Connectivity Mode

IC graph has three modes that can be assigned to a cell: Geometry(Polygon) Editing, Connectivity Editing, and Correct by construction.

The editing modes are differentiated by the level of editing constraints enforced by the built-in connectivity model and design rule checking algorithms, which can bu used or ignored.

• The Geometry Editing(GE) mode allows unrestricted polygon editing, it does not use or maintain the connectivity information, and does not prevent connectivity or physical design rule errors.
• The connectivity editing (CE) mode maintains connectivity data as edits occur, but does not prevent any errors in connectivity or physical design rules. You get a warning when connectivity is being changed by an edit, but the edit occurs. The CE mode is typically used in situations where you want to keep track of connectivity, but need the freedom to modify it. We will use this mode in the later lab of SDL design.
• The Correct By Construction(CBC) mode restricts editing to prevent changes to connectivity.