VLS-XL Assign instance pin to net - automatically create net on clicked target?

Hello,

In the past we had such capability to auto assign net on floating shapes but it has been removed because we had nobody using it.

Could you please open a ticket on the customer support in order for us to have a good case to resurrect this functionality?

As Mark explained it is much better/easier to have a schematic or a LVS result in order to bring back the connectivity.

A way to do what you want to do but which is much more painful is to select the instances one by one and to assign their terminals with Connectivity > Net > Propagate (assigning the terminals to a net which has the same name as the terminal ). The connectivity extractor would then propagate automatically the connectivity to shapes touching the instance terminals. The problem with that could be to have same net name assigned which is not what you want. 

Thanks,

Alex

Hi,

I can't understand the motivation behind doing that. It's a lot of effort to build a connectivity out of nothing in the layout space, basically negating the
intention of Layout XL to provide semi automation and doing layout with much less effort. You may have reasons.

Maybe it's easier and faster to manually build the schematic? Place your pins and devices ( ignore parameters to speed it up ) and wire them. Do the binding
to the layout. If the devices are bound you can update the schematic parameters from the layout source.

For creating nets out of thin air:
Can you do SKILL? I can't provide a complete solution but give some pointers.

You basically need a routine to:
1. get the selected shape and test if there is a net allready ( shape=car(geGetSelSet()); if !shape~>nets ... )
2. if there is no net/netTerm, you need to create a new one in the db ( net = dbCreateNet(cv "B") ; netTerm = dbCreateTerm(net net~>name "inputOutput") )
ofcourse you have to make sure the new netname does not exist already.
3. add the shape to the net and make it sticky ( dbAddFigToNet(shape net) shape~>lxStickyNet=t )

Kind regards,
Marc

I've got to agree that this limited case would probably not be a compelling enough reason for Cadence to bring this feature back - would we be the first and only to mention it, or, are you looking for more votes to help decide whether it's worthwhile? If it turns out to be something we use a lot, Marc's suggestions will probably work out nicely.

The instance pins are not yet touching the floating shapes - the goal is to see flight and drag lines between the two disjoint items, so, it doesn't sound like Propagate would be a fit there. So far I've been using two methods to create new nets: 1) add a label somewhere on the floating shape or something already connected to it, then extract layout with Layout XL Options -> Connectivity -> Controls -> Connectivity Assignment -> Assign shapes from attached labels checked; and 2) edit a floating shape and give it a (new, unique) net name directly. Basically we go with option 1) where we've already drawn labels during the VLS-L layout process, and option 2) elsewhere. Keeping the Navigator open and viewing the list of nets is a good way to make sure you can pick a unique net name; I've just been going with the alphabet but zero-padded numbers would probably work better for viewing in the navigator.

The schematics we use are not from Cadence, so, we use a CDL-like spice-like netlist to LVS against and that's really the only "connectivity source" we have to go from. As far as VLS-XL goes, there is no connectivity source. I've messed with SpiceIn a bit, and gotten it to work a few times for small test cases, but massaging our netlists to be fully usable by SpiceIn may not be an effective use of time. We've got some SKILL code to do a limited equivalent of "Generate all from source" by reading the netlist, and it's been a big help so far, but this was built for VLS-L and does not yet do connectivity - just devices. Now that we may have more access to XL for the long term, we'll probably try to add connectivity generation to that code.

Still, that code enhancement would address the case where we are starting a new cell, with an existing CDL as the "source". What we're really looking for here is a workflow to address the mid-stream case, where a lot of layout work has been done using VLS-L in a given cell (i.e. all the fets) and we want to use the flight lines and drag lines in VLS-XL for the remainder of the layout (analog devices, blocks, etc).

Creating a schematic from scratch to get the connectivity for the bits that we want sounds like an interesting option. Will probably try that out and see how it stacks up against other options (i.e. making the nets by hand like we're doing now, or working the SKILL).

It sounds like the SKILL solution would be fairly straight forward like you point out, and could mimic the user behavior of Connectivity -> Nets -> Assign, and maybe even map it to that menu entry. Would it be better and more expedient to ask for a CCS SKILL routine, or, to code it ourselves?

After you mentioned it, I just read up some on the sticky net topic. How does lxStickyNet interact with Layout XL Options -> Connectivity -> Controls -> Connectivity Assignment -> Keep shape assignment? The docs on that checkbox are a bit vague.