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         VSM  SIMULATION  

Proteus Virtual System Modelling (VSM) combines mixed mode circuit simulation, animated components and microprocessor models to form a system that can simulate complete microcontroller based designs. For the first time ever, it is possible to develop and test such designs before a physical prototype is constructed.

This is possible because you can interact with the design using on screen indicators such as LED and LCD displays and actuators such as switches and buttons. The simulation takes place in real time (or near enough to it): a 300 MHz Pentium II can simulate a basic 8051 system clocking at over 12MHz. Proteus VSM also provides extensive debugging facilities including breakpoints, and source level single stepping.

The VSM architecture allows additional animated models to be created by anyone, including end users. Whilst many types of animated model can be produced without resort to coding, a documented interface has been provided for developers to write their own models packaged as Windows DLLs. These models can implement purely electrical behaviour or combine this with graphical behaviour so that almost any kind of application specific peripheral can be simulated.

Screen shot of the ISIS schematic editor showing an 8051 calculator design that incorporates a numeric keypad and LCD display. The simulation is paused with the 8051 register window and source level debugging window visible.

Schematic Entry
Proteus VSM uses our proven ISIS schematic capture software to provide the environment for design entry and development. ISIS is a long established product and combines ease of use with powerful editing tools. It is capable of supporting schematic capture for both simulation and PCB design. Designs entered in to Proteus VSM for testing can be netlisted for PCB layout either with our own ARES product or with third party PCB layout tools. ISIS also provides a very high degree of control over the drawing appearance, in terms of line widths, fill styles, fonts, etc. These capabilities are used to the full in providing the graphics necessary for circuit animation.

Circuit Simulation
At the heart of Proteus VSM is ProSPICE. As with ISIS, ProSPICE is an established product that uses a SPICE3f5 analogue simulator kernel together with our own fast event-driven digital simulator to provide seamless mixed-mode simulation. The use of SPICE kernel lets you utilise any of the numerous manufacturer-supplied SPICE models now available and around 4000 of these are included with the package.

Graph based simulation is a kin to conventional simulation where you first draw the circuit, set-up source generators, select points to be monitored and then run the simulation. When the simulation is complete the results are displayed and you analyse these at your leisure. ISIS and ProSPICE make this as effortless as possible.

Having drawn the schematic, you choose the type of circuit analysis you require (transient, frequency, noise, etc.) by placing a Graph of the appropriate type on the schematic. You can place as many graphs as you want and can even have several graphs of the same type if you wish. Graph types supported include: Analogue, Digital and Mixed transient graphs as well as Frequency, Transfer, Noise, Distortion, Fourier, AC Sweep and DC Sweep and Audio graphs. The latter can be used to not only capture and display transient data but to also play it through a sound card.

Next, add and configure Generators to stimulate the circuit and Probes at points to be monitored. These can be dragged and dropped on the schematic like any other component and can also be reconfigured or dragged about between simulations. Analogue generators available include DC, Sine, Pulse, Piecewise Linear, File, Audio, Exponent and Single Frequency FM types and digital generators available include Edge, Pulse, Clock and Pattern types.

Finally you drag-and-drop one or more generators or probes on to a graph to choose what traces are displayed. A graph of a particular type with a given set of probes and generators is sufficient to tell ISIS and ProSPICE what part of the circuit to simulate, and what type of analysis to perform.

Post simulation you can maximise any graph, zoom in or out on the data as well as take timing, voltage and other measurements.

Edit Generator dialogue form for a Piecewise Linear generator. Setting up the generator involves simply drawing the required waveform.
Graphical Modelling
Graphical component modelling lets you create animated component models where the graphical appearance of the component is directly linked to the state of the model within the simulation. The method is relatively simple - make a library part in ISIS with several graphical states (e.g. various brightnesses of a light bulb) and link it to a simulator primitive which converts voltage, current or a logic condition into a state value. Mouse operated switches, buttons and potentiometers can also be created using a similar mechanism but in reverse. This simple scheme allows all manner of animated components to be created without any need for programming.

Screen shot of the ISIS schematic editor showing an 8051 calculator design that incorporates a numeric keypad and LCD display. The simulation is paused with the 8051 register window and source level debugging window visible.

Report Generation
The Bill of Materials report can include any of the properties assigned to the components in the design and ISIS lets you define the exact format of the report. Furthermore, it is possible to total up numeric properties for costings and so forth. The Electrical Rules Check (ERC) report provides a summary of common design errors such as shorted outputs and undriven inputs.

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