How do you connect a supply net to a domain's primary power/ground using set_domain_supply_net?
From PDVerse Low-Power Physical Design Mentor Guide · pdVerse Mentor Guide
Explanation
set_domain_supply_net takes an already-created supply net and designates it as a domain's primary power or primary ground. Once set, every cell inside that domain is implicitly considered connected to that net without touching each instance's PG pins by hand.
Implementation Walkthrough
After the domain and its supply nets exist, run set_domain_supply_net -primary_power_net -primary_ground_net . Mychip repeats this for all four domains -- crucially, PD_COP's primary power net is set to the switched net VDD1p0_SW rather than the always-on input net VDD1p0, because PD_COP is the domain meant to actually power down.
Command
set_domain_supply_net PD_COP -primary_power_net VDD1p0_SW primary_ground_net GNDSwitch-by-switch
-primary_power_net: the net implicitly wired to every cell's power
pin in the domain; -primary_ground_net: same, for ground. Every
power domain must have exactly one primary power net and one primary
ground net.Expected Tool Behavior
All logic inside the domain is now understood to draw from the given net, and the domain's power state in the PST tracks that net's voltage/off values.
Example
PD_CPU -primary_power_net VDD0p9 -primary_ground_net GND (an alwayson 0.9V domain) versus PD_COP -primary_power_net VDD1p0_SW primary_ground_net GND (a shutdown domain riding the switched virtual rail).
Common Mistake
Pointing a shutdown domain's primary power net at the always-on input rail instead of the switch's output rail -- this leaves the domain permanently powered and defeats the whole point of power gating it.
Likely Error Or Warning
This topic is not covered in enough depth here to give a fully reliable answer for a specific error string, though missing or inconsistent primary-supply connectivity is the kind of issue check_mv_design is meant to catch.
Debugging Approach
Use query_port_net / query_net_ports to confirm exactly which net a given port in the domain resolves to.
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