What does the create_power_domain command do in UPF?
From PDVerse Low-Power Physical Design Mentor Guide · pdVerse Mentor Guide
Definition
create_power_domain declares a new power domain — a named grouping of design elements (instances, ports) that share power management requirements — at a specified scope in the design hierarchy.
Mentor Explanation
Every power domain has a scope (the hierarchy level that is the root of the domain) and an extent (the actual set of design elements it covers), along with associated supply nets, a designated primary power and primary ground net, and any isolation/level-shifter/ retention synthesis strategies attached to it. A worked 'MYCHIP' example shows the command in practice: 'create_power_domain PD_MYCHIP -include_scope' for the top domain, and 'create_power_domain PD_CPU -elements {U_CPU}' for a sub-block domain, and similarly for PD_DSP and PD_COP. The basic syntax form is 'create_power_domain -elements {list} [-scope instance] domain_name' — for example 'create_power_domain -elements {U1 U2 U3} -scope Block1 PD1' — and it supports deferring the element list with an empty '-elements {}' followed later by '-update' once the membership is known.
Example
create_power_domain -elements {U1 U2 U3} -scope Block1 PD1 declares a domain named PD1, rooted at scope Block1, whose extent is instances U1, U2, and U3.
Why It Matters
This is the very first UPF command a beginner needs to internalize, since every other strategy command (isolation, level shifter, retention, switch) is defined relative to a domain that create_power_domain establishes.
Command
create_power_domain -elements {U1 U2 U3} -scope Block1 PD1;
create_power_domain PD_MYCHIP -include_scopeCommon Beginner Mistake
Forgetting that a power domain is a synthesis construct, not a netlist object — it doesn't 'exist' as a physical entity by itself; the tool uses it purely to organize which supply and management strategies apply to which elements.
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