RLC button in the Extract Menu. In addition, there is the !fx prompt line command which allows most of the interface to be controlled through text input. There are a number of variables (see C.20) which are used by the interface. Most of these are maintained through entry areas in the RLC Extraction panel, but can also be set with the !set command.

Briefly, selected conducting objects are added to an internal database associated with the interface. The physical properties of the layers are given in the technology file. The interface uses this information to create a three-dimensional representation of the selected objects and surrounding insulation layers. This representation can be ``refined'' through a partition editor, to reduce granularity in the simulation, thus improving accuracy. Locations of assumed connecting terminals, needed for FastHenry, can be defined. Output can be dumped in the form of FastCap or FastHenry input files, or as a ``.sav'' file to save the geometry for a future run. FastCap and FastHenry can be run directly, and the results, after some minimal post-processing, will be displayed (and saved in a file).



Subsections
next up previous contents index
Next: FastCap/FastHenry Interface Limitations Up: The Extract RLC Button: Previous: The Extract RLC Button:   Contents   Index
Stephen R. Whiteley 2012-04-01