Showing posts with label Wire load. Show all posts
Showing posts with label Wire load. Show all posts

Wire load models


Wire loading models contain all the information required by compile to estimate interconnect wiring delays. A typical Wire load model definition contains: area, resistance, capacitance, slope and fanout. All these attributes are given per unit length wire. Slope value is used to characterize linear fanout.

Generally wire load models are used in ASIC design. These wire load models will contain statistical values which are used in pre-layout simulation of ASIC. Since we are extracting resistance(R), capacitance(C) values in back end after place and route(P&R) phase we need to perform pre-layout simulation before P&R.

A wire load model attempts to predict the capacitance and resistance of nets in the absence of placement and routing information. The estimated net capacitance and resistance are used for delay calculation. Technology library vendors supply statistical wire load models to support estimation of wire loads based on the number of fanout pins on a net. You can set wire load models manually or automatically.