Method and apparatus for sequencing two digital signals

摘要

A first self-timing signal bi-phase-mark coded and having a data portion and a synchronization portion is to be sequenced by a second signal also having a data and a synchronization portion. The signals derived by differentiating only the level change at the end of each bit cell phase-lock an oscillator whose output provides the basic timing for a modulator stage. In the modulator stage, a flip-flop first changes state under control of the first signal. At the start of the synchronization portion of the first signal, a comparator furnishes a signal which switches control of the flip-flop to signals derived from differentiation of the second signal. When the second signal is binary coded, a NAND gate modulates the pulses from the second signal by pulses resulting from differentiating negative going edges of the signal derived from the phase-locked oscillator to create a signal for controlling the flip-flop so that it changes state in accordance with a bi-phase-mark code.