Games / Command flash cards / Timing reports / Annotation and power

Annotation and power

Each card shows a command to explain. A missed card returns later in the round and starts the schedule over. A card answered correctly moves up the schedule and next appears after 1, 3, 7, then 21 days. Keys 1 to 4 choose an option, h shows a hint, and Enter moves on. A hint keeps the card where it is on the schedule. An ordering card is answered by clicking its items in order, and one wrong click ends it. Time values are in nanoseconds. Progress is stored in this browser.

SourceThese cards follow the reporting commands of OpenSTA, the open-source static timing analyzer used by OpenROAD, and each answer links to that command in the OpenSTA command reference. Report commands are not a standard: other timers name and format their reports differently. The report excerpts are real OpenSTA output from the gcd example design. Reference: OpenSTA command reference (OpenSTA on GitHub).
All 5 cards in this section, with answers
  • report_parasitic_annotation -report_unannotated
    Reports parasitic coverage and lists the nets that lack it.

    Hint: Annotation means data loaded from a file; SPEF (Standard Parasitic Exchange Format) carries parasitics.

    Delays computed without parasitics on some nets are optimistic, so the coverage of the SPEF (Standard Parasitic Exchange Format) file is checked before sign-off timing is trusted. OpenSTA reference

  • report_annotated_delay -report_unannotated
    Summarizes SDF (Standard Delay Format) delay coverage and lists unannotated arcs.

    Hint: SDF (Standard Delay Format) carries delays. Ask what this reports about them.

    An SDF (Standard Delay Format) file gives delays directly instead of having them calculated. Arcs to and from top-level ports are included only with -from_in_ports and -to_out_ports. OpenSTA reference

  • report_annotated_check
    Summarizes how many timing checks received values from an SDF (Standard Delay Format) file.

    Hint: The same idea as the delay report, but for timing checks rather than delays.

    Timing checks (setup, hold, recovery, removal) can be annotated from an SDF (Standard Delay Format) file separately from delays, so their coverage is reported separately. OpenSTA reference

  • report_activity_annotation
    Summarizes which pins have annotated switching activity.

    Hint: Activity is how often pins switch, which is what a power calculation needs.

    Activity comes from simulation (read_vcd, read_saif) or from set_power_activity. Power depends on how often nets switch. Without annotated activity, default input activity is propagated, which is only an estimate. OpenSTA reference

  • report_power
    Reports internal, switching, and leakage power by cell group.

    Hint: Power splits into internal, switching, and leakage, reported per kind of cell.

    The groups are sequential, combinational, clock, macro, and pad, in watts. Without simulation activity, an input activity of 0.1 and duty of 0.5 are assumed and propagated through the logic. OpenSTA reference