Are you taping out in a non-CPF Encounter flow and want to know how to control adding addIsolationCell to isolate some signals with isolate high cells and some with isolate low cells? Then here is the answer of how to do it.
Basically you can use "–excNet/-nexNetFile" and "–selNet/-selNetFile" options of "addIsolation" command to achieve what you want:
[-forceIsoCellInPDHInst | -noForceIsoCellInPDHinst]
Example: only net1 and net2 from PD1 to PD2 need clamp low (assume you have two types of isolation cells, iso_high is clamp-high and iso_low is clamp-low)