What is a supply set in UPF?
From PDVerse Low-Power Physical Design Mentor Guide · pdVerse Mentor Guide
Definition
A supply set is an abstract, domain-independent collection of supply nets grouped around two functions — power and ground — accessed as SS.power and SS.ground, and created with the create_supply_set command; it lets UPF commands refer to 'the power and ground for this purpose' without hard-wiring specific net names everywhere.
Mentor Explanation
A beginner often assumes a 'supply' is always just one literal net, but a supply set is a level of abstraction above that — it's a named handle that can be pointed at whatever net makes sense in a given context, and can later be refined or associated with other supply sets. Think of it this way: every power domain automatically gets default supply set handles like primary, default_isolation, and default_retention, so strategies can reference 'this domain's isolation supply' generically rather than a specific net name.
Example
The associate_supply_set command lets you connect the functions of two or more supply sets to the same underlying net across nested scopes — e.g., associating a sub-block's supply set with its parent's so they resolve to the same physical rail.
Why It Matters
Supply sets are what make UPF strategies portable and hierarchical — the same set_isolation or set_retention strategy syntax can reference a supply set handle regardless of exactly which net backs it in a given block instantiation.
Command
create_supply_set supply_set_nameCommon Beginner Mistake
A beginner might try to use a supply net name where a supply set handle is expected (or vice versa) — these are different UPF object types, and commands like create_supply_set have their own naming rules distinct from create_supply_net.
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