Abstract: The data separator of this invention may be used for extracting clock and data signals from a serial stream of bits read from a magnetic disk or tape. The data separator is supplied with a "fast" clock pulse generated by a frequency multiplexer. After a lock indication from the frequency multiplier, during the first eight serial data pulses the frequency and phase of the data separator are synchronized to the serial data pulses. Then an early and late logic unit keeps track digitally of the cumulative phase difference between the incoming data stream and the output of the data separator. When the cumulative phase difference reaches predetermined limits, the phase of the output is adjusted. If a second phase adjustment is required in the same direction (i.e., early or late), the frequency of the output is adjusted.

Abstract: The data separator of this invention may be used for extracting clock and data signals from a serial stream of bits read from a magnetic disk or tape. The data separator is supplied with a "fast" clock pulse generated by a frequency multiplexer. After a lock indication from the frequency multiplier, during the first eight serial data pulses the frequency and phase of the data separator are synchronized to the serial data pulses. Then an early and late logic unit keeps track digitally of the cumulative phase difference between the incoming data stream and the output of the data separator. When the cumulative phase difference reaches predetermined limits, the phase of the output is adjusted. If a second phase adjustment is required in the same direction (i.e., early or late), the frequency of the output is adjusted.

Abstract: A frequency multiplier includes a ring oscillator having a number of logic gates arranged in a plurality of rings. Control inputs enable the selection of individual gates so as to connect them into the ring or, conversely, remove them from the ring. As additional gates are removed, the combined delay imposed by the gates remaining in the ring is reduced and the frequency of the oscillator increases. A variable delay element, preferably a group of tri-state inverters connected in parallel, is connected between two of the gates. The oscillator is fine tuned by controlling the delay inserted by the variable delay element. The frequency multiplier also includes a frequency comparator. A reference frequency is passed through a divide-by-K unit and the output of the ring oscillator is passed through a divide-by-N unit, N being greater than K.

Abstract: The present invention provides a phase-locked loop in which an internal oscillator is fed into a high resolution tapped delay line. One output of the tapped delay line is selected by selection logic to generate the output clock. The output clock is phase compared with the input signal, which is either a clock signal or a NRZ data signal, and in any case, is a signal with frequency that is a division by two of the frequency of the internal oscillator and the source of which is also the internal oscillator. Then a decision is made, according to the phase detection, whether to select the next output of the delay line, the previous one, or remain with the current one. Therefore, if a change in the frequency is needed, then if an integer multiple or division of the original frequency is selected for the internal oscillator, synchronization will be unchanged, and furthermore, both the output clock and the input signal will simultaneously switch to the new frequency.