// SPDX-License-Identifier: BSD-3-Clause // Copyright (c) 2024-2025, The OpenROAD Authors # Author: Dimitris K. Fotakis # Version: v1.0 # Date: 11052024 Major Flow Steps: to run rcx command: extract_parasitics Prerequisite Reading: run_extraction.README, Architecture.README ------------------------------------------------------------------------------------------- 1. Set User Options User Command: extract_parasitics function: makeBlockRCsegs_v2 ------------------------------------------------------------------------------------------- 2. Read Model File and Associate User Defined function: SetCornersAndReadModels_v2 Note 1: if not set with Tcl cmd: , all model file corners will be extracted Note 2: if user option lefRC is used, a single corner is generated ------------------------------------------------------------------------------------------- 3. Read Model File Organize distance based Coupling/Fringe values to calculate RC values for every signal wire function: SetCornersAndReadModels_v2/ReadModels_v2 Note 1: DensityModel is equivalent to Process Corner Note 2: basic format for every distance based model is defined as follows: capacitance units are in fF/nm resistance unist are in Ohms/nm ------------------------------------------------------------------------------------------- 3. Generate Full RC network for all nets function: makeRCNetwork_v2 Objects: dbCapNode, dbRSeg Important User Options: -max_res -no_via_merge_res -lefRC -lef_res Prerequisite Step: odb::orderWires is called before makeBlockRCsegs_v2 A. Create Resistance Table per Layer to drive RC Merging Note: Values from first process corner are used B. Create RC Segments and Capacitance Nodes by traversing dbWire object Associate one or more Physical wires to an RC segment (dbRSeg) SPEF structure is dependent on the RC network generation Physical wires will be extracted for Coupling Capacitance and Resistance based on user option: max_res drives RC segment Merging in a net Merging stops at instance and block terms and wire branches Note 1: via resistance can be taken from Model File or from LEF if Via Models don't exist Note 2: via resistance is added to the connecting wires if user option -no_merge_via_res is not set Note 3: Extracted coupling caps for the wire segments ------------------------------------------------------------------------------------------- 4. Extract Coupling Caps function: couplingFlow_v2 Important Objects: dbCCseg, extDistRC Important User Options: -skip_over_cell, -coupling_threshold, -context_depth -cc_model A. RC Network Generation (see step 3) Note: the following steps are repeated on horizontal and vertical directions B. Load Signal and Power Wires on Search object: Ath__gridTable Functions: addPowerNets, addSignalNets C. Load Signal and Power Wires on Geometric Search object: gs Functions: fill_gs4, addShapeOnGS, Important Note: add instance obstructions and pin shapes on Geometric search, unless user option -skip_over_cell D. Find coupling neighbors on object Ath__wire on both sides and all levels User option -cc_model controls how far in tracks coupling neighbors are found Function: couplingFlow_v2/FindCouplingNeighbors important object: extMain->_search, extMeasure->_search, extMeasureRC->_search Note 1: Coupling neighbors on different levels are called Diagonal Note 2: Coupling neighbors on different levels overlapping latterally are called Vertical Diagonal E. Find Segments of Wires that directly coupled with segments of other wires and over/under CrossOverlaps User Option -context_depth controls low and upper bound of metal levels for cross ovelaps Function: couplingFlow_v2/CouplingFlow/GetCouplingSegments F. Calculate Resistance of every coupling segment based on distance of neighbors of both sides Function: couplingFlow_v2/CouplingFlow/CalcRes G. Calculate Coupling and Fringe Capacitance of every coupling segment based on distance of neighbors of both sides and CrossOveral Context User Option -coupling_threshold controls the creation of coupling caps Function: couplingFlow_v2/CouplingFlow/ VerticalDiagonalCouplingAndCrossOverlap CreateCouplingCaps_overUnder, CreateCouplingCaps_over