What is a supply set in UPF, and how is it different from a plain supply net?
From PDVerse Low-Power Physical Design Mentor Guide · pdVerse Mentor Guide
Explanation
A supply net is a single conductor. A supply set (create_supply_set) is a higher-level, abstract object that bundles a power function and a ground function (accessed as SS.power / SS.ground) under one handle, and is domain-independent by default. It lets strategies and constraints refer to 'a supply' as a unit instead of juggling separate power-net and ground-net names everywhere.
Implementation Walkthrough
Create the abstract handle, then bind its functions to real nets: create_supply_set SS_NAME; create_supply_set -update -function {power net} -function {ground net}. Every power domain automatically gets a few standard handles for this purpose -- primary, default_isolation, and default_retention -- and create_power_domain -supply lets you define additional custom handles, named power_domain_name.supply_set_handle.
Command
create_supply_set PD_COP.primarySwitch-by-switch
-update: refine an already-created supply set later instead of
recreating it from scratch; -function {power|ground|nwell|pwell
net}: binds one electrical function of the set to a specific net.Expected Tool Behavior
Strategy commands (e.g. set_isolation -isolation_supply, set_level_shifter -input_supply/-output_supply) can reference the supply set handle instead of bare net names, and the same abstract set can be related across scopes with associate_supply_set.
Example
PD_COP.primary as the default handle combining the switched net VDD1p0_SW (power) and GND (ground) for PD_COP.
Common Mistake
Treating a supply set and a plain supply net as interchangeable, e.g. passing a bare net name into an option that expects a supply-set handle (or vice versa).
Likely Error Or Warning
This topic is not covered in enough depth here to give a fully reliable answer regarding a specific error message on this confusion.
Debugging Approach
Use report_supply_sets to see which functions (power/ground) are currently bound to which nets for each declared supply set.
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