In an era where an electronic circuit is a slab of silicon, designed by writing a language like VeriLog or VHDL, with virtually no need to understand the mathematics of circuit design, or the physics of semiconductor devices, we present a set of tools from a more gracious age. From an age when computers were still drawn by horses, and it took an engineer to design something. Not a software package.
Not content with offering this anachronism, we compound the injury by also describing a digital circuit simulator, which simulates digital logic at the device level, not the gate level.
I guess this is all precipitated by the fear that, one day, there will be nobody left who actually understands how or why stuff like VHDL works, and colleges will have stopped teaching mathematics, because it's all too hard, and too many people fail the courses - which isn't politically correct, because it damages their delicate egos....
Totally unrelated to analog simulation is a pot-pourri of Unix articles, with a leaning towards database applications. If you're not that good a programmer, they'll either help, or put you off, for good...
If you're interested in security, there are also a number of articles on the subject, specifically related to the Forticode Authentication system, which is the one we, ourselves, use. At the bottom of this page is a link to a description of how it works.
Design Simulation Systems Pty Ltd is an Australian company, which was originally born in Singapore, with the aim of developing most of the stuff described in these pages, until it was bought by the National Computer Board. It is now a consultancy, largely devoted to development work centred around Unix based security applications, and custom simulation model creation, in an environment of Sun servers.
So, what are these tools? I hear you ask...
GEX - a graphical schematic entry and editing tool
GSP - a high-speed schematic to SPICE netlist compiler
Graphical circuit stimulus editor
Vspice3 - a graphical simulator interface
Vspice3 Mathematical waveform manipulation tools
Vspice3 Digital Signal Processing waveform manipulation software
Laplace transfer function components for high level system simulation
SPICE2 simulation engine
SPICE3 simulation engine
Vmodel - A semiconductor device modelling tool
Vmodel2 - Data sheet to SPICE parameter extraction and curve-fitting tool
Comprehensive set of common semiconductor and mechanical component libraries
Reverse-engineering tool from SPICE netlist to GEX schematic drawing
Full Documentation in PostScript and Unix man page format
These tools are all available for free download, compiled for either Linux or Sun SPARC. No special gizmos, like Motif or Java are needed, and they'll run quite happily on anything with a working X11 library.
Among the downloads is a comprehensive set of component libraries, including a special library of Laplace-transform primitives, for behavioural high-level simulation. Additionally, there's a library of mechanical bits, like motors and gearboxes, for simulating servo systems and the like. Not to mention PCB tracks, op amps, SCR's etc.
Since even the most comprehensive library may miss the very device which you need to use, we also supply a set of component modelling tools
Vmodel will make a computer model from the characteristics supplied on the data sheet, while Vmodel2 accepts X-Y characteristic curve data, and accurately extracts and optimizes the relevant SPICE parameters by curve-fitting techniques
Far more interesting, is the fact that, when the simulation is finished, you can apply a whole heap of mathematical functions, including forward and inverse Fourier transforms, convolution and deconvolution functions and display results in the complex plane.
Nearly forgot: You can also download either the SPICE or Spice3 simulator (or boh), each of which has functionality that the other doesn't have.
Source code is available for an extortionate fee...
Can't make it work on your version of Linux?
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