The Intusoft CMSDK provides a
major breakthrough in HDL model development. It provides an easy
way to add tremendous functionality to SPICE without having to
deal with SPICE's intricacies. The CMSDK assists you in writing,
compiling, and using C code subroutines (XDL code models) with
IsSpice4 . The kit works with additions to the IsSpice4 simulator
core that tell the simulator how to parse the XDL model syntax
and call C code that defines the model's behavior (Figure above).
A new code model is created from two user generated files. First, the CMSDK uses a C language compiler to convert an easy to read text file into the C data structures required by the simulator. This "interface file" is an ASCII table that describes the model's ports and parameters. The model's behavior is described in another file using standard C syntax. These two portable files make up the XDL model's description. Special C macros and functions greatly simplify the details of interfacing the model to IsSpice4 . The complexities of SPICE are hidden; the CMSDK does most of the work for you. The result of a successful build is a code model library (Windows DLL) that can be accessed by the IsSpice4 simulator. There is no need to recompile the IsSpice4 executable each time a new model is added. The result is an incredibly simple development path that greatly reduces the effort in making new models and eliminates the need for you to learn about the internal workings of SPICE.
The use of a Windows DLL is unique to the Intusoft implementation of XDL. The C code describing the model's behavior is linked to the simulator via this external file rather than being bound within the executable program. This allows new models to be easily added and existing models to be modified without affecting the simulator. Although code models must be developed under Windows NT or Windows95, the resulting DLL can be used with IsSpice4 running under Windows 3.1x or NT on any compatible platform (x86, Mips, or Alpha). An expanding variety of over 42 analog, digital, and mixed analog/digital XDL models are currently shipped with the IsSpice4 simulator including a State Machine, MIDI controlled oscillator, s-domain (Laplace) transfer function, magnetic core, and sampled data filter elements. Intusoft is currently developing more models but expects users will share the DLLs and XDL model source code they develop.
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