BeginnerQuestion 27 of 40Source PDF page 25

What is a standard cell timing library (Liberty), and what does it contain?

From PDVerse STA Mentor Guide · pdVerse Mentor Guide

Short Answer

A standard-cell library holds the characterized timing (and power) data for every logic cell used in the design, and Liberty (.lib) is the structured, text-based format used to write that characterized data down.

Example

Inside a Liberty file you'll find timing arcs, delay and output-slew values as functions of input slew and output load, timing checks like setup, hold, recovery, removal, and pulse width, plus pin capacitances for every cell.

Why It Matters

Without this characterized data, the STA tool would have no idea how long a signal takes to pass through a given gate, or how much margin a flop's setup and hold checks require. The library is effectively the tool's dictionary of how every cell behaves electrically.

Command

report_lib -unit ns

Mentor Note — Common Mistake

Don't think of the library as just a list of cell names and functions. It's fundamentally a timing (and power) database, describing measured electrical behavior, not just logical behavior.

Visual explanationSTA context: What is a standard cell timing library (Liberty), and what does it…
STA context: What is a standard cell timing library (Liberty), and what does it…A three-step concept map summarizes the focus, core answer, and practical verification for What is a standard cell timing library (Liberty), and what does it contain?Question focusWhat is a standard celltiming library(Liberty), and what doesit…Core answerA standard-cell libraryholds the characterizedtiming (and power) datafor every…Verify in practicereport_lib -unit nsUnderstand → explain the mechanism → verify the assumptions

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