Why do some ICs in multisim have the Vss and GND pins missing?

[cds333]

Hey everybody,

I was hoping someone could tell me why some ICs, specifically the 4013BD, have the GND and Vcc pins missing.

The real chip has 8 pins per gate, for a total of 16 per chip, but the virtual one has only 6/12. It has thus far been impossible for be to build my circuit in multisim, since I can't hook up the 4013 to match my schematic. I have tried building the circuit (in multisim) with the 4013s as they are, but it does not work. I believe the Vcc and GND are vital for its operation.

Below is a screenshot of the 4013 in multisim, and the internal diagram of the 4013 from its datasheet. As you can see, pin 7 and 14 (Vss & Vdd) are nowhere to be found on the multisim component.

Other chips, such as the 555, have the Vcc and GND right where they're supposed to be. The 555 however is black, whereas the 4013 is blue- I don't know if the color of the components has anything to do with it.

I am still new to multisim, so please don't be too technical with your assistance, however I would greatly appreciate any help at all.

Thank You

(Just in case of an error, the image can be found here: http://cdesigns.us/images/temp/forum-ni-missingpins4013-20071105.JPG)

[GarretF]

Hi cds333:

The 4013 has "virtual pins", which is why you do not see them on the schematic. Virtual pins are automatically connected to nets, that is, you don't need to wire the component to the net, but you do need the create the net. To see this, double click on the component to show the properties, and select the Pins tab. You will see pin's VDD and VSS are connected to nets VDD and VSS. I suspect the reason they don't work is you haven't created the nets. The easiest way to create them is to place a Sources > POWER_SOURCES > VDD and Sources > POWER_SOURCES > VSS. Once you place these power sources on your schematic, the 4013 will be automatically connected to the nets.

In general, you will find these virtual pins on components in the TTL and CMOS groups.

The component colours is unrelated to these virtual pins. Black components have a model, but no footprint. Blue components have a model and a footprint. Green components have a footprint, but no model. Models affect the ability to simulate, and footprints affect the ability to transfer your design to Ultiboard.

I hope I've answered without being too technical.

[lacy]

Hi Garrett.

On this subject is there a way to make the hidden pin visible. I seem to recall that there was a way to do this, but my memory of how to do it is a little fuzzy. I think it has to be done in the symbol editor, but I am not sure of that. Anything you can tell me would be greatly appreciated.

[cds333]

Koekje,

Thanks for the info... I probably never would have figured that out; I had all but given up on it.

So basically the nets take the place of the DC powersource? And I should use them instead whenever I am working with the virtual CMOS components?

I'm sure there's a good reason for doing this. I'll just have to tweak my design a bit to get it to match my original schematic.

Thanks again for the assistance.

-cds

[GarretF]

For Lacy:

Thanks for correcting my terminology. They are hidden pins (not virtual pins). It is possible to make a hidden pin visible, but it is not easy. There isn't a property that you can toggle that makes the pins visible (you have to edit the symbol, edit the model, etc). If you wish to seem some of the changes you would have to make, look at the 4013BP_5V in the CMOS_5V_IC and CMOS_5V families for some hints.


For cds:

You are correct. The nets take the place of the DC power source, and you should use them when you are using parts from the TTL and CMOS families (but not from the "_IC" families).

[lacy]

Thanks for your reply and answer to my inquiry. I thought that was how to do it, but I wasn't sure at the time. Maybe hidden pin toggle could be added to the feature request list. I personally like the hidden pin deal, but on some schematics you do have to show all your connections including power going to the IC's. This would mainly be for repair tech's (like myself) convience for later repairs if necessary and especially if you are not the person doing those repairs (like a coal mine electrican for example) who may not have access to datasheets to find his power pins. If the schematic doesn't show that information that could cause problems later for person repair doing those repairs.

[GarretF]

 I agree that the ability to toggle the visibility would be helpful in the scenario you described. This feature has already been requested.