Connecting multiple ground domains

[stockstephanie]

In the PDK I am using, I have the option to use VSS core, VSS IO, or combined VSS pads. I would prefer to use the combined pads in my pad ring, but OpenROAD does not seem to understand that the VSS combined pad is driving both the VSSL and VSSH nets that are in the pad ring. It connects the VSSL nets to VSS, but created a NORTH_WEST_VSSH_RING net instance. Then LVS detects that these rings are shorted (which they are supposed to be), and then causes issues. In the combined cell, the pins are named VSS, not VSSL and VSSH like the others. Is there a way to easily drive both of these from one VSS pad rather than needing to use the VSS IO and VSS core pads?

[maliberty]

@gadfort does this description make sense to you?

[gadfort]

It seems like all that is needed is a global connect rule to specify they vssl and vssh should be connected to vss, the pad ring will not create nets if the pin are connected to an existing net.

[stockstephanie]

Are you talking about a global connection in the actual PDN generation or just in LVS?

[gadfort]

it would need to done during the pad ring generation otherwise when you call connect_by_abutment the new net will be created.