Digital Circuit Simulator

Logic simulation is the use of simulation software to predict the behavior of digital circuits. The Quartus II Web Edition, which can be downloaded for free, can be used as an educational tool for designing and simulating digital logic circuits. With our ready to run example projects, it is simple enough to facilitate the learning of the most basic concepts related to logic circuits to the more elaborate circuits subsequently.

First download and install Quartus II Web Edition v9.1. It is free and no license is required. This is the version we create our example projects.

To simulate any of example circuits provided

  • download the example project and unzip the folder.
  • click on the Quartus II project file - Quartus will start.
  • from the menu, click Processing->Start Compilation. Wait for the dialog window to indicate the completion of compilation to appear. Click OK.
  • from the menu, click Processing->Start Simulation. When the simulation completes, click OK and the results (waveform) will appear. Press Ctrl-W or click View->Fit in Window to see the whole waveform.
  • in the Project Navigator panel, click on the schematic symbol to view the schematic.

Projects available for download

  • Ring Counter - A ring counter is a Shift Register (a cascade connection of flip-flops) with the output of the last flip flop connected to the input of the first.
  • Johnson Counter - A Johnson counter is a modified ring counter, where the inverted output from the last flip flop is connected to the input to the first.
  • Up Down Counter - 2 bit up /down synchronous counter.