Crosstalk Noise vs Crosstalk Delay

Two nets running close together can interfere through coupling capacitance, producing two distinct effects.

Crosstalk delay occurs when one net switches fast and the other slow - the fast net speeds up or slows down the slow net, causing a timing error.

Crosstalk noise occurs when one net is idle (held at 0 or 1) while a neighbour switches; the coupling capacitor can inject an unwanted transition. It is driven by charge storage, supply noise or substrate noise, and a noise tool finds the worst-case glitch on the idle net (commands: report_noise, check_noise, update_noise).

KEY Crosstalk delay = timing shift between two switching nets; crosstalk noise = a glitch on an idle net.