Pulse propagation in an unterminated environment

The generally adopted design philosophy of interconnections between digital circuits considers it safe to use unmatched lines for short distances, and matched lines for long distances. These terms long and short are not usually meaningfully quantified. With higher-speed digital logic this philosophy has often degenerated into a `match every interconnection for safety¿ concept, with consequential increases in can count, complexity, down-time, volume and power consumption, leading to a degradation of overall system speed. This paper investigates the propagation of pulses down interconnections to discover the point where the matching of lines becomes essential. Bergeron diagrams are used in a theoretical analysis to predict the waveforms that will be generated by various lengths of interconnection; these results are subsequently compared with actual measurements on emitter-coupled logic working under similar conditions.