Data bit-to-clock alignment circuit with first bit capture capability

Abstract

A circuit for aligning the phase of a parallel data signal to a clock signal. The circuit includes a parallel data terminal for receiving a parallel data signal formed by multiple word bits, a clock terminal for receiving a clock signal, and a data ready terminal for receiving a data ready signal which has a logic state transition aligned with a first information bit of the parallel data signal. A plurality of data signal delay and sampling circuits connected to the clock terminal and the parallel data terminal provide time-slice bit samples of each information bit of the parallel data signal. A comparator and decision circuit coupled to the clock terminal and at least one of the data signal delay and sampling circuits compares and selects one of the plurality of time-slice bit samples which is phase aligned with the clock signal. A multiplexer circuit coupled to each data signal delay and sampling circuit and to the comparator and decision circuit outputs the selected time-slice bit sample of each word bit of the parallel data signal as the phase-aligned parallel data signal. A first-bit intialization circuit connected to the clock terminal and the data ready terminal and coupled to the multiplexer causes the time-slice bit samples corresponding in time to the logic state transition of the data ready signal to be outputted as a first one or more information bits of the phase-aligned data signal before the comparator and decision circuit operates to compare and select one of the plurality of time-slice bit samples.