Modeling, simulation, and measurement considerations of high-speed digital buses

Some of the major limiting factors of high-speed buses are discussed. It is shown that on loaded backplanes, the propagation delay is a function of the device´s trigger threshold. The stub-ringing phenomenon is also discussed. For single, capacitively loaded stubs, the ringing frequency is shown to be lower than what is expected from quasi-lumped models. A simple dual-stub butterfly model is introduced to predict the ringing of backplanes. This model predicts the stub ringing in high-impedance states of TTL buses of high-level states of BTL buses. It is shown that the damping factor of the oscillation depends on the ratio of stub spacing and stub length, and is a very weak function of the termination resistance used at the end of the backplane