net groups within subcircuits?

[dbur]

I have subcircuits I want to have net groups inside of.  Typically these are LVDS clock pairs that need differential routing, etc.

When I replicate the subcircuit corresponding nets are added to net groups with the same names as the other subcircuit instances.

I believe this will cause problems when I enforce the layer rules for the groups in UB.

Am I misunderstanding something?

Is this a bug?

Is there a work around?

Thanks.

[GarretF]

Hi,

When you copy a subcircuit, Multisim also copies the names of the net groups. Yyou can then assign the nets in the subcircuit to a different net group. I think this should achieve what your're looking for.

[dbur]

Yes, that's what I was afraid I was stuck with.  OK for few groups but tediuous if there are many and you have to do it for every subcircuit.

[GarretF]

Hi dbur,

If you have a version of Multisim with the spreadsheet, this should be very easy to do and in a way that is much less prone to errors than manually assigning net groups. I would assign it as follows.

Suppose my design has two instances of the same subcircuit, as shown below.

The spreadsheet normally shows all nets, in this case, the subcircuit has 3 nets, for a total of 6.

First, click the button second from the right in the spreadsheet to only show nets on the selected page (it is the one with the dotted border and arrow at the bottom right). Then select mysubcircuit(SC1) and you'll ony see nets 1, 2, and 3.

Click the Net group column header to select the entire column.

Click in any one of the cells to start ending, I've given a name group1.

Repeat for all of the other instances, giving each a different name. When your done, click the Show All button again, and you're done.

[dbur]

This seems like it only handles the nets that are brought out of the subcircuit with SC connectors, and not internal nets.  I have 23 different net groups inside each subcircuit and only one comes out through the connectors.

[GarretF]

This will handle nets in the subcircuits. To show/assign the nets in the subcircuit, just select the appropriate sheet/subcircuit in the design toolbox and you'll see those nets. You need to be viewing the page that you want to assign properties for. That's really the advantage of this technique because you use Multisim to automatically filter out nets not in the particular sheet/subcircuit.

If you're still not sure what I mean, I can see if I can put together a little video to make it more clear.