UPF 1.0 Ch1 overview

1.1 Key characteristics of UPF
"UPF provides the ability for electronic systems to be designed with power as a key consideration early in the process."==>
"It accomplishes this through the ability to allow the specification of implementation-relevant power information early in the design process — RTL (register transfer level) or earlier."
(UPF captures the low power design intention and makes sure this intention is carried through the whole design process.)

"A UPF specification defines how to create a supply network to supply power to each design element, how the individual supply nets behave with respect to one another, and how the logic functionality is extended to support dynamic power switching to these logic design elements."
(This statement pretty much summarized UPF's usage)

1.2 Power supply network design intent
"To help manage the complexity of the supply network specification, power domains are defined to group elements from the logic hierarchy that share common supply needs"
(Explaining power domain)

"In addition to the primary supply, UPF provides automation and well-defined semantics for retention and isolation supplies"

"The supply network consists of supply ports, switches, and supply nets. Supply network objects are defined within the context of a power domain. Supply ports provide the supply interface to power domains and switches. Switches control the supply distribution. Supply nets connect supply ports."

"A UPF supply network also defines a directed acyclic graph (DAG)."

"To capture situations which are never intended to occur, UPF also provides the ability to define legal and illegal states using power state tables (PSTs). This PST information can then be used for optimizing the implementation."

"Implementation tools can use that information to infer level shifters wherever a signal crosses from a power domain operating at a voltage level that may be different than the voltage level of another power domain to which it connects."

1.3 Extending logic specification
"Isolation is required to ensure undefined outputs from powered-down design elements do not drain power from those design elements that are not powered down. Isolation also ensures a specific logic value is driven from the power domain’s outputs."==>
"UPF supports the specification of isolation strategies that provide information on the clamp values and location of the isolation logic."

"Retention is the ability to save the value of a sequential element in a power domain prior to switching off the power to that element and then later restoring its value after power has been enabled for the element."