For example, if malformed characters were appearing on the LCD display setting a hardware breakpoint on the busy line would be a good place to start investigating. If a problem is identifiable as a hardware fault, then using hardware breakpoints will pause the simulation whenever the fault condition occurs. In addition to traditional debugging where you set one or breakpoints in your source and then step the code when they are triggered, Proteus allows you to set breakpoints on the schematic so that a hardware condition can trigger a breakpoint. This works just like your favourite software debugger, except that as you single step the code, you can observe the effect on the entire design - including all the electronics external to the microcontroller. Whilst Proteus VSM is already unique in its capability to run near real time simulations of complete micro-controller systems, its real power comes from its ability to perform these simulations in single step mode.

With over 750 supported micro-processor variants, many thousands of embedded SPICE models and one the worlds largest libraries of embedded simulation peripherals, Proteus VSM remains the first choice for embedded simulation. It is anything but a simple software simulator since the interaction of all these peripherals with the external circuit is fully modelled down to waveform level and the entire system is therefore simulated. The VSM CPU models fully simulate I/O ports, interrupts, timers, USARTs and all other peripherals present on each supported processor.

If the program code writes to a port, the logic levels in circuit change accordingly, and if the circuit changes the state of the processor's pins, this will be seen by your program code, just as in real life. It simulates the execution of your object code (machine code), just like a real chip. The micro-controller model sits on the schematic along with the other elements of your product design. The most exciting and important feature of Proteus VSM is its ability to simulate the interaction between software running on a microcontroller and any analogue or digital electronics connected to it.

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