Synchronizing method and apparatus

Apparatus for synchronizing a regularly occurring clock pulse train in frequency to the average of a bunched clock pulse train corresponding to data, the apparatus comprising:

• a FIFO having a given number of storage locations, an empty flag storage cell for each location, and a full flag storage cell for each location;
• an oscillator producing as an output signal the regularly occurring clock pulse train;
• means for filling the FIFO with the data responsive to the bunched clock pulse train and emptying the FIFO responsive to the output signal;
• means for producing an error signal that represents the state of the FIFO;
• means for setting an empty flag in the empty flag storage cell of a storage location and resetting a full flag in the full flag storage cell of the storage location when data is read out of the corresponding storage location;
• means for setting a full flag in the full flag storage cell of a storage location and resetting an empty flag in the empty flag storage cell of the storage location when data is written into the corresponding storage location;
• means for summing either the empty flags or the full flags to produce an error signal that represents the state of the FIFO;
• and
• means for applying the error signal to the oscillator to change the frequency of the output signal so the state of the FIFO remains approximately constant.