netlists - one for the full-chip extraction and one for the ECO-affected nets.

• ECO extraction matches full-chip accuracy by intelligently choosing which nets to re-extract: besides the nets directly changed, it also selects neighboring nets based on their coupling capacitance to the ECO nets.
• The COUPLE_TO_GROUND command should be set to NO in the ECO flow.
• Net E is the ECO net, modified to fix a timing violation. Net A couples to net E - a directly ECO-affected net. Net N does not couple to net E but couples to net A - an indirectly ECO-affected net.
• StarRC includes net E and net A, but not net N, in the ECO netlist (the file named by NETLIST_ECO_FILE). The coupling capacitance between net A and net N shows up as a dangling capacitance under net A, and PrimeTime can read the ECO netlist and adjust net N's coupling and total capacitance accordingly.
• If you do an LVT swap on a cell, StarRC does not re-extract the connected wires or replace them in the netlist.
• Full-chip extraction netlists are written to the file named by NETLIST_FILE; ECO extraction netlists are written to the file named by NETLIST_ECO_FILE.
• The ECO_MODE command controls ECO extraction, with options YES, RESET and NO (the default).
• The first StarRC run is always a full-chip extraction, since a reference run must exist before any ECO extraction. Later runs can be full-chip or ECO depending on how many nets the ECO affects relative to design size; StarRC keeps both a full netlist and an ECO netlist, and PrimeTime can read both.

An ECO extraction is performed unless one of these conditions applies:

• If the design database has no logical or physical changes since the previous extraction, StarRC performs no extraction and does not update the netlists.
• If the star directory is missing, the tool runs a full-chip extraction