Data Sheet

LABCENTER ELECTRONICS LTD.
186
Important Notes
Quite a lot is happening when we run a simulation in Proteus that might not be immediately
apparent.
Firstly, the micro-controller on the schematic is executing the compiled firmware file in exactly
the same way as a physical PIC would execute its programmed firmware. Working with the
VSM Studio IDE simply automates the 'programming' step by sending the output file to the
schematic after a successful compile.
You will have noticed that almost all of the wires on the schematic end in a terminal with a
name. For those unfamiliar with terminal connections it is worth explaining how this works. On
the schematic, any two terminals with the same name are considered connected (like a 'virtual'
wire). For example, the RC3 and RC4 terminals at the side of the temperature sensor
correspond to the RC3 and RC4 terminals connected to the I2C pins on the PIC processor.
We tend to lay out schematics like this to avoid spaghetti wiring and to split the schematic into
easily identifiable logical blocks. The important thing to understand is that all signals travel on
the visible wires. This means that you can attach a voltage probe or measurement instrument
anywhere that you can see a wire (indeed, we will do both later in the tutorial). All that Proteus
does is 'jump' the signal between the two terminal ends as though there was a single wire
connection. You can read up more on this type of connectivity in the Proteus reference manual.
Finally, the status bar at the bottom of the application reports the simulation time elapsed.
Depending on the power of your computer, the clock speed of the processor and complexity of
the schematic, a particular simulation may not run in real time but it will always run
synchronously and the execution time is reported on the status bar.
As an example, on a particularly slow computer this simulation in clock mode may not advance
as the clock on the wall advances but it will always advance as the simulation time advances.