When you create circuits with digital components in Multisim is important to note properly configure their supply (VCC) and ground (GND). Multisim many digital components such terminals have hidden to save space, For example, take as reference the counter 74190N:
the symbolism of this component we can see that does not include power and ground terminals, but in reality if such points exist and are necessary for simulation. We will open the component's properties and go to the tab terminals ; in the field find hidden terminals VCC and GND (power and digital ground):
This means that for this component to function properly require placing VCC and GND references somewhere in the circuit so that they are virtually connected to the counter.
But there is more to take into account digital simulations Multisim. Go to menu Simulate >> Configuration ng Mixed-Mode Simulation:
In the previous window we have two options: ideal simulation and real simulation. The theory tells us that if we select the first option is not necessary to place the references to VCC and GND on the circuit, but I prefer and recommend to always use the second option (real simulation) it will give us better results. As indicated by this option, you must place the digital reference power and ground.
To see this practice so I will recommend an example of Multisim. Go to the File menu >> Open Samples ... Navigate to the folder Educational Sample Circuits>> Digital Circuits and open the file UpDwnCounter . This is a counter circuit in which we see the use of VCC and GND:
Experiment VCC and GND deleting and changing the configuration of Mixed-Mode Simulation, what is the result? Do you see the difference?
I welcome your comments,
Fernando