Circuit and method for recovering synchronization information from a signal

Abstract

A synchronizer circuit includes an input terminal, an output terminal, and a recovery circuit coupled to the input and output terminals. The input terminal receives an input signal that includes a sync mark, and the recovery circuit is operable to recover the sync mark from the input signal and to generate a synchronization signal on the output terminal in response to the recovered synchronization mark. For example, such a synchronizer circuit can recover the synchronization mark from a read signal and locate the beginning of a data stream for a Viterbi detector that is separate from the circuit. By performing the sync-recovery function in a separate circuit, one can reduce the complexity and increase the data-recovery speed of the Viterbi detector. Furthermore, the synchronizer circuit can recover the sync mark by executing state-transition routines in alignment with the input signal. For example, one can align the synchronizer circuit's state-transition routines to the preamble of the read signal. Such alignment increases the circuit's noise immunity, and thus allows the circuit to recover the sync mark from a read signal having a SNR that is lower than the minimum read-signal SNR of prior sync-recovery circuits. Furthermore, such alignment reduces the time needed for the circuit to reliably detect the sync mark, and thus allows one to shorten the pad of the data forerunner.