Design Techniques During the ECO Phase

Things to do at the start of the ECO phase:

• Freeze all clock routes.
• Fix all critical cells.
• Freeze all critical nets.
• Set the ECO-mode settings: disable update-timing (optimization commands are not run), disable automatic legalize (call it only when needed), and disable ecoRoute (call it only when needed).

Automated approach:

• Use the ECO flow.
• Apply net corrections or revert changes through a DEF.

Manual approach (verify twice):

• Implement the ECO by hand using connect/disconnect or attachTerm/detachTerm.
• Correct nets with manual routes.
• Free up routing tracks by removing power/ground and using them for signal routes; freeze all such manual routing with set_attribute/setAttribute and apply the COVER attribute (Cadence) so the cells cannot be modified by anyone.

KEY In ECO: freeze clocks/critical nets, set ECO-mode flags off, then apply automated or carefully verified manual fixes.

Interactive Design Mode

• In interactive mode the designer decides on and applies the fixes directly.
• The tool only optimizes up to the defined constraints or a fixed runtime; once those limits are reached and the expected result is not achieved, the designer must step in and fix the remaining issues interactively.

KEY Interactive mode lets the designer fix what the tool cannot resolve within its constraints or runtime.