DCircuit Lab HD is a tool for simulating combinatorial and sequential digital circuits.

Circuits can be simulated in two ways:

1) one single step: all the outputs values are evaluated at the same time.

2) step by step: outputs and gates are evaluated one step a time. This shows how each gate's output changes and how changes propagate through the circuit. This feature is very useful to understand complex circuits behavior.
At the end of each simulation step, each gate may have a different color:

￭ black: gate's output unchanged during the just ended simulation step
￭ dark green: gate's output evaluated during the just ended simulation step
￭ light green: gate's output evaluated during the just ended simulation step, gate needs to be evaluated again during the next simulation step
￭ blue: gate needs to be evaluated during the next simulation step

At the end of the simulation, each wire's color corresponds to the digital value carried on itself: red for 1 and gray for 0.

If circuit contains clock inputs, it's simulation is dynamic. This means that outputs change accordingly to the clocks. During this dynamic simulation, user can change inputs values to study the circuit behavior. Once the simulation is stopped, a circuit timing chart is available.

Circuits are built using basic components, gates and flip-flops:

￭ input pins
￭ output pins
￭ clock
￭ wires
￭ 2 inputs and 3 inputs AND gates
￭ 2 inputs and 3 inputs NAND gates
￭ 2 inputs OR gates
￭ 2 inputs NOR gates
￭ 2 inputs XOR gates
￭ NOT gates
￭ Flip-flop RS, JK, T, D
￭ Multiplexer (4 outputs)
￭ Demultiplexer (4 inputs)

Circuits may be controlled by means of the following gesture:

￭ Drag: to move the circuit into the desired position
￭ Tap on a gate: to modify the gate
￭ Double Tap on a gate: to modify the gate
￭ Double Tap on a input pin: change its value from 1 to 0 or from 1 to 0
￭ Pinch: to zoom in and out
￭ Double finger double Tap: to reset position and zoom level to the original values

Circuits may be easily stored and reused.

Some video tutorials are available to learn using the application. Visit the site to see the tutorials.